Search Results (312)

Fluidized solidified soil (FSS) has emerged as a promising material for marine pile scour remediation, yet its limited construction window and vulnerability to hydraulic erosion before sufficient curing constrain its broader application. This study systematically evaluates FSS formulations based on dredged sediment, cement partially replaced by silica fume (i.e., 0%, 4%, 8%, and 12%), and quicklime activation under three water–solid ratios (WSR, i.e., 0.525, 0.55, and 0.575). Experimental assessments included flowability tests, unconfined compressive strength, direct shear tests, and microstructural analysis via XRD and SEM. The results indicate that SF substitution significantly mitigates flowability loss during the 90–120 min interval, thereby extending the operational period. Moreover, the greatest enhancement in mechanical performance was achieved at an 8% SF replacement: at WSR = 0.55, the 3-day UCS increased by 22.78%, while the 7-day cohesion and internal friction angle rose by 13.97% and 2.59%, respectively. Microscopic analyses also confirmed that SF’s pozzolanic reaction generated additional C-S-H gel. However, the SF substitution exhibits a pronounced threshold effect, with levels above 8% introducing unreacted particles that disrupt the cementitious network. These results underscore the critical balance between flowability and early-age strength for stable marine pile scour repair, with WSR = 0.525 and 8% SF substitution identified as the optimal mix. Full article

Additive manufacturing (AM) has brought significant breakthroughs to the construction sector, such as the ability to fabricate complex geometries, enhance efficiency, and reduce both material usage and construction waste. However, several challenges must still be addressed to fully transition from conventional construction practices to innovative and sustainable green alternatives. This study investigates the use of non-cementitious traditional mixtures for green construction applications through 3D printing using Liquid Deposition Modeling (LDM) technology. To explore the development of mixtures with enhanced physical and mechanical properties, natural pine and cypress wood shavings were added in varying proportions (1%, 3%, and 5%) as sustainable additives. The aim of this study is twofold: first, to demonstrate the printability of these eco-friendly mortars that can be used for conservation purposes and overcome the challenges of incorporating bio-products in 3D printing; and second, to develop sustainable composites that align with the objectives of the European Green Deal, offering low-emission construction solutions. The proposed mortars use hydrated lime and natural pozzolan as binders, river sand as an aggregate, and a polycarboxylate superplasticizer. While most studies with bio-products focus on traditional methods, this research provides proof of concept for their use in 3D printing. The study results indicate that, at low percentages, both additives had minimal effect on the physical and mechanical properties of the tested mortars, whereas higher percentages led to progressively more significant deterioration. Additionally, compared to molded specimens, the 3D-printed mortars exhibited slightly reduced mechanical strength and increased porosity, attributable to insufficient compaction during the printing process. Full article

The pursuit of sustainable alternatives to portland cement has become a global imperative within the construction sector, driven by the need to reduce carbon dioxide emissions and energy consumption. Among the promising alternatives, agricultural ashes have garnered attention for their potential as alternative supplementary cementitious materials (ASCMs), owing to their inherent pozzolanic properties when appropriately processed. However, the availability and utilization of these ashes have predominantly been concentrated in tropical and subtropical regions, where such biomass is more abundant. This review offers a comprehensive bibliometric analysis to identify and assess agricultural ashes (specifically switchgrass, barley, sunflower, and oat husks) that are cultivated in temperate and cold climates and exhibit potential for SCM application. The analysis aims to bridge the knowledge gap by systematically mapping the existing research landscape and highlighting underexplored resources suitable for cold-region implementation. Key processing parameters, including incineration temperature, retention duration, and post-combustion grinding techniques, are critically examined for their influence on the resulting ash’s physicochemical characteristics and pozzolanic reactivity. In addition, the effect on fresh, hardened, and durability properties was evaluated. Findings reveal that several crops grown in colder regions may produce ashes rich in reactive silica, thereby qualifying them as viable ASCM candidates and bioenergy sources. Notably, the ashes derived from switchgrass, barley, oats, and sunflowers demonstrate significant reactive silica content, reinforcing their potential in sustainable construction practices. Hence, this study underscores the multifaceted benefits of contributing to the decarbonization of the cement industry and circular economy, while addressing environmental challenges associated with biomass waste disposal and uncontrolled open-air combustion. Full article

