This study investigated the working performance of mortar after CO₂ injection and mixing. Three curing regimes — carbonation curing, water curing, and combined carbonation-water curing (WC) — were employed to identify the most effective environment and method for curing and strength enhancement. The influence of recycled aggregate strength on the damage evolution of recycled concrete was analyzed using model concrete specimens and the digital image correlation (DIC) technique. The results indicate that specimens subjected to combined carbonation-water curing exhibited the lowest porosity, with a reduction of 1.7%–2.0% compared with those under carbonation curing alone, which showed the highest porosity. Moreover, the damage evolution process demonstrated clear regularity, and the strain development exhibited a relatively predictable trend. The higher the water-to-cement ratio of the CO₂-injected mixed mortar, the lower its fluidity, with reductions ranging from 7.3% to 13.3%. Conversely, a lower water-to-cement ratio resulted in a greater loss of workability after CO₂ injection mixing. In addition, a pronounced strength difference between the new and old mortar matrices led to strain concentration within the old mortar region.

The rapid growth in lithium production has led to a substantial accumulation of lithium slag, an industrial by-product. To promote the sustainable recycling of this waste and alleviate environmental concerns, this study explored the feasibility of incorporating lithium slag into cement-stabilized clay for use as a pavement base. The study comprehensively evaluated the mechanical properties, microstructural characteristics, and environmental-economic viability of cement-lithium slag stabilized clay with different lithium slag substitution rates (0, 6.25%, 12.5%, 18.75%, 25%, and 50%). Experimental findings indicated that the unconfined compressive strength (UCS) exhibited a convex trend where it initially rose and subsequently declined as the substitution rate increased, culminating in a peak value at an 18.75% substitution rate. Specifically, after 7 days of curing, the specimen with 18.75% substitution rate demonstrated a distinct strength enhancement of 37.76% over the 0 substitution rate, suggesting its suitability for higher-traffic pavement base. Regarding durability, although the UCS fluctuated (increasing then decreasing) with the number of wetting–drying cycles, the inclusion of lithium slag effectively improved the material’s resistance, with 18.75% again proving to be the optimal substitution rate. Specimen photos post-UCS testing and wetting–drying cycles revealed that cement-lithium slag stabilized clay exhibited the least severe failure characteristics at a 18.75% substitution rate. At the 18.75% substitution rate, reactive SiO₂ and Al₂O₃ in lithium slag underwent pozzolanic reactions with Ca(OH)₂ generated from cement hydration, forming additional C-S–H, networked C-A-S–H, and ettringite crystals, thereby increasing the strength of the stabilized clay. At the 18.75% substitution rate, cement-lithium slag stabilized clay achieved the best balance among compressive strength, environmental benefits, and economic efficiency. These findings offer valuable insights for utilizing cement-lithium slag stabilized clay in road base construction.

This study explores the use of coal gangue powder (CGP) to enhance the workability of ground granulated blast-furnace slag (GGBS)-based geopolymer pervious concrete (GPCC) and promote the reuse of industrial waste. CGP was introduced as a partial replacement for GGBS at rates ranging from 0 to 50%. The impact of CGP on the multiscale properties of GPCC was evaluated, including rheology, mechanical strength, permeability, frost resistance, and pore structure. Incorporating CGP improved paste flowability by reducing yield stress, plastic viscosity, and thixotropy. However, mechanical strength declined with increasing CGP content. At 40% replacement, the 28-day compressive strength dropped to 17.9 MPa, falling below the C20 strength class defined in relevant specifications. Although CGP increased total porosity, permeability decreased. This was likely due to bottom pore blockage caused by changes in flow behavior. Frost resistance also diminished at higher CGP rates, with over 7% mass loss and 20% strength loss after 25 freeze–thaw cycles. Pore structure analysis revealed a shift toward larger pores, reducing compactness and long-term durability. When CGP content was limited to 30% or less, GPCC maintained a balanced performance across strength, permeability, durability, and workability. These results highlight the potential of CGP-based geopolymers in sustainable infrastructure applications, especially in sponge cities and pervious pavement systems.

