Search Results (359)

High-performance and ultra-high-performance fiber-reinforced concretes (HPFRC/UHPFRC) have emerged as advanced cementitious composites capable of achieving superior mechanical performance, durability, and structural efficiency compared with conventional concrete. However, their widespread adoption remains challenged by relatively high material costs and significant embodied environmental impacts associated with elevated binder and fiber contents. This study presents a comprehensive life-cycle review of advanced high-performance cementitious composites, evaluating their sustainability from raw material extraction and mix design to structural application, service life, and end-of-life considerations. The review synthesizes current knowledge on material composition, production processes, structural performance, durability characteristics, and environmental impacts through the framework of life-cycle assessment (LCA). Particular attention is given to the influence of mix-design parameters, including binder composition, supplementary cementitious materials (SCMs), aggregate systems, and fiber type, on embodied carbon, energy demand, and mechanical performance. A dataset compiled from published experimental studies covering high-performance and ultra-high-performance concrete mixtures is analyzed to examine relationships between compressive strength, embodied energy, and carbon footprint, highlighting the dominant role of cementitious binders and fiber production in environmental impacts. Although advanced fiber-reinforced concretes generally exhibit higher cradle-to-gate emissions than conventional concrete, their superior mechanical properties, improved durability, reduced material demand, and extended service life can substantially reduce life-cycle environmental impacts at the structural level. The review further discusses emerging strategies for developing low-carbon high-performance cementitious composites, including clinker reduction, recycled and alternative fibers, optimized particle packing, and AI-assisted mix design. Finally, key research gaps are identified, particularly regarding standardized LCA methodologies, long-term durability data, harmonized performance-based functional units, and circular-economy strategies for material recycling and reuse. The findings highlight that performance-based life-cycle evaluation is essential for accurately assessing the sustainability potential of advanced high-performance cementitious composites in resilient and low-carbon infrastructure systems. Full article

This study investigates accelerated carbonation as a low-energy alternative to autoclave curing in the production of fiber cement composites reinforced with lignocellulosic fibers. The effects of both curing routes on physical–mechanical performance, durability, and microstructural evolution were systematically evaluated before and after 25 wetting–drying cycles. Carbonation-cured composites achieved mechanical performance comparable to autoclaved materials, while exhibiting higher bulk density (≈1.37–1.38 g/cm³) and a reduction of approximately 15% in total void volume. Water absorption values were up to 17% lower than those of autoclaved counterparts. After accelerated aging, both systems showed stable mechanical properties, with increases in modulus of elasticity of approximately 21% (autoclaved) and 26% (carbonated), indicating ongoing hydration and densification processes. Thermogravimetric analysis revealed carbonation degrees of approximately 16–17%, corresponding to CO₂ uptake values of up to 35.8 kg/m³ of fiber cement. X-ray diffraction confirmed the consumption of portlandite and the formation of calcium carbonate phases, contributing to pore refinement and matrix densification. Microstructural observations indicated improved fiber–matrix interaction in carbonated composites due to the precipitation of carbonation products at the interface, whereas autoclaved materials exhibited signs of fiber degradation associated with hydrothermal curing. These effects were reflected in higher deformation capacity and specific energy retention in carbonated systems. Overall, accelerated carbonation represents a promising alternative to autoclave curing, delivering comparable mechanical performance while enhancing fiber durability, refining pore structure, and enabling CO₂ sequestration within the cementitious matrix. Full article

