Sustainability of Recycling Waste Ceramic Tiles in the Green Concrete Industry: A Comprehensive Review

Abstract

Ceramic tiles classified as non-biodegradable are made from fired clay, silica, and other natural materials for several construction applications. Waste ceramic tiles (WCTs) are produced from several sources, including manufacturing defects; surplus, broken, or damaged tiles resulting from handling; and construction and demolition debris. WCTs do not decompose easily, leading to long-term accumulation in landfills and occupying a significant amount of landfill space, which has substantial environmental impacts. Recycling WCTs offers several critical ecological benefits, including reducing landfill waste and pollution, conserving natural resources, lowering energy consumption, and supporting the circular economy, which in turn contributes to sustainable construction and waste management practices. In green concrete manufacturing, WCTs are widely utilized as replacements for cement, fine, and coarse aggregates, and the recycling level in the concrete industry is an increasingly explored practice aimed at promoting sustainability and reducing construction waste. From this view, this paper reports the innovative technologies, advancements in green concrete performance, and development trends in the reuse of WCTs in the production of systems. The effects of WCTs on fresh, engineering, microstructural, and durable properties, as well as their environmental performance, are reviewed. In conclusion, the use of technologies for recycling WCTs has demonstrated potential in promoting sustainability and supporting the transition toward a more environmentally friendly construction industry. This approach offers a practical contribution to sustainable development and represents significant progress in closing the recycling loop within the construction sector.

1. Introduction

Waste from ceramic tiles, primarily generated during manufacturing, construction, renovation, and demolition activities, includes broken tiles, rejected batches, and unused off-cuts [1,2]. These wastes are non-biodegradable and chemically stable, leading to long-term accumulation in landfills. Their disposal poses significant environmental concerns, including land degradation, increased landfill burden, and the unnecessary consumption of natural resources due to the lack of recycling practices [3]. Additionally, the energy-intensive production of ceramic tiles contributes to carbon emissions, and improper disposal can lead to dust generation and the leaching of trace elements, further impacting soil and water quality. Annually, over 10 million square meters of ceramic tiles are produced worldwide [4]. An accurate survey revealed that nearly 15 to 30% of the material goes to waste in the process of ceramic manufacturing [5]. Therefore, addressing ceramic tile waste through sustainable management and recycling is essential to reduce environmental impacts and promote resource efficiency in the construction industry. Several estimates indicate that ceramic tiles-related sectors around the world generate large quantities of waste each year, most of which ends up in landfills. Both the recycling and discarding procedures of ceramic waste are expensive, leading to environmental concerns. Therefore, the concrete industry could gain significant advantages by properly recycling this waste as a substitute for OPC or/and natural aggregates, creating a mutually beneficial outcome for the construction sector and the environment [6].

Nowadays, various green concretes with improved properties have been developed by blending WCT powder with OPC or replacing fine and coarse natural aggregates with crushed ceramic tiles. The incorporation of WCTs into concrete was found to appreciably enhance the durability and strength of the resulting products. It has been realized that environmentally amiable and sustainable construction components can be a suitable alternative to traditional concrete. This recycling of ceramics into concrete has two significant benefits, such as solving the waste dumping issues of ceramic industries and the development of sustainable binders and aggregates [7,8]. Numerous studies [5,8,9,10] have shown that waste ceramics possess strong resistance to biological degradation. Owing to their high silica–alumina content and crystalline structure, ceramics have emerged as a viable alternative to cement, capable of improving both the strength and durability of concrete [11,12,13]. Despite this potential, the use of ceramics as a replacement for ordinary Portland cement (OPC) in construction remains limited [7,10]. Expanding the application of waste ceramics in concrete production is therefore essential for developing high-performance, sustainable concrete at a reduced cost. As major consumers of ceramic waste, construction industries worldwide have the potential to play a crucial role in addressing various environmental challenges [14]. The cement industry can integrate ceramic materials without requiring substantial modifications to the existing production or application methods. Additionally, the reuse of ceramic waste can help lower landfill expenses, preserve natural resources, and reduce energy consumption, thereby promoting environmental sustainability. The extensive research over the years has highlighted the significant benefits construction industries can gain by recycling industrial ceramic waste into cement-free concrete, contributing to long-term sustainable development [15,16,17,18].

According to the existing research, ceramic waste shows considerable potential as a substitute for sand and natural aggregates in concrete and mortar applications [5,19]. In recent years, extensive studies have been conducted on the use of various types of waste ceramics in concrete, including wall and floor tiles [20], sanitary ceramics [21], electrical insulators [22], bone China ceramics [23], and ceramic bricks [24]. López et al. [25] demonstrated that replacing 10–50% of conventional sand with white ceramic in concrete results in tensile and flexural strengths comparable to those of concrete made with river sand, while significantly increasing the compressive strength (CS). Similarly, Pacheco-Torgal et al. [7] found that using ceramic sand instead of natural sand does not compromise strength and improves impermeability, resistance to chloride ion penetration, and performance under accelerated aging conditions. Senthamarai et al. [8] evaluated the CS and chloride ion resistance of mortars containing ceramic waste aggregates, concluding that fine ceramic aggregates enhance CS and substantially increase resistance to chloride ion penetration. They identified 20% ceramic aggregate as the optimal proportion for maximizing both mechanical performance and durability. According to [26], replacing 15% to 30% of natural sand with ceramic fine aggregates in high-performance concrete improves both compressive strength and chloride ion resistance, likely due to an internal curing effect. In a study conducted by Binici et al. [26], the authors reported that incorporating 40% ceramic fine aggregate can increase the compressive strength, improve abrasion resistance, and decrease chloride ion penetration depth.

Given the significant potential of waste ceramics as viable alternatives to OPC and natural aggregates in producing high-performance mortars and concretes, this study aims to provide a comprehensive review of innovative technologies, advancements in sustainable concrete performance, and development trends in the recycling of waste ceramics in the concrete and construction industries. The flow chart of recycling WCTs as a binder and filler replacement in green concrete is presented in Figure 1. Firstly, utilizing WCTs as a partial replacement for OPC and its effect on workability, strength, and durability performance has been widely evaluated. Secondly, the effect of WCTs as a replacement for fine and coarse natural aggregates on fresh and engineering properties is reviewed. Finally, the environmental benefits of recycling waste ceramics in the concrete industry and their contribution to combating climate change and achieving sustainability goals are also discussed. It is suggested that the broad adoption of environmentally friendly modified concrete with waste ceramic tiles could play a key role in reducing carbon emissions.

2. Significance of Recycling Industrial Waste in Concrete

The number of building projects is constantly increasing to meet the needs of various industries, but this also generates waste that must be managed. A sizable proportion of artificial waste is generated during building construction and cleanup operations, which also produce a substantial amount of construction waste. Professionals are highly concerned about the improper disposal of this trash, as it has serious negative consequences for society and the environment [27]. One necessary type of waste is construction and demolition waste, such as floor and wall ceramic tiles. Construction waste accounts for roughly half of the waste that is landfilled around the world [28]. Municipal waste management has led to increased recycling rates of 70% in the U.S. and 90% in Europe [29]. Nonetheless, municipal trash management has not been successful in many countries, where recycling rates are less than 10%. Ceramic waste is one of the most common types of waste generated during construction and demolition, and it can cause significant environmental pollution when disposed of in landfills [30]. Moreover, ceramic products are key components of construction, with clay, carbides, silica, metal oxides, and other earthy elements being the key materials used to produce ceramics [31]. Examples of commonly manufactured ceramics include wall tiles, floor tiles, sanitary ware, and household ceramics [32]. The global ceramic tile manufacturing size increased to 18.2 billion m² in 2021, from approximately 12.6 billion m² in 2019 [33]. Up to 30% of the ceramics produced worldwide are expected to be wasted. Most such waste is disposed of in disorganized piles and landfills, even though it could be immediately repurposed (for example, to fill excavation trenches) [34]. Over 45% of this waste is expected to be ceramics [35]. As ceramic materials are brittle by nature, manipulating and fastening them on building sites results in wasteful fragments. Every year, production errors and demolition materials contribute significantly to the levels of WCTs produced. WCTs originate mainly from two sources: the ceramic industry, due to production processes or defects, and construction activities, either during the building or demolition phase. Most WCTs are produced throughout the stages of manufacturing, construction, and demolition within the building life cycle. Moreover, dumping WCTs in landfills can contaminate the air, soil, and groundwater. Many researchers have highlighted the adverse impacts that WCTs have on the environment [36]. As WCTs are non-decomposable, long-term problems have emerged, including environmental pollution, illegal dumping, and health problems [37]. Therefore, to prevent environmental issues that could result from the inappropriate disposal of WCTs, the optimal management of WCTs must be investigated. Reusing this waste in concrete reduces the environmental effects that cement and WCTs generate, which is an interesting and long-term green option [38]. The strategy of redirecting WCTs from the dumpsite and using them to produce concrete is in line with the circular economy, which helps to preserve valuable land for better uses than waste disposal and reduces the burden of waste management on the construction industry. Furthermore, utilizing WCTs in sustainable building materials may result in lower construction costs, reduced energy consumption, and lower pollution, while requiring fewer raw materials.

3. Waste Ceramic Tiles for Cement Replacement

3.1. Physical Properties and Chemical Composition

As shown in Figure 2, there are two WCT colors, namely white [39] and red [40]. The red color is believed to be caused by high levels of iron oxide (Fe₂O₃) [7]. The waste ceramic tile powder (WCTP) particles appear to be rounder and more uniform after fine grinding takes place. WCTPs have a specific gravity in the range of 2.30 to 2.80. Due to variations in the grinding method used (such as the quantity of material in a ball mill and the duration of grinding), the stated physical attributes of the WCTPs vary between studies. The results from scanning electron microscopy reveal that the WCTPs are made up of uneven, angular particles that resemble cement. Figure 3a illustrates the surface morphology of WCTPs [41]. As presented in Figure 3b, the grain size gradation of WCTPs eventually becomes comparable to that of cement [39]. The physical properties of WCTPs, including the medium particle size, specific surface area, and specific gravity, were found to be 3.3–35 μm [2,41,42,43], 12.2–12.8 m²/g [41,43], and 2.35–2.65 [31,41,43,44,45].

Based on the material composition, waste tile ceramics are generally categorized into two types: white and red. White tile ceramics are manufactured using purified clays or kaolin, which contain low levels of iron oxide (typically less than 1%). In contrast, red tile ceramics are usually produced from natural clays with a high iron oxide content (normally greater than 5%). The chemical composition of tile ceramics is primarily influenced by the type and source of raw materials used for their production. In

Table 1. The WCTPs’ chemical composition utilizing X-ray fluorescence (XRF) analysis.

Refs	SiO2	Al2O3	Fe2O3	CaO	MgO	Na2O	LOI	Other	SiO2 + Al2O3	SiO2 + Al2O3 + Fe2O3
[51]	61.72	22.31	1.24	6.67	0.65	0.96	3.96	2.49	84.03	85.27
[52]	59.90	18.80	7.64	6.47	0.72	1.41	1.16	3.90	78.7	86.34
[41]	72.60	12.20	0.80	0.02	0.99	0.73	1.05	11.61	88.8	89.60
[30]	78.30	15.90	0.10	0.90	-	1.45	1.78	1.57	94.20	94.30
[50]	68.85	18.53	4.81	1.57	0.72	2.01	0.48	3.03	87.38	92.19
[53]	74.10	17.80	3.57	1.11	-	0.01	0.49	2.92	91.90	95.47
[14]	67.83	19.68	0.86	7.42	0.34	0.22	0.18	3.47	87.51	88.37
[54]	68.60	17.10	0.80	1.70	2.5	0.03	1.78	7.49	85.70	86.50
[55]	67.30	19.80	2.50	2.30	-	0.01	0.03	8.06	87.10	89.60
[56]	67.51	16.92	0.75	1.33	-	4.8	2.54	6.15	84.43	85.18
[57]	60.50	28.09	1.02	4.20	0.89	-	1.20	4.10	88.59	94.79
[58]	57.40	17.98	6.20	5.72	3.16	2.37	-	7.17	75.38	81.58
[59]	66.57	21.60	1.41	2.41	2.0	2.9	-	3.11	88.17	89.58
[60]	64.32	19.23	0.94	1.71	10.32	-	-	3.48	83.55	84.49
[61]	66.39	18.14	3.79	3.60	-	-	-	8.08	84.53	88.32
[62]	61.20	18.60	5.0	5.80	1.80	-	2.40	5.20	79.80	84.50
[63]	66.0	19.0	6.0	1.80	0.90	2.1	1.75	2.45	85.0	91.0

, the chemical composition of WCTPs is presented through a compilation of data from different studies. It is evident that the content of alumina and silica is high in WCTPs, while small amounts of magnesium and sodium oxides was also detected in the evaluated WCTPs. In most studies summarized in Table 1, white ceramics were found to have a higher Al₂O₃-SiO₂ content compared to red ceramics. However, numerous studies have indicated that the calcium oxide (CaO) content in the chemical composition of tile ceramics—particularly white ceramics—is generally very low, typically ranging from 0.02% to 6.67%. Additionally, the reported oxide composition of waste ceramic tile powders (WCTPs) varies across different studies, primarily due to differences in the raw materials used during the manufacturing process, such as their mineralogical and chemical characteristics [46]. WCTPs’ ignition loss is less than 4%. To some extent, the difference in loss on ignition is related to the concentrations of SiO₂ and Al₂O₃. A high clay mineral content results in a greater loss on ignition, accompanied by higher concentrations of SiO₂ and Al₂O₃ [47]. Previous studies [48,49,50] have found that WCTPs contain more than 70% silica, alumina, and iron oxide, meeting the ASTM 618 criteria [51] and making them suitable for use as pozzolanic materials. Silica and alumina are readily available, which promotes the pozzolanic reaction and strengthens concrete. The superior pozzolanic properties of WCTPs stem from their oxide nature. The pozzolanic characteristics of WCTPs have prompted numerous investigators to investigate their potential as sustainable cementitious materials (SCMs) for use in concrete production in order to promote sustainability.

3.2. Leaching of Waste Tile Ceramics

Recycling waste materials, such as ceramic tiles, in the production of cement-based products offers both environmental and engineering advantages. However, it is essential to evaluate the leaching behavior of potentially harmful elements within these new materials, as they may pose risks to human health and the environment. The leaching resistance of cement-based materials at the end of their service life has become a significant focus in the recent research. It is generally agreed that the leachability of substances depends on their solubility, which is influenced by several factors, including pH, the formation of inorganic complexes, the presence of dissolved organic matter, and redox conditions. In a study conducted by Medina et al. [64], the leaching performance of concrete incorporating recycled ceramic aggregate was assessed in conditions involving direct contact with water intended for human consumption. The results indicated a slight increase in alkali concentrations (Na and K) and a decrease in the levels of other elements (B, Si, Cl, and Mg) in the water. Importantly, all detected concentrations remained below the regulatory limits established for drinking-water quality.

