Search Results (477)

Portland cement is widely used in construction, but it contributes significantly to global CO₂ emissions. This study evaluates the potential use of construction and demolition waste (CDW) and marble powder (MP) as supplementary cementitious materials, in line with circular economy goals. Both wastes were ground finer than cement and characterised chemically and physically. Binary and ternary blends with 5% and 10% replacement were tested in pastes and mortars for fresh properties, mechanical performance, and durability. Setting time, soundness, and workability remained within standard limits. Compressive strength decreased moderately, with 28-day activity indices between 82 and 88%, confirming the low reactivity of the supplementary cementitious materials. Sorptivity decreased in all mixes, and chloride resistance improved in the 10CDW and 10MP blends. However, the ternary mix showed increased chloride migration. Carbonation depth increased in all mixes, indicating the need for protective measures in carbonation-prone environments. Replacing 10% of cement with CDW or MP can avoid 70–80 kg of CO₂ per tonne of binder and reduce landfill waste. These materials can be used as low-carbon fillers in cement-based systems, provided that their durability limitations are considered in design. Full article

The UPV technique has been widely employed to predict the hardened properties of Portland cement mixtures. This article assesses the hardened properties of alkali-activated blast furnace slag mortars by comparing UPV measurements with compressive strength and dry density and calculating the dynamic modulus of elasticity from UPV results. The mixtures were prepared varying the type of activator (sodium metasilicate and sodium silicate), the content of Na₂O in the activators (3.0, 4.5, 6.0, and 7.5%), and the water/binder ratio. The results showed that exponential models showed medium and high determination coefficients (R²), which explained the correlation between UPV and hardened properties. It was observed a limitation on the measurements of UPV, which did not surpass 4.4 km/s, which made it difficult to predict compressive strength value above 50 MPa. The dynamic modulus of elasticity calculated from UPV showed reliable results, even varying the Poisson’s coefficient between 0.15 and 0.25. Lastly, it was also observed that a correlation between the content of C-S-H and UPV suggested that this technique can also be used to predict the evolution of the hydration products in alkali-activated slag mixtures. Full article

Basic oxygen furnace slag (BOFS) is one of the major by-products of the steelmaking industry. Its limited utilization as a construction material is primarily attributed to its chemical properties, which hinder its stability and hydraulic activity due to its high free lime (f-CaO) content. This paper explores the performance of supplementary cementitious material (SCM) synthesized with ground granulated blast furnace slag (GGBFS), freshly produced BOFS (f-BOFS), and stockpiled BOFS (s-BOFS). A total of 10 mixtures with ordinary Portland cement (OPC) replacement percentages were assessed, maintaining a total replacement of 50% OPC, incorporating 15%, 25%, and 35% of each material by weight. The laboratory experimental program encompassed material characterization, fresh and hardened properties, pozzolanic activity, and durability assessment, with comparative studies conducted for each evaluation item. Test results indicate that f- or s-BOFS, when used with GGBFS, can be a viable alternative SCM with the potential for hydraulic activities and pozzolanic reaction. The newly synthesized SCMs demonstrated improved strength development in mortar mixtures. The mixture containing [15% f-BOFS + 35% GGBFS] achieved a 28-day compressive strength of 20.6 MPa, while the [25% BOFS + 25% GGBFS] blend reached a compressive strength of 19.7 MPa. These mixtures meet Grade 80 criteria as per ASTM C989/C989M Standard Specification for Slag Cement for Use in Concrete and Mortars. A performance-based ranking system was developed by integrating results from flowability, air content, strength activity index, drying shrinkage, alkali–silica reaction, and sulfate attack. The novelty of this work lies in assessing BOFS–GGBFS blends as SCMs using this multi-criteria approach to identify the most sustainable and technically viable mixtures. Moreover, the study highlights the influence of storage-induced weathering by directly comparing the reactivity and performance of f- and s-BOFSs in ternary blends, providing new insights into optimizing the utilization of slag. Notably, regardless of f- and s-BOFSs, proportions of [15% BOFS + 35% GGBFS] demonstrated superior strength development and achieved an excellent overall ranking. These findings confirm the potential of such slag blends as suitable SCMs for mortar and concrete applications, thereby advancing the sustainability and efficiency of cementitious materials. Full article

