Search Results (987)

Recycled powder (RP), a by-product with a particle size smaller than 150 μm, is generated during the processing of construction and demolition waste (CDW) for recycled aggregate production. RP mainly consists of recycled concrete powder and recycled brick powder. Previous studies have demonstrated that RP can serve as a supplementary cementitious material (SCM) in concrete production. Due to the heterogeneity of parent materials with different ages, service environments, and compositions, the physicochemical properties and reactivity of RP vary significantly, which largely accounts for the inconsistent results reported in the literature. This paper presents a critical review of the application of RP as an SCM in construction. The preparation technologies, chemical and physical properties, microstructural characteristics, and activation methods of RP are systematically examined. Owing to its irregular and rough surface morphology, RP tends to reduce workability and increase water demand when incorporated as an SCM. Nevertheless, when the replacement level and median particle size are limited (typically below 30% and 20 μm, respectively), RP can contribute through micro-filling, nucleation, and limited pozzolanic effects, thereby mitigating adverse impacts on mechanical and durability properties. The mechanisms and effectiveness of mechanical grinding, thermal activation, chemical activation, and CO₂ treatment are comparatively evaluated. Moreover, the incorporation of RP in cement-based materials offers significant economic and environmental benefits. Full article

The accelerating climate emergency places the built environment under increasing pressure as both a major source of greenhouse gas emissions and a system highly vulnerable to climate impacts. Buildings contribute substantially to global operational energy use and embodied carbon, while much of the existing stock remains poorly adapted to changing climatic conditions. This paper examines the role of artificial intelligence (AI) in improving energy efficiency, enabling circular material flows, and enhancing resilience across the building lifecycle. Based on a structured synthesis of recent peer-reviewed literature, institutional reports, and documented case examples, the study maps AI applications in design, construction, operation, and end-of-life stages, including generative design, predictive maintenance, digital twins, and construction and demolition waste analytics. The analysis shows how AI can reduce operational energy demand, optimize material use, and support reuse and recycling strategies, while enabling new software-driven business models in the building sector. The paper argues that AI’s effectiveness depends on data availability, interoperability, regulatory alignment, and workforce capabilities, and that its benefits are maximized when integrated with circular economy strategies and supportive policy and financial frameworks. This integrated perspective highlights pathways for reducing emissions and improving the resilience of the built environment under climate stress. Full article

Construction and Demolition Waste (CDW) management represents a growing global challenge due to the large volume and heterogeneous nature of materials involved. This study addresses this issue by developing an automated classification system based on computer vision and deep learning, aiming to enhance efficiency and sustainability compared to manual sorting methods. A representative dataset was collected in a recycling facility, and multiple convolutional architectures were evaluated, with ResNet50 employing transfer learning achieving the best performance. The model was integrated into a web-based prototype capable of processing both still images and real-time video, offering visualization and interpretability tools for users. In addition to performance evaluation, the system’s cybersecurity and resilience were analyzed, focusing on data integrity, secure model deployment, and robustness against potential cyber threats. Experimental results demonstrate competitive classification accuracy and stable operation under realistic conditions. The study confirms the technical feasibility of the approach and emphasizes the importance of incorporating cybersecurity considerations into AI-driven industrial solutions, establishing a foundation for secure, scalable, and sustainable CDW management systems. Full article

Among Construction and demolition waste (CDW) has become a persistent challenge for urban sustainability, particularly in developing countries where institutional capacity and market coordination remain limited. While the reuse of CDW is widely recognized as technically feasible, its commercialization continues to face underlying obstacles. This research examines the factors limiting the consolidation of the CDW market in Maceió, Northeast Brazil, a city that recently experienced a large-scale geotechnical disaster and a sudden increase in CDW generation. The analysis is guided by the question: Which factors most strongly constrain the development of the CDW market in Maceió, and how do they interact? A mixed-methods design was adopted, combining survey data analyzed through the Relative Importance Index (RII), descriptive statistics, and ANOVA with semi-structured interviews involving professionals from construction, waste management, and public agencies. The results reveal five interconnected groups of barriers. The most influential are the absence of effective public policies (RII = 0.89), lack of fiscal incentives for recycling (RII = 0.88), fragmented legislation (RII = 0.87), and the systematic devaluation of recycled materials (RII = 0.85). Environmental constraints linked to land subsidence (RII = 0.90) further intensify market instability. Together, these findings show that CDW commercialization is shaped by interacting regulatory, economic, and cultural factors, underscoring the need for coordinated policy, fiscal, and governance responses in vulnerable urban contexts. Full article