3D-printed mortar (3DPM) is associated with significant cement consumption, which raises substantial environmental concerns. This study investigates the reuse of sugarcane bagasse ash (SBA), which has a high SiO₂ content, in 3DPM to reduce carbon emissions and to promote sustainable development. The raw SBA was first dried and then ground. Then, five mixtures with varying SBA dosages, ranging from 0 to 20% cement replacement, were developed and tested. This study examines the effects of SBA on key properties of 3DPM, such as flowability, hydration kinetics, setting time, and compressive strength. The results indicate that increasing SBA content reduces the flowability of the mixtures. It significantly reduces the setting time from 207.5 min of the control mix to 49.5 min as the replacement ratio is 20% due to finer particles. The isothermal calorimeter test results indicate that SBA accelerates the cement hydration process, potentially reducing the usage of an accelerator in 3DPM. Including SBA in the mortar mix significantly increased compressive strength within the first 24 h and also up to 28 days. This accelerated reaction boosts the early-age strength development of the concrete mixture, making it especially suitable for applications that demand rapid strength gain.

Efficient utilization of waste slurry resources is a pivotal strategy in urban engineering construction, aligning with the global “dual carbon” goals of sustainability and carbon neutrality. To quantitatively assess the carbon emission intensity and mitigation potential associated with the utilization and disposal of urban waste slurry (UWS), a life cycle assessment (LCA) framework was adopted. A partial cradle-to-site LCA was conducted for a representative project in Shanghai, China, encompassing all key stages from material extraction to on-site application. An inventory of the materials and fossil fuel energy utilized during construction was compiled to calculate the primary energy consumption and the corresponding embodied carbon. Carbon emission accounting using SimaPro software was conducted for three UWS resource utilization methods: subgrade backfill material (SBM), scour protection backfill material (SPBM), and fluid self-compacting backfill material (FSCBM). Based on the analysis results, recommendations were proposed to enhance carbon emission reduction measures for utilization. The results indicate the following order of carbon emissions from UWS: SPBM (93.1 kg CO₂-eq/m³) > FSCBM (47.1 kg CO₂-eq/m³) > SBM (41.8 kg CO₂-eq/m³). The solidification treatment of UWS has emerged as the dominant contributor to carbon emissions across all utilization pathways, accounting for 59.33%, 61.33%, and 64.12% of the total emissions for SBM, FSCBM, and SPBM, respectively. Notably, in the SPBM route, transportation emissions alone account for 37.8% of the total emissions. These findings suggest that the adoption of low-carbon curing agents and the optimization of transportation methods can significantly reduce overall carbon emissions. Furthermore, from a long-term environmental perspective, direct landfill disposal of UWS constitutes the least sustainable management option, with the highest carbon emissions at 123.62 kg CO₂-eq/m³. Compared to plain concrete and recycled aggregate concrete per unit volume, SBM achieves significant carbon reductions of 51.3% and 22.0%, respectively. Consequently, the resource utilization of UWS, especially through SBM, demonstrates significant potential to mitigate environmental impacts, offering a promising pathway for sustainable development in the construction materials sector.

While extensive thermal comfort research exists for severe cold and hot-humid climates, studies focusing on moderate climate zones remain scarce and fragmented. To address this gap, this study synthesizes one of the most temporally extensive and typologically comprehensive field investigations (2006–2022) in such zones, with a primary focus on Kunming. By analyzing 7 289 subjective questionnaires across diverse building types (residential, office, educational, healthcare), this study quantifies the seasonal thermal neutral temperatures, revealing a mean of 23.3 ℃ in summer (range: 21.6–25.0 ℃) and 18.1 ℃ in winter (range: 15.6–21.4 ℃). A key finding is the significant disparity between the winter neutral temperature and the measured average indoor temperature (14.5 ℃), highlighting a critical comfort deficit during colder months. Furthermore, this study pioneers the explicit inclusion of vulnerable groups and explores synergies between comfort attainment and energy efficiency. Based on these findings, we propose actionable indoor temperature setpoints of 23.0–25.0 ℃ for summer and 17.0–19.0 ℃ for winter, alongside tailored architectural design strategies. This study provides a robust, data-driven foundation for refining building standards and optimizing energy-efficient design in understudied moderate climate zones.