3.3. Effect of Waste Tile Ceramics on Concrete Fresh Properties

The fresh properties of modified paste, mortar, and concrete—such as flowability and initial and final setting times—are significantly affected by the dosage of WCTPs used as a partial replacement for OPC. These effects are also influenced by the chemical composition, physical characteristics, and mineralogical properties of the WCTPs, leading to variations in outcomes, even at similar replacement levels. Nevertheless, a consistent trend has been observed: incorporating WCTPs up to 30% generally improves workability by reducing the viscosity of the OPC binder. In contrast, higher replacement levels result in a notable decrease in workability, primarily due to the increased water absorption capacity of the ceramic-based binders. Additionally, the initial and final setting times of binders modified with WCTPs tend to increase with a higher ceramic content. This behavior is attributed to the reduction in CaO content, which slows early hydration and leads to longer setting times compared to control samples containing only OPC. Discrepancies in the findings among researchers can also be attributed to differences in mix design parameters, such as the type of cement used, the presence of supplementary materials, water-to-cement ratios, and variations in fine or coarse aggregates or fiber content and types. As shown in Table 2, the application of WCTPs affects the workability of the concrete mixture. Generally speaking, it increases the need for water, and this requirement becomes more prominent as the WCTP content increases. The non-uniform shape and important water absorption properties of CTP are responsible for this [48,65]. Furthermore, unevenly shaped WCTP particles have been shown to increase interlocking, which increases friction between the particles and increases the energy needed for the mixture to flow (a phenomenon known as yield stress) [66]. Moreover, the workability of cement-based mixtures decreases when finer-sized WCTPs are used instead of OPC, which has a larger surface area and requires more mixing water. Hilal et al. [65] also found that the workability of mortar was reduced when cement was replaced with WCTPs. Their research findings indicated that workability decreased when the level and fineness of WCTPs were increased above those of the control samples, and this was primarily a result of the WCTPs’ fineness [67]. The finer WCTP grains fill the voids and reduce the porosity of cement-based composites, ultimately densifying the matrix.

Consequently, the use of WCTPs causes the matrix to stiffen, reducing the flowability of the cement-based composite. Conversely, other research has demonstrated that the workability of cement-based composites is enhanced when WCTPs are used in place of cement. The workability of the concrete mixture is dependent on the differences in each researcher’s processing procedures, particularly the size and type of WCTPs employed. The amount of WCTPs ground at a time, the equipment utilized, and the length of the grinding process all play a role in determining the particle size of WCTPs, which ultimately affects the workability of the concrete. Generally, replacing a high volume of cement with ceramic powder increases water demand, which can lead to reduced workability. To address this issue, numerous researchers [6,68] strongly recommend incorporating superplasticizers into the cement matrix to enhance workability. Superplasticizers improve the flowability and consistency of concrete, facilitating easier placement and consolidation.

The time it takes for a cement paste to set is influenced by several factors, including the water–binder ratio, fineness, mineral composition, and chemical composition [69,70]. In Table 2, it is evident that most researchers agree that applying WCTPs prolongs the setting time. It was revealed by Pitarch. et al. [62] that the cement paste’s initial setting time was delayed by up to 20 min when WCTPs replaced the cement, and this was primarily due to the relatively lower cement content in the WCTP samples than 100% OPC samples, which reduces the activation phase and prolongs the setting process. Nonetheless, adding finer-sized WCTPs produces different outcomes due to the impact that fineness has on chemical reactivity. Other researchers, such as El-Kattan et al. [69], have found that setting times were reduced for mixtures containing ultrafine WCTPs in place of cement. The large surface area causes open pores to become filled, while the high pozzolanic activity of silicate-rich WCTPs reduces the setting time. Furthermore, a larger grain surface area facilitates nucleation and the development of hydration products, thereby increasing the system’s reaction rate. Thus, it is reasonable to conclude that the setting time of concrete paste is impacted by the application of WCTPs with different levels of fineness.

Table 2. Effects of WCTPs on the flowability and setting times of proposed concretes.

Refs	Median Particle Size, µm	Replacement Level, %	Flowability, mm	Setting Times, min	Results
[48]	17.3	10, 20, 30	55–70	Increased	It has been found that the workability of the proposed concrete is significantly influenced by the ceramic content and the setting time trend, which increases with the increasing content of WTCPs in the matrix up to 30%.
[62]	14	15, 25, 35, 50		Initial: 147, 154, 160, 163 Final: 228, 225, 222, 217	It was found that both the initial and final settings were slightly influenced by the content of WCTPs as OPC replacement. For the initial setting time, replacing the OPC with 15–50% of WCTPs results in an increase in the setting time from 147 min to 163 min. Unlike the final setting time, the trend was to decrease with increasing the content of WCTPs. Increasing the replacement level to 50% resulted in a decrease in time from 239 min to 217 min.
[71]	˂53	15, 25, 35,50	-	Increased	The results show that the inclusion of WTCPs as OPC replacement leads to an increase in the initial setting of proposed mixtures.
[69]	≤70	1, 3, 5	-	Initial: 190, 199, 210 Final: 260, 268, 280	In general, and compared to control mixtures, the inclusion of WCTPs in the matrix led to an increase in both initial and final setting times, from 190 and 260 min to 210 and 280 min, respectively.
[63]	10	10, 20, 30	-	Initial: 111, 117, 117 Final: 160, 174, 175	The inclusion of WCTPs as OPC replacement slightly increases both the initial and final setting times. Compared to 87 min, replacing the OPC by 10, 20, and 30% of WCTPs leads to an extension of the initial setting time to 111, 117, and 117 min, respectively. A similar trend of results is observed for the final setting time, and the inclusion of the WCTPs leads to an increase in time from 155 min to 160, 174, and 175 min.
[57]		5, 10, 15, 20	85, 90, 92, 105	-	It has been found that replacing OPC with WCTPs enhances the workability performance, and the slump value trend increases from 80 mm to 105 mm with an increase in the level of replacement from 0% to 20%. For the replacement level in the range of 5–15, the degree enhancement is classified as medium; however, the 20% replacement level is classified as high enhancement.
[72]		5, 10, 15, 20, 25	109, 105, 96, 90, 81	-	the authors evaluated the effect of WCTPs as an OPC replacement in 1% sisal fiber-reinforced concrete. In comparison to the control mix (100% OPC), the increasing level of replacement to 5, 10, 15, 20, and 25% resulted in a drop in slump values from 120 mm to 109, 105, 96, 90, and 81 mm, respectively. The loss of workability is attributed to the lower specific gravity of WCTPs compared to OPC.
[58]	≤75 µm	20, 40, 60	240, 220, 200		The results indicate that the prepared mortar workability is significantly influenced by WCTP content as cement replacement. Increasing the replacement level to 60% results in a decrease from 260 mm to 200 mm or below, depending on the particle size used in WCTPs. Specimens prepared with fine WCTPs (≤No. 45) showed a worse workability performance. The decrease in workability is primarily attributed to the characteristics and fineness of the ceramic materials used in the concrete. Typically, finer WTCP particles enhance matrix densification by filling voids and reducing the overall porosity. As a result, the incorporation of WTCPs leads to a stiffer matrix, thereby diminishing workability. The high absorption capacity of WTCPs further influences this reduction. Moreover, the use of very fine ceramic particles increases the surface area, which in turn raises the absorption rate and contributes to decreased workability.
	≤45 µm	20, 40, 60	220, 200, 180
[73]		5, 10, 15, 20, 25, 30	120, 90, 80, 80, 70, 70		The concrete workability trend decreases with increasing the replacement level from 5% to 30%, which is attributed to the high porosity of ceramics compared to OPC, increasing the water demand in the mixture and reducing the flowability performance.
[74]	98% ≤ 90 µm	5, 10, 15, 20	42, 45, 48, 50		The results indicate that the inclusion of 5, 10, 15, and 20% of WTCPs as OPC replacement leads to improved workability and achieved slump values of 42, 45, 48, and 50 mm compared to a 30 mm slump of the control mixture, respectively.
[59]	89.1% ≤ 45 µm	5, 15, 20, 25, 30	0.40: 94, 92, 89, 85, 82 0.50: 107, 108, 103, 99, 95 0.60: 118, 117, 112, 109, 106		For all the prepared concrete mixtures, the workability trend increases with the water-to-cement ratio from 0.40 to 0.50 and 0.60. However, the inclusion of WCTPs in the concrete matrix as an OPC replacement negatively affects the workability performance and leads to a decrease in slump values. For the water-to-cement ratio of 0.40, the increasing WCTPs from 0% to 30% resulted in a reduction in slump from 95 mm to 82 mm, respectively. A similar trend of results was observed for both 0.50 and 0.60 water-to-cement ratios, and the slump readings dropped from 110 and 120 mm to 95 and 106 mm, respectively, with an increasing replacement level from 0% to 30%.
[75]		10, 20, 30	50, 40, 30	-	The slump values trend to decrease from 60 mm to 50, 40, and 30 mm with increasing the replacement level of OPC by 10, 20, and 30% of WTCPs, respectively.
[76]		10, 20, 30	90, 99, 100	-	The results show a slight improvement in mortar workability with increasing levels of replacement to 10, 20, and 30% of WTCPs.
[60]	14.32	10, 20, 30, 40, 50	180, 105, 30, 22, 17	-	The substituted OPC by 10, 20, 30, 40, and 50% of WTCPs resulted in a drop in slump values from 195 mm to 180, 105, 30, 22, and 17 mm, respectively. The decrease in workability is primarily due to the higher specific surface area of the ceramic material compared to cement. As a result, additional water is needed to coat the particles when this waste is incorporated into the mixture.
[61]	-	5, 10, 15, 20, 25, 30	58, 54, 50, 47, 43, 41	Initial: 30/70 Final: 540/475	The workability of concrete mixtures tends to decrease with increasing WCTP content as an OPC replacement. Compared to 60 mm, the slump values decreased to 58, 54, 50, 47, 43, and 41 mm with the inclusion of 5, 10, 15, 20, 25, and 30% of WTCPs in the matrix, respectively.

Table 2. Effects of WCTPs on the flowability and setting times of proposed concretes.

Refs	Median Particle Size, µm	Replacement Level, %	Flowability, mm	Setting Times, min	Results
[48]	17.3	10, 20, 30	55–70	Increased	It has been found that the workability of the proposed concrete is significantly influenced by the ceramic content and the setting time trend, which increases with the increasing content of WTCPs in the matrix up to 30%.
[62]	14	15, 25, 35, 50		Initial: 147, 154, 160, 163 Final: 228, 225, 222, 217	It was found that both the initial and final settings were slightly influenced by the content of WCTPs as OPC replacement. For the initial setting time, replacing the OPC with 15–50% of WCTPs results in an increase in the setting time from 147 min to 163 min. Unlike the final setting time, the trend was to decrease with increasing the content of WCTPs. Increasing the replacement level to 50% resulted in a decrease in time from 239 min to 217 min.
[71]	˂53	15, 25, 35,50	-	Increased	The results show that the inclusion of WTCPs as OPC replacement leads to an increase in the initial setting of proposed mixtures.
[69]	≤70	1, 3, 5	-	Initial: 190, 199, 210 Final: 260, 268, 280	In general, and compared to control mixtures, the inclusion of WCTPs in the matrix led to an increase in both initial and final setting times, from 190 and 260 min to 210 and 280 min, respectively.
[63]	10	10, 20, 30	-	Initial: 111, 117, 117 Final: 160, 174, 175	The inclusion of WCTPs as OPC replacement slightly increases both the initial and final setting times. Compared to 87 min, replacing the OPC by 10, 20, and 30% of WCTPs leads to an extension of the initial setting time to 111, 117, and 117 min, respectively. A similar trend of results is observed for the final setting time, and the inclusion of the WCTPs leads to an increase in time from 155 min to 160, 174, and 175 min.
[57]		5, 10, 15, 20	85, 90, 92, 105	-	It has been found that replacing OPC with WCTPs enhances the workability performance, and the slump value trend increases from 80 mm to 105 mm with an increase in the level of replacement from 0% to 20%. For the replacement level in the range of 5–15, the degree enhancement is classified as medium; however, the 20% replacement level is classified as high enhancement.
[72]		5, 10, 15, 20, 25	109, 105, 96, 90, 81	-	the authors evaluated the effect of WCTPs as an OPC replacement in 1% sisal fiber-reinforced concrete. In comparison to the control mix (100% OPC), the increasing level of replacement to 5, 10, 15, 20, and 25% resulted in a drop in slump values from 120 mm to 109, 105, 96, 90, and 81 mm, respectively. The loss of workability is attributed to the lower specific gravity of WCTPs compared to OPC.
[58]	≤75 µm	20, 40, 60	240, 220, 200		The results indicate that the prepared mortar workability is significantly influenced by WCTP content as cement replacement. Increasing the replacement level to 60% results in a decrease from 260 mm to 200 mm or below, depending on the particle size used in WCTPs. Specimens prepared with fine WCTPs (≤No. 45) showed a worse workability performance. The decrease in workability is primarily attributed to the characteristics and fineness of the ceramic materials used in the concrete. Typically, finer WTCP particles enhance matrix densification by filling voids and reducing the overall porosity. As a result, the incorporation of WTCPs leads to a stiffer matrix, thereby diminishing workability. The high absorption capacity of WTCPs further influences this reduction. Moreover, the use of very fine ceramic particles increases the surface area, which in turn raises the absorption rate and contributes to decreased workability.
	≤45 µm	20, 40, 60	220, 200, 180
[73]		5, 10, 15, 20, 25, 30	120, 90, 80, 80, 70, 70		The concrete workability trend decreases with increasing the replacement level from 5% to 30%, which is attributed to the high porosity of ceramics compared to OPC, increasing the water demand in the mixture and reducing the flowability performance.
[74]	98% ≤ 90 µm	5, 10, 15, 20	42, 45, 48, 50		The results indicate that the inclusion of 5, 10, 15, and 20% of WTCPs as OPC replacement leads to improved workability and achieved slump values of 42, 45, 48, and 50 mm compared to a 30 mm slump of the control mixture, respectively.
[59]	89.1% ≤ 45 µm	5, 15, 20, 25, 30	0.40: 94, 92, 89, 85, 82 0.50: 107, 108, 103, 99, 95 0.60: 118, 117, 112, 109, 106		For all the prepared concrete mixtures, the workability trend increases with the water-to-cement ratio from 0.40 to 0.50 and 0.60. However, the inclusion of WCTPs in the concrete matrix as an OPC replacement negatively affects the workability performance and leads to a decrease in slump values. For the water-to-cement ratio of 0.40, the increasing WCTPs from 0% to 30% resulted in a reduction in slump from 95 mm to 82 mm, respectively. A similar trend of results was observed for both 0.50 and 0.60 water-to-cement ratios, and the slump readings dropped from 110 and 120 mm to 95 and 106 mm, respectively, with an increasing replacement level from 0% to 30%.
[75]		10, 20, 30	50, 40, 30	-	The slump values trend to decrease from 60 mm to 50, 40, and 30 mm with increasing the replacement level of OPC by 10, 20, and 30% of WTCPs, respectively.
[76]		10, 20, 30	90, 99, 100	-	The results show a slight improvement in mortar workability with increasing levels of replacement to 10, 20, and 30% of WTCPs.
[60]	14.32	10, 20, 30, 40, 50	180, 105, 30, 22, 17	-	The substituted OPC by 10, 20, 30, 40, and 50% of WTCPs resulted in a drop in slump values from 195 mm to 180, 105, 30, 22, and 17 mm, respectively. The decrease in workability is primarily due to the higher specific surface area of the ceramic material compared to cement. As a result, additional water is needed to coat the particles when this waste is incorporated into the mixture.
[61]	-	5, 10, 15, 20, 25, 30	58, 54, 50, 47, 43, 41	Initial: 30/70 Final: 540/475	The workability of concrete mixtures tends to decrease with increasing WCTP content as an OPC replacement. Compared to 60 mm, the slump values decreased to 58, 54, 50, 47, 43, and 41 mm with the inclusion of 5, 10, 15, 20, 25, and 30% of WTCPs in the matrix, respectively.