Water-based elastomeric waterproofing membranes based on styrene–acrylic (S/A) copolymers have emerged as an important class of materials for modern construction due to their combination of flexibility, adhesion, environmental compatibility, and long-term durability. These membranes form seamless protective layers capable of accommodating substrate movement while preventing water ingress across a wide range of building structures. Recent advances in polymer chemistry and emulsion technology have significantly improved the performance of S/A systems, particularly in terms of crack-bridging capability, weather resistance, and UV stability. In addition, optimized formulations incorporating functional fillers, rheology modifiers, and hybrid polymer architectures enable improved mechanical performance and impermeability. This review provides a comprehensive overview of S/A elastomeric waterproofing membranes, covering polymer chemistry, formulation strategies, physico-mechanical properties, durability mechanisms, and real-world construction applications. The review also compares S/A systems with alternative waterproofing technologies such as polyurethane (PU), cementitious coatings, and bituminous membranes. Finally, emerging developments in advanced polymer architectures, nano-reinforced coatings, and sustainable formulations are discussed, highlighting future research directions for high-performance waterproofing systems. Full article

Agricultural waste materials can serve as functional constituents in cement-based composites through three pathways: (i) organic bio-aggregates that lower density and alter thermal behavior, (ii) lignocellulosic fibers that control cracking and improve post-cracking resistance, and (iii) agro-ash supplementary cementitious materials (SCMs) that densify pore structure and reduce permeability when ash quality and curing are controlled. This review draws on 98 papers, with coconut shell aggregate and coir/coconut fibers as the core focus; agro-ash SCMs (notably palm oil fuel ash, POFA, and rice husk ash, RHA) enter where they clarify mechanisms or inform hybrid design. Rather than cataloging compressive-strength data, the synthesis is organized around controllable process inputs (feedstock conditioning, mix design, curing) and the interface-governed mechanisms that determine performance: interfacial transition zone (ITZ) character and pore connectivity. In coconut shell systems, density reductions come at a cost: elastic modulus drops and moisture sensitivity rises unless shell conditioning, particle packing, and matrix refinement are managed. In fiber systems, gains in toughness and residual capacity are bounded by mixing workability and by the long-term stability of the fiber–matrix bond under alkaline and wet–dry exposure. A mix must first meet strength, serviceability, and transport requirements before its embodied impact is compared with conventional alternatives. The contribution is to reframe these systems around controllable processing and interface mechanisms instead of tabulated strength values; preparation, treatment, and characterization data are consolidated into bounded design windows, an explicit core versus supporting evidence convention is applied, and sustainability is judged under functional equivalency rather than per-volume carbon. Full article

To promote the high-value utilization of industrial solid wastes and address the disposal of excavated soils, a novel low-carbon composite cementitious material, solid waste-based geopolymer cement (SGPC), was developed, consisting of soda residue (SR), granulated blast furnace slag (GGBS), phosphogypsum (PG), and ordinary Portland cement (PC) in a mass ratio of 10:81:9:25, with industrial solid wastes accounting for 80% of the binder. The effects of water-to-solid ratio (W/S = 0.41–0.49) on the workability, mechanical performance, and microstructural evolution of SGPC-stabilized soil were systematically investigated to provide a sustainable alternative to conventional cement-based stabilizers. The results indicate that the optimum water-to-solid ratio is 0.43 (SGPC43), with a 28-day unconfined compressive strength of 1450 kPa, exceeding the engineering requirement of 0.8 MPa and reaching over 85% of that of a pure cement system (C43). The flowability remained 163 mm after 60 min, with initial and final setting times of 43 h and 58 h, respectively. Microstructural analysis revealed that the alkalinity provided by soda residue promotes the hydration of slag and phosphogypsum, forming interwoven calcium (alumino) silicate hydrate (C–(A)–S–H) and ettringite (AFt), which fill pores and form a dense structure, thereby enhancing mechanical performance. Environmental and economic assessments show that the CO₂ emission of SGPC43 per ton of binder decreases from 930 kg CO₂-e/t to 235 kg CO₂-e/t (approximately 74.7% reduction), while the material cost decreases from 110 USD/t to 53 USD/t (approximately 51.8% reduction). A simplified uncertainty analysis indicates that the carbon reduction remains at 70% ± 5% and the cost reduction at 50% ± 5%, confirming the robustness of the results. Overall, SGPC43 demonstrates excellent engineering performance, environmental benefits, and economic feasibility, highlighting its potential as a low-carbon and sustainable stabilizing material. Full article