Fiber-reinforced polymer composites (FRPCs) are increasingly used in construction due to their high performance and low environmental footprint. However, their widespread adoption has raised concerns over end-of-life management, particularly under European regulations mandating high recycling rates for construction and demolition waste (CDW). This study evaluates different systems for the chemical recycling of FRPCs through microwave (MW)-assisted solvolysis using green solvents, including deep eutectic solvents (DESs) and biobased acetic acid. The process targets thermoset resin depolymerization while preserving fiber integrity, operating at reduced temperatures (≤230 °C) and lower energy demand than conventional techniques, such as pyrolysis. A systematic experimental design was applied to CDW-derived polyester composites and extended to industrial epoxy and vinyl ester composites. Among the tested solvents, glacial acetic acid + ZnCl₂ (5 wt.%), achieved the highest degradation efficiency, exceeding 94% in small-scale trials and maintaining over 78% upon upscaling. Recovered fibers showed moderate property retention, with tensile strength and elongation losses of ~30% and ~45% for infusion-based epoxy composites, while those from pultrusion-based epoxy composites exhibited 16–19% and retained similar properties to the virgin material, respectively. The method facilitates fiber recovery with limited degradation and aligns with circular economy principles through solvent reuse and minimizing environmental impact. Full article

The renovation of dilapidated housing has become a focal point of social concern. However, traditional approaches—such as repair and reinforcement or unified demolition and relocation—face bottlenecks that hinder sustainability. There is an urgent need to explore new models for addressing the risks posed by dilapidated residential buildings. In recent years, multiple regions have explored the “original demolition and original reconstruction” approach for dilapidated housing. For instance, Zhejiang Province introduced the “Resident-led Renewal” model, sparking widespread attention and discussion. This model is characterized by residents serving as the primary investors. However, the manner in which stakeholders—particularly residents—collaborate in governance and interact during the renovation process under this model remains unclear. Using the Zhegong New Village original demolition and reconstruction project as a case study, this paper employs social network analysis to construct relational networks encompassing information, trust, consultation, and support. It quantitatively reveals the characteristics of social networks among stakeholders and their interactive practices within the Resident-led Renewal model. Findings reveal that in this case, “Resident-led Renewal” primarily manifested through residents serving as principal investors and establishing a Self-Driven Renewal Committee to submit the original demolition and reconstruction application on behalf of residents to local authorities. In stakeholder interactions, the government and community neighborhood committees play a coordinating role in the renovation process. However, resident organizations and residents themselves ranked lower in metrics such as reciprocity and degree centrality, indicating their limited influence during the renovation process. To alleviate the pressure of the government’s excessive involvement and enhance resident participation in the “original demolition and original reconstruction” process, efforts should focus on: raising residents’ awareness and capacity for participation; ensuring accessible channels for resident involvement; clarifying the rights and responsibilities of all stakeholders; and establishing a standardized approval process for “original demolition and original reconstruction” projects. This approach would realize a “Resident-led Renewal” model characterized by government guidance and resident participation. Full article