The valorization of wood waste in cement-based materials offers a promising path toward reducing the environmental footprint of the construction sector. While short-term properties of wood–cement composites have been studied, their long-term durability remains a critical uncertainty for practical application. This study investigates the long-term mechanical behavior of Portland-cement mortars incorporating 5% by mass of four types of wood waste: spruce, oak, beech, and oriented strand board (OSB). Specimens were subjected to flexural and compressive tests after 28 days and approximately 242 days of curing under natural laboratory conditions to assess the evolution of their properties. The results demonstrate that the long-term performance is highly dependent on the wood type. Composites with spruce sawdust, oak, beech, and OSB exhibited remarkable stability, with strength variations generally within ±8% over the extended period, supporting a scenario of matrix stabilization. In contrast, mortar with spruce shavings suffered a significant strength reduction of approximately 25%, indicating susceptibility to degradation, likely due to its high-water demand and porous resulting matrix. All wood-composite mortars showed a substantial density reduction of 20–36% compared to the reference. The findings confirm that OSB and oak waste provide the best overall performance, combining higher initial strength with excellent long-term stability. This research concludes that carefully selected wood waste can produce durable, lightweight cement composites viable for non-structural applications, thereby supporting the integration of circular economy principles in sustainable construction. Unlike previous studies that primarily assessed short-term strength, this paper provides one of the few comparative long-term assessments under natural curing conditions, highlighting the stabilization–degradation mechanisms across wood types. Full article

This study investigates the potential of alkali bypass dust (ABD) as a supplementary material to partially replace cement in paste and mortar formulations. The selection of ABD is motivated by the dual objectives of utilizing an industrial waste product to promote sustainable construction and reducing the carbon footprint associated with cement production. The chemical and mineralogical composition of ABD was characterized using X-ray fluorescence (XRF) and X-ray diffraction (XRD), revealing a composition similar to Portland cement but with a notably lower CaO content (44.32%) and the presence of calcite, portlandite, quartz, and free lime. The incorporation of ABD as a cement replacement significantly influenced the fresh and hardened properties of the mixtures. In paste mixtures, results demonstrated a proportional increase in water demand and setting times with higher ABD content, attributed to its lower reactivity and higher water absorption. Mechanical properties were adversely affected; compressive and flexure strengths in paste mixtures decreased substantially, with a 40% reduction observed at just 10% replacement. This was corroborated by a decrease in density, an increase in water absorption, and a significant drop in ultrasonic pulse velocity (UPV), indicating a more porous and less dense microstructure. In mortar mixtures, a 30% cement replacement with ABD yielded compressive and flexure strengths that remained within acceptable ranges for plastering and masonry applications, despite a reduction in workability. The findings suggest that while high-volume ABD replacement negatively impacts performance, a 30% replacement level presents a viable, sustainable alternative for specific non-structural applications, contingent upon further durability assessments. Full article

The use of wood waste as a component in cementitious composites represents a promising strategy for reducing environmental impact and promoting circular economy principles in the construction sector. This study examines the influence of five types of wood waste, spruce sawdust, spruce shavings, oak, beech, and oriented strand board (OSB), on the properties of Portland cement mortars. A constant 5% by mass of sand was replaced with each wood residue, and mixtures were tested for flowability, density, flexural, and compressive strength at 7, 14, and 28 days. Our results show that wood addition reduces density by 20–36% and compressive strength by 70–85%, depending on species and particle morphology. Denser materials (oak and OSB) resulted in composites with higher mechanical strength, suggesting a more effective particle packing and interfacial interaction compared to porous particles (spruce sawdust, shavings), which led to higher water demand and reduced strength. Beech showed the highest flexural strength, indicating potential for bending-dominated applications. The study demonstrates the feasibility of using selected wood residues for lightweight, non-structural cement composites and outlines the need for future microstructural validation through SEM and porosity analyses. Full article