Seawater and sea sand as constituents in concrete are valuable alternatives to freshwater and river sand. Further, the use of seawater and sea sand in projects located in the proximity of a sea/ocean can reduce the overall project cost and lower the carbon footprint. Nevertheless, seawater contains high concentrations of chloride (Cl⁻), sulphate (SO₄²⁻) and magnesium (Mg²⁺), which can react with tricalcium aluminate (C₃A) in cement and the byproduct calcium hydroxide (Ca(OH)₂), and form Friedel’s salt, delayed ettringite and brucite, respectively. These chemical compounds are aggressive and can degrade the strength and durability of the concrete. Differences in the physical properties of sea sand compared to river sand can also lead to weak and porous concrete. In reinforced concrete, steel bars are susceptible to corrosion due to the formation of corrosion products as a result of high concentrations of Cl⁻. Whilst mitigation strategies such as the use of supplementary cementitious materials (SCMs) and fibre-reinforced polymer (FRP) reinforcements have been investigated in the literature, no validated method that enables the use of concrete with seawater and sea sand has been established. Based on research reported in the literature, the present study investigates the chemistry, strength and microstructure of concrete mixed with seawater and sea sand as a means of establishing their use in concrete without compromising the properties of the concrete. The study shows that the compressive strength of seawater–sea sand mixed concrete (SWSSC) is increased in the short term (up to 28 days) due to the formation of additional chemical compounds in the former. However, the long-term (i.e., beyond 28 days) compressive strength of concrete reduces by up to 20% after one year due to the weakening of the microstructure (more flaws/expansions), which further reduces the durability of the reinforced concrete. Although the long-term degradation of SWSSC has been noticed, the underlying causes are not fully understood. The present critical review study provides chemical and microstructural insight into the degradation of concrete with seawater and sea sand, and the current developing understanding is used to develop a mitigation strategy towards the use of seawater and sea sand in real-world concrete applications. Full article

Rapid population growth is increasing housing demand and accelerating the expansion of the built environment in Egypt. However, practical and sustainable residential building decarbonization remains constrained by limited supplies of supplementary cementitious materials, limited structural timber resources, code restrictions on cement reduction, and cost sensitivity. This study evaluates two Egyptian multi-unit residential case studies—one affordable housing project and one middle-class housing project—to assess whether wall-system substitution can reduce both embodied and operational carbon under local material, code, and cost constraints. An integrated BIM-based digital twin workflow was used to link quantity takeoff, finite-element structural assessment, and whole-building energy simulation. An architectural BIM model was used for material quantification, wall-system definition, and energy-model inputs. A structural model was used to assess the effects of reducing wall density on reinforcement and concrete demand under gravity and seismic load combinations. Operational performance was assessed through cooling-focused energy simulations under hot-arid climatic conditions representative of Egypt’s new desert cities. Alternative wall systems were then evaluated through scenario- based material substitution and revised structural and energy assessments. The results show that reinforcement, concrete, and wall- core materials account for about 80% of total embodied carbon, while cooling accounts for about 72% of operational emissions. Non-structural cement uses, mainly mortars and finishes, account for 36% of total cement demand, ranging from 161 to 229 tons per building across the two case studies. Replacing conventional partition walls with lightweight, energy-efficient alternatives reduced embodied carbon by up to 35.2%, operational carbon by about 15.7% to 16.5%, and total life-cycle carbon by about 17.4% to 17.5% over a 60- year service life. The average savings per building corresponded to avoiding about 30 tons of steel, 165 m³ of ready-mix concrete, and 191 m³ of mortar, with net cost savings of about 3.15 million EGP per building. These results identify a practical pathway toward more sustainable, lower-carbon Egyptian residential buildings without increasing project cost. Full article