3.4. Concrete Dry Density

The CS of concrete is significantly impacted by the dry density, thus rendering it one of the most important properties. Applying WCTPs to concrete facilitated a decrease in the hardened density of the concrete, as WCTPs have an inferior particle density compared to cement. In line with this, a study conducted by Hilal et al. [65] revealed that applying WCTPs with a lower specific gravity value than cement results in the production of concrete that has a lower dry density. Other researchers have also identified similar patterns.

3.5. Compressive Strength Development

As presented in Table 3, numerous studies have investigated the impact of varying replacement levels of ordinary Portland cement (OPC) with waste ceramic tiles on the mechanical properties of modified concrete, including compressive, flexural, and tensile strengths. It is well established that strength development is influenced not only by the replacement level but also by the chemical composition, physical characteristics, and mineralogical properties of the ceramic material, as well as other components in the mix, such as OPC, aggregates, and chemical admixtures. The water demand of the concrete mix is significantly influenced by the specific surface area and chemical composition of the ceramic, necessitating adjustments to the water-to-cement ratio for each mix based on the type and characteristics of the waste ceramic used. Minor variations in the reported strength results can be attributed to these factors. Generally, incorporating 5% to 15% of waste ceramic tends to improve the compressive strength by increasing the availability of dissolved silica, which contributes to the formation of denser gel structures. However, increasing the ceramic content beyond this range may result in a slight reduction in strength, with the degree of strength loss becoming more pronounced as the replacement level increases. This decline is primarily due to the presence of a high amount of unreacted silica, which weakens the bond strength and leads to an unsatisfactory early strength performance. The researchers have discovered that when the level of substitution increases, the 28-day compressive strength of the cement-based composite decreases due to the presence of WCTPs. Nonetheless, a slight decline in compressive strength was evident when cement was substituted with up to 10% WCTP [30,55]. The analysis revealed that, over 28 days, the compressive strength of the test samples dropped by up to 15% compared to the control samples. In general, the relative fineness of WCTPs in contrast to cement may have caused an apparent decrease in the compressive strength [51]. Lower fineness levels relative to cement usually result in reduced pozzolanic and filling properties. Interestingly, as the substitution ratio increased above 20%, a significant decrease in the 28-day compressive strength was observed. The predominant diluting effect is primarily responsible for this reduction in compressive strength [77]. Nonetheless, at later phases of the curing process, particularly at 90 and 365 days, the mix’s compressive strength decreased somewhat despite the addition of up to 30% WCTP. After 365 days of curing, Pitarch et al. [62] identified a 35% WCTP reduction in mortar strength relative to the reference mortar. The observed behavior can be explained by the progressive reaction that the WCTP surface experiences with calcium hydroxide (CH) at later phases [78]. This reaction results in the formation of a substantial amount of calcium silicate hydrate (C-S-H) on the surface, as illustrated in Figure 4. The cement and filler particles form a solid bond as a result of this process, which helps the subsequent stages of compressive strength growth.

The effects of white and red WCTPs as a cement substitute on mortar were investigated by Lasseuguette et al. [79]. The outcome demonstrated that, except for the 15% mortar, which was comparable to the control for up to 56 days and longer than 90 days, all blended mortars had somewhat lower compressive strengths than the OPC mortar (23.2 MPa versus 21.8 MPa). For up to 56 days, blended cement has been found to have higher concentrations of C-S-H. Meanwhile, the blended samples contained up to 12.5% C-S-H, compared to only 4% C-S-H in the normal OPC. Additionally, reactivity levels were found to be higher in white ceramics than in red ceramics. In the samples containing 15% white ceramics, 5% more C-S-H was absorbed than in the 15% red ceramic sample. This may be because the silica concentration is higher in white ceramics than in red ceramics, indicating potentially higher reactivity. Additionally, it was asserted by Pitarch. et al. [62] that there were no significant changes in the compressive strengths of mortars when up to 25% WCTPs partially replaced OPC.

In a study conducted by El-Kattan et al. [69], the researchers investigated the impact of incorporating ceramic powder at varying replacement levels (1%, 3%, and 5%) as a substitute for white cement across different curing ages. As illustrated in Figure 5, the inclusion of 1% ceramic powder in the white cement matrix notably improved the development of compressive strength at both the early and later stages. This improvement was attributed to the enhanced hydration process and the additional formation of C-S-H gel. The ultrafine waste ceramic powder is considered an amorphous silicate source, where the surplus hydration products contribute to pore refinement through a filling effect. Moreover, the smooth surface texture of ceramic powder enhances the cohesiveness and workability of the mix during the hydration process. However, as the replacement level of ceramic powder increases, the compressive strength tends to decline due to the dilution of the cementitious content and high demand for water, which results in a reduced hydration process and a higher porosity within the cement matrix.

Moreover, Heidari et al. [50] fabricated concrete by employing WCTPs to replace up to 15% cement and found that there was a significant reduction in CS at an early stage. This was due to the WCTPs serving as a filler without having a pozzolanic impact at an early stage. Nonetheless, compressive strength data reveal that, after 28 days, the mixture containing WCTPs had strength comparable to that of the control samples. Similar trends in the performance of water-cured mortar were also noted by Mohammadhosseini et al. [80] after partial cement replacement with WCTPs was included. Furthermore, recent studies have revealed that heat therapies could counteract the negative effects of WCTPs on strength. For example, a study by Taher et al. [51] revealed that, when subjected to heat treatment, the compressive strength of WCTPs increased. The findings demonstrate that adding thermally treated WCTPs up to 50% produced concrete with equal strength to the control sample.

However, other research has revealed that the inclusion of WCTPs, even at a low substitution level, has a beneficial effect, as it boosts reactivity and the material’s capacity to function as a micro-filler. According to earlier research, the optimal cement-to-WCTPs ratio is between 10% and 20%, which produces a notable improvement in compressive strength after 28 days, which can range from 5 to 22%. In a separate study, the replacement of cement with nano-WCTPs resulted in a notable 40% improvement in compressive strength after 28 days compared to the control group. According to Xu et al. [30], 25% WCTPs is the ideal amount since it results in specimens with the best strength value. The application of WCTPs as a cement replacement below 45% enhances the compressive strength of UHPC. This may be the result of WCTPs’ pozzolanic activity and their reaction with CH, which promotes cement hydration and the formation of the C-S-H gel [2]. Densifying UHPC involves packing the pores with C-S-H gel, whereas producing more C-S-H gel enhances compressive strength and lowers porosity (Figure 6). Nevertheless, UHPC strength can be reduced by employing up to 55% WCTPs. A pozzolanic reaction can occur when there is an excessive drop in the cement content because it hinders the hydration process and produces less C-S-H gel and calcium hydroxide [81]. According to Mansoori et al. [44], the use of WCTPs in place of cement affects the compressive strength of self-compacting concrete. The findings indicate that applying 10% and 20% WCTPs results in a 7% and 19% reduction in compressive strength, respectively. As the 28-day compressive strength of the specimens was over 20 MPa, they can be considered suitable for use in structural concrete. The effects that WCTPs have on the CS of different cement-based composites can be seen in Table 3.

3.6. Flexural Strength Development

Prior research has shown that when the replacement level increases, the addition of WCTPs causes the flexural strength of the cement-based composite to diminish during the 28-day curing stage. Previous studies [82,83] have shown that adding up to 10% WCTPs causes a slight decrease in flexural strength after 28 days, with the largest recorded declines occurring between 5.8% and 17%. Nonetheless, after a lengthy healing period of 56 days or more, the adverse effects of WCTPs on strength gradually diminished. The formation of more calcium silicate hydrate (C-S-H) gels may result from a subsequent hydration reaction that takes place between WCTPs and calcium hydroxide (Ca (OH)₂). These gels produce a denser matrix structure by efficiently filling the pores and interfacial transition zone (ITZ). Many studies have found that adding 5–35% of WCTPs in place of cement significantly increases the flexural strength of cement-based composites after 28 days [72]. The pozzolanic reactivity of WCTPs is responsible for the strength enhancement that was observed. This enhanced the densification of the microstructure, rendering the sample more pliable.

Furthermore, WCTPs are considered to be a filler material that can partially fill in the gaps and/or apertures between cement, improving the granules’ physical density. Nonetheless, previous studies have shown that, when the substitution ratio surpasses 35%, there is a reduction in compressive strength. This is primarily due to the well-known dilution effect. Xu et al. [30] revealed that ultrahigh-performance concrete (UHPC) is produced when up to 35% of WCTPs is used as a replacement, and this improves the flexural strength relative to the control samples after 7 and 28 days of curing. This study also highlighted that the same mix had less strength than the control sample after three days of curing. A similar pattern was highlighted by Li et al. [82], who revealed that the strength of concrete fabricated with 10% WCTPs was lower than the control samples after 7 days of curing. It was also found to have enhanced the flexural strength following 28 days of curing.

WCTP-based concrete has low early strength due to the incompleteness of the pozzolanic reaction that is required to produce the C-S-H gel (which enhances the strength increment). Moreover, the flexural strength of concrete can be increased by mixing a suitable content of WCTPs at 6%, 10%, and 35% as a partial substitute for cement. Moreover, it was revealed by Tawfik. et al. [54] during a study of the effects that nano-WCTPs has on the flexural strength of concrete when applied as a cement substitute that using nano-sized particles in smaller percentages could effectively enhance the strength of concrete. The use of a finer material promotes a quicker chemical reaction, resulting in the formation of high amounts of C-S-H gel over a shorter time period than when larger-sized pozzolanic ash is employed [84]. The difference in the results is likely due to the diverse oxide composition and uniqueness of the approach used to process pozzolanic ash, which affects the material’s particle size. Although applying large quantities of WCTPs would create a more sustainable construction material, the strength of the concrete would be compromised. In Table 3, the effects that WCTPs have on the flexural strength of different cement-based composites are presented.

3.7. Tensile Strength Development

Furthermore, not only does the splitting tensile strength of concrete provide important information about the incremental cracking patterns that occur during periods of tensile stress, but it also allows us to indirectly evaluate the load under which cracking occurs [85]. Recent studies have revealed that WCTPs can reduce the splitting tensile strength of cement-based composites over the course of 28 days [51,85]. There is also a directly proportional relationship between the magnitude of this loss and the extent of substitution. Nonetheless, only a small (13%) reduction in splitting tensile strength was achieved when the cement was substituted with 10% WCTPs. As was also the case with compressive strength, the observed reduction in tensile strength is attributed to the comparable or relatively lower fineness of WCTPs compared to cement. Interestingly, there was also a substantial decrease in tensile splitting strength after 28 days when a substitution ratio in excess of 30% was used [55]. The primary reason for this reduction in tensile strength is the predominant dilution effect. However, the addition of 30% WCTPs caused a relatively lower reduction in the splitting tensile strength toward the end of the curing process, especially after 56 and 90 days of curing. Furthermore, Mohammadhosseini et al. [80] found that adding WCTPs to the mortar can enhance the splitting tensile strength when allowed to cure for longer periods of time. When compared to plain concrete, the blended cement–WCTP mortar was found to have a somewhat reduced early strength (approximately 4%). However, after 90 days of curing, there was a 15% increase in strength. The quantity of binding gel produced is also lower when WCTPs are used, which, in turn, reduces the cement content and facilitates the hydration process. The WCTPs’ pozzolanic reaction changes the microstructure of the mortar, rendering it stronger and denser than the control sample. Conversely, prior research has revealed that replacing cement with WCTPs increases the splitting tensile strength by approximately 5–25%, with such increases varying between 4% and 18% [86]. There are two primary reasons for the apparent increase in the splitting tensile strength: the pozzolanic process that occurs within the cement matrix and the filling effect generated by the minute particles in the concrete matrix. A study by Tawfik. et al. [54] found that using higher-fineness, nano-sized WCTPs increases the splitting tensile strength of concrete. When 6% nano-WCTPs were used in place of cement, the most significant increase in the splitting tensile strength was observed. It is thus essential to evaluate the enhancements that can be made to the methods of producing WCTPs with high pozzolanic reactivity, as this can facilitate the utilization of high-volume waste to produce concrete with improved strength. In Table 3, the effects of WCTPs on the splitting tensile strength of various cement-based composites are presented.

Table 3. Effect of WCTP content as OPC replacement on the strength properties of concrete specimens, such as compressive, flexural, and tensile strengths.