This research paper provides new insights into the impact of accelerated mineralization of alkaline waste materials on the physical and mechanical behavior of low-carbon cement-based mortars. Standardized eco-cement mortars were prepared by replacing Portland cement with 7% and 20% proportions of three alkaline waste materials (white ladle furnace slag, biomass ash, and fine concrete waste fraction) that had been previously carbonated in a static reactor at predefined humidity and CO₂ concentration. The mortars’ physical (total/capillary water absorption, electrical resistivity) and mechanical properties (compressive strength up to 90 d of curing) were analyzed, and their microstructures were examined using mercury intrusion porosimetry and computed tomography. The results reveal that carbonated waste materials generate a greater heat of hydration and have a lower total and capillary water absorption capacity, while the electrical resistivity and compressive strength tests generally indicate that they behave similarly to mortars not containing carbonated minerals. Mercury intrusion porosimetry (microporosity) indicates an increase in total porosity, with no clear refinement versus non-carbonated materials, while computed tomography (macroporosity) reveals a refinement of the pore structure with a significant reduction in the number of larger pores (>0.09 mm³) and intermediate pores (0.001–0.09 mm³) when carbonated residues are incorporated that varies depending on waste material. The construction and demolition waste (CCDW-C) introduced the best physical and mechanical behavior. These studies confirm the possibility of recycling carbonated waste materials as low-carbon supplementary cementitious materials (SCMs). Full article

The steep incline in the rising need for sustainable construction materials has marked the emerging trend of comprehensive research on utilizing waste glass powder (WGP) as a partial substitute for fine aggregates, such as cement, and coarse aggregates in concrete preparation. This review thoroughly examines WGP-incorporated concrete in terms of its mechanical and durability properties. It explores compressive, tensile, and flexural strength, as well as its resistance to freeze–thaw cycles, sulfate attack, and chloride ion penetration. The characteristic microstructure densification, strength development, and durability performance can be attributed to the pozzolanic activity of WGP that forms additional calcium silicate hydrate (C-S-H). The review also highlights the optimal replacement levels of WGP to balance mechanical performance and long-term stability while addressing potential challenges, such as alkali–silica reaction (ASR) and reduced workability at high replacement ratios. By consolidating recent research findings, this study highlights the feasibility of WGP as a sustainable supplementary cementitious material (SCM), promoting eco-friendly construction while mitigating environmental concerns associated with glass waste disposal. Full article

This study investigates the use of Glass Fine Aggregate (GFA) and Fly Ash (FA) in mortar for Alkali–Silica Reaction (ASR) mitigation through a multidimensional evaluation. GFA was used to replace river sand in 20% increments up to 100%, while FA replaced cement at 10%, 20%, and 30%. Three GFA size ranges were considered: <1.18 mm, 1.18–4.75 mm, and a combined fraction of <4.75 mm. At 100% replacement, <1.18 mm GFA reduced ASR expansion to 0.07%, compared to 0.2% for <4.75 mm and 0.46% for 1.18–4.75 mm GFA. It also improved long-term strength by 25% from 28 days to 6 months due to pozzolanic activity. However, refining GFA to below 1.18 mm increased environmental impacts and resulted in a 4.2% increase in energy demand due to the additional drying process. Incorporating 10% FA reduced ASR expansion to 0.044%, had no significant effect on strength, and decreased key environmental burdens such as toxicity by up to 18.2%. These findings indicate that FA utilisation offers greater benefits for ASR mitigation and environmental sustainability than further refining GFA size. Therefore, combining <4.75 mm GFA with 10% FA is identified as the optimal strategy for producing durable and sustainable mortar with recycled waste glass. Full article