To meet the carbon emission challenges posed by the large-scale application of traditional cement-based materials, incorporating industrial by-products at high dosages into high-performance concrete serves as a sustainable strategy. Based on this approach, low-carbon high-performance concrete (LC-HPC) has been developed, featuring low carbon emissions alongside high strength and high toughness. This study investigates the emission reduction potential, strength, peak strain, stress–strain relationship, and their stochastic properties of high-performance concrete incorporating high dosages of industrial by-products through a comprehensive experimental program involving 360 specimens across 10 groups, subjected to uniaxial and splitting tensile tests. The key variables include the cement replacement ratio (r_CRR), steel fiber (SF) volume fraction, and polypropylene fiber (PF) volume fraction, which are considered random factors potentially influencing tensile performance. Results demonstrate that incorporating industrial by-products can reduce carbon emissions in LC-HPC by 49.49% to 65.66% compared to conventional high-performance concrete. Meanwhile, the incorporation of hybrid fibers improves peak tensile stress by 42.7% and peak tensile strain by 54.0%, while also substantially enhancing residual stress and ductility. Notably, PF contributes to mitigating the high variability introduced by SF, reducing the coefficient of variation in peak stress and peak strain by up to 30.25% and 44.85%, respectively. Based on the test results, a new stochastic stress–strain model for LC-HPC tensile behavior is developed and validated, which can effectively predict the uniaxial tensile stochastic mechanical response, thereby providing a reliable theoretical basis and technical support for the refined design and stochastic evaluation of LC-HPC structural performance.

Mass timber (MT) has become a prominent construction material due to its strong structural performance and notable carbon sequestration capacity. This study examines the properties of MT sourced from various wood species, offering designers key insights to assess design compliance and evaluate substitution potential across species. It highlights the practical applications and advantages of MT (glued laminated timber, cross-laminated timber, dowel laminated timber, parallel strand lumber, and laminated veneer lumber). The study investigates the current main wood species used in MT, elucidating the reasons behind the dominance of softwood. In addition, a comprehensive review of wood properties is conducted to compare the growth rate, fire resistance, and durability between softwood and hardwood species. It further conducts an analysis of hardwood’s application potential by examining general characteristics, mechanical properties, and performance in various application scenarios. Notwithstanding, challenges related to adhesive distribution and bond-line integrity are also indicated. The study further discusses hybrid and artificial wood, emphasizing their emerging roles in construction. In addition, it discusses effective manufacturing, protective, and monitoring methods for MT. An evaluation of mechanical, thermal, acoustic, and seismic performance reinforces that MT is suitable for diverse construction scenarios. The study also addresses factors influencing swelling, shrinkage, and creep behaviors in MT. In conclusion, while MT exhibits superior properties relative to solid wood, its application in structural design remains complex, necessitating further research to enhance its role in sustainable building practices.

Water retention curves are used to describe the degree of water saturation in porous materials. These curves exhibit hysteresis, meaning that the relationship between water content and applied suction depends on the wetting and drying history of the material and environmental conditions. This study investigates the effect of hysteresis on the durability of concrete made from recycled concrete aggregates (RCA), demonstrating that the Van Genuchten model can be applied to such recycled materials. A chemo-hydraulic, multiscale finite element squared (FE²) model was developed and validated. This model represents chloride ingress within the unsaturated porous structure of concrete. The constitutive equations are formulated at the mortar scale based on experimentally measured intrinsic material properties. Through numerical homogenization, these properties are upscaled to simulate the macroscopic behavior of concrete made with 100% RCA. Hysteresis calibration properties were also obtained experimentally. Experimental validation confirms that the Van Genuchten model can be applied to recycled aggregate concrete. A sensitivity analysis of the hysteresis model parameters revealed that water content is significantly impacted. However, this influence is less pronounced when studying chloride ingress.