Refs	Replacement Level	CS, MPa	FS, MPa	STS, MPa	Findings
[57]	5, 10, 15, 20	33.26, 32.55, 31.99, 30.13	-	3.26–2.97	Findings: Compared to 28.92 MPa, the inclusion of 5–20% of WCTPs as OPC replacement leads to an improvement in the CS to 33.26, 32.55, 31.99, and 30.13 MPa for the specimens evaluated at 28 days of age with increment percentages of 15, 12.6, 10.6, and 4.2%, respectively. A similar trend of results was observed for the STS test, and the cylinder specimens prepared with WCTPs achieved an enhancement from 3.8% to 13.5%. It is a summary of the percentage of 5% WCTPs, the optimum replacement level, and the other four levels.
[72]	5, 10, 15, 20, 25	40.3, 41.7, 37.1, 34.1	5.31–6.73	4.31–3.14	Specimens prepared with a CS of 40 MPa, in which 10% of OPC was replaced by WCTPs, demonstrated a 3.5% increase in strength. However, increasing the replacement level to 25% led to a 14.8% reduction in strength. A similar trend of results was reported for FS and STS, and the optimum value was achieved with 10% of WCTP content. The differing effects of WCTPs on the CS of concrete at various replacement levels may be attributed to several factors. A key factor is the variation in the chemical composition and specific gravity between OPC and WCTPs. Typically, WCTPs contain a higher silica content and have a lower density compared to OPC. As a result, replacing OPC with WCTPs can lead to a less dense concrete mix, potentially reducing its CS. Additionally, the particle size distribution of WCTPs may influence the overall strength. The presence of larger particles can create voids or weak zones within the concrete matrix, thereby weakening its structure. Furthermore, the pozzolanic activity of WCTPs may be less effective than that of OPC, which could result in slower early-strength development. Other factors, such as the water–cement ratio, curing conditions, and the quality of raw materials, also play important roles in determining concrete strength. Therefore, optimizing these parameters is essential to achieve the desired performance when incorporating ceramic waste powder as partial cement replacement.
[58]	≤No. 75: 20, 40, 60 ≤No. 45: 20, 40, 60	24.9, 22.2, 18.7 26.6, 23.4, 20.4	- -	- -	Compared to the CS of the control specimens (23.1 MPa), replacing 20% of ordinary OPC with waste WCTPs led to a slight improvement in strength. However, increasing the replacement level to 60% resulted in a significant reduction in CS values. The results also indicate that specimens prepared with finer WCTPs (≤No. 45) exhibit a better performance than those containing coarser particles. The decrease in strength at replacement levels of 40% and above is attributed to the high ceramic content in the mix, which increases the silica concentration. This may interact with the calcium hydroxide produced during cement hydration, potentially diminishing CS. Notably, the higher strength observed in group-B specimens is likely due to the finer particle size of the WCTPs, which may contribute to a more homogeneous matrix structure.
[73]	5, 10, 15, 20, 25, 30	62.5, 59, 54.5, 50.8, 47.4, 43.9			Compared to the control specimens’ CS (62.4 MPa), replacing OPC with 5% achieved almost similar strength values (62.5 MPa). However, increasing the level of replacement to 10%, 15%, 20%, 25%, and 30% leads to an increase in the loss of strength to 5.5%, 12.7%, 18.6%, 24.1%, and 29.6%, respectively.
[74]	5, 10, 15, 20	41.4, 45, 47.3, 44.2	5.91–6.25	3.12–3.39	In comparison, the CS of the control specimen (37.1 MPa) achieved after 28 days of curing age, replacing the OPC with 5, 10, 15, and 20%, leads to an enhancement of the strength and increases its values to 41.4, 45, 47.3, and 44.2 MPa, respectively.
[59]	5, 15, 20, 25, 30	38.2, 39.3, 40.1, 35.7, 30.1	5.02–5.94	4.92–5.29	The results show that the inclusion of WCTPs as OPC positively affects the strength performance at levels of 5, 15, and 20%, and the specimens achieved the highest enhancement of 6.1% with 20% of WCTPs. However, raising the replacement level to 25% and 30% resulted in a drop in strength, causing a loss of 5.6% and 20.3%, respectively. A similar trend of results was observed for FS and STS, with specimens containing 20% WTCPs as OPC replacement achieving the highest strength performance among the other ratios. A negative effect was observed with increasing the water-to-cement ratio, and the strength trend decreased with increasing the water content. Specimens prepared with a 0.50 water-to-cement ratio showed a loss in strength between 1.7% to 7.8% at 28 days. A significant loss of strength was observed for specimens prepared with a 0.60 water-to-cement ratio, ranging from a 15.9% to 17.8% loss. For a high water content (0.50 and 0.60), specimens prepared with a high content of WCTPs (30%) showed a reduced loss of strength of 1.7% and 15.9%, respectively.
[75]	10, 20, 30	21, 19, 20	-	-	Compared to concrete prepared with OPC only as a control specimen, replacing OPC with 10%, 20%, and 30% of WTCPs leads to a decrease in CS from 22 MPa to 21, 19, and 20 MPa, respectively.
[60]	10, 20, 30, 40, 50	38.4, 40.2, 39.6, 37.7, 30.1			Compared to 38.1 MPa, the inclusion of 10, 20, and 30% of WCTPs as OPC replacement leads to an enhancement of strength by 7.4, 16.2, and 13.2%, respectively. However, the greatest loss of strength (15.2%) was observed with specimens prepared with 50% of WTCPs as OPC replacement.
[61]	5, 10, 15, 20, 25, 30	36.1, 35, 29.9, 28.7, 22.6, 23.5		2.37–3.25	In comparison to the CS of control specimens (33.2 MPa), the inclusion of 5 and 10% of WCTPs as OPC replacement slightly increased the CS to 36.1 and 35 MPa. However, continuing to increase the replacement level to 15, 20, 20, 25, and 30 resulted in a drop in strength to 29.9, 28.7, 22.6, and 23.5 MPa, respectively.
[48]	10, 20, 30	22.9, 23.1, 23.7, 25.4	-	1.67–3.64	Both CS and STS were found to be enhanced by replacing the OPC with 10, 20, and 30% of WCTPs. In comparison to the 22.9 MPa CS achieved with control specimens, the inclusion of 10, 20, and 30% of WCTPs slightly improved the strength to 23.1, 23.7, and 25.4 MPa, respectively.
[62]	15, 25, 35, 50	48, 42, 38, 29	-	-	At 28 days of age, it was observed that replacing OPC with 15%, 25%, 35%, and 50% of WCTPs resulted in a drop in CS from 50 MPa to 48, 42, 38, and 29 MPa, respectively.
[69]	1, 3, 5	Increased	-	-	Specimens prepared with 1% of WCTPs as OPC replacement achieved the best strength performance by 9.8%. However, the increased replacement level to 3 and 5% caused a loss of strength by 1.9 and 14.7%, respectively.
[77]	10, 20, 30, 40, 50	21.3, 23.5, 24.6, 17.9, 17.5	-	-	The results indicate that replacing OPC with 30% of WTCPs leads to an increase in strength from 20.8 MPa to 24.6 MPa. However, the strength trend drops with increasing the level of replacement to 40% and 50%.
[54]	2, 4, 6, 8, 10	28.8, 29.3, 29.7, 29.2, 28.7	3.4–3.6	2.3–2.5	In comparison to the strength of control specimens (27.6 MPa), the replacement of OPC by 2, 4, 6, 8, and 10% of WCTPs leads to an enhancement of strength to 28.8, 29.3, 29.7, 29.2, and 28.7 MPa, respectively. A similar trend of results was observed for FS and STS, and all the specimens prepared with WCTPs displayed a better performance than the control specimens.
[87]	15, 25, 35, 50	40, 45, 40, 34	-	-	The inclusion of 25% of WCTPs as OPC replacement leads to an increase in the CS from 38 MPa to 45 MPa. However, raising the replacement level to 50% results in a lower gel formulation and a drop in strength to 34 MPa.
[31]	5, 10, 15, 20, 25	50.4, 53.9, 47.2, 45.6, 42.8	6.14, 6.15, 5.98, 5.29, 5.15		Specimens prepared with 10% WCTPs as OPC replacement achieved the highest CS (53.9 MPa) and FS (6.15 MPa) among the adopted levels, compared to control specimens (48.5 MPa and 5.68 MPa).
[55]	10, 20, 30, 40, 50	20.9, 22.7, 24.5, 18.1, 17.9	-	-	In comparison to OPC specimens, the inclusion of 10, 20, and 30% of WCTPs as OPC replacement leads to an increase in CS from 20.4 MPa to 20.9, 22.7, and 24.5 MPa, respectively. However, increasing the replacement level to 40 and 50% leads to a drop in strength below 18.1 MPa.
[51]	Unburned 10, 20 Burned 10, 20	32.9, 26.8 36.4, 34.0	5.3, 4.8 6.2, 5.8	4.5, 3.6 4.9, 4.6	At 28 days, all the specimens prepared with unburned and burned ceramics displayed lower CS, FS, and STS compared to control specimens (38.6, 6.4, and 5.2 MPa).

Table 3. Effect of WCTP content as OPC replacement on the strength properties of concrete specimens, such as compressive, flexural, and tensile strengths.

Refs	Replacement Level	CS, MPa	FS, MPa	STS, MPa	Findings
[57]	5, 10, 15, 20	33.26, 32.55, 31.99, 30.13	-	3.26–2.97	Findings: Compared to 28.92 MPa, the inclusion of 5–20% of WCTPs as OPC replacement leads to an improvement in the CS to 33.26, 32.55, 31.99, and 30.13 MPa for the specimens evaluated at 28 days of age with increment percentages of 15, 12.6, 10.6, and 4.2%, respectively. A similar trend of results was observed for the STS test, and the cylinder specimens prepared with WCTPs achieved an enhancement from 3.8% to 13.5%. It is a summary of the percentage of 5% WCTPs, the optimum replacement level, and the other four levels.
[72]	5, 10, 15, 20, 25	40.3, 41.7, 37.1, 34.1	5.31–6.73	4.31–3.14	Specimens prepared with a CS of 40 MPa, in which 10% of OPC was replaced by WCTPs, demonstrated a 3.5% increase in strength. However, increasing the replacement level to 25% led to a 14.8% reduction in strength. A similar trend of results was reported for FS and STS, and the optimum value was achieved with 10% of WCTP content. The differing effects of WCTPs on the CS of concrete at various replacement levels may be attributed to several factors. A key factor is the variation in the chemical composition and specific gravity between OPC and WCTPs. Typically, WCTPs contain a higher silica content and have a lower density compared to OPC. As a result, replacing OPC with WCTPs can lead to a less dense concrete mix, potentially reducing its CS. Additionally, the particle size distribution of WCTPs may influence the overall strength. The presence of larger particles can create voids or weak zones within the concrete matrix, thereby weakening its structure. Furthermore, the pozzolanic activity of WCTPs may be less effective than that of OPC, which could result in slower early-strength development. Other factors, such as the water–cement ratio, curing conditions, and the quality of raw materials, also play important roles in determining concrete strength. Therefore, optimizing these parameters is essential to achieve the desired performance when incorporating ceramic waste powder as partial cement replacement.
[58]	≤No. 75: 20, 40, 60 ≤No. 45: 20, 40, 60	24.9, 22.2, 18.7 26.6, 23.4, 20.4	- -	- -	Compared to the CS of the control specimens (23.1 MPa), replacing 20% of ordinary OPC with waste WCTPs led to a slight improvement in strength. However, increasing the replacement level to 60% resulted in a significant reduction in CS values. The results also indicate that specimens prepared with finer WCTPs (≤No. 45) exhibit a better performance than those containing coarser particles. The decrease in strength at replacement levels of 40% and above is attributed to the high ceramic content in the mix, which increases the silica concentration. This may interact with the calcium hydroxide produced during cement hydration, potentially diminishing CS. Notably, the higher strength observed in group-B specimens is likely due to the finer particle size of the WCTPs, which may contribute to a more homogeneous matrix structure.
[73]	5, 10, 15, 20, 25, 30	62.5, 59, 54.5, 50.8, 47.4, 43.9			Compared to the control specimens’ CS (62.4 MPa), replacing OPC with 5% achieved almost similar strength values (62.5 MPa). However, increasing the level of replacement to 10%, 15%, 20%, 25%, and 30% leads to an increase in the loss of strength to 5.5%, 12.7%, 18.6%, 24.1%, and 29.6%, respectively.
[74]	5, 10, 15, 20	41.4, 45, 47.3, 44.2	5.91–6.25	3.12–3.39	In comparison, the CS of the control specimen (37.1 MPa) achieved after 28 days of curing age, replacing the OPC with 5, 10, 15, and 20%, leads to an enhancement of the strength and increases its values to 41.4, 45, 47.3, and 44.2 MPa, respectively.
[59]	5, 15, 20, 25, 30	38.2, 39.3, 40.1, 35.7, 30.1	5.02–5.94	4.92–5.29	The results show that the inclusion of WCTPs as OPC positively affects the strength performance at levels of 5, 15, and 20%, and the specimens achieved the highest enhancement of 6.1% with 20% of WCTPs. However, raising the replacement level to 25% and 30% resulted in a drop in strength, causing a loss of 5.6% and 20.3%, respectively. A similar trend of results was observed for FS and STS, with specimens containing 20% WTCPs as OPC replacement achieving the highest strength performance among the other ratios. A negative effect was observed with increasing the water-to-cement ratio, and the strength trend decreased with increasing the water content. Specimens prepared with a 0.50 water-to-cement ratio showed a loss in strength between 1.7% to 7.8% at 28 days. A significant loss of strength was observed for specimens prepared with a 0.60 water-to-cement ratio, ranging from a 15.9% to 17.8% loss. For a high water content (0.50 and 0.60), specimens prepared with a high content of WCTPs (30%) showed a reduced loss of strength of 1.7% and 15.9%, respectively.
[75]	10, 20, 30	21, 19, 20	-	-	Compared to concrete prepared with OPC only as a control specimen, replacing OPC with 10%, 20%, and 30% of WTCPs leads to a decrease in CS from 22 MPa to 21, 19, and 20 MPa, respectively.
[60]	10, 20, 30, 40, 50	38.4, 40.2, 39.6, 37.7, 30.1			Compared to 38.1 MPa, the inclusion of 10, 20, and 30% of WCTPs as OPC replacement leads to an enhancement of strength by 7.4, 16.2, and 13.2%, respectively. However, the greatest loss of strength (15.2%) was observed with specimens prepared with 50% of WTCPs as OPC replacement.
[61]	5, 10, 15, 20, 25, 30	36.1, 35, 29.9, 28.7, 22.6, 23.5		2.37–3.25	In comparison to the CS of control specimens (33.2 MPa), the inclusion of 5 and 10% of WCTPs as OPC replacement slightly increased the CS to 36.1 and 35 MPa. However, continuing to increase the replacement level to 15, 20, 20, 25, and 30 resulted in a drop in strength to 29.9, 28.7, 22.6, and 23.5 MPa, respectively.
[48]	10, 20, 30	22.9, 23.1, 23.7, 25.4	-	1.67–3.64	Both CS and STS were found to be enhanced by replacing the OPC with 10, 20, and 30% of WCTPs. In comparison to the 22.9 MPa CS achieved with control specimens, the inclusion of 10, 20, and 30% of WCTPs slightly improved the strength to 23.1, 23.7, and 25.4 MPa, respectively.
[62]	15, 25, 35, 50	48, 42, 38, 29	-	-	At 28 days of age, it was observed that replacing OPC with 15%, 25%, 35%, and 50% of WCTPs resulted in a drop in CS from 50 MPa to 48, 42, 38, and 29 MPa, respectively.
[69]	1, 3, 5	Increased	-	-	Specimens prepared with 1% of WCTPs as OPC replacement achieved the best strength performance by 9.8%. However, the increased replacement level to 3 and 5% caused a loss of strength by 1.9 and 14.7%, respectively.
[77]	10, 20, 30, 40, 50	21.3, 23.5, 24.6, 17.9, 17.5	-	-	The results indicate that replacing OPC with 30% of WTCPs leads to an increase in strength from 20.8 MPa to 24.6 MPa. However, the strength trend drops with increasing the level of replacement to 40% and 50%.
[54]	2, 4, 6, 8, 10	28.8, 29.3, 29.7, 29.2, 28.7	3.4–3.6	2.3–2.5	In comparison to the strength of control specimens (27.6 MPa), the replacement of OPC by 2, 4, 6, 8, and 10% of WCTPs leads to an enhancement of strength to 28.8, 29.3, 29.7, 29.2, and 28.7 MPa, respectively. A similar trend of results was observed for FS and STS, and all the specimens prepared with WCTPs displayed a better performance than the control specimens.
[87]	15, 25, 35, 50	40, 45, 40, 34	-	-	The inclusion of 25% of WCTPs as OPC replacement leads to an increase in the CS from 38 MPa to 45 MPa. However, raising the replacement level to 50% results in a lower gel formulation and a drop in strength to 34 MPa.
[31]	5, 10, 15, 20, 25	50.4, 53.9, 47.2, 45.6, 42.8	6.14, 6.15, 5.98, 5.29, 5.15		Specimens prepared with 10% WCTPs as OPC replacement achieved the highest CS (53.9 MPa) and FS (6.15 MPa) among the adopted levels, compared to control specimens (48.5 MPa and 5.68 MPa).
[55]	10, 20, 30, 40, 50	20.9, 22.7, 24.5, 18.1, 17.9	-	-	In comparison to OPC specimens, the inclusion of 10, 20, and 30% of WCTPs as OPC replacement leads to an increase in CS from 20.4 MPa to 20.9, 22.7, and 24.5 MPa, respectively. However, increasing the replacement level to 40 and 50% leads to a drop in strength below 18.1 MPa.
[51]	Unburned 10, 20 Burned 10, 20	32.9, 26.8 36.4, 34.0	5.3, 4.8 6.2, 5.8	4.5, 3.6 4.9, 4.6	At 28 days, all the specimens prepared with unburned and burned ceramics displayed lower CS, FS, and STS compared to control specimens (38.6, 6.4, and 5.2 MPa).