This study investigates the combined use of waste glass cullet (WGC) and snail shell powder (SSP) as a sustainable binary cementitious system to enhance the mechanical performance and durability of concrete, particularly for rigid pavement applications. Nine concrete mixes were formulated: a control mix, four mixes with 5%, 10%, 15%, and 20% WGC as partial cement replacement, and four corresponding mixes with 1% SSP addition. Slump, compressive strength, and flexural strength were evaluated at various curing ages. Results showed that while WGC reduced workability due to its angular morphology (slump decreased from 30 mm to 20 mm at 20% WGC), the inclusion of SSP slightly mitigated this reduction (21 mm at 20% WGC + 1% SSP). At 28 days, compressive strength increased from 40.0 MPa (control) to 45.0 MPa with 20% WGC and further to 48.0 MPa with the addition of SSP. Flexural strength also improved from 7.0 MPa (control) to 7.8 MPa with both WGC and SSP. These improvements were statistically significant (p < 0.05) and supported by correlation analysis, which revealed a strong inverse relationship between WGC content and slump (r = −0.97) and strong positive correlations between early and later-age strength. Microstructural analyses (SEM/EDX) confirmed enhanced matrix densification and pozzolanic activity. The findings demonstrate that up to 20% WGC with 1% SSP not only enhances strength development but also provides a viable, low-cost, and eco-friendly alternative for producing durable, load-bearing, and sustainable concrete for rigid pavements and infrastructure applications. This approach supports circular economic principles by valorizing industrial and biogenic waste streams in civil construction. Full article

This study investigates the effects of the combined addition of MgO expansive agent (MEA) and rice husk ash (RHA) on the performance of concrete. Results show that MEA absorbs water and competes with superplasticizers for adsorption, reducing early-age fluidity. In the later stages, its reaction with RHA generates M-S-H gel, accelerating slump loss. At early ages (up to 7 days), due to the slow hydration of MEA and partial replacement of cement, fewer hydration products are formed. Additionally, the pozzolanic reaction of RHA has not yet developed, resulting in the low early strength of concrete. In the later stages, Mg(OH)₂ fills pores and enhances compactness, while the pozzolanic reaction of RHA further optimizes the pore structure. The internal curing effect also provides the moisture needed for continued MEA hydration, significantly improving later-age strength. Moreover, in the post-cast strip of a tall building, the internal curing effect of RHA ensures the effective shrinkage compensation by MEA under low water-to-cement ratio conditions. The restraint provided by reinforcement enhances the pore-filling effect of Mg(OH)₂, improving concrete compactness and crack resistance, ultimately boosting long-term strength and durability. Full article

The alkali–silica reaction (ASR) is a critical concern for concrete durability, yet its assessment remains challenging and directly impacts mixture design decisions. This review shows that the inconsistencies are more prevalent in mitigation evaluations compared to aggregate reactivity assessments, mainly due to the chemical variations in supplementary cementitious materials (SCMs). A validated framework is suggested to determine the optimal SCM replacement levels for ASR mitigation based on extensive field data, offering direct guidance for mix design decisions involving potentially reactive aggregates. The combination of the accelerated mortar bar test (AMBT) and the miniature concrete prism test (MCPT) is shown to be a reliable alternative for the concrete prism test (CPT) in aggregate reactivity. Also, their extended versions, AMBT (28-day) and MCPT (84-day), can be applied for SCMs mitigation evaluation. Given the slower reactivity of SCMs compared to ordinary Portland cement (OPC), the importance of incorporating indirect test methods, such as the modified R3 test and bulk resistivity is underscored. In addition, emerging sustainability shifts further complicate ASR assessment, including the adoption of Portland limestone cement (PLC), the use of seawater in concrete, and the declining availability of fly ash (FA) and slag. These changes call for updated ASR testing specifications and increased research into natural pozzolans (NPs) as promising SCMs for future ASR mitigation. Full article