The durability of cementitious mortars exposed to freeze–thaw (F/T) cycles and abrasion remains a challenge in sustainable infrastructure, motivating the exploration of alternative fiber reinforcements with lower environmental impact. There is a notable gap in understanding the behavior of natural-fiber-reinforced composites, particularly their response to freeze–thaw cycles and abrasion. Additionally, data on the physical and mechanical properties of mortars that use sheep wool and Spanish broom fibers as cement composite reinforcement remain limited. This study investigates the influence of industrially produced fibers (polypropylene and glass) and natural fibers (sheep wool and Spanish broom, with different treatments) on the F/T cycles and abrasion resistance of cement mortars. Six mixtures were prepared, including a reference and five fiber-reinforced mortars (FRM) with 0.5% fiber content by binder mass. The workability of fresh mortar, abrasion resistance, flexural strength, compressive strength, and specific fracture energy were evaluated at the age of 56 days and after 56 F/T cycles. Results indicate that fiber addition reduced workability and compressive strength and no FRM has increased flexural strength at 56 days. Polypropylene- and NaOH-treated Spanish broom fibers improved flexural performance after FT exposure, exceeding the reference mortar flexural strength by up to 23%. All FRMs have significantly enhanced fracture energy, with increases up to 2.6 times compared to the reference mortar, and maintained improved values after F/T cycling. For the selected amount of fiber, abrasion resistance remained within the same performance class for all mixtures. Polypropylene and hydroxide treated Spanish broom FRMs demonstrated the highest potential for improving F/T resistance and toughness, while FRM with untreated or seawater-treated natural fibers require further optimization for durability in alkaline environments. Understanding the behaviour of local natural fibers under extreme conditions is essential for developing durable, sustainable construction materials. Full article

The construction sector is responsible for significant global energy consumption and CO₂ emissions, largely driven by carbon-intensive materials such as ordinary Portland cement and steel. In response to increasing decarbonization and circular economy demands, several strategically relevant categories of sustainable construction materials have been developed, particularly natural and bio-based systems, recycled and waste-derived materials, low-carbon cementitious binders, and emerging multifunctional composites. However, research remains fragmented across material classes and performance metrics. This systematic review evaluates advances published between 2018 and 2026 following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 methodology. Peer-reviewed studies were systematically identified and analyzed to compare mechanical performance, durability, embodied carbon reduction, and life-cycle environmental impacts across these selected material pathways. The results indicate substantial decarbonization potential. Low-carbon cementitious materials report CO₂ reductions of approximately 10–75% relative to conventional systems, while engineered timber and bamboo demonstrate 28–70% lower carbon footprints due to reduced embodied energy and biogenic carbon storage. Recycled aggregates and industrial by-products enhance circularity but remain sensitive to transport distance and processing intensity. Trade-offs between mechanical capacity and environmental performance are evident in lightweight and bio-based systems. Overall, sustainability gains are maximized through integrated hybrid construction strategies rather than isolated material substitution. This review provides a comparative evidence-based synthesis and identifies key research gaps and implementation challenges for accelerating low-carbon construction. Full article

