Development of Sustainable Concrete Using By-Products as a Green Material, and Potential Solutions for Sustainability in Mass Concrete Construction—Comprehensive Review

Abstract

The production of concrete strongly influences the environment. It is a versatile and sustainable construction material capable of creating a wide range of structures. It has always been indispensable as a material for the engineering and construction industry, including applications in hydraulic structures (e.g., dams, underwater tunnels, sluices, and other concrete structures), where mass concrete is a fundamental material in the construction industry. Developing sustainable concrete as an alternative construction material to the traditional one provides a reduction in the carbon dioxide footprint with regard to cement use and waste material disposal in landfills. This paper provides a comprehensive review of current trends and opportunities in sustainable construction using mass concrete. It underscores the importance of incorporating eco-friendly practices to mitigate environmental impact by using by-products as green materials. The review highlights how optimizing clinker content, supplementary cementitious materials (SCMs), and aggregates can improve the strength, durability, and thermal stability of mass concrete. Strategic material selection helps minimize thermal cracking, extend service life, and reduce environmental impact. Future research should focus on developing advanced mix design strategies and standardized practices for sustainable infrastructure.

1. Introduction

In recent decades, climate change has intensified, with scientific evidence now clearly linking the majority of these changes to human-generated carbon dioxide emissions and the resulting global warming [1]. If humanity fails to limit global warming to 1.5 °C or 2 °C, there is a significant hazard of disrupting climate stability. This stability has been crucial in maintaining the conditions necessary for human survival and prosperity on Earth [2]. The construction sector accounts for 32% of natural resource extraction and contributes 39% of energy- and process-related carbon dioxide (CO₂) emissions [3]. It is widely recognized that carbon dioxide stands as the primary contributor to the greenhouse effect [4]. The European Union has set ambitious goals under the “Green Deal” and the European “Climate Act”. It aims to reduce greenhouse gas (GHG) emissions by at least 55% by 2030 compared to 1990 levels and to achieve climate neutrality by 2050 [5]. To mitigate the emissions of greenhouse gas, recycling waste materials and preserving natural resources is essential. Increasing the use of recycled aggregates and cement-based products can enhance the environmental compatibility of concrete [6].

Concrete, a fundamental and widely used building material in the construction industry [7], ranks as the second most consumed material on Earth due to its extensive range of applications, and global cement production reaching approximately 4.1 billion tons in 2021, and annual concrete consumption nearly seven times higher [8]. Concrete is a mixture of cement, water, and combined fine and coarse aggregates. Modern concrete formulations can be far more complex, incorporating a variety of additional constituents. Such materials as pozzolans, fly ash, blast-furnace slag, silica, recycled concrete aggregate, polymers, fibres, and superplasticizers are used as components of concrete [9]. Nevertheless, it is worth noting that not all materials essential for producing conventional concrete are entirely user-friendly or environmentally sustainable. A prime example is the production of Ordinary Portland Cement (OPC), a critical binder in traditional concrete, which is related to substantial CO₂ emissions into the atmosphere. Notably, the amount of CO₂ released is nearly equivalent to the quantity of OPC produced [10]. The production of Portland cement (PC) demands considerable energy, releasing great amounts of carbon dioxide (CO₂) [11] to the atmosphere. The global concrete industry is estimated to consume around 10 billion tons of sand and natural rock annually. At the same time, over 11 billion tons of construction and demolition (C&D) waste are generated each year, with concrete waste amounting to approximately 50–70% [12]. Considering the current challenges posed by limited aggregate resources and advancements in the concrete industry, identifying suitable alternative materials for durable concrete has become both essential and imperative [13]. The depletion risks associated with natural aggregate resources and the global shift toward sustainable, eco-friendly concrete have driven the increased use of waste from industrial processes and recycled concrete aggregate (RCA). Although complete substitution of natural aggregates with RCA can negatively impact the properties of fresh concrete mix and hardened concrete, its suitability and adherence to worldwide standards for concrete are achieved when RCA is incorporated at recommended replacement rates or subjected to proper treatments [14]. Şimşek et al. [15] replaced natural coarse aggregates with 100% RCA, reducing the concrete compressive strength by up to 27% after 90 days. However, the use of fly ash helped mitigate some mechanical losses, particularly in longer curing periods. They attributed this decline to the numerous interfacial zones and the inherently high porosity of the recycled aggregates. Tang et al. [16] observed a decline in concrete’s mechanical properties and durability alongside increasing CDW content. However, they found that reducing the water/cement ratio to 0.3 significantly optimized the properties of concrete. For instance, the compressive strength of concrete with 50% CDW improved by 74.2%, and resistance to chloride penetration by 28%. de Matos et al. [17] investigated concretes where fine aggregate was partially replaced with WFS, finding no significant changes in mechanical properties—including compressive strength, flexural strength, and modulus of elasticity—up to a 30% replacement of natural aggregate. Aggarwal and Siddique [18] investigated the impact of partially replacing fine aggregate with equal proportions of waste foundry sand and bottom ash at varying percentages on concrete properties. Their findings reveal that replacing 30% of natural sand with equal amounts of waste foundry sand and bottom ash improves compressive strength, splitting tensile strength, and the modulus of rupture. Various powders have been investigated as possible alternatives to Portland cement [7,19,20]. A.S. El-Dieb and D.M. Kanaan [21] investigated the addition of ceramic waste powder (CWP) to partially replace cement in concrete mixtures. In their study, they replaced cement with 10%, 20%, 30%, and 40% of CWP by mass. The results indicated that replacing cement with 10% of CWP was optimal for an increase in strength, while replacing cement with CWP between 10% and 20% by mass enhanced workability retention. Additionally, a 40% replacement level was found to be necessary for durability enhancement.

Mass concrete has been widely utilized in the construction of critical infrastructure, including hydroelectric dams, nuclear power plants, and coastal structures, over the past several decades. The primary focus in the process of design and execution of mass concrete structures is addressing temperature control and thermal stresses [22]. Due to the significant heat generated during the reaction of cement hydration in mass concrete, the temperature inside the mass element becomes much higher than the temperature on the surface, leading to high tensile stress on the concrete surface and resulting in extensive cracking. During the cooling stage, the foundation constrains the mass concrete’s shrinkage, which can cause substantial as well as transverse, shrinkage cracks [23]. In massive concrete structures, cracks and fissures appear (see Figure 1) both in the early and later stages of concrete hardening. During setting and hardening, chemical and physical reactions occur, causing changes in volume. Initially, concrete expands due to water adsorption by the cement gel, followed by plastic shrinkage caused by water evaporation from the surface. The magnitude of plastic shrinkage relies on the type and amount of cement, the water-cement ratio (w/c), the sedimentation of the concrete mix, and the rate of hardening. Sedimentation of the concrete mix depends on the amount of water, the type of cement, the fineness of its grains, and the amount of fine aggregate. This phenomenon can be reduced by using mineral additives (e.g., fly ash) and plasticizing admixtures, reducing the amount of water needed. In the later stage of binder hydration, autogenous (self-induced) shrinkage occurs, which increases with the amount of cement and higher temperatures of the hardening binder. The magnitude of autogenous shrinkage depends on the cement composition. Drying shrinkage is also observed, which continues until equilibrium is reached between the moisture content of the concrete and the ambient relative humidity. This shrinkage depends on the dimensions of the element and is greater with a higher w/c ratio and lower ambient humidity. The relative humidity of the surroundings also has an impact on the extent of carbonation shrinkage, which occurs in the surface layers of concrete [24].