This study investigates the mechanical behavior and numerical modeling of lightweight hollow block timber shear wall systems for seismic performance evaluation. Compression tests on panel materials and pull-out tests on threaded stainless-steel rod connections were conducted to characterize the mechanical properties of key structural components. The experimental results revealed significant anisotropy in bamboo composite panels, with compressive strength in the transverse direction reaching approximately 47–48 MPa, while the parallel configuration exhibited lower strength values of 9–12 MPa. Pull-out tests showed that increasing the embedment length from 120 to 150 mm improved post-slip stability and delayed the onset of rigid-body motion, although no clear monotonic increase in peak load was observed. Based on the experimental results, both detailed fiber models and simplified numerical models were developed in OpenSees. The simplified model using the Seismic Analysis of Woodframe Structures (SAWS) material successfully reproduced the cyclic load–displacement behavior of the shear walls while significantly reducing computational cost compared with the fiber model. Time-history analyses of a three-story lightweight structure demonstrated that the proposed modeling method can effectively predict structural displacement responses under peak ground accelerations ranging from 0.1 g to 0.5 g. The proposed approach provides an efficient analytical framework for seismic performance assessment and design of lightweight timber structures.

Coal gangue (CG), a massive by-product of coal mining, presents both environmental challenges and opportunities as a sustainable alternative to natural aggregates in concrete. However, its high porosity, variable composition, and inferior properties often limit the performance of coal gangue aggregate concrete (CGAC). This review provides a comprehensive and systematic analysis of recent advances in CGAC research, with a clear aim to bridge the gap between material characteristics and structural applications, covering the physicochemical properties of CG, mechanical behavior, durability issues, modification strategies, structural performance, and life cycle assessment. Key findings indicate that while raw CG aggregates generally reduce concrete strength and durability—especially in high-grade mixes—effective improvements can be achieved through matrix modification (e.g., fly ash, fibers, nano‑SiO₂) and aggregate treatment (e.g., calcination, coating). Structurally, CGAC in composite systems such as concrete-filled steel tubes retains over 95% stiffness even at full aggregate replacement. Life cycle assessment studies confirm that using CG sand in concrete can lower costs by 25%–30% and carbon footprint by 18%–22%, provided transport distances are optimized. The study concludes that CGAC represents a viable, eco-friendly construction material that supports waste valorization and resource conservation. Future efforts should focus on standardizing durability evaluation, advancing high-value applications, and promoting its integration into industrial practice.

This study evaluates the whole-life environmental and energy performance of cross-laminated timber (CLT) versus reinforced concrete in office buildings, using 't Centrum (Westerlo, Belgium), Belgium’s first certified circular CLT office building, as a real-world case study. Life cycle assessment (LCA) was conducted following ISO 14040/44 and EN 15978 (stages A1–A5, B4, B6, C3–C4; 50-year horizon), combined with dynamic energy simulation in DesignBuilder. Four construction material scenarios and four heating, ventilation, and air conditioning (HVAC) configurations were assessed. Net life cycle global warming potential (GWP) for the CLT reference scenario is 9.97 kg CO₂e/(m²·year), representing a 30% reduction compared to the best-performing concrete alternative (14.34 kg CO₂e/(m²·year)), reported using the EN 15804 + A2 − 1/ + 1 biogenic carbon convention with fossil and biogenic flows disaggregated separately. Although CLT’s lower thermal mass increased overheating risk, adding bio-based thermal inertia materials reduced thermal discomfort hours by up to 25% per EN 16798–1 adaptive comfort criteria, with negligible carbon impact (< 1%). Operational energy consumption was comparable across structural systems. HVAC equipment accounts for 68% of material-related emissions in CLT buildings due to repeated replacement cycles over the building lifespan. Sensitivity analysis (Morris method) identified the electricity mix and HVAC system type as dominant uncertainty sources. In high-performance Belgian buildings, embodied carbon, not operational energy, is the decisive lifecycle factor, and CLT combined with bioclimatic design and low-carbon HVAC systems represents a credible circular pathway toward carbon–neutral construction in temperate climates.