3.8. Sulphate Attack Resistance

If sulphate is present in soil or saltwater, it can damage the OPC concrete that comes into contact with it. Moreover, when calcium hydroxide reacts with a sulfate solution in concrete, calcium aluminate sulfate hydroxide is created. When this sulphate solution reacts with calcium sulphate, calcium sulphate (CaSO₄) is produced. Moreover, expansion results from the formation of ettringite [88]. As stated by Samadi et al. [2], mortar samples immersed in 5% Na₂SO₄ and containing 40% WCTPs experience a decrease in the loss of compressive strength. After being immersed for 18 months, the residual strength of samples containing 0% and 40% WCTPs dropped by 41.1% and 16.8%, respectively. Furthermore, it was reported by Mohammadhosseini et al. [80] that the OPC mortar lost 0.7% of its original mass after three months of immersion in the solution, although the WCTP mortar gained 1.7%. Similarly, Li et al. [82] revealed that mortars consisting of 5% and 10% WCTPs were less vulnerable to spalling and cracking on the surface. As illustrated in Figure 7, the authors [89] found that replacing OPC with 10 and 20% of WCTPs could significantly improve the durability of proposed concrete by reducing the expansion percentage. In fact, no spalling or cracks occurred when the WCTP content was 20%. The incorporation of WCTPs, which breaks down weak calcium hydroxide to create more C-S-H gel, makes the concrete’s interior structure denser and more resistant to sulphate attack. By densifying the pore structure, C-S-H gel formation reduces the porosity of cement-based composites and enhances their resistance to sulfates. It is essential to examine the effect of varying fineness on the ability of concrete to resist a sulphate attack. Thus, future research should focus on examining the sulphate resistance of high-performance concretes that incorporate WCTPs as a partial substitute for cement.

3.9. Acid Attack Resistance

Acid attack resistance is fundamental for external concrete applications. Mohit et al. [90] examined the impacts that WCTPs (as a cement substitute) have on concrete subjected to a hydrochloric acid attack. After being left to cure for 56 days, the mass loss of the control sample was found to be 8.64%, while the mass loss of concrete with 5, 10, 15, 20, and 25% WCTPs was 7.11%, 7.74%, 7.92%, 8.37%, and 9%, respectively. Meanwhile, the compressive strength of the sample mixtures containing 5, 10, 15, 20, and 25% WCTPs decreased by 50.1%, 54.8%, 53.2%, 56.7%, and 56.8%, respectively. This was reduced by 56.2% in the control sample. As demonstrated in Figure 8, the concrete samples containing 5% WCTPs experienced the lowest loss in strength over time, while the mixtures containing 25% WCTPs displayed the worst strength loss following exposure to an acid attack. As less C-S-H gel forms due to the reduced cement content (which also has an impact on the pozzolanic reaction), the concretes fabricated using WCTPs over the recommended quantity showed poor resistance to acid attacks. Similar results were reported by Rodhia et al. [91], who found that using WCTPs as a cementing agent increased the specimens’ resistance to sulfuric acid compared to the control specimens. By slowing the transfer of the acid solution and densifying the concrete’s structure through a pozzolanic reaction, concrete containing WCTPs has the ability to withstand an acid attack. The acid resistance of binary, ternary, or quaternary blended cement concrete using WCTPs as a partial cement substitute is still unknown. Thus, to create a high-volume WCTP blended cement mix that demonstrates excellent resistance to acid attacks, further research is required.

Rodhia et al. [91] investigated the impact of replacing OPC with WCTPs at varying levels (10%, 30%, 50%, 70%, and 90%) on the durability performance of concrete, specifically its resistance to acid attacks. The study employed two types of 2% acid solutions—sulfuric acid (H₂SO₄) and hydrochloric acid (HCl). Concrete specimens were immersed in these solutions for 56 days, after which the reduction in compressive strength was measured. As illustrated in Figure 9, the strength performance was assessed both before and after exposure to acid. Notably, after 56 days, the concrete mixtures exposed to sulfuric acid exhibited a greater weight loss and a greater reduction in compressive strength at all replacement levels compared to those exposed to hydrochloric acid. The more severe deterioration observed in the sulfuric acid solution can be attributed to several contributing factors. The compressive strength ratio under HCl exposure was consistently higher than that under H₂SO₄ exposure, largely due to the higher concentration of hydrogen ions (H⁺) in sulfuric acid. Acid attacks on foam concrete typically result in the dissolution of cement hydrates and calcium hydroxide, accompanied by the formation of calcium salts [92]. Hydrochloric acid primarily reacts with calcium hydroxide and has a relatively minimal effect on calcium silicate hydrate (C-S-H) gels. The resulting reaction products can further interact with the calcium aluminate (C₃A) present in the cement. In foam concrete containing HCl, both soluble and insoluble salts are formed, with calcium chloride (CaCl₂) being water-soluble. When the acid attack is superficial, as in the tested mixes, much of the CaCl₂ dissolves in water [93]. Although the pozzolanic activity of ceramic powder contributes to long-term strength development, it provides limited resistance against aggressive sulfuric acid environments compared to hydrochloric acid.

3.10. Porosity, Capillary Sorptivity, and Drying Shrinkage

Capillary sorptivity refers to a porous substance’s capacity to absorb liquid water via its open and connected capillary pores. In a study conducted by Xu et al. [39], the effect of WCTPs as OPC replacements on the porosity performance of low-carbon ultrahigh-performance concrete was reported. For all the specimens, the porosity of concrete tended to decrease with increasing the curing age from 7 to 28 days; a significant enhancement of specimens’ structure prepared with 55% of WCTPs was observed after 28 days of curing, which led to a drop in the porosity readings from 29.8% to 7.9%. As shown in Figure 10, the authors found that both early and late porosity reading trends to increase with increasing the content of ceramic in the concrete matrix. Li et al. [82] note that using up to 40% WCTPs to replace cement results in a decline in the sorptivity of mortar. Additionally, when 40% WCTPs are applied, there can be a reduction in the water absorption capacity of up to 60% when the percentage of WCTPs is 40%. In line with this, Chen et al. [14] replaced 10% of recycled aggregate concrete with ceramics and observed a significant reduction in secondary water absorption. This may be because WCTPs have a smaller grain size than cement, generating the micro-filler effect [14]. The pozzolanic reaction caused by adding WCTPs produces a more homogeneous mortar matrix. The formation of vast quantities of C-S-H gel after adding a suitable percentage of WCTPs can help make the concrete’s interior structure more compact [94].

Furthermore, a study conducted by El-Dieb and Kanaan [49] investigated the impacts that WCTPs had on drying shrinkage when applied as a cement substitute. The results showed that when WCTP replacement was increased, the tendency for drying shrinkage decreased for all mixes. A significant reduction in drying shrinkage was observed when the replacement was higher than 20% for all grades. When WCTPs were used in quantities over 20% (relative to the control mixture), there was a reduction in drying shrinkage in the range of 29–60%. Mixtures of 50 MPa experienced a 28–53% reduction in drying shrinkage when more than 20% WCTPs were used.

The drying shrinkage of the 75 MPa mixes decreased by 25–27%. It was revealed by Kanaan and EL-Dieb [95] that the drying shrinkage values were reduced by 5–60% compared to the control mix when WCTPs were applied in quantities of up to 40%. Meanwhile, the drying shrinkage decreased by 12–27% when high-performance concrete mixes were used. Ebrahimi et al. [42] reported that the drying shrinkage of cement mortars decreases as the content of WCTPs increases, reaching its lowest value at a replacement level of up to 40%. This reduction in drying shrinkage is attributed to the extremely fine particles of WCTPs and their pozzolanic properties. By reducing the free water content in the capillary pores, WCTPs significantly decreased the drying shrinkage of the mortar [96]. A delayed reaction in which pozzolanic ash absorbs large amounts of water on its surface and releases it into the environment during cement hydration, reducing the capillary pressure between the particles, is the primary cause of the reduction in drying shrinkage, according to Steiner et al. [97]. The other major factor is cement dilution. The reduced drying shrinkage of fiber-reinforced self-compacting concrete containing WCTPs and micro-silica as cement substitutes was also noted by Mansoori et al. [44]. It would also be beneficial to conduct further research to examine the drying shrinkage of WCTP-blended cement with fiber-reinforced concrete, high-strength concrete, and ultrahigh-performance concrete.

3.11. Resistance to Heating

The effects that WCTPs have on the fire performance of concrete have also been investigated by Mohit and Sharifi [31] who found that using WCTPs as a cement substitute at 5%, 10%, and 15% improved the compressive and flexural strength up to temperatures of 400 °C. Meanwhile, the highest compressive and flexural strengths were observed at 600 and 800 °C, respectively, with blends of 20% and 25%. This is evident in Figure 11, which displays both the residual compressive strength and surface appearance of concrete specimens exposed to 800 °C. Moreover, cracking on the surface of concrete containing WCTPs was much lower at temperatures between 600 and 800 °C, particularly for samples consisting of 25% and 20% WCTPs. Additionally, it was noted by Hilal et al. that the peak value for the compressive strength of 36 MPa was obtained for specimens containing 20% WCTPs at temperatures of up to 800 °C. Similarly, the research by Al Arab et al. [55] revealed that there was a mass loss for WCTP-based pastes of approximately 15%, compared to 25% for the control sample. Applying WCTPs thus enhances the fire resistance of concrete by forming C-S-H through the pozzolanic reaction. Generally, adding an appropriate quantity of pozzolanic ash as a partial replacement for cement enhances the fire resistance of concrete. Nonetheless, further research is required to determine the effectiveness of WCTPs with varying fineness and content in terms of fire resistance in modern cement-based concretes.

4. Waste Tile Ceramics as Aggregate Replacements

4.1. Physical Properties of Waste Ceramic Tile Aggregates

The durability and strength of concrete are significantly enhanced by the physical, mechanical, and chemical properties of waste ceramic tile aggregates (WCTAs). The WCTAs’ physical properties, such as bulk density, specific gravity, crushing value, impact value, and water absorption, were found to be 1218–1468 kg/m³ [4,20,98,99,100,101], 2.15–2.55 [4,98,100,102,103], 9.5–35.4% [4,48,71,98,100,102], 12.5–26.9% [20,48,103,104,105], and 0.18–2.70% [20,48,100,102,105,106]. Both the bulk density and specific gravity of WCTAs are lower than those of natural coarse aggregates (NCAs). In comparison to NCAs, WCTAs exhibited lower density and higher porosity, which resulted in greater water absorption. The bulk densities of coarse WCTAs, as reported in the literature, fell between the 1280 and 1920 kg/m³ range that the American Concrete Institute (ACI) specifies for standard aggregates. The water absorption of WCTAs ranges between 0.55% and 14.4%, and the main reason for this substantial absorption is the material’s porous structure. Compared to most NCAs, WCTAs have a higher water absorption rate that is less than 2% [107]. When compared to other waste materials, they showed a reduced absorption capability. The primary causes of the variations in WCTAs’ physical characteristics are the tile composition and firing temperatures [108]. As reported in the reference [109], WCTAs have a distinguishable angular shape, and when compared to NCAs, their surface texture is determined to be rougher. The crushing procedure is what causes visible fissures. Both wall and floor tile aggregates have clearly identifiable pores, as reported by Li et al. [110], with wall tile aggregates having substantially bigger pores than natural coarse aggregates.

4.2. Workability Performance

In

Table 4. Effect of fine and coarse WCTAs on workability of proposed concrete.

Refs	Type of Replacement	Replacement Level	Slump	Discussion
[113]	Fine or coarse	0, 20, 45, 100	121, 120, 118, 116	Numerous studies have indicated that incorporating waste ceramic tiles as fine and/or coarse aggregates in both normal and self-compacting concrete tends to slightly reduce workability and decrease the slump values of the tested mixtures. The reduction in workability generally increases with higher replacement levels. A significant decline in workability is particularly evident when the replacement level reaches up to 50%. This reduction is primarily attributed to two factors. First, the high water absorption capacity of ceramic materials increases the water demand of the mixture, thereby lowering its workability. Second, the irregular shape of the ceramic aggregates, resulting from the crushing process, increases internal friction within the mix, further diminishing the workability of the concrete.
[114]	Fine or coarse	0, 10, 20, 30	78, 75, 70, 67
[115]	Fine or coarse	0, 15, 30, 45, 60	70, 58, 50, 43, 38
[19]	Fine or coarse	0, 10, 20, 30, 40, 50, 100	190, 178, 161, 150, 142, 139, 119
[116]	Fine or coarse	0, 20, 50, 100	18.2, 14.8, 19.4, 9.1 18.2, 18.4, 19.6, 23.6
[37]	Fine or coarse	0, 15, 20, 30	50, 50, 40, 30
[117]	Fine or coarse	0, 20, 40, 60, 80, 100	120, 118, 108, 100, 100, 90
[45]	Fine or coarse	0, 10, 20, 30, 50, 100	60, 70, 80, 98, 90, 122
[118]	Fine or coarse	0, 5, 10, 15, 20	52, 47, 43, 35, 30
[4]	Coarse aggregates	0, 10, 20, 30, 40, 50	0.40: 10 to 0 0.50: 45, 40, 35, 30 0.60: 120, 115, 105, 100, 90, 85
[32]	Fine/Coarse aggregates	0, 25, 50, 75, 100	Fine: 118, 120, 117, 115, 112, 100 Coarse: 118, 115, 110, 90, 40
[119]	Fine aggregates	0, 20, 40, 60, 80, 100	725, 710, 700, 682, 671, 664
[120]	Fine or/and coarse aggregates	0, 10, 20, 30, 40, 50	F: 36, 25, 26, 28, 30, 31 C:36, 22, 20, 17, 16, 15 FC: 36, 20, 22, 19, 18, 16
[101]	Coarse aggregates	0, 25, 50, 75, 100	Workability tends to decrease with the increase in ceramic coarse aggregates, and the T500 flow time increases from 4 to 4.2, 4.5, 5, and 5S.
[121]	Coarse aggregates	0, 20, 40, 60	73, 67, 64, 60
[112]	Fine aggregates	0, 20, 40, 60, 80, 100	559, 518, 497.5, 472, 426, 398

, the impacts that WCTAs have on the workability of cement-based composite material are illustrated. Overall, the workability of cement-based composites containing WCTAs decreases when higher levels of WCTAs are used to replace natural aggregates (NAs). The reduction in workability may be due to the increased roughness and irregular shape of the WCTAs’ surface in comparison to NAs [102,111,112]. Moreover, the decrease in the workability of cement-based composites is caused by the interlocking of the WCTAs, which causes increased frictional resistance [109]. The porous nature of WCTAs also renders the mixture more capable of absorbing water. Alves et al. [113] point out that increasing the water–cement ratio can effectively address this reduction in workability. Furthermore, it is possible to mitigate the negative impacts on the workability of the cement-based composite by pre-soaking WCTAs in suitable water, which saturates the WCTAs.