The construction industry’s heavy reliance on Ordinary Portland Cement (OPC) significantly contributes to global CO₂ emissions, prompting the search for sustainable alternatives. This study investigates the partial substitution of Portland cement with construction and demolition waste (CDW) powder and concrete waste (CON) powder in mortar mixes. Replacement levels of 5%, 10%, 15%, and 20% by weight were tested following EN 196-1 standards to evaluate the mechanical performance of the resulting materials. X-ray diffraction (XRD), X-ray fluorescence (XRF), and thermo-gravimetric analyses confirmed that CDW and CON powders consist mainly of quartz and calcite, with chemical compositions compatible with cementitious systems. Mechanical testing revealed that compressive strength was maintained or slightly improved at replacement levels up to 10%, while higher substitutions led to moderate reductions due to dilution effects. The use of CDW and CON powders effectively transformed a 52.5 R Type I cement into a 42.5 R Type II equivalent, demonstrating the feasibility of producing sustainable binders with acceptable performance. Full article

The construction industry is a major consumer of natural resources and a significant source of CO₂ emissions. Although numerous studies have addressed cement reduction through supplementary materials, the replacement of natural aggregates has received less attention despite its high environmental relevance. Practical application of recycled aggregate concrete remains limited due to complex classification and testing requirements. This study investigates the use of locally crushed construction and demolition waste as aggregate for new structural concrete with minimal on-site preparation. The goal was to maximize recycled material utilization while ensuring adequate performance. Demolition materials from normal- and high-strength concrete, 3D-printed concrete, and fired clay bricks were crushed using jaw and impact crushers, and the entire particle size curve was incorporated into new mixtures. Two compositions were tested: 50% and 75% recycled aggregate combined with natural quartz sand, without increasing cement content. Compressive strength and density were evaluated at 28 and 90 days. High-strength concrete waste provided strengths close to the reference mixture, while normal concrete and brick aggregates resulted in lower but still structural-grade concretes. The strengths achieved ranged between 35 MPa and 73 MPa, which is between 48% and 98% of the reference value, respectively. A linear relationship was found between density and compressive strength, enabling estimation from simple measurements. The results confirm that uncontaminated demolition waste can be efficiently reused on site with limited testing, supporting circular construction and reduced environmental impact. Full article

The construction industry is undergoing a rapid digital transformation, with Digital Twins (DTs) and Extended Reality (XR) as two emerging technologies with great potential. Despite their potential, there are several challenges regarding DT and XR use in construction projects, including implementation barriers, interoperability issues, system complexity, and a lack of standardized frameworks. This study presents a systematic literature review (SLR) of DT and XR technologies—including Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR)—in the construction industry. The study analyzes 52 peer-reviewed articles identified using the Web of Science database to explore thematic findings. Key findings highlight DT and XR applications for safety training, real-time monitoring, predictive maintenance, lifecycle management, renovation or demolition, scenario risk assessment, and education. The SLR also identifies core enabling technologies such as Building Information Modeling (BIM), Internet of Things (IoT), Big Data, and XR devices, while uncovering persistent challenges including interoperability, high implementation costs, and lack of standardization. The study highlights how integrating DTs and XR can improve construction by making it smarter, safer, and more efficient. It also suggests areas for future research to overcome current challenges and help increase the use of these technologies. The primary contribution of this study lies in deepening the understanding of DT and XR technologies by examining them through the lenses of their benefits as well as drivers for and challenges to their adoption. This enhanced understanding provides a foundation for exploring integrated DT and XR applications to advance innovation and efficiency in the construction sector. Full article

Geopolymer mortars were produced from construction and demolition waste using a binary binder of recycled brick powder/recycled concrete powder (RBP/RCP = 70/30 wt%), activated with a hybrid alkaline solution (NaOH/Na₂SiO₃/KOH) and reinforced with sisal fibres at 0–2 wt%. Mechanical performance (compression and three-point bending) and microstructure–phase evolution (XRD, FTIR, SEM-EDS) were assessed after low-temperature curing. Sisal addition delivered a strength–toughness trade-off with a reproducible optimum at ~1.0–1.5 wt%; at 2.0 wt%, fibre clustering and connected porosity reduced the effective load-bearing section, penalising flexure more than compression. Microstructural evidence indicates coexistence and co-crosslinking of N-A-S-H and C-(A)-S-H gels—enabled by Ca from RCP—leading to matrix densification and improved fibre–matrix anchorage. Fractographic features (tortuous crack paths, bridging, and extensive pull-out at ~1.5 wt%) are consistent with an extended post-peak response and higher fracture work without compromising early-age strength. This study achieves the following: (i) it identifies a practical reinforcement window for sisal in RBP/RCP geopolymers, (ii) it links gel chemistry and interfacial phenomena to macroscopic behaviour, and (iii) it distils processing guidelines (gradual addition, workability control, gentle deaeration, and constant A/S) that support reproducibility. These outcomes provide a replicable, low-embodied-CO₂ route to fibre-reinforced geopolymer mortars derived from CDW for non-structural and semi-structural applications where flexural performance and post-peak behaviour are critical. Full article