Figure 1. Types of cracks in mass concrete. (a) through cracks, (b) deep cracks, and (c) surface cracks [25].

As illustrated in Figure 1, cracks that appear in mass concrete structures can be categorized into three types: (a) through cracks, (b) deep cracks, and (c) surface cracks [25].

To reduce the impact of thermal stress on the durability of concrete structures, various technological processes are employed, including concrete cooling, staged concreting, and careful selection of concrete constituents. Among these methods, lowering the heat of cement hydration is the most effective approach [26]. Additionally, advancements in the innovative application of supplementary cementitious materials (SCMs) in mass concrete placements can significantly enhance the concrete properties. These innovations offer a range of engineering, economic, and ecological benefits [27]. A summary of literature reviews on mass concrete is presented in Table 1. This table shows the year of publication, authors, source materials, aggregates, slump, experiments, and remarkable conclusions. Despite these studies, significant research gaps remain, particularly regarding the impact of different cementitious materials and recycled aggregates on the properties of mass concrete in building construction.

Table 1. Outline of literature review on by-products in mass concrete.

Authors (Year)	Source Material	Aggregates	Slump (mm)	Experiments	Remarkable Conclusions
Ahad et al. (2018) [28]	BT, FA	NA	28–72	Slump, Compressive Strength, UPV, Changes in Temperature, Thermal and XRD Analysis, Morphological Investigation	Enhanced Compressive Strength, Lowest Temperature in FA Concrete, BC Effectiveness in Temperature Control.
Lu et al. (2024) [29]	FA, GBFS	NA	190–215	Concrete workability, Mechanical properties, Heat of hydration	The best performance was achieved with a C:FA:GBFS ratio of 6:3:1 and 8% HECRA, yielding 48.46 MPa CS at 28 days, meeting C35 requirements.
Machowska (2020) [30]	GGBFS, CFBC fly ash	NA	≈200	Consistency, air content, hardening temperature, compressive strength, Waterproofness, freeze/thaw resistance	A concrete mix with slag and CFBC fly ash binder is non-workable without a plasticizer. Increased compressive strength is observed when using a higher ratio of CFBC fly ash to slag.
Huo et al. (2023) [31]	GGBFS	NA, RA	100–220	Slump, air content, chloride contents, Temperature History, Compressive Strength, Rebound Number, Micro-Analysis	Reduced concrete slump, GGBFS reduces hydration heat, at 28 days of age, high-volume GGBFS reduces compressive strength compared to ONN.
Somolinos et al. (2020) [32]	CNFs	NA	(-)	Fire + compressive strength testing	1% of CNFs boosts compressive strength by 19.5% (normal) and 13% (after fire). 2% CNFs increase fire temperature by 25%. SEM analysis shows improved bonding and reduced spalling.

BT: Bentonite, FA: Fly ash, UPV: Ultrasonic pulse velocity, NA: Natural aggregates, GBFS: Granulated blast furnace slag, HECRA: High-Efficiency Crack-Resistant Agent, GGBFS: Ground granulated blast furnace slag, CFBC fly ash: fly ash from circular fluidized-bed combustion of brown coal, RA: Recycled aggregates, ONN: (OPC (Ordinary Portland cement)–NCA (Natural coarse aggregate)–NFA (Natural fine aggregate)), CNFs: carbon nanofibers, SEM: Scanning Electron Microscopy.

Past research has explored various methods to mitigate the high heat generated during the hydration of cement in mass concrete. Numerous studies have examined the early-age thermal and mechanical behaviour of mass concrete structures [33,34,35,36,37]. Current research on mass concrete largely emphasizes numerical simulations or finite element modelling [38,39,40] to predict thermal cracking and stress development. This review highlights potential alternatives for base raw materials and explores strategies for enhancing sustainability in mass concrete. Key issues, including material selection, environmental impact, mix design, durability, and the carbon footprint of mass concrete, are examined. Special attention is given to recycling, particularly the synergistic use of multiple supplementary cementitious materials (SCMs) as partial replacements for Portland cement. Additionally, the reuse of aggregates from construction and demolition waste is addressed, along with the effects of material selection on properties that influence mix design and durability. Overall, this review emphasizes best practices for incorporating SCMs and recycled aggregates to achieve an optimized mass concrete design that balances mechanical performance, hydration behaviour during curing, and environmental sustainability.

2. Research Approach and Methodology

The pursuit of sustainability in the construction industry has driven the innovative strategies improving the durability of concrete while significantly reducing its carbon footprint [41]. Sustainable concrete can be achieved by incorporating “green” materials that feature a significant percentage of eco-friendly, recycled, or recyclable resources, demand minimal maintenance, consume low inherent energy, and deliver excellent durability [42]. In addition to the CO₂ emissions generated during cement production, the construction industry heavily relies on the extraction of sand and gravel as aggregates. It is expected that the global consumption of natural aggregates (NA) reaches approximately 32 billion tons annually, with a growth rate of around 5% per year. The extraction of natural aggregates (NA) leads to significant environmental impacts, including the disturbance of natural soil layers, acceleration of erosion processes, deforestation in extraction zones, river siltation, and exposure of groundwater tables, among other concerns [43]. Minimizing the deployment of raw materials in the construction industry is a key principle in producing sustainable concrete [44]. The focus of this research is to explore pathways to achieving sustainability in the construction industry, with particular emphasis on the role of recycled materials in reducing the carbon footprint. The Flowchart employed in this study is outlined in Figure 2.

Figure 2. Flowchart of Review Scope.

This review adopts a systematic approach to identify, analyse, and synthesize existing research on the importance of adopting eco-friendly practices to reduce the environmental impact of mass concrete by utilizing industrial by-products and optimizing mix design to achieve suitable mechanical and thermal performance. The objective is to consolidate experimental findings and analytical insights from previous studies to establish key trends and knowledge gaps related to binder composition, supplementary cementitious materials, and aggregate properties that are compatible with sustainability and the circular economy.

A comprehensive literature search was conducted using major scientific databases, including Scopus, ScienceDirect, Google Scholar, and the ASCE Library, covering publications from 2001 to 2025. The search employed the following keywords and their combinations: “mass concrete”, “green material”, “Recycled Materials”, “by-products”, “sustainability”, “mix design”, “compressive strength”, “hydration heat”, “fly ash”, “GGBFS”, “Portland clinker”, “thermal cracking”, and “supplementary cementitious materials”.

The identification of studies related to mass concrete was carried out based on specific inclusion criteria. The selection focused on peer-reviewed journal articles, conference papers, and technical reports that provided experimental or analytical data on mass concrete. Studies containing quantitative information on mix composition, compressive strength, and thermal control were considered. After applying these criteria, the studies that met all requirements were included in the final analysis. This methodological approach ensures that the discussion and conclusions are grounded in a coherent synthesis of verified experimental evidence across multiple independent investigations.