This study investigates the effects of supplementary cementitious materials (SCMs) on the material performance of foamed concrete containing lightweight coarse aggregates, namely hydrophobically modified expanded perlite (EP). The EP aggregates were treated with a sodium methyl silicate solution to impart water-repellent properties prior to being incorporated into the foamed concrete mixtures. Ordinary Portland cement (OPC) was partially replaced with various SCMs, namely, silica fume (SF), mineral powder (MP), and metakaolin (MK) at substitution levels of 3%, 6%, and 9%. Key indicators to evaluate the material performance of foamed concrete included 28-day uniaxial compressive strength, thermal conductivity, mass loss rate under thermal cycling, volumetric water absorption, and shrinkage. The results noted that all three SCMs improved the uniaxial compressive strength of foamed concrete, with MP achieving the greatest improvement, approximately 97% at the 9% replacement level. Thermal conductivity increased slightly with the addition of SF or MP but decreased with MK, highlighting the superior insulation capability of MK. Both SF and MK reduced the mass loss rate under thermal cycling, with SF exhibiting the highest thermal stability. Furthermore, MK was most effective in minimizing water absorption and shrinkage, attributed to its high pozzolanic reactivity and the resulting refinement of the microstructures. Full article

Fiber–cement composites have been increasingly studied for sustainable construction applications, but durability issues—particularly fiber degradation in alkaline environments—remain a challenge. This study aimed to evaluate the individual and combined effects of furfurylated sisal fibers and nanoclay additions on the physical and mechanical performance of autoclaved fiber–cement composites, seeking to enhance fiber durability and matrix compatibility. All the composites were formulated with CPV-ARI cement and partially replaced with agricultural limestone to reduce the environmental impact and production costs. Sisal fibers (2 wt.%) were chemically modified using furfuryl alcohol, and nanoclays—both hydrophilic and surface-functionalized—were incorporated at 1% and 5% of cement weight. The composites were characterized for physical properties (density, water absorption, and apparent porosity) and mechanical performance (flexural and compressive strength, toughness, and modulus). Furfurylation significantly improved fiber–matrix interaction, leading to higher flexural strength and up to 100% gain in toughness. Nanoclay additions reduced porosity and increased stiffness, particularly at 5%, though excessive content showed diminishing returns. The combination of furfurylated fibers and functionalized nanoclay provided the best results in maintaining a compact microstructure, reducing water absorption, and improving mechanical resilience. Optical microscopy confirmed improved fiber dispersion and interfacial bonding in composites containing furfurylated fibers and functionalized nanoclay. These findings highlight the effectiveness of integrating surface-treated natural fibers with pozzolanic additives to enhance the performance and longevity of fiber–cement composites. Full article

A structure of composite cement with 15 wt.% thermally activated clay shales has been developed. The phase composition and properties of aluminosilicate rocks of the Kazakhstan deposits—Mynaral and Kuyuk—have been studied. It has been shown that aluminosilicates are related to clay shales by their composition. The regularities of thermal activation processes of aluminosilicates have been established, and it has been shown that pozzolanic activity increases for all compositions with an increase in the heat treatment temperature from 700 to 900 °C. The clay shale of the Mynaral deposit is characterized by the highest activity. The physicomechanical properties of the obtained composite cements–including Portland cement clinker, gypsum, and thermally activated clay shale—have been studied. It has been shown that when replacing up to 15 wt.% Portland cement clinker with thermally activated clay shales, there is no decrease in the strength properties of the composite cement. The obtained results allow us to consider heat-treated clay shales as active mineral additives. Full article

