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.