Newly developed polymer-based grinding chemicals demonstrate superior dispersion, grinding, and strength outcomes compared to traditional amine-based additives. This study provides a comprehensive analysis of the mechanisms underlying the improved performance of polymers in the grinding process. It examines the influence of polymer-based grinding aids (A1-A2-A3) on the hydrophobicity and rheological behavior of CEM I 42.5 R Portland cement. A systematic analysis was conducted using six different grinding aids, comprising three synthesized polycarboxylate ether (PCE)-based polymers and three commercial amine group products. Key properties, including surface tension, hydrophobicity (water contact angle, WCA), slump flow, FT-IR, and rheological parameters, were evaluated. Among the compounds tested, the A2 polymer exhibited the most favorable performance, achieving a high contact angle (131.7°), low surface tension (56.7 dyn/cm), and enhanced mortar fluidity (25 cm slump flow). FT-IR spectroscopy confirmed strong interactions between A2 and cement particles, particularly in the CH₃ bonding regions. Rheological analyses further revealed that A2—2.5 g significantly decreased viscosity and improved shear stress response, indicating superior dispersion and water reduction capability. The findings highlight A2 as a promising eco-efficient additive for enhancing the efficiency, performance, and workability of cementitious systems through polymer-based grinding technology. Full article

The risk of explosive spalling in high-strength cement-based materials during fire exposure poses a significant threat to structural integrity. To help mitigate this issue, this study explores the use of expanded polystyrene (EPS) beads as both a lightweight filler and a potential spalling-reduction agent in lightweight geopolymer and conventional cementitious mortars. Two EPS-containing mortars were developed: a lightweight alkali-activated slag (LWAS) mortar and a conventional lightweight Portland cement (LWPC) mortar, both incorporating EPS beads as a 50% volumetric replacement for sand. Specimens from both mortars were subjected to elevated temperatures of 200 °C, 400 °C, and 600 °C at a heating rate of 10 °C/min to simulate a rapid-fire scenario. Following thermal exposure, two cooling regimes were employed: gradual cooling within the furnace and rapid cooling by water immersion. Mechanical performance was evaluated through compressive, splitting tensile, and impact tests at room and elevated temperatures. Microstructural analysis was also conducted to examine internal changes and heat-induced damage. The results indicated that LWAS showed remarkable resistance to spalling, remaining intact up to 600 °C due to its nanoporous geopolymer structure, which allowed controlled steam release, while LWPC failed explosively at 550 °C despite EPS pores. At 400 °C, EPS beads enhanced thermal insulation in LWAS, lowering internal temperature by over 100 °C, but increased porosity led to faster strength loss. Both mortars gained strength at 200 °C from continued curing, yet LWAS retained strength better at high temperatures than LWPC. Microscopy revealed that EPS created beneficial fine cracks in the slag matrix but harmful voids in cement. Overall, LWAS composites offer excellent spalling resistance for fire-prone environments, though reinforcement is recommended to mitigate strength loss. Full article

The growing generation of solid waste, driven by urbanization and industrialization, represents one of today’s greatest environmental challenges. The construction industry can play a key role in this scenario by incorporating recycling and waste reuse practices. Glass, a fully recyclable material, is still largely disposed of in landfills. A promising alternative is the use of ground glass in cementitious materials, partially or completely replacing cement or aggregates. Thus, in this paper, the effect of partially replacing Portland cement with ground glass of different colors including green, blue, transparent, amber, and colorful (all colors used mixed) in proportions of 15 and 35% in mortars was evaluated. The ground glasses were characterized by laser granulometry and chemical analysis. The properties of the mortars were then evaluated in the fresh and hardened state (apparent specific gravity, mechanical strength, water absorption, and open porosity). Regarding workability, the highest improvement observed was 6.8% for the 35% colored glass series compared to the reference series. In terms of entrapped air, there was an increase of up to 18.8% in the 35% green glass series. At 28 days of hydration, the 15% colored glass series obtained a 33% increase in flexural strength compared to the REF series. In the microstructure, it was found that a 15% glass presence was sufficient to reduce the portlandite index from 16.04 to 13.53, while a 35% glass presence was sufficient to reduce it to 7.51% portlandite, equivalent to a 54% reduction, suggesting significant potential for the reaction of the finer glass fractions with portlandite. This study suggests that the use of glass waste in a cementitious matrix can provide an environmentally appropriate alternative for recycling this material, contributing to a sustainable application and increased recycling rates of glass waste. Full article