3. Sustainability in Concrete

Sustainability refers to preserving the ability of ecological functions that enable and improve societal quality of life. Achieving this requires analysing and understanding feedback mechanisms and, more broadly, the dynamic interconnections between ecological and social systems [45]. Sustainability should aim for a win-win solution that delivers environmental benefits to society [46]. Environmental sustainability refers to maintaining a balance in the use of natural resources. It is defined as “…meeting the needs of the present generation without jeopardizing the ability of future generations to meet their own needs” [46]. This concept emphasizes a precautionary approach to activities that impact the environment, aiming to prevent irreversible harm [47]. As cities grow, the impact of development issues on human life and production becomes more evident. In recent decades, various factors have negatively impacted the planet’s sustainable development, notably including the construction industry. To address these challenges and prevent irreversible damage, sustainable construction methods are proposed. The construction industry is the largest global consumer of energy and a major source of greenhouse gas emissions. In 2018, buildings alone accounted for 36% of worldwide use of energy and 39% of CO₂ emissions related to energy [48,49], as shown in Figure 3, with building operations, building materials, and construction accounting for 28% and 11%, respectively, creating a total of 39% of energy-related CO₂ emissions in the building sector. This highlights the urgent need for decarbonization strategies across both operational and embodied carbon sources. Without significant improvements in material efficiency, renewable energy integration, and circular construction practices, emissions from this sector are expected to continue rising in parallel with global urbanization and infrastructure development.

Figure 3. Carbon dioxide emissions in different sectors (the bar chart elaborated based on [50]).

Due to the vast quantities of materials used for cement and concrete production, the combined cement and concrete industries are estimated to contribute approximately 6% to 8% of global man-made CO₂ emissions. This percentage is expected to rise in the coming decades as countries in Asia, Africa, and South America, which are considered “less developed” continue or embark on large-scale industrialization [51]. Table 2 displays the global annual production of selected materials in 2016, of which Concrete is the most widely used material in the world.

Table 2. Global annual production of selected materials in 2016 [51].

Materials	Production
Concrete	30 billion (approx.)
Portland cement	4.6 billion
Steel	1.63 billion
Coal	7.7 billion
Wood	3 billion (approx.)
Food produced for human consumption	4 billion (approx.)
Wheat	730 million
Salt	280 million
Sugar	175 million
Gold	187,200 tonnes throughout all of human history, which would occupy a 21 m3 cube!

The adoption of sustainable concrete systems has garnered significant attention in the global construction engineering community. This growing interest stems from the substantial and rapid rise in carbon emissions and environmental impacts arising from standard concrete production and the broader construction industry. For example, the utilization of supplementary cementitious materials, geopolymer binders, recycled aggregates, and industrial or agricultural waste contributes towards advancing more sustainable concrete solutions [52]. Another strategy to prevent further ecological damage is the application of recycled concrete aggregate in structural concrete [53]. A sustainable concrete structure minimizes societal impact throughout its entire lifecycle. This involves considering both short-term and long-term effects during design. An integrated sustainable design process not only lowers project and operational costs but also requires tools and methods to quantify and compare the environmental impacts of the goods and services involved [54].

Life cycle assessment (LCA) is a systematic tool used to assess the ecological impact of products or processes throughout their full life span. This includes stages such as raw material extraction, manufacturing, usage, and end-of-life (EOL) disposal or recycling. As a result, LCA is commonly referred to as a “cradle-to-grave” approach for assessing the impact on the environment [55]. The overall methodology/framework that researchers have followed for evaluating the LCA model is presented in Figure 4, which is a schematic overview of the Life Cycle Assessment (LCA) framework, structured into its four main phases. It begins with defining the goal and scope, which sets the system boundaries and establishes the functional unit. This is followed by life cycle inventory analysis, where energy and material inputs, as well as emissions and waste outputs, are quantified. Finally, the impact assessment results are interpreted to identify the most influential stages and support evidence-based decision-making.

Figure 4. Overall framework of LCA (the figure elaborated based on [56,57,58]).

Environmental Issues and Carbon Footprint Analysis (CFP)

The global construction industry, a vital driver of economic growth and societal progress, depends extensively on concrete as a core building material [59]. Concrete is widely regarded as a more sustainable building material compared to other building materials, such as steel, as illustrated in Figure 3. However, its extensive consumption has overshadowed this advantage due to substantial CO₂ emissions and the depletion of natural resources. Consequently, the concrete industry bears a critical responsibility in steering global efforts toward achieving net-zero carbon emissions by 2050. This pivotal role is underscored by the industry’s significant contribution to global anthropogenic CO₂ emissions, positioning it as a key player in advancing environmental sustainability [60]. The pie chart in Figure 5 compares the embodied carbon of different building materials, measured in kg CO₂ per kg of material. A clear disparity is observed between steel and concrete. It confirms that reinforcement steel is the dominant contributor to embodied emissions in concrete-based structures. This indicates that material selection strategies aimed at reducing embodied emissions should prioritise the optimisation of steel usage or substitution. However, concrete has the lowest embodied carbon amount, since concrete is used in large quantities, based on Table 2, its total environmental impact can still be considerable.

Figure 5. Embodied carbon (kg CO₂/kg) of common building materials (the pie chart elaborated based on [60]).

Concrete has become the most commonly used construction material, with global production exceeding 10 billion tonnes per year and steadily increasing [61]. Partial substitution of cement or clinker in concrete mixtures reduces environmental impact. According to the International Energy Agency (IEA), lowering the clinker-to-cement ratio from the current 0.65 to 0.60 could cut cumulative CO₂ emissions from cement production by up to 37% by 2050 [62]. Carbon Footprint Analysis is a widely utilized method in environmental impact assessments. It quantifies the total carbon dioxide emissions, both direct and indirect, generated by a particular activity or the cumulative effect associated with a product throughout its entire life cycle [63].

Extensive research and analyses have been conducted to accurately assess the carbon footprint of concrete [64,65,66]. The net emissions for different concrete mix types are calculated by combining emissions from material and processes (ΣE_i) and subtracting emissions reductions (ΣER_i). The net emissions for Control Concrete (natural aggregate) are shown below [64]:

$$\mathrm{N}\mathrm{e}\mathrm{t} \mathrm{E}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{s}={\sum }_i^n{E}_i$$

(1)

If recycled materials (RCA) are used in the mixed concrete design, the emissions from the RCA processing (E_i) should be included, while considering a reduction for landfill avoidance (ER). Consequently, Formula (1) will be modified as follows:

$$\mathrm{N}\mathrm{e}\mathrm{t} \mathrm{E}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{s}=({\sum }_i^n{E}_i)- ({\sum }_i^n{ER}_i)$$

(2)

Another method for carbon footprint analysis is the CML2001 method, which focuses on limiting quantitative modelling to the early stages of the causal chain, thereby reducing the uncertainty of results. One of the most critical datasets was obtained from the GaBi database (Version 10.5). This dataset includes information on the production of conventional raw materials such as cement, sand, gravel, and tap water, as well as recycled construction waste. Using the life cycle assessment (LCA) approach, the carbon footprint (CFP) and carbon reduction potential of Compression Cast Waste Rubber Concrete (CCWRC) were evaluated. The findings indicate that the CFP of CCWRC incorporating conventional coarse aggregates is reduced by 37–50% compared to traditional concrete and by 28–46% compared to uncompressed rubber concrete [65].