This study systematically analyzes the combined effects of crystallization admixtures (CA), basalt fibers (BF), and microorganisms in alkali-activated Portland cement–slag (AAPCS), as well as their influence on mechanical properties and self-healing behavior. Through mechanical testing, strength recovery analysis, crack repair evaluation, water absorption measurements, and microstructural characterizations (X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry–Derivative Thermogravimetry (TG–DTG), and Scanning Electron Microscopy–Energy Dispersive Spectroscopy (SEM–EDS)), the self-healing mechanisms is elucidated, supported by statistical analysis of the data. The results show that improvements in mechanical properties, strength recovery, and water absorption are statistically significant at a confidence level of p < 0.05. B0.3C20 exhibited 28 d compressive and flexural strengths of 35.6 MPa and 6.6 MPa, respectively, representing increases of 43.5% and 34.7% compared with B0C0 (24.8 MPa and 4.9 MPa). After 28 d of self-healing, B0.3C10 achieved a strength recovery rate of 28.2%. The crack repair results show that the combined effect of CA and BF increases the maximum healed crack width to 0.81 mm. Water absorption tests show that the capillary absorption coefficient of B0.6C20 (0.034) is reduced by 60% compared with B0C0 (0.085), indicating significantly improved impermeability. XRD and FTIR confirmed that C-(A)-S–H and CaCO₃ are the main healing products, while TG and SEM–EDS further demonstrated the promoting impact of CA and BF on microbial self-healing performance.

Ultra-high performance concrete (UHPC) typically relies on high cement/clinker content, leading to elevated cost and environmental burdens. This study develops a lower-carbon UHPC by (i) reducing cement demand through partial cement replacement with gold tailings (GT, 10%–30% by mass) and (ii) externally incorporating pre-wetted coal gangue ceramsite (CGC, 200–600 kg/m³) as a porous aggregate providing internal curing. Workability, mechanical properties, autogenous deformation, heavy-metal leaching, and microstructure (SEM) were investigated, together with a life cycle assessment (LCA) per 1 m³ of UHPC. Increasing GT replacement and CGC content decreased flowability. At 28 d, GT replacement reduced compressive strength, reaching a 20.01% drop at 30% GT; when CGC was added to the 20% GT mixture, compressive strength slightly increased at moderate dosages (maximum + 2.76%), while flexural strength decreased with CGC addition. GT markedly mitigated autogenous shrinkage (up to 51.44% reduction), and mixtures with pre-wetted CGC and an expansive agent exhibited a late-age net expansion tendency. Leaching concentrations of Mn and Ba were far below regulatory limits (Mn ≤ 0.027 5 mg/L; Ba ≤ 0.235 6 mg/L). LCA results indicate that T2C4 (chosen as a balanced option within the investigated design space) reduces global warming potential by 32.95% and lowers non-renewable energy demand by 31.34% relative to the reference UHPC. Overall, GT directly reduces cement consumption, and CGC, when normalized to a 1 m³ functional unit, can partially replace conventional constituents, offering additional potential for clinker and carbon reduction within the defined cradle-to-gate boundary.

This study investigates the potential use of dowels made from thick strip bamboo panel and bamboo scrimber as eco-friendly and cost-effective connectors for timber structures. Mechanical behaviors were analyzed through three-point bending tests and half-hole bearing tests between dowel and spruce–pine–fir (SPF) lumber. The results show that bamboo scrimber dowels significantly outperform thick strip bamboo panel dowels in bending performance, with an average yield strength of 68.29 MPa—higher than that of thick strip bamboo panel dowels (38.56 MPa). Under parallel-to-grain loading, the embedment strength of bamboo scrimber dowels (30.34 MPa) greatly exceeded that of thick strip bamboo panel dowels (10.76 MPa). In contrast, both dowel types exhibited comparable bearing performance under perpendicular-to-grain loading. Digital image correlation (DIC) analysis reveals distinct strain localization patterns and failure mechanisms, consistent with observed damage modes. Current timber design standards tend to overestimate the capacity of bamboo dowel connections, indicating limited applicability. This study provides experimental data and results analysis to support the design and implementation of bamboo dowel connections, thereby advancing the use of bamboo materials into timber engineering.