This study examines magnesium potassium phosphate cements (MKPCs) modified with industrial wastes for extrusion-based 3D concrete printing, evaluating the rheological properties (workability, setting time), mechanical performance and printability of formulations incorporating secondary materials: Mg dross waste (up to 20 wt.%, replacing MgO), calcined sewage sludge (up to 10 wt.%, replacing KH₂PO₄), alternative fillers such as glass from municipal solid waste glass and from construction and demolition waste and ground blast furnace slag, benchmarked against volcanic ash. The baseline MKPC exhibited initial/final setting times of 34/109 min, good workability and compressive strengths of 29 MPa (1 day)/28 MPa (28 days). Optimal low-waste mixes (e.g., using municipal glass or 20 wt.% Mg dross) shortened the initial setting to 19–25 min (decreasing 24–42%), reduced the slump by 9–18% yet remained printable at laboratory-scale and achieved 1-day strengths >23 MPa/28-day >31 MPa (comparable or superior). Glass from municipal waste proved most promising, due to superior workability, lighter aesthetics and strength gains, supporting circular economy goals while substantially reducing material costs; higher waste levels compromised fluidity and buildability. Mineralogical analyses confirmed K-struvite formation alongside residual periclase, validating these formulations for upscaling sustainable 3D printing. Full article

To meet 2050 climate targets, the construction sector must reduce CO₂ emissions and transition toward circular material flows. Recycled aggregates (RA) derived from construction and demolition waste (CDW) and industrial byproducts such as oil shale ash (OSA) show potential for use in concrete, although their application remains limited by standardisation and performance limitations, particularly in structural uses. This study aims to develop and evaluate low-strength, resource-efficient concrete mixtures with full replacement of natural aggregates (NA) by CDW-derived aggregates, and partial or full replacement of cement CEM II by OSA–metakaolin (MK) binder, targeting non-structural 3D-printing applications. Mechanical performance, printability, cradle-to-gate life cycle assessment, eco-intensity index, and transport-distance sensitivity for RA were assessed to quantify the trade-offs between structural performance and global warming potential (GWP) reduction. Replacing NA with RA reduced compressive strength by ~11–13% in cement-based mixes, while the aggregate type had a negligible effect in cement-free mixtures. In contrast, full cement replacement by OSA-MK binder nearly halved compressive strength. Despite the strength reductions associated with the use of waste-derived materials, RA-based cement-free 3D-printed specimens achieved ~30 MPa in compression and ~5 MPa in flexure. Replacing CEM II with OSA-MK and NA with RA lowered GWP by up to 48%, with trade-offs in the air-emission, toxicity, water and resource categories driven by the OSA supply chain. The cement-free RA mix achieved the lowest GWP and best eco-intensity, whereas the CEM II mix with RA offered the most balanced multi-impact profile. The results show that regionally available OSA and RA can enable eco-efficient, structurally adequate 3D-printed concrete for construction applications. Full article