Carbon emissions during concrete production primarily result from energy consumption. The carbon emission factor of energy measures the greenhouse gases produced per unit mass of energy consumed and is essential for assessing the environmental effects of different energy sources. The greenhouse gas emissions associated with energy use depend on the processes involved in energy production and its application. These emissions can be modelled and calculated using a specific methodology, which is expressed in the following formula [67]:

$$GH{G}_{ener}= {\sum }_{i=1}^n{E}_i{F}_{GHG,i}$$

(3)

$GH{G}_{ener}$ is the total amount of greenhouse gas (GHG) emissions in the energy production and application processes, expressed in CO₂ equivalents. Here, E_i refers to the fossil energy used for energy and electricity production, which includes the consumption of Class power (a category of energy). $F_{GHG,i}$ denotes the carbon emission factor for energy class i.

Life cycle carbon emissions of ready-mixed concrete products per unit are calculated using the following formula [67]:

$$GH{G}_{manu}=GH{G}_{mine}+GH{G}_{ener}+GH{G}_{tran}$$

(4)

$GH{G}_{manu}$ = the carbon emissions for the production of a unit of ready-mixed concrete.

$GH{G}_{mine}$ = the total emission amount of GHG in the material production process, the CO₂ equivalent.

$GH{G}_{ener}$ = is the total emission amount of GHG in energy production and application process, the CO₂ equivalent.

$GH{G}_{tran}$ = is the total carbon emission amount during transportation of various materials, products, and energy, the CO₂ equivalent.

Circular Ecology has developed an embodied carbon calculator specifically for concrete, which is integrated into the freely available database of embodied carbon for materials: the ICE (Inventory of Carbon and Energy) database. Originally established as a research initiative at the University of Bath, the ICE database was created by Dr. Craig Jones in collaboration with Circular Ecology and Professor Geoffrey Hammond. This resource provides valuable data for assessing the environmental impact of materials [68].

Carbon footprint assessment in sustainable concrete design typically relies on life cycle-based methodologies that account for emissions from material production, energy use, and transportation. Common approaches calculate net emissions as the sum of embodied impacts from constituent materials and processing steps, with deductions applied when recycled aggregates are used to reflect landfill avoidance or material substitution benefits. Tools such as the mentioned above CML2001 method streamline uncertainty by focusing on upstream emissions, while databases like GaBi and the ICE (Inventory of Carbon and Energy) provide standardized emission factors for cement, aggregates, water, and recycled inputs. Energy-related emissions are often quantified separately using carbon emission factors linked to fuel or electricity consumption. Together, these methodologies enable comparative evaluations of conventional and recycled aggregate concretes, with studies showing up to 50% reductions in embodied carbon when alternative materials such as RCA or waste rubber are incorporated.

4. Recycled Materials

4.1. Construction and Demolition Waste

The annual demolition of old buildings generates a significant amount of solid waste, with concrete waste being a primary component of construction and demolition debris. To address this issue, scientists are working to transform waste concrete into recycled concrete, a secondary material suitable for construction, as shown in Figure 6. Although this material is less durable, it provides notable ecological benefits by reducing waste and conserving natural resources. Recycling and reusing concrete waste as aggregate not only minimizes the volume of debris but also promotes sustainable practices in the construction industry [12,69,70].

Figure 6. Material flow cycle for aggregates (the figure elaborated based on [68]).

Construction and demolition waste (C&DW) may be utilized in place of coarse or fine aggregate in concrete, as well as in a finely ground form serving as a filler material. Studies have shown that replacing natural aggregates with construction and demolition waste (C&DW) in concrete requires adjustments to maintain workability. The high porosity and water absorption of C&DW often necessitate an increase in water or superplasticizer dosage. However, research indicates that pre-saturating the C&DW effectively mitigates the loss of workability. Additionally, pre-saturation has been found to enhance resistance to internal steel corrosion, contributing to improved durability in concrete applications [43]. Figure 7 presents the particle shapes of recycled aggregates (a) and natural aggregates (b).

Figure 7. The particle shapes of recycled aggregates and natural aggregates [71].

A review focused on coarse aggregates derived from the reuse of agricultural and industrial wastes (furnace slag, oil palm shell, coconut shell, waste ceramic tiles, glass, expanded polystyrene, lightweight expanded clay aggregate, recycled concrete aggregate, sintered and cold-bonded artificial aggregate). It concluded that, in the fresh state, the workability of concrete containing these aggregates is largely governed by the water absorption characteristics of the alternative aggregates used. In the hardened state, it was observed that the lower crushing strength of alternative coarse aggregates leads to a subsequent reduction in the compressive strength of the concrete [72]. A study investigated the use of ceramic waste (CW) as a partial replacement for coarse aggregates, observing a decreasing trend in slump with increasing CW content. At a replacement level of 50%, the slump value was reduced by approximately 39% compared to the reference concrete. The incorporation of CW in concrete impacts the cohesiveness of the mixture, as the increased water absorption and the shape of CW particles contribute to a reduction in workability [73]. Table 3 provides an analysis of the properties of Natural Aggregates (NA) and Recycled Aggregates (RA) commonly used in concrete production. Key parameters such as material composition, shape, size distribution, environmental impact, availability, cost, durability in concrete, and strength are examined. This comparison highlights the advantages and limitations of each aggregate type, offering insights into their suitability for sustainable construction applications.

Table 3. Characteristics of natural and recycled aggregates [Author, 2025].

Property	Natural Aggregates (NA)	Recycled Aggregates (RA)
Source	Obtained from quarries, rivers, or gravel pits	Sourced from C&D waste (concrete, masonry, etc.)
Size Distribution	Well-graded with controlled particle sizes	More variable, requiring sorting and processing
Material Composition	Homogeneous, typically consists of rock or gravel	Heterogeneous, varying based on the waste source
Shape	Either rounded or angular, offering good workability	Angular and irregular, which may impact workability
Availability	Widely available, though extraction can impact ecosystems	Depends on the availability of local C&D waste
Environmental Impact	High due to extraction and transportation	Lower, supporting recycling and minimizing waste
Strength	High compressive strength	Can be lower, depending on the quality of the recycled material
Durability in Concrete	Excellent, with high resistance to weathering	Variable, with quality control essential for ensuring durability
Cost	Generally higher due to extraction and transportation costs	It can be more cost-effective, particularly when local recycling options are available

4.2. Waste Foundry Sand (WFS)

Waste foundry sand (WFS), also known as spent foundry sand (SFS) or used foundry sand (UFS), is a by-product generated during the manufacturing of castings from ferrous and nonferrous metals. The molding and casting processes in foundries require the use of size-specific, high-quality silica sand. Once the sand can no longer be reused in the foundry, it is removed and classified as waste foundry sand. Depending on the casting binder system, WFS is divided into two distinct types: clay-bonded sand (green sand) and chemically bonded sand [74]. Table 4 shows that WFS production in China is impressively higher than in other countries.