The growing demand for sustainable construction materials has intensified efforts to reduce the environmental impact of Portland cement. This study investigates the effect of partial substitution of cement with metakaolin (MK, 5–15 wt.%) and biosilica (BS, 5 wt.%) on the physical, mechanical, and microstructural properties of cementitious mortars. The influence of a polycarboxylate ether-based superplasticizer (Mf) and ultrasonic treatment (ULT) was also evaluated. The mortars were characterized through setting time, density, water absorption, flexural and compressive strength tests, as well as FTIR and SEM analyses. Water absorption decreased from 12.21% to 9.8%, indicating improved pore refinement and densification. Flexural strength of all modified mortars exceeded that of the control mix: from 10.0% to 89.9% at 7 days, and from 4.7% to 50.4% at 28 days. The compressive strength improved markedly with MK and BS incorporation, from 20.8% to 51.3% at 7 days and from 9.7% to 35.2% at 28 days compared to the control sample. FTIR and SEM results confirmed enhanced pozzolanic activity and formation of C–S–H gel. The synergistic use of MK, BS, and Mf—especially with ultrasonic dispersion—yielded denser, stronger, and more sustainable cementitious composites. Full article

This systematic review applies the PRISMA methodology (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) to evaluate the use of recycled sand, obtained from construction and demolition waste (CDW), in mortars for civil construction. A total of 24 studies published between 2020 and 2025 were analyzed, retrieved from the Scopus and Web of Science databases. The main objective is to assess the technical feasibility and environmental benefits of recycled sand in mortars, while addressing research gaps such as the lack of standardized methodologies and the limited understanding of durability at higher replacement levels. Given the significant resource consumption and waste generation in the construction sector, the study highlights emerging trends in adopting recycled sand as a sustainable alternative to natural aggregates. Findings indicate that optimal replacement levels range between 30 and 50% in ordinary Portland cement (OPC) mortars, and up to 100% in geopolymer mixtures when appropriate processing and activation methods are applied, without compromising mechanical performance. Reported benefits include cost reduction, lower carbon footprint, and enhanced compactness. However, challenges such as higher porosity and the need for optimized mix designs, and high heterogeneity of CDW sources and processing methods remain. Overall, the review confirms that recycled sand is a technically viable and environmentally beneficial material for mortar production, though future research must focus on harmonizing test protocols and long-term performance evaluation. In addition, a bibliometric analysis was conducted to map scientific output on this topic, identifying key countries, journals, and publication trends. Full article

Cementitious binders have long been a keystone of construction, evolving from ancient lime mortars in Neolithic structures to the widespread use of Portland cement in the 19th century, which remains critical in modern construction. This review traces the historical development of cementitious binders and highlights how their widespread adoption has also brought significant environmental challenges, particularly carbon dioxide emissions and intensive energy consumption. To mitigate these impacts, supplementary cementitious materials (SCMs), such as fly ash, slag, and silica fume, have been adopted to reduce clinker consumption and improve sustainability. Despite these advancements, cement continues to be one of the largest industrial contributors to global emissions. In response, alternative binders have been explored. Alkali-activated binders (AABs) demonstrate considerable potential to reduce emissions while offering enhanced durability and performance. These emerging technologies provide a pathway toward more sustainable construction practices. This review is based on a structured survey of the peer-reviewed literature, conference proceedings, and technical reports up to 2025, synthesizing key themes related to historical evolution, environmental impacts, and emerging low-carbon alternatives. The findings aim to inform the development of sustainable building materials for the future. Full article