Glass wool waste constitutes a rapidly increasing fraction of construction and demolition residues, yet it remains one of the most challenging insulation materials to recycle. Its non-combustible nature, extremely low bulk density, and high fibre elasticity preclude energy recovery and severely limit conventional mechanical recycling routes, resulting in long-term landfilling and loss of mineral resources. Converting glass wool waste into a fine mineral powder represents a potentially viable pathway for its integration into low-carbon construction materials, provided that industrial scalability, particle-size control, and chemical compatibility with cementitious binders are ensured. This study investigates the industrial-scale milling of end-of-life glass wool waste in a ventilated horizontal ball mill. It compares two grinding routes: a corundum-free route (BK) and an abrasive-assisted route (ZK) employing α-Al₂O₃ corundum to intensify fibre fragmentation. Particle size distribution was quantified by laser diffraction using cumulative and differential analyses, as well as characteristic diameters. The results confirm that abrasive-assisted milling significantly enhances fragmentation efficiency and reduces the coarse fibre fraction. However, the study demonstrates that this gain in fineness is inherently coupled with the incorporation of α-Al₂O₃ into the milled powder, introducing a chemically foreign crystalline phase that cannot be removed by post-processing. From a cement-oriented perspective, this contamination represents a critical limitation, as α-Al₂O₃ may interfere with hydration reactions, aluminate–sulfate equilibria, and microstructural development in Portland and calcium sulfoaluminate binders. In contrast, the corundum-free milling route yields a slightly coarser, chemically unmodified powder, offering improved process robustness, lower operational complexity, and greater compatibility with circular economy objectives. The study establishes that, for the circular reuse of fibrous insulation waste in cementitious systems, particle fineness alone is insufficient as an optimization criterion. Instead, the combined consideration of fineness, chemical purity, and binder compatibility governs the realistic and sustainable reuse potential of recycled glass wool powders. Full article

The accelerated carbonation of fresh concrete and recycled aggregates is one of the safest methods of CO₂ sequestration as it mineralizes CO₂, preventing its escape into the atmosphere. CO₂ injection during batching of concrete improves its strength and may partially replace Portland cement, as with supplementary cementitious materials (SCMs). The curing of concrete by incorporation of CO₂ also accelerates early strength development, which may enable early stripping of formwork/moulds for precast and in situ construction. The carbonation process may also be used for the beneficiation of recycled aggregates sourced from demolition waste. The CO₂ mineralization technique may also be used for producing low-carbon, carbon-neutral, or carbon-negative concrete constituents via the carbonation of mineral feedstock, including industrial wastes like steel slag, mine tailings, or raw quarried minerals. This research paper analyses various available technologies for CO₂ storage in concrete, CO₂ curing and mixing of concrete, and CO₂ injection for improving the properties of recycled aggregates. Carbon dioxide can be incorporated into concrete both through reaction with hydrating cement and through incorporation in recycled aggregates, giving a product of similar properties to concrete made from virgin materials. In this contribution we explore the various methodologies available to incorporate CO₂ in both hydrating cement and recycled aggregates and develop a protocol for best practice. We find that the loss of concrete strength due to the incorporation of recycled aggregates can be mitigated by CO₂ curing of the aggregates and the hydrating concrete, giving no negative strength consequences and sequestering around 30 kg of CO₂ per cubic metre of concrete. Full article

Concrete waste generated from the demolition of structures constitutes a significant source of waste worldwide. Recycled concrete aggregates (RCA) obtained from this waste exhibit disadvantages such as high porosity and low mechanical strength; therefore, they are not used in pavement structures without improvement. This study investigates the feasibility of using RCA improved with waste-based stabilizers as highway subbase material. RCA was used as fine aggregate and blended with basalt aggregate (BA) at different replacement ratios. The mixtures were subjected to California Bearing Ratio (CBR) tests to determine the optimum RCA content. Subsequently, unconfined compressive strength (UCS) tests were conducted using calcium carbide slag (CCS) as an activator and sewage sludge ash (SSA) as pozzolanic material at various proportions. The experimental results indicated that the mixture containing 35% RCA exhibited the most favorable performance, while higher RCA contents resulted in significant reduction in CBR values. The highest UCS value was obtained in the mixture containing 30% waste additive by weight of RCA with a CCS:SSA ratio of 3:7. For this mixture, CBR reached 315%, and displacement measured in the cyclic plate loading test under a load of 35 kN was 2.5 mm. This mixture provides sustainable and mechanically suitable alternatives for highway subbase applications. Full article