Table 4. WFS production in million metric tons (Mt) [75].

Country	WFS Production
China	48.75
India	11.49
United States of America	11.30
Brazil	3.00
South Africa	1.00
Spain	1.00
Poland	0.70

Clay-bonded sand (green sand) utilizes clay as a binder. In contrast, chemically bonded sand employs chemical binders for its composition. Green sand typically comprises 85–95% silica sand, 4–10% bentonite clay as the binding agent, and 2–10% carbonaceous additives to enhance the surface finish of castings. Additionally, it contains trace amounts of oxides, MgO, K₂O, and TiO₂. On the other hand, chemically bonded sand (chemical foundry sand) consists predominantly of 93–99% silica sand with 1–3% chemical binder [76]. The primary constituent of waste foundry sand (WFS) is silica sand (SS), which is widely used in the foundry industry due to its abundance and cost-effectiveness compared to alternative sand types. To enhance the compaction of SS during the preparation of mould boxes, binders are commonly added to maintain the shape and rigidity of the molds. The selection of binders depends on the size of the cast part and the type of alloy being utilized. Furthermore, the classification of WFS is determined by the type of binder employed in the process [75]. Waste foundry sand (WFS) can be effectively used as a partial replacement for fine aggregates in producing high-quality ready-mixed concrete (RMC). However, the addition of WFS should be less than 20% not to cause adverse effects on mechanical properties, environmental performance, or microstructural integrity. Studies have shown that incorporating WFS as a partial sand replacement can enhance compressive strength, although some findings indicate a reduction in strength. These variations are likely influenced by factors such as the casting process and the specific industrial origin of the WFS, which significantly affect its physical and chemical properties [77]. Research has been conducted to examine the abrasion and strength properties of concrete incorporating Waste Foundry Sand (WFS), where natural sand was replaced with WFS at varying proportions of 0%, 5%, 10%, 15%, and 20% by mass. The mechanical and abrasion properties were evaluated, revealing a strong relationship between abrasion resistance and mechanical performance, regardless of the WFS content or age. The findings identified 15% WFS as the optimal replacement level for concrete production. Another study investigated the strength, durability, and microstructure of concrete incorporating used foundry sand (UFS). The findings revealed that concrete with foundry sand was resistant to the carbonation process and rapid chloride penetration [78].

Table 5 presents the mechanical properties of Waste Foundry Sand (WFS) as reported in various studies. This compilation provides a comprehensive overview of the variability in WFS properties based on different sources, offering important indications of its potential suitability as a sustainable material in concrete production and other construction applications. Table 6 presents the chemical properties of WFS used by various authors in their research studies.

Table 5. Physical properties of Waste Foundry Sand (WFS).

Sources	Type	Density (kg/m3)	Water Absorption (%)	Fineness Modulus	Specific Gravity	Moisture Content (%)
[79]	WFS	1784	5.00	2.32	2.79	(-)
[80]	WFS	1820	0.75	(-)	2.64	0.2
[81]	WFS	(-)	1.40	1.80	2.45	(-)
[82]	WFS	(-)	0.90	2.37	2.36	0.6
[83]	WFS	1638	1.30	1.78	2.61	(-)

Table 6. The chemical properties of Waste Foundry Sand (WFS).

Sources	SiO2	Al2O3	Fe2O3	CaO	MgO	SO3	Na2O	K2O	P2O5	TiO2	Mn2O3	Cr2O3	LOI (%)
[84]	84.90	5.21	3.32	0.58	0.67	0.29	0.50	0.97	0.05	0.19	0.08	0.37	2.87
[85]	81.85	10.41	1.81	1.21	1.97	0.84	0.76	0.49	-	-	-	0.025	6.93
[86]	87.48	4.93	1.31	0.22	0.18	0.07	-	-	-	-	-	-	5.81
[87]	83.93	0.21	0.95	1.03	1.77	0.057	-	-	-	-	-	-	2.19
[88]	87.91	4.70	0.94	0.14	0.30	0.09	0.19	0.25	0.00	0.15	0.02	-	5.15

4.3. Cementitious Materials

Modern developed societies rely on a built environment heavily dependent on cement-based materials, enabling the construction of complex and massive structures at low cost and in virtually any location using water, gravel, sand, and cementitious powder. Over the past 65 years, cement production has increased nearly 34-fold, while the global population has grown less than threefold [89]. Table 7 presents the major countries contributing to worldwide cement production in 2023.

Table 7. Top 5 cement production countries, 2023 [90].

Countries	Production in a Million Metric Tons
China	2100
India	410
Vietnam	110
United States	91
Iran	65

Reducing the amount of cement in concrete can significantly lower the carbon footprint and mitigate environmental impact. With the rise of industrialization, vast quantities of industrial waste are being generated worldwide. The disposal of these waste materials contributes to environmental pollution, highlighting the urgent need for sustainable solutions [91]. Supplementary cementitious materials (SCMs), utilized in the cement industry, generally comprise industrial by-products, natural pozzolans, and processed minerals with hydraulic or pozzolanic characteristics. In their raw form and when mixed with water alone, most SCMs do not exhibit significant hydraulic reactions or cementitious value. However, when finely ground and exposed to alkaline aqueous conditions or calcium hydroxide, they undergo a chemical reaction known as the pozzolanic reaction. This process produces hydration products similar to those formed in Portland cement systems [92]. Extensive research has been conducted on the partial replacement of cement by industrial waste such as fly ash [93], recycled concrete powder (RCP) [94], rice husk ash [95], Ceramic Waste Material [96], waste brick [97], Olive Waste Ash [98].

4.3.1. Fly Ash (FA)

Fly ash (FA) is a prevalent industrial waste generated from the combustion of solid fuels. It is a fine, powdery material primarily consisting of unburned carbon (UC), metal oxides such as silicon (Si), iron (Fe), calcium (Ca), and aluminium (Al), along with various other inorganic compounds [91].

The combustion of coal in power plants generates two sorts of coal ash: bottom ash (BA) and fly ash (FA). These materials are among the most abundant and complex anthropogenic by-products. Fly ash constitutes over 80% of the total coal ash produced, while the remainder is bottom ash. Due to their potential to cause significant environmental harm, such as air, water, and soil pollution, neither BA nor FA can be directly released into the environment. Bottom ash particles are typically collected using water systems at the base of the boiler, whereas fly ash particles are captured from flue gases through electrostatic or mechanical precipitation. Currently, a large portion of fly ash is disposed of in landfills or stored at coal power plants. This practice not only requires extensive land use but also contributes to soil contamination, posing further environmental challenges. According to ASTM C618 [99] and ASTM C618-15 [100], fly ash (FA) is classified as Class F or Class C. Both types must contain more than 50% of SiO₂, Al₂O₃, and Fe₂O₃. Class C fly ash typically has 50–70% of these oxides and more than 18% CaO, while Class F fly ash has over 70% oxides and less than 18% CaO. Class C fly ash, derived from low-rank coals, is rich in calcium and has strong cementitious properties, providing higher early strength and better abrasion resistance in concrete. In contrast, Class F fly ash, produced from higher-rank coals, is mainly pozzolanic, offering better long-term strength and durability. It is suitable for cement replacement in precast and reinforced concrete, with high-volume use further enhancing performance [101]. Fly ash, a by-product of coal combustion in power plants, exhibits natural variability influenced by multiple factors. These include the type of coal, its mineral composition, the degree of coal pulverization, the furnace design, oxidation conditions, and handling and storage practices before use. Furthermore, even within a single plant, the properties of fly ash can vary due to fluctuations in operational load over 24 h. This inconsistency presents a major challenge to the widespread and efficient use of fly ash as a pozzolanic or cementitious material in cement and concrete applications [102]. The chemical properties of fly ash (FA) have been extensively analysed and studied by numerous researchers, as summarized in Table 8.