Unprocessed glass waste is commonly disposed of in landfills, posing a significant environmental threat worldwide due to its non-biodegradable nature and long decomposition period. The volume of this waste continues to increase annually, driven by increasing consumption of electronic and household devices, as well as the growing popularity and end-of-life disposal of solar panels and other glass products. Therefore, to promote the development of the circular economy and the principles of sustainability, it is necessary to address the problem of reusing this waste. This review article examines the chemical and physical properties of various types of glass waste, including window glass, bottles, solar panels, and glass recovered from discarded electronic and household appliances. It was determined that the most promising and applicable reuse, which does not require high energy consumption, could be in the manufacture of concrete, which is the most developed construction material worldwide. Glass waste can be incorporated into concrete in three different particle sizes according to their function: (a) cement-sized particles, used as a partial binder replacement; (b) sand-sized particles, replacing fine aggregate; and (c) coarse aggregate-sized particles, substituting natural coarse aggregate either partially or fully. The article analyses the impact of glass waste on the properties of concrete or binder, presents controversial results, and provides recommendations for future research. In addition, the advantages and challenges of incorporating glass waste in ceramics and asphalt concrete are highlighted. Full article

This research focuses on the impact of a pozzolanic additive (zeolite) on the durability properties of concrete and the evaluation of the surface finish of the final product (concrete). Durability is one of the key characteristics of concrete that ensures the performance of concrete structures, landscaping elements, and products over their lifetime and beyond. To reduce CO₂ emissions, replacing part of traditional cement with pozzolanic additives is necessary. We tested concrete mixes in which up to 20% of cement was replaced with a pozzolanic additive. Concrete flow and entrained air content were measured. The following properties of hardened modified concrete were determined: density, ultrasonic pulse velocity, water absorption, freeze–thaw resistance, and mechanical properties after 7 and 28 days of curing. The compressive strength values were normalised and expressed in MPa/g to obtain a deeper insight into the effect of a pozzolanic additive on the mechanical properties of concrete. The test results showed that the pozzolanic additive selected for testing reduced the flowability, density, and ultrasonic pulse velocity; increased entrained air content; and reduced the porosity of concrete. The compressive strength results at 28 days (normalised and expressed in MPa/g) showed that all specimens modified with up to 20% zeolite had a higher compressive strength than that of the reference specimen (from 0.0138 to 0.0164). Freeze–thaw resistance results showed that 15% was the optimum content of zeolite additive that could replace cement in the mix to obtain concrete with appropriate durability properties. Concrete surface finish evaluation tests showed that 15% of the pozzolanic additive is recommended to obtain a good-quality surface finish of exposed concrete. Full article

With the increasing demand for lithium resources and the enhancement of global environmental awareness, how to efficiently and environmentally develop clay-type lithium resources is of great strategic significance for future development. Clay-type lithium slag (LS) is a byproduct resulting from the extraction of lithium from clay-type lithium ores. Its primary chemical constituents include SiO₂ and Al₂O₃, and it exhibits potential pozzolanic properties. Clay-type lithium ore is of low grade, so a large amount of clay-type LS is produced during its production. In this study, calcined clay-type LS, limestone powder (LP), and cement clinker were used as the main raw materials to prepare low-carbon LC³ cementitious materials. The study focused on the effect of clay-type LS and LP on the new mixing properties, mechanical properties, hydration kinetics, and microstructure formation and transformation of the cementitious materials. The findings revealed that incorporating clay-type LS and LP significantly raised the standard consistency water demand of cement and reduced the setting time of the binding material. While clay-type LS and LP initially weakened the mechanical performance of the cement mortar, it enhanced these properties in the later stages. The compressive strength of LC-10 and LC-20 at 180 days exceeded that of the reference by 3.7% and 1.1%, respectively. In addition, the number of micropores between 3 and 20 nm in LC³ cement increased significantly. It showed that the addition of clay-type LS and LP could optimize the pore structure to some extent. According to research, the optimal content of clay-type LS and LP should not exceed 30%. This method not only consumes the solid waste of clay-type LS, but also facilitates the green and low-carbon transformation of the cement industry. Full article