4.3. Fresh and Dry Densities

The various studies in this field generally agree about how adding higher amounts of WCTAs affects the density of cement-based composites. The findings have generally revealed that fresh and dry densities decrease linearly with increased WCTA replacement [4,65,121]. As the ratio of NA to WCTA substitution increases, the density decreases. This seems to make sense, given that WCTAs have a lower density than NAs. Furthermore, a higher percentage of voids is caused by the irregular and rough shape of WCTAs [105,108]. A review of the literature revealed that when comparing WCTA mixes to a control blend, the fresh density decreased by 14% to 20% [65]. Likewise, there is a reduction in dry density from 2260 kg/m³ (for 0% replacement) when NCAs are fully replaced by coarse WCTAs [108]. Furthermore, it has been found in other studies that the dry density of cement-based composites decreases when WCTAs are used as a replacement [100,105].

4.4. Compressive Strength Development

Compressive strength was the primary mechanical behavior examined in the research focusing on WCTA concrete. The CS performance of a cement-based composite after replacing coarse aggregate with WCTAs is shown in Table 5. When coarse WCTAs are added, the compressive strength of concrete usually increases [4,105,111,114]. The decrease in concrete’s 28-day compressive strength with WCTAs replacing NCAs is shown in Table 5. According to numerous studies, replacing NCAs in the range of 5–30% with coarse WCTAs significantly increases the compressive strength from 5% to 25% [122,123]. The irregular shape and coarse texture of WCTAs facilitate more effective interlocking between the aggregates and the cured cement paste, and this ultimately causes the evident increase in compressive strength over 28 days [32]. Furthermore, it should be noted that WCTAs, being a permeable material, provide a moist atmosphere for the hydration process of the cement paste to occur. This results in a decline in autogenous shrinkage, which, in turn, increases the compressive strength of the cement-based composite [30,124].

The 28-day compressive strength of the cement-based composite also increases when fine WCTAs are used optimally. Table 5 demonstrates how the amount of substituted aggregate impacts the concrete’s 28-day compressive strength, which includes fine WCTAs. In comparison to traditional concrete, the application of fine WCTAs at up to 60% in place of natural fine aggregates (NFAs) typically yields superior CS, with a 5 to 30% increase after 28 days [125,126]. The irregular shape and rough surface of the particles may contribute to the higher compressive strength of cement-based composites containing WCTAs [127]. The water content of the fine WCTAs is another factor contributing to the rise in compressive strength. This enables the cement to hydrate sufficiently through internal curing, and thus increases the hydration of the cement and enhances the quality of cement-based composites [128,129]. The pozzolanic characteristics of fine WCTAs contribute to the increase in compressive strength. Additionally, due to the mixture’s consistent particle size distribution and high concentration of extremely small WCTA particles, which enhanced particle packing, the mixture containing fine WCTAs was compacted more efficiently [129,130].

4.5. Splitting Tensile Strength

Table 5 presents the change in the 28-day splitting tensile strength of concrete when WCTAs are applied (as a function of the proportion of replaced aggregates). Increased 28-day splitting tensile strength is often achieved by replacing NCAs with coarse WCTAs in the range of 5–40%, with increases ranging from 3% to 21%. It is possible that this increase in the 28-day splitting tensile strength is associated with the same factors that impact compressive strength increases, namely the irregular morphology and coarse texture of WCTAs. As a permeable material, WCTAs create a moist environment. Moreover, the incorporation of coarse WCTAs can refine the pore system, causing the volume of capillary pores to increase and the volume of macropores to decrease [21,32].

By contrast, the splitting tensile strength seems to be comparable or slightly lower when a replacement ratio of over 50% is applied. The change in the 28-day splitting tensile strength of concrete containing fine WCTAs can be seen in Table 5. Many relevant studies have found that, when WCTAs are added as a fine aggregate, there is a notable improvement in the splitting tensile strength [131]. The findings of various studies have revealed that compressive strength increases significantly (by 5% to 30%) when 60% WCTAs are used in place of NFAs [119,131,132]. The strength increases over the curing period in proportion to the fine WCTA content. Moreover, substituting fine WCTAs for 50% of the NFAs was found to enhance the splitting tensile strength by as much as 30% [32,119]. The range of 20–60% was the ideal replacement level of NFAs with WCTAs, beyond which the compressive strength steadily decreased [130]. It is also important to note that the fineness modulus is greater in the fine WCTAs than the NFAs, which causes the densification of the mixture and a decrease in macropores, rendering strength development more efficient.

4.6. Flexural Strength

Table 5 presents the change in the 28-day flexural strength (FS) of concrete containing coarse WCTAs. It has been revealed in many studies that applying 20% WCTAs in place of NCA has comparable or even enhanced FS than traditional concrete [133,134,135]. Furthermore, when the curing age increases, ultrahigh-performance concrete (UHPC) with WCTAs exhibits a rising trend in the ratio of FS to CS. This suggests that UHPC with WCTAs increases more quickly in its FS than in its CS. As a result, the material’s toughness likewise gradually increases over time. The ratio of FS to CS reaches a maximum value of 0.143 when the WCTA content is 80%, which represents a 20% increase over the control group [112]. Moreover, as the WCTA content rises, there is a progressive increase in the flexural strength-to-compressive strength ratio, which indicates that WCTAs have a more positive impact on FS than CS.

Likewise, after 28 days of curing, concrete with fine WCTA particles frequently shows a greater FS than concrete with natural fine aggregates. The variation in the 28-day FS of concrete with fine WCTAs in relation to the degree of NCA substitution is displayed in Table 5. When compared to regular concrete, replacing NFAs with fine WCTAs in a percentage between 10% and 60% usually results in a 14.2% to 45% improvement in FS values [112,126].

Table 5. Effect of WCTAs as NFAs and NCA replacement on the mechanical properties of proposed concretes.

Refs	Type of Aggregates	Replacement Level	CS	FS	STS
[4]	Coarse aggregates	0, 10, 20, 30, 40, 50	31.2, 32.3, 31.6, 31, 29.7, 28.5	-	-
[105]	Coarse aggregates	0, 5, 10, 15, 20, 25	Cs7: 35, 37, 39, 41, 38, 36 Cs:28 42, 45, 47, 51, 48, 46	6.52, 6.63, 6.68, 6.73, 6.67, 6.64	3.25, 3.32, 3.5, 3.65, 3.48, 3.37
[118]	Coarse aggregates	0, 5, 10, 15, 20	Cs7: 20.4, 16.2, 17.5, 15.5, 14.4 CS28: 32.6, 28.3, 29.5, 27.1, 26.1	Fs7: 3.9, 4.2, 4.7, 4.3, 3.4 Fs28: 7.5, 6.2, 7, 5.1, 4.3	-
[32]	Fine/Coarse aggregates	0, 25, 50, 75, 100	FA: 24, 24.8, 25, 25.4, 28.6 CA: 24, 24.5, 24.8, 26, 32	-	-
[119]	fine aggregates	0, 20, 40, 60, 80, 100	42, 47, 51, 55, 49, 41	7.1, 7.8, 8.1, 8.6, 7.5, 6.5	5.8, 7.6, 7.9, 8.3, 6.7, 6.4
[37]	Coarse aggregates	0, 14, 20, 30	37.8, 38.5, 40.2, 38.3	-	-
[98]	Coarse aggregates	0, 10, 20, 30, 50, 100	31.1, 28.8, 24.9, 24.4, 22.2, 21.6	6.1, 6.0, 5.6, 5.1, 4.7, 4.6	3.7, 33.4, 3.25, 3.18, 3.14, 2.95
[114]	Coarse aggregates	0, 10, 20, 30	21.1, 21.4, 22.8, 24.9	-	-
[116]	Fine or Coarse aggregates	0, 20, 50, 100	36.2, 34.1, 34.9, 34.6 36.2, 35.5, 35.9, 38.7	-	2.64, 2.64, 2.48, 2.65 2.64, 2.54, 2.33, 2.47
[120]	Fine or/and Coarse aggregates	0, 10, 20, 30, 40, 50	20.4, 19.8, 17.5, 16.1, 10.8, 8.4 20.4, 20.2, 20.8, 21.6, 20.6, 16.3 20.4, 20.5, 24.1, 19.3, 15.2, 9.9	2.98, 3.1, 3.14, 2.86, 2.64, 2.46 2.98, 3.14, 3.18, 3.22, 3.04, 2.71 2.98, 3.24, 3.36, 3.17, 2.78, 2.39	2.3, 2.14, 2.08, 1.96, 1.84, 1.55 2.3, 2.35, 2.41, 2.23, 1.98, 1.92 2.3, 2.47, 2.56, 2.43, 2.36, 2.06
[101]	Coarse aggregates	0, 25, 50, 75, 100	57.4, 61.4, 57.0, 54.0, 50.0	6.72, 7.06, 6.44, 5.99, 5.46	-
[136]	Coarse aggregates	0, 10, 20, 30	CS-28 CA-64.2, 60.4, 58.2, 54.6 CB-64.2, 71.1, 68.9, 63.9 CC-64.2, 65.7, 61.2, 58.3	-	CA-3.9, 4.1, 4, 3.9 CB-3.9, 4.7, 4.5, 4.2 CC-3.9, 4.7, 4.4, 4.3
[121]	Coarse aggregates	0, 20, 40, 60	75.9, 77.3, 80.5, 78.1	4.86, 5.1, 5.41, 5.24	6.12, 6.15, 6.31, 6.28
[112]	Fine aggregates	0, 20, 40, 60, 80, 100	126, 120, 131, 134, 124, 142	14.9, 15.3, 15.1, 17.8, 18, 18.5	-

Table 5. Effect of WCTAs as NFAs and NCA replacement on the mechanical properties of proposed concretes.

Refs	Type of Aggregates	Replacement Level	CS	FS	STS
[4]	Coarse aggregates	0, 10, 20, 30, 40, 50	31.2, 32.3, 31.6, 31, 29.7, 28.5	-	-
[105]	Coarse aggregates	0, 5, 10, 15, 20, 25	Cs7: 35, 37, 39, 41, 38, 36 Cs:28 42, 45, 47, 51, 48, 46	6.52, 6.63, 6.68, 6.73, 6.67, 6.64	3.25, 3.32, 3.5, 3.65, 3.48, 3.37
[118]	Coarse aggregates	0, 5, 10, 15, 20	Cs7: 20.4, 16.2, 17.5, 15.5, 14.4 CS28: 32.6, 28.3, 29.5, 27.1, 26.1	Fs7: 3.9, 4.2, 4.7, 4.3, 3.4 Fs28: 7.5, 6.2, 7, 5.1, 4.3	-
[32]	Fine/Coarse aggregates	0, 25, 50, 75, 100	FA: 24, 24.8, 25, 25.4, 28.6 CA: 24, 24.5, 24.8, 26, 32	-	-
[119]	fine aggregates	0, 20, 40, 60, 80, 100	42, 47, 51, 55, 49, 41	7.1, 7.8, 8.1, 8.6, 7.5, 6.5	5.8, 7.6, 7.9, 8.3, 6.7, 6.4
[37]	Coarse aggregates	0, 14, 20, 30	37.8, 38.5, 40.2, 38.3	-	-
[98]	Coarse aggregates	0, 10, 20, 30, 50, 100	31.1, 28.8, 24.9, 24.4, 22.2, 21.6	6.1, 6.0, 5.6, 5.1, 4.7, 4.6	3.7, 33.4, 3.25, 3.18, 3.14, 2.95
[114]	Coarse aggregates	0, 10, 20, 30	21.1, 21.4, 22.8, 24.9	-	-
[116]	Fine or Coarse aggregates	0, 20, 50, 100	36.2, 34.1, 34.9, 34.6 36.2, 35.5, 35.9, 38.7	-	2.64, 2.64, 2.48, 2.65 2.64, 2.54, 2.33, 2.47
[120]	Fine or/and Coarse aggregates	0, 10, 20, 30, 40, 50	20.4, 19.8, 17.5, 16.1, 10.8, 8.4 20.4, 20.2, 20.8, 21.6, 20.6, 16.3 20.4, 20.5, 24.1, 19.3, 15.2, 9.9	2.98, 3.1, 3.14, 2.86, 2.64, 2.46 2.98, 3.14, 3.18, 3.22, 3.04, 2.71 2.98, 3.24, 3.36, 3.17, 2.78, 2.39	2.3, 2.14, 2.08, 1.96, 1.84, 1.55 2.3, 2.35, 2.41, 2.23, 1.98, 1.92 2.3, 2.47, 2.56, 2.43, 2.36, 2.06
[101]	Coarse aggregates	0, 25, 50, 75, 100	57.4, 61.4, 57.0, 54.0, 50.0	6.72, 7.06, 6.44, 5.99, 5.46	-
[136]	Coarse aggregates	0, 10, 20, 30	CS-28 CA-64.2, 60.4, 58.2, 54.6 CB-64.2, 71.1, 68.9, 63.9 CC-64.2, 65.7, 61.2, 58.3	-	CA-3.9, 4.1, 4, 3.9 CB-3.9, 4.7, 4.5, 4.2 CC-3.9, 4.7, 4.4, 4.3
[121]	Coarse aggregates	0, 20, 40, 60	75.9, 77.3, 80.5, 78.1	4.86, 5.1, 5.41, 5.24	6.12, 6.15, 6.31, 6.28
[112]	Fine aggregates	0, 20, 40, 60, 80, 100	126, 120, 131, 134, 124, 142	14.9, 15.3, 15.1, 17.8, 18, 18.5	-

4.7. Modulus of Elasticity

The elastic behavior of cement-based composites is significantly impacted by the addition of WCTAs in place of natural fine and/or coarse aggregates. The relationship between the percentage of aggregate substituted and the respective change in the varying ages’ modulus of the elasticity of concrete with WCTAs were reported by several studies [111,121,137,138]. In a study conducted by Zareei et al. [121], the authors reported that increasing the replacement of coarse aggregates by 40% of WCTAs could enhance the modulus of concrete by 2.9%. However, increasing the replacement level to 60% caused a 1.2% drop in the modulus compared to the control specimens. Additionally, the authors observed similar behavior for the ceramic when combined with the fiber-reinforced concrete, as shown in Figure 12. From the results reported in Figure 13, the authors found [101] that the inclusion of 25, 50, and 75% of coarse WCTAs in the matrix of concrete containing calcium carbonate could contribute to enhancing the modulus of elasticity by 18, 5, and 2%, respectively. The elastic modulus of concrete consisting of WCTAs generally rises as the WCTA content increases. Moreover, the increase in the elasticity modulus of WCTA-containing concrete mixtures becomes significant when the entirety of the natural coarse aggregates is replaced by WCTAs [137,138]. This increase in the modulus of elasticity can reach 26.9% in comparison to the control concrete, with a total replacement of 100% [111]. The substantial increase in the elasticity modulus can be attributed to the increased angular morphology and textured surface of WCTAs compared to natural coarse aggregates. There is a proportional relationship between this increase and the aggregate replacement ratio. Thus, there is a clear correlation between the elasticity modulus and the number of angular aggregates [111]. Nonetheless, other studies have revealed that the application of coarse WCTAs to replace NCAs can reduce the elastic modulus of cement-based composites [139,140,141,142]. The apparent misalignments in the results of relevant studies may be due to the different physical properties of the WCTAs applied.