Table 8. The chemical properties of cementitious materials have been studied by numerous researchers.

Chemical Composition	Cement			FA			RHA			BFS
	[91]	[103]	[104]	[91]	[103]	[104]	[91]	[105]	[106]	[107]	[108]	[109]
CaO	63–68	67.3	63.72	19–25	39.6	12.5	0.5–3.8	1.39	1.31	37.2	47.08	41
SiO2	18–34	19.8	21.38	34–36	30.8	50.15	75–91	74.35	93	34.0	29.13	35.54
Al2O3	3–6	5.1	5.63	16–22	9.9	30.51	0–3.9	1.379	0.35	16.40	20.59	13.65
Fe2O3	1–4	3.1	3.56	6–14	5	2.08	0.1–1.1	1.029	0.23	0.5	1.58	0.39
MgO	0.5–4	0.8	2.15	3–7.8	0.4	0.088	0.2–0.8	1.06	0.41	6.29	1.11	4.11

4.3.2. Rice Husk Ash (RHA)

In 2019, global paddy rice production reached 782 million tons, resulting in approximately 172 million tons of rice husk and 43 million tons of rice husk ash (RHA). These numbers emphasize the potential of utilizing RHA as a partial replacement for cement, supporting environmental protection and combating climate change. By mitigating the demand for cement and minimizing the environmental risks associated with disposing of waste RHA, this approach offers a sustainable solution to mitigate ecological challenges [110]. Rice husk ash (RHA) is typically defined as an agricultural by-product generated from the controlled combustion of rice husk at temperatures below 800 °C. This process yields approximately 25% ash, composed of 85% to 90% amorphous silica and around 5% alumina, giving it strong pozzolanic properties [111]. The quality of rice husk ash (RHA) is linked to its amorphous SiO₂ content, which is affected by factors such as the duration, temperature, and conditions of the thermal treatment process [112,113]. Due to the high silica content in ash, the extraction of silica is highly efficient. This has led to increasing consumption of fine amorphous silica in the production of cement and concrete, particularly for applications in bridges, marine environments, nuclear power plants, and cellulose-cement composites [114]. The incorporation of RHA (Rice Husk Ash) in cement-based materials not only lowers the heat of hydration but also enhances strength and durability. Additionally, it reduces cement costs and offers various environmental advantages [115]. Table 9 shows the physical properties of RHA.

Table 9. The physical properties of RHA.

Property	[116]	[117]	[118]	[106]	[119]
Mean particle size (µm)	7.30	25.0	3.80	-	6.00
Specific gravity (g/cm3)	2.10	2.3	2.06	2.20	2.10
Fineness: passing 45 mm (%)	-	-	99.0	-	-
Specific surface area (m2/g) (Blain)	-	-	36.47	0.24	2.33

4.3.3. Blast Furnace Slag

Blast furnace slag (BFS) is one of the most widely utilized supplementary cementitious materials (SCMs) globally. As a common by-product of iron production, it is mainly composed of silicates and aluminosilicates originating from the iron ore, along with calcium oxide derived from the limestone used in the blast furnace process [107]. On average, approximately 300 kg of slag is produced per ton of pig iron [120]. According to the World Steel Association, global pig iron production reached over 1300 million tons (Mt) in 2022, with China alone contributing 863.8 Mt, as shown in Table 10 [121].

Table 10. Global pig iron production [121].

Regions	Global Pig Iron Production in 2022 from World Steel Association (Mt)
Asia	1085.6
European Union (27)	70.7
Russia & other CIS + Ukraine	60.9
South America	29.7
North America	29.2
Other European	15.8
Oceania	4.3
Africa	2.7
Middle East	2.5

This significant output results in the generation of approximately 259 Mt of blast furnace (BF) slag in China and 390 Mt globally. With mounting environmental concerns and stricter landfill regulations, the steel industry is increasingly focused on developing sustainable methods to fully utilize this slag and transform it into valuable products [119].

5. Mass Concrete Application and Specifications

Mass concrete applies to any large volume of concrete where the dimensions are such that special precautions are needed to manage the heat generated during cement hydration and the resulting changes in volume, to reduce the risk of cracking [122]. The design of mass concrete structures typically emphasizes durability, cost-effectiveness, and thermal control, while strength is usually considered a secondary factor [122,123].

Dams, bridge piers, massive foundations, and retaining walls are the common applications, where the considerable volume of concrete requires careful temperature control to prevent thermal cracking [123].

Figure 8 illustrates that mass concrete is highly beneficial for large-scale projects such as hydraulic structures, foundations, and pavements. An interesting example of its application can be found in Mumbai, India, where the city authorities have adopted mass concrete as the standard material for street pavements. Local engineers have determined that this system performs better and is more durable than asphaltic concrete alternatives under the city’s hot and humid climate conditions.

Figure 8. Application of mass concrete in larger-scale projects [124,125,126,127].

Mass concrete structure is expected to experience significant temperature development, making it essential to monitor and control its thermal behaviour in accordance with established specifications. These specifications set an allowable maximum temperature of 71.1 °C and a maximum temperature differential of 19.4 °C, both of which are critical for maintaining the structural integrity of the concrete. The maximum temperature limit is primarily intended to prevent long-term durability issues, such as delayed ettringite formation, which can cause cracking due to internal expansion, and a reduction in ultimate strength caused by an increase in internal pore size. Determining the exact temperature differential that leads to thermal cracking is challenging, as such cracking often interacts with other complex material properties. Nevertheless, larger temperature differentials increase the likelihood of thermal cracking, since greater internal restraint produces tensile stresses on the surface [128].

The cement hydration reaction is the primary source of temperature-induced stress in concrete, and this stress can be managed by reducing the amount of cement used in construction. However, lowering the cement content can affect the overall strength of the structure, which makes it necessary to incorporate supplementary measures. These include the use of water-reducing agents, the application of blended materials to achieve a balanced mix ratio, and the use of low-heat cement to limit the heat generated during hydration [129]. The heat released during cement hydration is related to the fineness of cement particles, which should be increased to the possible extent without affecting the activity of cement. Aggregate is a crucial material that supports and fills concrete, consisting of loose granular particles that account for approximately 80% to 83% of the total volume of large concrete structures. Therefore, when preparing mass concrete, it is essential to carefully select high-quality aggregate. The performance of mass concrete can be enhanced by incorporating various admixtures, such as water-reducing agents, retarding agents, and expansion agents. This approach can effectively reduce the occurrence of cracks in large-volume concrete. Typically, mass concrete admixtures consist of a micro-expansion agent combined with high-efficiency retarding and water-reducing agents. These admixtures increase the setting time, decrease cement and water consumption, slow down the peak temperature of the concrete, reduce thermal tensile stress, improve water resistance, and mitigate expansion forces [130]. Best Practices for Mass Concrete Mix Design are shown in Figure 9.