The global construction industry urgently requires sustainable alternatives to ordinary Portland cement (OPC) to mitigate its immense carbon footprint. Red mud (RM), a highly alkaline bauxite residue, presents tremendous but challenging potential as a supplementary cementitious material. This review systematically bridges the gap between atomic-level interfacial bonding mechanisms and macroscopic engineering performance, highlighting how these properties are significantly dictated by specific RM sources (e.g., Bayer vs. Sintering processes). We first elucidate advanced pretreatment strategies, notably CO₂ mineralization, which synergistically mitigates extreme alkalinity and sequesters carbon. Crucially, the fundamental bonding mechanisms are decoded: beyond physical filling, RM integration induces significant micro-morphological densification via intense aluminosilicate depolymerization—evidenced by the Al[VI] to Al[IV] coordination shift—and the quantitative integration of approximately 40% reactive iron phases into stable Fe-S-H networks. By clearly distinguishing between traditional hydration and clinker-free alkali-activation pathways, we evaluate holistic structural parameters beyond mere 28-day compressive strength (40–67 MPa), explicitly addressing flexural capacity, modulus of elasticity, and volume stability. Environmental assessments confirm exceptional heavy metal immobilization (>95% efficiency, leaching < 0.010 mg/L) and a substantial 50–80% reduction in Global Warming Potential (GWP), provided the environmental burden of alkaline activators is rigorously accounted for. Furthermore, the long-term risk of Alkali–Silica Reaction (ASR) is evaluated as a primary durability concern. Finally, to overcome persistent rheological bottlenecks, this paper highlights transformative future trajectories, particularly data-driven Machine Learning (ML) for complex mix optimization and 3D concrete printing for advanced infrastructure. Ultimately, this review provides a robust theoretical foundation and a pragmatic roadmap for upcycling RM into safe, high-performance, and ultra-low-carbon building materials. Full article

As natural and anthropogenic hazards intensify, improving the performance of reinforced-concrete (RC) infrastructure within a resilience-oriented assessment framework while limiting environmental burdens has become an important challenge for sustainable construction. In this context, this study proposes an OpenBIM-based digital-twin methodology to compare two equivalent RC structural scenarios: a conventional solution and an alternative incorporating unprocessed waste sheep wool fibres into cementitious materials. Using an IFC-based model of a high-rise building, the workflow enables automated extraction of structural quantities and a consistent building-scale assessment of material use, environmental impacts, and circularity indicators. Laboratory evidence from the literature is translated into element-level performance criteria through a dual-factor selection strategy based on key structural properties and secondary indicators related to cracking and post-cracking behaviour. The results show that the wool-fibre alternative enables the incorporation of a relevant amount of waste wool into the structure while causing only negligible increases in embodied energy and carbon emissions relative to the conventional RC scenario. The selected formulations also maintain or improve the governing mechanical and serviceability-related factors, indicating potential benefits in crack control, toughness, and repairability. Overall, this methodology provides a reproducible pathway for linking laboratory-scale material innovation with building-scale digital assessment, supporting more sustainable and performance-aware decision-making in RC construction. Full article

The progressive phase-out of coal-fired power plants in Portugal has significantly reduced the availability of fly ash (FA) as a supplementary cementitious material (SCM), reinforcing the need for sustainable alternatives. Waste glass powder (WGP), characterized by its high amorphous silica content, has emerged as a promising candidate; however, most studies focus on ultrafine particles or isolated performance indicators, lacking an integrated technical, environmental, and economic assessment. This study evaluates cement pastes incorporating 25% WGP (by volume) with different particle size distributions, including fineness levels comparable to cement and FA. Mechanical performance, grinding energy demand, carbon footprint, and cost were systematically analyzed. The results indicate that WGP is technically viable as an SCM, with a median particle size (D₅₀) of approximately 48 µm providing the most balanced performance. Although finer particles enhance pozzolanic reactivity, the associated increase in grinding energy and economic cost offsets these gains. The findings demonstrate that optimizing particle size, rather than maximizing fineness, enables a technically robust and industrially realistic use of WGP. This approach supports circular economic strategies and contributes to the decarbonization of the construction sector by identifying an efficient replacement pathway for FA under resource-scarcity conditions. Full article