A linear regression analysis was conducted to examine the relationship between compressive strength and the modulus of elasticity [121]. As illustrated in Figure 14, a direct correlation exists between these two properties, leading to the development of the following equation based on the analysis:

$$fc=5.0594Ec-135.97$$

This equation can be used to estimate the compressive strength of WCTAs and waste carpet fiber-reinforced high-strength concrete (HSC) based on its modulus of elasticity. Moreover, the R-value of 0.94 demonstrates the reliability of the linear regression analysis and confirms that the proposed equation provides a satisfactory level of accuracy.

4.8. Water Absorption and Porosity

As the water absorption characteristics of concrete are critical to defining its quality and strength, the water absorption characteristics of WCTA-based cementitious composites are detailed in this section. It has been discovered through multiple studies that the concrete’s water absorption capacity increases when the amount of WCTAs in the concrete increases [108]. Moreover, replacing NCAs in concrete with WCTAs significantly increases porosity and absorption. After 28 days, Paul et al. [45] found that, in comparison to the reference concrete, the absorption increases by roughly 130, 142, 150, 174, and 221% in concrete with WCTA contents of 10, 20, 30, 50, and 100%, respectively.

The reason why the WCTAs have a higher absorption coefficient is that they possess a better absorption capacity than the NCAs. Furthermore, the increased number of voids in mixtures containing WCTAs create an empty vessel, which renders such mixtures able to absorb higher quantities of water [65]. The research performed by Amin et al. [20] revealed that adding mineral admixtures to replace cement can reduce the water absorption of ultrahigh-performance concrete consisting of coarse WCTAs. Additionally, in comparison to normal concretes, the capillary absorption of concretes that had been prepared with coarse WCTAs exhibited noticeably higher values [143]. This increase is most likely due to the enhanced pore connectivity of the coarse-grained aggregate mixture across each grain. However, other researchers have found that water absorption gradually decreases as the coarse WCTA content rises, with a small increase observed when the degree of replacement of course WCTAs reaches a particular threshold [116,144]. Well-graded CTA is added to samples to boost the filling capacity and decrease water absorption [120]. Additionally, because WCTAs are porous, they retains a high degree of internal moisture, which promotes gel formation and pore sealing [138]. The admixture of WCTAs in place of NCAs in concrete can thus have two distinct impacts on the permeability of the cement-based composite. The impacts that WCTAs have on the water absorption of different cement composites when used in place of coarse aggregates can be seen in Figure 15. It clearly can be seen with the addition of a high amount of waste ceramic to the matrix of self-curing concrete (Figure 15a) [138] and self-compacting concrete (Figure 15b) [101] that the water absorption values tend to increase slightly.

Until a certain point, the water absorption decreases as fine WCTAs are added in greater amounts to replace NFAs [145]. Meena et al. [119] found in another study that using up to 60% fine WCTAs reduced water absorption when compared to other alternatives. According to the results, less than 2% water is absorbed. Harikaran et al. [146] observed a similar outcome, demonstrating that adding 50% fine WCTAs decreased the water absorption of self-compacting concrete to 1.9% and that increasing the replacement ratio further led to a minor rise in water absorption. According to the findings by other researchers [145,147], the water absorption of different cement-based composites decreased and enhanced at greater replacement ratios when up to 20% fine WCTAs were used as NFAs. This may be caused by the presence of minuscule WCTA particles that refine the pore size [109], causing the water-to-cement ratio to decline [145]. This ratio reduction ultimately results in a decrease in the thickness and permeability of the interfacial transition zone. Meanwhile, other findings have demonstrated that the addition of fine WCTAs improves the water absorption of composites [148]. Moreover, the porous nature of WCTAs and their greater absorption capacity relative to NFAs can cause the porosity of cement-based composites to increase. It is reasonable to state that there could be two conflicting effects on water absorption by using fine WCTAs in cement-based composites instead of NFAs [126]. The relative importance of each factor thus determines how much of an influence WCTAs have on concrete’s ability to absorb water. The impacts that WCTAs have on the water absorption of different cement-based composites when used in place of fine aggregates are presented in Figure 16. The results show that increasing the replacement level of fine aggregates to 30% leads to an increase water absorption from 4.58% to 5.43% [149].

4.9. Resistance to Sulphate Attack

A relationship has been observed between the resistance to expansion caused by sulphate attack and the rise in the fine fraction of WCTAs [2,150]. A portion of the fine WCTAs undergoes a pozzolanic reaction that reduces the amount of surplus ettringite that is typically created by the reaction of sulphate and calcium hydroxide [151]. Because fine WCTAs reduce the amount of secondary ettringite in concrete, it can better withstand the expansion caused by sodium sulphate. Furthermore, the inclusion of WCTA particles with an angular shape and coarse surface leads to advantageous interlocking with the cement paste, enhancing resistance to sulfuric acid attacks [151]. Importantly, the fine WCTAs’ pozzolanic activity supersedes the increased porosity of concrete mixtures containing WCTAs, making them more resilient to sulfate attacks.

4.10. Drying Shrinkage

According to Elçi’s [108] study, the drying shrinkage of concrete increases when WCTAs are used in place of NCAs. According to the findings, the aggregate shrinkage values for wall and floor tiles are 2.42 and 1.37 times higher than those of the control samples, respectively. WCTAs’ high water absorption levels may explain this. Younis et al. [138] reported on the occurrence of early and late shrinkage in another investigation. Drying shrinkage is decreased when WCTAs are added to self-curing concrete to serve as a coarse aggregate. The “reservoir effect” is a phenomenon evident in porous WCTA materials. This effect reduces shrinkage at a constant water-to-cement ratio as the absorbed moisture is progressively released into the concrete mixture throughout the drying process [152,153]. Conversely, the cement-based composites’ drying shrinkage was reduced when fine WCTAs were used in place of NFAs. Likewise, Meena et al. [109] found that replacing river sand with fine WCTAs in the production of self-compacting concrete significantly contributed to reducing drying shrinkage, as can be seen in Figure 17. The observed reduction in shrinkage suggests that the aggregates contributed to at least partially mitigating the self-desiccation process, which occurred in parallel with external drying over a specified duration. The angular particle-parking of fine WCTAs may be responsible for this decline in drying shrinkage [153].

5. Structural Applications of Waste Ceramic Tiles

Due to their superior mechanical properties, including enhanced compressive, tensile, and flexural strength, as well as a satisfactory modulus of elasticity compared to conventional concrete, WCT-based modified concretes are well-suited for various structural applications [154]. In reference [155], the authors investigated the impact of using WCTPs, as well as fine and coarse WCTAs, as replacements for OPC and natural aggregates on the structural behavior of reinforced concrete beams. Their findings indicated that the ultimate load capacity, crack formation, and total deflection were significantly affected by the level of replacement and the amount of ceramic waste incorporated into the concrete matrix. All tested beam specimens failed in flexure, with numerous cracks appearing in the tension zone of the concrete. The initial crack was observed in the mid-span tension region between the two-point loads, where a pure bending moment is present and maximum tensile stress occurs at the bottom of the beam. As the applied load increased, both the number and depth of cracks grew. Continued loading resulted in the widening of existing cracks and the development of additional vertical cracks along the length of the constant moment region, extending upward.

The authors [155] examined the influence of WCTs on various characteristics of the tested beams, including the initiation of cracks, the number and depth of cracks, beam deflection, ultimate moment capacity, and the total number of cracks after failure, as summarized in

Table 6. Structural properties of reinforced concrete prepared with WCTs as the binder and aggregates replacement [155].

Beam Code		Reinforced Concrete Beams
		Control, 0% WCTs	100% C-WCTs	100% F-WCTs	100% WCTAs	40% WCTPs
WCTPs:F-WCTAs:C-WCTAs		0:0:0	0:0:100	0:100:0	0:100:100	40:100:100
At first crack load	Load, kN	14	10	14	14	12
	Deflection, mm	3.67	2.97	3.04	2.69	3.01
At ultimate load	Load, kN	47.6	44.9	45.8	47.1	45.7
	Deflection, mm	28.46	21.67	20.55	17.52	16.12
Total number of cracks		16	12	13	12	15
Correlation of first crack load to ultimate load, %		29	22	31	30	26
Ultimate moment capacity, kN.m		21.4	20.2	20.6	21.2	20.6
Theoretical moment capacity, kN.m		13	13	13	13	13
Percentage compared to the control beam, expressed as a percentage		100	94	96	99	96
Depth of neutral axis at first crack load, mm		74	71	73	61	79
Depth of neutral axis at ultimate load, mm		61	48	46	43	61

. In the control specimen made with conventional concrete, the first crack emerged at a load of 14 kN, located at the mid-span of the effective length. This initial cracking occurred at approximately 29% of the ultimate load. As the applied load increased, the initial crack deepened, and additional cracks formed on both sides of the original one. The crack propagation gradually extended outward from the initial crack until the beam failed. In specimens where WCTAs were used to replace fine or coarse aggregates, the first crack also occurred at 14 kN, matching the control specimen. Additionally, the total number of cracks in both specimens was identical. While the general pattern of crack propagation across the effective span was similar for all specimens, the total number of cracks before failure varied. These variations in the initial crack loads and crack patterns may be attributed to the effects of the recycled ceramic aggregates on the beams’ load-bearing capacity. Overall, no significant differences were observed in the number of cracks or the ultimate load-bearing capacity among the different beam types.

The control beam specimen exhibited the greatest mid-span deflection under ultimate load conditions compared to the other beam specimens. Specifically, the control beam showed a deflection of 28.46 mm, whereas the beam incorporating WCTs deflected by 17.52 mm, despite both beams sustaining nearly identical ultimate loads. This reduced deflection in the WCT-modified beam is likely attributed to the inherent physical properties of the ceramic material, which confer greater stiffness than that of the control specimen. Table 6 presents the maximum deflection and ultimate load values for all tested beams. A comparison of these deflections reveals that the WCTA beam experienced approximately 39% less deflection than the control beam, even though both demonstrated comparable flexural strength capacities.

The authors present the distribution of cracks along the span of the beam specimens [155] in Figure 18. In all cases, the initial crack appeared at the mid-span of the beam, corresponding to the pure moment region. For the control specimen, three out of sixteen total cracks (19%) were located in this region. The number of cracks within the pure moment region for the 100% C-WCTs, 100% F-WCTs, 100% WCTs, and 40% WCTPs specimens was 3, 3, 2, and 4, respectively. This corresponds to 25% of cracks for the 100% C-WCTs and 40% for the WCTPs, and 17% for the 100% F-WCTs, occurring in the pure moment region. These variations may be attributed to the properties of the ceramic material used in casting and the ultimate load-bearing capacity of each specimen. Overall, the total number of cracks among the beam specimens ranged from 12 to 16. The results indicate that as the applied load increases, both the deflection and the number of cracks also increase.

6. Convolutional-Based Deep Learning Models

The integration of computer vision algorithms and AI modeling into the assessment of waste ceramic-based sustainable concrete offers significant research and practical benefits. From a research perspective, these technologies enable a more precise, consistent, and automated analysis of concrete properties, such as crack propagation (as shown in Figure 19), surface texture, and color changes, which are key indicators of durability. By using image-based data and machine learning models, the researchers can detect early signs of deterioration, predict long-term performance, and correlate physical and microstructural changes with mechanical behavior [156]. This enhances our understanding of how ceramic waste materials influence concrete durability under various environmental and loading conditions [157,158].

In practical applications, AI-driven models improve the efficiency and reliability of quality control and structural health monitoring in real time [160]. These tools reduce the need for destructive testing and human error while enabling the continuous, large-scale monitoring of infrastructure made with ceramic-based concrete [161,162]. Additionally, predictive AI models can support the optimization of mix designs by simulating durability outcomes based on material inputs and exposure conditions. This leads to more sustainable construction practices, promotes the reuse of industrial waste, and supports the development of durable, eco-friendly concrete alternatives for modern infrastructure [163,164].

Kshirsagar et al. [165] used an artificial neural network and regression model for the prediction and modeling of mechanical properties of concrete modified with ceramic wastes. When evaluating the compressive and tensile strength, the authors found that the R² value was 0.70, whereas the ANN model achieved a higher value of 0.87. Due to its improved accuracy in predicting the strength characteristics of ceramic-based cement and structural stiffness, the ANN model demonstrates strong potential as a reliable tool for modeling different types of concrete. In a related study by Joudah et al. [6], the Random Forest Regressor—a type of ensemble learning method—was employed to predict the compressive strength of concrete mixtures incorporating high volumes of waste ceramics as replacements for cement and aggregates. The results demonstrate a strong predictive capability, with a correlation coefficient of 0.92 between the predicted and experimental compressive strength values, as illustrated in Figure 20. This finding emphasizes the significant influence of individual mix components on strength development and highlights the potential of artificial intelligence in optimizing concrete mix designs to improve performance and sustainability.

7. Ceramic Waste’s Impacts, Risks, and Sustainable Benefits

7.1. Wastes Impact the Environment

Yearly, billions of metric tons of unsustainable industry, agriculture, and human-generated wastes are disposed in landfill, entering our environment and polluting every ecosystem around the world [166]. With the rapid development, it is expected that the generation of total waste will increase by more than 60% by 2050. In other words, we are creating more waste than ever. It is reported that 62% of global waste is collected in controlled municipal facilities, with the remaining 38% dumped, burned, or discarded. Of the total municipal waste that is collected, 19% is recycled, and the rest ends up in landfill. The increasing disposal the waste in landfill significantly leads to an increase in greenhouse gases (GHGs), which are directly released into the atmosphere. As well as the increasing waste in landfill, environmental and human health are being deeply impacted by this lack of environmental accountability and awareness.

It is well known that the construction industry produces many types of waste during the building and construction process, maintenance, and demolition stages, and this waste has a significant impact on the environment. It breaks down ecosystems, uses up natural resources, and creates clouds of pollution. Construction waste, when mismanaged, acts like a relentless flood. It keeps pouring into already brimming landfills. The overflow of waste can create many environmental hazards. It leads to toxic air and water pollution, which impacts wildlife and public health. Meanwhile, methane, a potent greenhouse gas, worsens global warming.

Improperly disposed of ceramic and glass can end up in landfill, where they take hundreds to thousands of years to break down. This not only contributes to landfill overflow but can also result in the release of toxic substances. When ceramic and glass are not recycled, the opportunity to reuse valuable materials is lost. This increases the demand for raw materials and the associated environmental impacts of their extraction and processing. One of the qualities of ceramic and glass, compared to other materials, is that they can be endlessly recycled. Effective waste management is crucial for reducing harmful environmental impacts and enhancing sustainability. By understanding what happens to ceramic and glass waste, implementing proper disposal practices, and recognizing the consequences of improper recycling, the concrete industry can contribute to a greener future while reaping the environmental and economic benefits of recycling.