As a key component of the New Western Land-Sea Corridor in China, the high-quality construction of the Pinglu Canal holds considerable significance. Concrete, the most widely used construction material in the project, presents several distinctive engineering characteristics, including large-scale applications over long spans, complex structures for water-saving ship locks, stringent durability requirements, tight construction schedules, and constrained working spaces. These factors not only create technical challenges but also pose a severe, systemic low-carbon challenge due to the huge carbon emission baseline and high carbon intensity associated with concrete construction. This study analyzes the key challenges for concrete engineering in the Pinglu Canal, and proposes a framework for solutions that integrates structural safety with low-carbon synergy across multiple stages and multiple levels. Based on this framework, this study further summarizes the demonstration solutions already implemented in the Pinglu Canal. Drawing from the Pinglu Canal case, this study aims to provide theoretical references and practical guidance for the low-carbon construction of modern canal engineering projects.

Deep soil mixing (DSM) is a proven in situ ground improvement technique conventionally employing cement/lime as hydraulic binders. Escalating concerns regarding greenhouse gas emissions and chemical durability of these materials have prompted the exploration of sustainable alternatives, notably supplementary cementitious materials (SCMs) and alkali-activated binders (AABs). This review consolidates recent progress in binder innovations, mix design approaches, and performance evaluation for sustainable DSM. Emphasis is placed on microstructural evolution, mechanical and durability characteristics, and field applicability. Publication trend analyses demonstrate the rapid growth of DSM-related research and the increasing focus on sustainable binders over the last 15 years (2011–2025). Reviewed studies indicate that SCM- and AAB-based systems can achieve engineering performance comparable to cement-treated soils under specific mix designs and curing conditions, although differences in soil type, water content, specimen preparation, and curing regime limit direct quantitative comparisons across studies. Binder treatment consistently enhances stiffness, reduces permeability, and improves resistance to consolidation, though the creep and dynamic response of AAB-stabilized soils remain underexplored. Field studies, though limited, indicate that optimized blends can meet or surpass design requirements, although variability and long-term performance remain concerns. Environmental aspects, including leachability, life-cycle assessment, and cost–performance trade-offs of alternative binders, are critically reviewed, and future research priorities are outlined to advance sustainable DSM practices.

The structural application of recycled aggregate concrete (RAC) is severely hindered by its low elastic modulus, primarily caused by porous adhered mortar and defective interfacial transition zone (ITZ). This study proposes a novel biomimetic mineralization strategy to construct an enamel-like hydroxyapatite (HAp) coating on recycled coarse aggregates (RCA), restoring the macroscopic stiffness of RAC. The effects of mineralization temperature and duration on the elastic modulus of RAC were systematically investigated. The results showed that the optimal treatment at 60 °C and 24 h achieved exceptional elastic modulus recovery, increasing by 20.5% at 7 d and 17.4% at 28 d (reaching 28.4 GPa). Notably, this stiffness recovery significantly outpaced compressive strength enhancements. The stress–strain response showed that RAC changed from a deformable response to a stiffer load-bearing behavior after biomimetic mineralization, as evidenced by the reduced peak strain of 0.001 68 and the steeper post-peak descending branch. Microstructural and X-ray computed tomographic analyses revealed the underlying densification mechanisms. The biomimetic mineralized layer not only reduced the mesoscale pore fraction, but also effectively filled interfacial defects via localized Ca-O-P enrichment. This localized densification successfully narrowed the ITZ width from roughly 60 μm to 30–40 μm. Biomimetic mineralization transformed the deformation mode of RAC to a favorable stress-transfer behavior by densifying the adhered mortar and reinforcing ITZ between new mortar and RCA to form a continuous, rigid HAp-reinforced transition layer, providing an effective pathway for improving the deformation resistance and high-value utilization of RAC.