Population growth and rapid urbanization have significantly increased construction activities and the demand for building materials. It is estimated that approximately 39% of global CO₂ emissions are associated with the construction sector, with nearly 8% directly attributed to Portland cement production. In addition to greenhouse gas emissions, the cement industry is responsible for substantial environmental impacts, including natural resource depletion, soil degradation, and air and water pollution. In this context, the development of alternative and more sustainable binder systems has become a global research priority. Geopolymers have emerged as promising materials produced through either alkaline or acid activation routes, offering advantages such as a reduced carbon footprint, high durability, and rapid strength development. Among these systems, acid-activated materials, particularly phosphate-based geopolymers, differ fundamentally from conventional alkali-activated binders in terms of reaction chemistry and binding phases. The formation of aluminum phosphate (AlPO₄) networks plays a key role in governing the mechanical performance and microstructural stability of these materials. This mini-review provides a critical overview of the fundamental principles of acid activation applied to alternative cementitious materials, with emphasis on dissolution mechanisms, polycondensation reactions, and the nature of binding phases in phosphate-based systems. Unlike previous reviews, this study integrates recent findings on reaction mechanisms with a comparative analysis between acid and alkaline activation routes, highlighting underexplored aspects of precursor reactivity and binder formation. The main types of acids used as activators, the influence of precursor chemical composition, and the conceptual differences between acid and alkaline activation are discussed. In addition, recent advances, current challenges, and future perspectives of acid activation are addressed, highlighting its potential as a viable low-carbon binder route for sustainable construction materials, with strong prospects for partially replacing Portland cement, particularly in high-performance applications requiring enhanced chemical resistance and thermal stability. Full article

The copper industry generates approximately 24.6 million tons of copper slag (CS) annually, equivalent to about 2.2 tons of CS per ton of copper produced, creating a major waste management challenge. Meanwhile, concrete is one of the most widely used construction materials worldwide, with nearly 11 billion tons produced each year. This high demand requires large volumes of natural aggregates, leading to environmental impacts associated with their processing and transportation. This study evaluates mortar and concrete mixtures incorporating CS to assess the feasibility of valorising this industrial waste as an alternative aggregate in cementitious materials. The experimental programme included in this study tests to determine the workability and mechanical properties for different aggregate replacement ratios. The results show that replacing 40% of the fine aggregate with CS improves mortar performance, increasing compressive and flexural strength by at least 13.9% compared with reference mixtures. For concrete, up to 100% aggregate replacement was feasible, achieving compressive strength gains of up to 11.9%. Given that aggregates represent about 70–80% of the concrete volume, the incorporation of CS offers a promising strategy for large-scale waste valorisation and natural resource conservation. Full article

In engineered cementitious composites (ECCs), the use of fine quartz sand is associated with high cost and is unfavorable for reducing ECC shrinkage. Moreover, the mining and processing of fine quartz sand impose negative environmental impacts. At the same time, the polyethylene (PE) or polyvinyl alcohol (PVA) fibers added to ensure ECC ductility are expensive, which limits the widespread application of ECCs. With the aim of waste utilization and cost reduction while improving efficiency, this study employs geopolymer aggregate (GPA) as an alternative to fine quartz sand and partially replaces PE fibers with steel fibers to develop an economical and environmentally friendly geopolymer aggregate ECC. Six groups of ECC specimens with different mix proportions were designed and tested under uniaxial compression, flexural loading, and uniaxial tension. Different aggregate types (fine quartz sand and geopolymer aggregate) and volume fraction ratios of PE fibers to steel fibers (0:2.0, 0.5:1.5, 1.0:1.0, 1.5:0.5, and 2.0:0) were adopted to investigate their effects on mechanical properties, microstructural characteristics, and material sustainability. The experimental results reveal the failure process and deformation characteristics of the ECCs at different loading stages. The results indicate that geopolymer aggregate, owing to its lower stiffness and fracture energy, can promote multiple cracking behavior in ECCs. Although the complete replacement of quartz sand with porous GPA initially causes a slight reduction in the compressive and flexural strengths of the matrix, the hybridization strategy—partially replacing PE fibers with steel fibers—effectively compensates for this strength loss while maintaining excellent ductility. By comparing sustainability indicators with those of conventional ECCs, the results demonstrate that hybrid fiber geopolymer aggregate ECCs can effectively reduce material costs and carbon dioxide emissions. These findings verify the sustainability of producing green ECCs using industrial solid waste as an aggregate and provide guidance for the application of environmentally friendly geopolymer aggregate ECCs. Full article