Meanwhile, ceramic tile waste generated from manufacturing factories, construction sites, and building demolition projects disposed of in landfill causes land pollution and many environmental problems [49,167]. A significant percentage of this waste is recycled into current ceramic products and processes; however, it is not currently possible to recycle all the waste generated. As a result, an important amount of waste is destined for landfill or used as very low-added-value fillers. To achieve a zero waste-to-landfill strategy, the waste generated must be reduced, especially tile ceramic waste. We need to adopt sustainable design principles and practice efficient construction methods, reusing and recycling different types of waste, such as in the concrete industry, as high-volume OPC replacements or as fillers to replace natural fine and coarse aggregates.

7.2. Risk of Ceramic Waste

The major environmental impact of ceramic tiles is air pollution, which leads to several adverse impacts on the Earth, including ozone layer depletion, global warming, acidification, and eutrophication. Ceramic and porcelain tiles are composed of natural materials, like clay, feldspar, and quartz, and are generally a healthy choice. They can, however, contain toxic additives in their pigments, frits, and glazes. Historically, one major health concern has been the use of heavy metals, such as lead, in glazes.

It is the dust that ceramic tiles can emit that may cause issues. During installation or removal, dust has the potential to cause toxic effects on health. For instance, exposure to ceramic tiles results in the release of airborne dust that causes health issues, such as asthma, chronic bronchitis, silicosis, and pneumoconiosis, when inhaled. Again, this is why tilers wear masks to protect themselves from inhaling dust and wear gloves to avoid possible cuts and scratches. They also wear safety shoes or boots to avoid hurting their feet if a tile or tiles fall on them. During processes that generate dust, they use breathing protection, safety glasses, and appropriate clothing to avoid exposure to dust. However, once the ceramic is placed and left undisturbed to dry, it poses no risk.

7.3. Environmental Benefits of Recycling Waste Materials in the Concrete Industry

Recycling by-products, industrial, and agricultural waste materials, such as those in the construction industry, has many environmental and economic benefits, such as reducing landfill waste, carbon footprint, costs; conserving natural resources; and creating durable construction materials. Integrating ceramic tile waste into concrete production presents notable environmental advantages and supports sustainable development. As illustrated in Figure 21, recycling waste ceramic tiles helps to decrease the volume of refuse sent to landfills, thereby alleviating the pressure on landfill capacity and reducing environmental pollution. In the cement and concrete industry, the use of recycled materials reduces the need for extracting natural resources. Concrete produced using recycled ceramic tiles and glass bottle waste as fine and/or coarse aggregates, or as partial replacements for cement, emits fewer greenhouse gases compared to concrete made from virgin materials. Additionally, incorporating these recycled materials can lower production costs due to reduced raw material and transportation requirements. Concrete containing recycled ceramic and glass waste may also exhibit improved strength and durability compared to conventional concrete. Utilizing ceramic waste in construction materials enables the industry to lower its ecological impact and actively contribute to a more sustainable and environmentally responsible future.

7.4. Life Cycle Assessment of Recycling WCTs in the Concrete Industry

A life cycle assessment (LCA) provides a systematic method for evaluating these environmental impacts, from raw material extraction through processing, use, and final disposal. The integration of waste ceramics as a partial replacement for cement, fine, or coarse aggregates in concrete has shown reductions in carbon footprint, energy consumption, and resource depletion across various LCA studies. For example, studies have shown that replacing 20–30% of cement with ground ceramic waste reduces CO₂ emissions by approximately 20–25% per cubic meter of concrete. This is attributed to the lower embodied energy of ceramic waste compared to clinker production, which emits approximately 850–900 kg of CO₂ per ton. Several case studies have demonstrated the environmental advantages of incorporating waste ceramic in concrete production through comprehensive LCA. In an Asian study conducted in Pakistan, replacing 30% of natural aggregates with ceramic waste led to a reduction in global warming potential (GWP) and significant energy savings during the production phase [114]. The authors reported that incorporating waste ceramic as a replacement for conventional aggregate contributes to the development of sustainable concrete. The higher the proportion of ceramic waste used in the mix, the greater the sustainability of the resulting concrete. A Malaysian study further confirmed these findings, showing that the use of recycled ceramic tiles as a coarse aggregate or cement replacement reduced CO₂ emissions, along with lowering water consumption and acidification potential, especially when the materials were sourced locally [2,96,168]. Similarly, the research in India revealed that substituting cement with ceramic tile powder created a reduction in CO₂ emissions and improved environmental performance across indicators, such as fossil fuel depletion and human health impacts [105,151,169]. These case studies collectively highlight the potential of waste ceramic recycling to enhance the sustainability of the concrete industry while reducing its ecological footprint.

7.5. Carbon Dioxide Emissions, Energy Saving, and Economic Benefits

Minimizing the consumption of natural resources and promoting the effective reuse of industrial waste are among the most practical strategies for achieving sustainable development and a cleaner environment. It is essential to limit the generation and disposal of waste materials that have significant ecological impacts. Incorporating solid waste into the production of construction materials can lead to the development of more sustainable and environmentally friendly products. However, these alternative materials must either be cost-competitive with conventional products or offer clear environmental benefits to construction projects.

To assess the sustainability of mortar or concrete made with recycled WCTs compared to traditional concrete, several key factors are typically considered. These include greenhouse gas emissions, production costs, and energy consumption during the manufacturing process. These indicators are primary motivators for adopting WCT-based concrete, although additional factors also play a significant role. These include technical performance, leaching behavior, water usage, the presence of harmful substances, emissions of other non-environmentally friendly gases during production, and the volume of industrial waste diverted from landfills through its use in concrete. In conducting an environmental benefits analysis, particular attention is paid to the impacts associated with the extraction and processing of raw materials and binders, as well as transportation, which are commonly evaluated within the concrete production industry.

In their study, Samadi et al. [2] investigated the impact of incorporating WCTs as both binder and aggregate replacements on the sustainability performance of proposed mortar mixtures. The findings revealed that variations in WCT content significantly affected carbon dioxide emissions, energy consumption, and production costs. As illustrated in Figure 22, sustainability and environmental performance were assessed based on total production cost, greenhouse gas emissions, and energy usage associated with WCTPs, OPC, fine WCTAs, and natural river sand. The authors observed that the grinding process for WCTPs consumed considerably less energy during manufacturing compared to the production of OPC, resulting in lower costs and reduced greenhouse gas emissions. Specifically, the energy required to produce OPC was 5.13 GJ/ton, more than four times the 1.12 GJ/ton needed for WCTPs. This disparity was attributed to the higher energy demand, cost, and emissions linked to OPC, which released 0.904 tons of greenhouse gases per ton, compared to just 0.045 tons per ton for WCTPs. Consistent with these emission trends, OPC also incurred the highest production costs among the materials studied. Therefore, reducing OPC content in the mortar mixtures was essential for minimizing energy use, lowering production costs, and enhancing overall sustainability and environmental performance.

The influence of replacing OPC and fine aggregates with WCTPs and WCTAs, respectively, on greenhouse gas emissions and energy consumption in blended cement is illustrated in Figure 22a–f. The findings indicate that increasing the proportion of WCTs in mortar mixtures leads to a reduction in both greenhouse gas emissions and energy usage. Blended cements incorporating any percentage of WCTPs consistently emitted fewer greenhouse gases compared to standard OPC-only mixtures. Specifically, producing one ton of blended cement containing 40% WCTs results in the release of only 1 m³ of greenhouse gases—a decrease of more than 37% relative to the conventional mix. Additionally, energy consumption dropped from 3.02 GJ/m³ to 2.13 GJ/m³. In contrast, substituting natural river sand with WCTAs had a minimal effect on emissions and energy use, likely due to the inherently low environmental impact of river sand extraction. Overall, the low levels of greenhouse gas emissions observed in mortar samples using WCTPs as a binder highlight the potential for developing a simple and sustainable material with reduced reliance on OPC.

The authors [2] assessed the cost-effectiveness of replacing traditional materials with WCTPs and WCTAs in the proposed mortar samples, in comparison to ordinary Portland cement (OPC) and natural river sand. The use of a high proportion of WCTPs (i.e., 40%) as a substitute for OPC resulted in significant cost savings. Incorporating WCTPs as a binder contributed meaningfully to the development of sustainable construction materials. Furthermore, the complete replacement of river sand with WCTAs showed considerable potential in promoting environmentally friendly products, thereby supporting more sustainable practices in civil engineering.

The study conducted by Ikponmwosa and Ehikhuenmen [100] investigated the impact of replacing natural coarse aggregates with varying proportions of WCTAs—specifically 0%, 25%, 50%, 75%, and 100%—on the cost-effectiveness of concrete production, as illustrated in Figure 23. WCTAs are derived from waste materials commonly generated in ceramic manufacturing processes, such as the production of tiles and pottery, and thus hold no intrinsic economic value [170]. Nonetheless, the use of WCTAs in concrete entails certain costs associated with transportation, crushing, and grinding to achieve the appropriate particle sizes. These expenses were included in the cost–benefit analysis by Ikponmwosa and Ehikhuenmen [100]. The analysis revealed that the cost per cubic meter of concrete declined as the proportion of WCTAs increased, with a full 100% replacement yielding a 13.1% reduction in cost. However, due to the adverse effects of high WCTA content on concrete properties—such as reduced workability and mechanical strength—the authors recommended limiting WCTA usage to a maximum of 75%, which still offers nearly a 10% reduction in cost per cubic meter [100]. Additionally, Gautam et al. [171] emphasized that incorporating WCTAs into construction practices not only reduces material costs, but also advances sustainability objectives. Nonetheless, the existing studies primarily focus on WCTAs as a replacement for coarse aggregates. Therefore, further research is recommended to explore the potential benefits of utilizing WCTAs as substitutes for cement or fine aggregates in concrete production.

In a study by Santos et al. [60], the authors calculated the Global Warming Potential (GWP) values for various concrete mixtures, all designed to achieve a compressive strength of 54 MPa, as illustrated in Figure 24. The results reflect the material consumption required for each mix to reach this strength level. The bi value is directly related to binder consumption; therefore, mixtures with lower binder index values use less binder. Since cement contributes the highest CO₂ emissions among the concrete constituents, mixtures with a higher binder content resulted in greater GWP values. Replacing ordinary Portland cement (OPC) with varying proportions of WCTPs resulted in a reduction in the GWP of the reference concrete, primarily due to decreased cement usage. Although the consumption of other components varied among the mixtures, cement usage had a significant impact on the final GWP. Thus, incorporating WCTs offers an effective strategy for reducing greenhouse gas emissions in concrete production, while also enhancing certain concrete properties as previously discussed.

8. Conclusions

Based on the reviewed literature, the following conclusions can be made:

Waste ceramic tiles (WCTs) represent a significant portion of modern construction waste. Therefore, recycling them plays a crucial role in promoting sustainable construction waste management. WCTs can be effectively utilized as recycled cement, fine, and coarse natural aggregates in the concrete industry, providing a sustainable approach to minimizing waste materials.

In the production of modern concrete, WCTs have been successfully used for the production of ultrahigh-performance, self-curing, and self-compacting concretes.

The workability of proposed mortar and concrete is slightly influenced by WCT content as a binder or filler replacement. The flowability of fresh mixtures tends to decrease with increasing WCTs’ replacement level, which is attributed to porosity and high water absorption, as well as the irregular shape of ceramic particles. Therefore, it is recommended to develop cement-based composites using WCT blends to achieve a consistent slump, rather than designing them based on a fixed water-to-binder ratio.

Waste ceramic tile powders (WCTPs) can be used as a partial replacement for cement, as their combined content of silicates, aluminates, and iron oxide generally exceeds the 75% threshold outlined in ASTM 618. Incorporating up to 30–35% WCTPs into cement-based composites improves their mechanical performance, including compressive strength, flexural strength, and split tensile strength. When used at a replacement level of up to 20%, WCTPs also contribute to improved durability of the composites. Specifically, mixtures containing up to 30% WCTPs show reductions in drying shrinkage, permeability, chloride ion penetration, and carbonation, along with increased resistance to sulphate attack.

The proportion of natural fine or/and aggregates replaced with waste ceramic tile aggregates (WCTAs) can range from 0% to 100%, depending on the intended application and the required performance characteristics of the concrete.

Using waste ceramic materials as fine and/or coarse aggregates to replace natural aggregates in the production of sustainable concrete has demonstrated comparable or slightly improved strength performances compared to control specimens.

The findings indicate that recycled WCT is a highly effective substitute for traditional concrete made with cement or/and natural aggregates, and it is appropriate for both structural and non-structural applications. Using WCTs in place of cement or/and natural aggregates can greatly reduce environmental impact by minimizing the need for natural resource extraction and decreasing the amount of construction and demolition waste sent to landfills.

In structural applications involving WCTs, reinforced concrete beams incorporating WCTs as cement, fine, and/or coarse aggregates demonstrated a satisfactory performance when compared to the control beam. This indicates that ceramic waste can be efficiently repurposed to produce environmentally sustainable concrete suitable for structural applications.

Incorporating waste ceramics into the concrete industry can significantly reduce global warming potential. Replacing ordinary Portland cement with waste ceramic powder has been shown to notably decrease energy consumption and carbon dioxide emissions, primarily due to the high energy demands of cement production. Nonetheless, the challenges related to landfill use and the conservation of natural resources persist and cannot be entirely resolved. Overall, ceramic waste-blended concretes have demonstrated improved performance and energy efficiency, offering both technical and environmental benefits that may contribute to lower construction costs and enhanced sustainability.

9. Recommendations and Future Research Directions

The use of waste ceramic tiles presents several practical challenges and raises significant environmental concerns. It is now broadly recognized that increasing cement production contributes substantially to global warming. Major environmental issues related to cement manufacturing include high energy demand, emissions of pollutants, and large-scale carbon dioxide output. In response, numerous strategies have been introduced to mitigate these impacts, such as recycling industrial and agricultural waste as cement substitutes, employing carbon capture technologies, utilizing nanomaterials and nanotechnology, and promoting the development of geopolymer technology. Producing high-performance concrete that incorporates large quantities of waste ceramic powder is a crucial step toward minimizing the environmental footprint of cement and improving concrete durability. These advancements also support the creation of low-cement, eco-friendly concrete materials. The authors recommend that future studies concentrate on examining the microstructure, durability, and mechanical behavior of concrete made with high volumes of waste ceramic materials.

Future research on recycling waste tile ceramics and other types of ceramic waste in concrete and geopolymer applications should focus on optimizing their processing methods, enhancing their pozzolanic reactivity, and evaluating their long-term performance in harsh environmental conditions. Special attention should be paid to the synergistic effects of combining ceramic waste with other industrial by-products, such as fly ash, slag, or nanosilica, to develop high-performance, sustainable binders. Investigations into the durability, shrinkage behavior, and microstructural evolution of ceramic-based geopolymer composites are also crucial. A promising research topic is the development of fiber-reinforced geopolymer composites incorporating ceramic waste for structural and non-structural applications. For future review papers, a comprehensive analysis of the environmental benefits, life cycle assessment, and challenges of integrating various ceramic wastes in alkali-activated and blended cement systems is recommended.