Figure 9. Challenges and Solutions in Mass Concrete [Author, 2025].

Figure 9 presents the common challenges associated with mass concrete, along with corresponding solutions, as documented in the literature [131,132,133,134]. The best concrete for a massive structure is the one that possesses properties that minimize thermal and structural stresses during hardening. Such concrete should evolve only a small amount of heat during cement hydration to ensure a low hardening temperature, while having high thermal conductivity to allow rapid dissipation of heat from the structure. A high heat capacity is also desirable, as it contributes to maintaining a lower temperature rise during hardening. Additionally, the concrete should have a small coefficient of thermal expansion to reduce deformation, along with minimal shrinkage to lower early-age deformation. A low modulus of elasticity combined with high creep is advantageous because it helps decrease the stresses that develop within the structure, while high tensile strength enhances the resistance against early-age cracking. Together, these properties ensure durability, stability, and reduced risk of thermal cracking in massive concrete structures [132]. Effective temperature control is vital for ensuring compliance with performance and durability specifications, as excessive thermal gradients can lead to cracking, reduced strength, and long-term durability issues. The best practices in temperature control in mass concrete structures rely on a combination of low-heat mix design, controlled placement conditions, and proper curing conditions. The application of blended cements, pre-cooled materials, insulation of exposed surfaces, as well as embedded cooling pipes is common. Temperature monitoring is typically carried out using thermocouples positioned at the core and near the surface, with continuous data logging to track thermal gradients. To prevent cracking, specifications often limit the maximum core temperature to 65–70 °C, and the difference in temperature between the core and surface of the mass structure should be less than 20 °C, supported by predefined contingency actions if thresholds are exceeded. The projects maintain concrete strength, minimize cracking, and extend the service life of mass structures by implementing these practices, thus directly supporting compliance with both performance and durability requirements.

6. Discussion

6.1. Mix Compositions

The selection of materials for mass concrete is primarily governed by the properties of the cement, the type and quantity of mineral additives, and the water-to-binder ratio. Since the consistency of a concrete mix depends on its composition, increasing the binder content generally leads to reduced workability [26,30]. In this review, the investigated cementitious materials, drawn from various studies [26,30,31,132], include Portland cement, Portland clinker, GGBS, fly ash, and minor constituents. Mixes were designed by partially replacing cement with these admixtures a mass-for-mass basis, while maintaining a constant water-to-binder ratio of 0.5. For specimens 10 to 14, a superplasticizer was also incorporated.

The aggregates used comprised four types: natural coarse aggregate (NCA), natural fine aggregate (NFA), recycled coarse aggregate (RCA), and recycled fine aggregate (RFA). Natural gravel and river sand were used in specimens 1 to 3, while gravel served as the coarse aggregate in specimens 4 to 14. Recycled coarse and fine aggregates were in types only in specimen 3. The fine-to-coarse aggregate ratio was set at 0.75 for specimens 1 to 3, and 0.43 for the remaining specimens. Detailed mix proportions for the mass concrete are provided in Table 11 and Table 12.

Table 11. Composition of different cementitious materials in the concrete mix [26,30,31,132].

Type	Cement	Cementitious Materials				Water	W/CM
		Portland Clinker	GGBFS	Fly Ash	Minor Constituents
Specimen 1	360	0	0	0	0	180	0.5
Specimen 2	90	0	270	0	0	180	0.5
Specimen 3	90	0	270	0	0	180	0.5
Specimen 4	0	287.1	0	0	12.9	150	0.5
Specimen 5	0	204.9	81.3	0	13.8	150	0.5
Specimen 6	0	197.1	0	89.7	13.2	150	0.5
Specimen 7	0	123.3	176.7	0	0	150	0.5
Specimen 8	0	186.6	54.6	58.8	0	150	0.5
Specimen 9	0	96.9	103.2	99.9	0	150	0.5
Specimen 10	0	0	210	90	0	150	0.5
Specimen 11	0	0	180	120	0	150	0.5
Specimen 12	0	0	150	150	0	150	0.5
Specimen 13	0	0	120	180	0	150	0.5
Specimen 14	0	0	90	210	0	150	0.5

Table 12. Composition of different aggregates in the concrete mix [26,30,31,132].

Type	Fine Aggregate	Recycled Fine Aggregate	Coarse Aggregate	Recycled Coarse Aggregate	Admixture Sika Visco Crete V600, [kg]	Aggregate Fine/Coarse
Specimen 1	775	0	1027	0	0	0.75
Specimen 2	775	0	1027	0	0	0.75
Specimen 3	0	755	0	1000	0	0.75
Specimen 4	583	0	1360	0	0	0.43
Specimen 5	583	0	1360	0	0	0.43
Specimen 6	583	0	1360	0	0	0.43
Specimen 7	583	0	1360	0	0	0.43
Specimen 8	583	0	1360	0	0	0.43
Specimen 9	583	0	1360	0	0	0.43
Specimen 10	585	0	1365	0	3	0.43
Specimen 11	585	0	1365	0	3	0.43
Specimen 12	585	0	1365	0	3	0.43
Specimen 13	585	0	1365	0	3	0.43
Specimen 14	585	0	1365	0	3	0.43

The composition of a mass concrete mix directly influences its consistency, thermal behaviour, and mechanical properties. Cement type, mineral additives, and water-to-binder ratio determine workability and early-age hydration, which influence the heat evolution and strength development. Aggregate type and grading have a great impact on the concrete mix’s density, thermal conductivity, and dimensional stability. A clear understanding of these material effects enables the design of mixes that reliably achieve the required strength and long-term durability.

From the selected literature, detailed information was extracted regarding binder type and content, mineral admixtures, water-to-binder ratios, aggregate type and gradation, and compressive strength values at various curing ages (7, 28, and 90 days). To ensure consistency, all numerical data were normalized to standard units.