In the preparation of rubber-recycled cement mortar (RRCM), recycled fine aggregates (RFA) were used to replace 95% of natural fine aggregates (NFA) by mass, with an additional 5% of NFA replaced by rubber particles (RP). Additionally, nano-silica (NS) was incorporated to replace ordinary Portland cement (OPC) by mass at a replacement of 0%, 1%, 2%, 3%, and 4%. The study aimed to investigate the effects of NS on the mechanical properties, freeze–thaw resistance, and microstructure of RRCM, using techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), and scanning electron microscopy (SEM) to reveal the enhancement mechanisms. The results indicated that the compressive strength and flexural strength of RRCM at 28 days decreased by 10.3% and 10.1%, respectively, compared to NCM. After adding 1–3% NS, the mechanical properties of RRCM were improved, with the enhancements increasing as the NS content increased. Specifically, RRCM3 exhibited a 7.7% and 7.6% improvement in compressive and flexural strength, respectively, compared to RRCM0. After 30 freeze–thaw cycles, the strength loss rate of RCM was 27.51%, whereas the strength loss rate of RRCM3 was reduced to 20.13%, with better overall appearance integrity. Moreover, NS promoted the hydration of cement; reduced the contents of tricalcium silicate (C₃S), and dicalcium silicate (C₂S) and calcium hydroxide (CH); and facilitated the formation of additional hydration products that filled the interfacial transition zone (ITZ). The incorporation of 3% NS was found to provide the optimal improvement in RRCM. Full article

Natural supplemental cementitious materials (SCMs) with pozzolanic qualities, such as rice husk ash (RHA) and sugarcane bagasse ash (SCBA), are a promising alternative to the currently used SCMs that are becoming increasingly unavailable. This work presents a comprehensive comparative examination of their impact on mortar properties when OPC was partially replaced by RHA and SCBA. The percentage substitution of OPC with ashes was 0, 5, 10, and 15%. The air content, consistency, compressive strength, flexural strength, and shrinkage of the mortar were investigated primarily. Microstructural characteristics were analysed using porosimetry, MIP, and SEM photography. According to the study, up to 10% replacement of OPC with RHA or 15% with SCBA has the potential to be used as a partial cement substitute while maintaining good mechanical qualities. Mortars with up to 15% SCBA exhibited no significant change in compressive strength after 28 days or a decrease with <11%, while for 10% RHA, there was no difference in compressive strength or increase. Use of 5% RHA decreased shrinkage by 35%, while addition of 5% SCBA by 30%. Obtained results demonstrated the usefulness of SCMs in masonry mortars. Full article

The construction industry increasingly seeks sustainable solutions to reduce environmental impact and energy consumption. This study explores the innovative use of industrial sludge generated from the wastewater treatment of detergent manufacturing as a partial substitute for Portland cement in mortar production. The sludge, characterized by high SiO₂ (46.58%) and CaO (28.66%) content, was incorporated at substitution rates of 0% to 30%. Mortars were prepared and tested according to NF EN 196-1 standards for mechanical strength, and thermophysical properties were assessed using the Hot Disk TPS 1500 system. The results demonstrate that up to 20% sludge replacement maintains acceptable mechanical performance (compressive strength: 12.63 MPa at 28 days vs. 13.91 MPa for the control; flexural strength: 3.93 MPa vs. 4.65 MPa) while significantly enhancing thermal insulation. Thermal conductivity decreased from 1.054 W/m·K (0% sludge) to 0.797 W/m·K (20% sludge), and thermal diffusivity dropped from 0.6096 mm²/s to 0.504 mm²/s. XRD analysis revealed the formation of new phases, such as gismondine, indicating beneficial pozzolanic activity. These findings highlight the dual benefit of valorizing detergent sludge and improving building energy efficiency, offering an eco-efficient alternative to traditional mortars aligned with circular economy and low-carbon construction goals. Full article