6.2. Results

6.2.1. Mechanical Performance

The bar chart in Figure 10 illustrates the compressive strength results (in MPa) at 7, 28, and 90 days. Specimens 4 to 9 achieved the highest compressive strengths, especially at 90 days (up to 60 MPa); specimens 1 to 3 showed relatively low strength values, particularly at 7 days. Specimens 10 to 14 showed moderate strength levels (~24–27 MPa at 90 days and ~19–23 MPa at 28 days). This study demonstrates the significant impact of mixture composition on the compressive strength of concrete over time. The variations in compressive strength are largely influenced by the binder composition. Specimen 1, which contained 360 kg of Portland cement without any supplementary materials, exhibited an early strength of approximately 12 MPa at 7 days. In comparison to Specimen 1, Specimens 2 and 3 exhibited lower early strength due to slower hydration. However, with extended curing, compressive strength increased significantly as a result of the continued formation of C–S–H gel from GGBFS. Specimen 4, containing 287.1 kg of Portland clinker, achieved a significantly higher early strength of 44.8 MPa, emphasizing the critical role of clinker in early strength development. Significantly lower early-age compressive strength is observed in concretes made of non-clinker constituents. In contrast, specimens with supplementary cementitious materials like Ground Granulated Blast Furnace Slag (GGBFS) and Fly Ash, such as specimen 7 (176.7 kg GGBFS), showed lower early strength but significant long-term gains (22 MPa at 7 days, 44 MPa at 28 days, and 56 MPa at 90 days), emphasizing the role of these materials in enhancing durability and ultimate strength through pozzolanic reactions. Increasing compressive strength during curing is observed in all the considered recipes of concrete. For specimens 10 to 14, it can be observed that compressive strength increases when fly ash is added to the binder. This indicates a greater degree of conversion in binder components and confirms the role of fly ash in activating the reaction of blast furnace slag binding and hardening. This tendency was observed when studying slag and fly ash pastes [135]. The strength tests of the specimens 2 and 3, prepared with the use of the same type of binder but different types of fine and coarse aggregate (natural vs. recycled), revealed the potential of RCA/RFA in mass concrete. The compressive strength of specimens with RCA and RFA after 7 and 28 days of curing is higher by 30% (specimen 2: 7 MPa and specimen 3: 10 MPa) and 12%, respectively (specimen 2: 15 MPa, specimen 3: 17 MPa). This test confirms that the use of RCA/RFA in mass concrete is promising. Replacing the natural aggregates in mass concrete with recycled ones, derived from the construction and demolition debris, offers considerable environmental benefits, primarily through the reduction of natural resource consumption and landfill waste. Overall, the study underscores the importance of balancing cement content, supplementary materials, recycled aggregates, and admixtures to optimize concrete mixtures for specific applications, ensuring both early strength and long-term performance while promoting sustainability. Future research could further explore the combined effects of these components on durability and environmental impact.

Figure 10. Compressive strength for 7, 28, and 90 days [26,30,31,132].

6.2.2. Thermal Performance

The hardening of concrete is strongly influenced by the heat generated during binder hydration. When supplementary mineral materials are used in place of a portion of the base binder, the maximum hardening temperature of concrete is significantly reduced, as shown in Table 13. These materials slow down the hydration reactions, resulting in both a lower peak temperature and a delayed time at which that peak is reached. This effect is particularly noticeable when materials with low early reactivity, such as certain industrial by-products, are incorporated. The results presented can be generalized to full-scale structures, as the simulation shown in one article [30] revealed the changes in the temperature within a massive block of 3 × 3 × 3 m. However, in situ tests of the presented concrete compositions (Table 13) would be a valuable source of information.

Table 13. Peak temperature during hardening of different mass concrete [26,30,31,132].

Type	Cement Type	Peak Time (h)	Tmax (°C)
Specimen 1	High OPC	~50	28.7
Specimen 2	OPC + GGBFS	~100	24.5
Specimen 3	OPC + GGBFS	<100	26.0
Specimen 4	CEM I 42.5R	~36	~55
Specimen 5	CEM II/B-S 32.5R	~36	~45
Specimen 6	CEM II/B-V 32.5R	~36	~42
Specimen 7	CEM III/A 32,5N-LH/HSR/NA	~60	~40
Specimen 8	CEM V/A (S-V) 32.5R-LH/HSR/NA	~48	~38
Specimen 9	VLH V/B (S-V) 22.5	~48	~35
Specimen 10	Fly Ash+ GGBFS	~12	24.1
Specimen 11	Fly Ash+ GGBFS	~27	24.5
Specimen 12	Fly Ash+ GGBFS	~21	25.5
Specimen 13	Fly Ash+ GGBFS	~31	24.9
Specimen 14	Fly Ash+ GGBFS	~26–30	26

The reduction in peak temperature compared to conventional mixtures can be substantial, in some cases exceeding 20 °C. Alongside this reduction, the onset of maximum temperature may occur many hours later, which further decreases the risk of rapid internal heating. The risk of early crack formation can also be mitigated by the appropriate selection of aggregate, with specific attention to its thermal properties, i.e., thermal conductivity, heat capacity, and thermal expansion coefficient.

In mass concrete structures, where temperature gradients between the surface and the core are critical, these effects are highly beneficial. Slower and lower heat release reduces the difference between internal and external temperatures, thereby minimizing the risk of thermal cracking. Experimental results confirm that mixtures with higher contents of slowly reacting mineral components reach their temperature peak later and at a lower value than mixtures rich in conventional binder.

Overall, controlling the heat of hydration through partial replacement of the binder with mineral additions is an effective way to improve the thermal stability of concrete, particularly in large-volume applications such as dams and tunnels. The delayed and reduced heat evolution helps mitigate internal stresses, lowers the likelihood of cracking, and enhances the long-term durability of concrete structures.

The growing availability of carbon footprint assessment tools and standardized emission databases such as GaBi and ICE suggests a clear pathway toward the future certification of green concrete products. As life cycle assessment methodologies become common and widely used, the rate of substitution the raw materials with recycled ones can be quantified, and concrete mixes incorporating industrial by-products or recycled aggregates can be accurately described. This could be the first step towards certification regulations that recognize both embodied carbon reduction and material circularity.

The integration of ESG (Environmental, Social, and Governance) Key Performance Indicators standards into the concrete industry is increasing. The core environmental KPIs in the concrete industry are water and energy consumption, as well as the carbon footprint of concrete and recycled material content. Social indicators such as worker safety and supply chain transparency are being formalized. In the EU, the KPIs are mandatory under sustainability reporting regulations, directing the concrete sector toward unified ESG dashboards that align material production with broader corporate accountability standards.

7. Conclusions

For advancing the performance of mass concrete, the strategic balance of cement, clinker, and supplementary cementitious materials (SCMs) such as fly ash and ground granulated blast furnace slag (GGBFS) is essential. While clinker ensures early-age strength, SCMs enhance long-term strength and durability through pozzolanic activity and help control temperature rise during the hydration process. The careful selection of aggregates, considering their thermal and expansion properties, further improves structural stability under thermal gradients. To achieve the best results, mass concrete design should prioritize partial cement replacement with SCMs, the use of chemical admixtures for consistency, and well-graded natural or recycled aggregates. This approach not only ensures early and long-term strength but also improves thermal stability, extends service life, and reduces the environmental footprint of construction. By integrating these strategies, engineers can deliver sustainable, durable, and resilient mass concrete solutions suited for critical infrastructure such as dams, bridges, and tunnels.

Placements of large concrete structures require meticulous control of temperature rise due to the heat of hydration. Future research should focus on multi-by-product SCM systems to optimize performance across different service conditions. Studies on durability in aggressive environments, including sulphate exposure, chloride ingress, and freeze–thaw cycles, are particularly needed to ensure long-term resilience. Moreover, large-scale pilot and field studies are recommended to validate laboratory findings under real construction conditions.

In addition, the exploration of nanomaterials offers promising opportunities to enhance hydration, permeability, and fatigue resistance. The relationship between heat of hydration and pozzolanic activity should also be examined in greater detail, as excessive thermal gradients can lead to cracking and durability issues. Finally, advanced characterization methods such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) are recommended to evaluate the microstructural development of optimized mixtures.