This study develops a low-carbon binder, oyster shell powder-calcined construction muck cement (OCMC), by incorporating thermally activated construction muck and waste oyster shell powder into an LC 3 -type system. The material aims to promote the high-value utilization of construction and shell wastes while reducing the consumption of conventional cementitious raw materials. We evaluated its mechanical properties, hydration heat, and microstructure. Results identify an optimal 45% substitution rate (30% calcined muck, 15% oyster shell powder) that balances strength and sustainability. At this ratio, reactive alumina synergizes with oyster shell carbonates to generate carboaluminates, densifying the pore structure and ensuring high compressive strength. Furthermore, this mix effectively lowers hydration heat, mitigating early-age thermal cracking risks. A preliminary environmental assessment suggests that the A45 mixture could reduce carbon emissions and energy consumption by approximately 36.3% and 24.1%, respectively, relative to the control group, highlighting the low-carbon potential of OCMC while maintaining considerable mechanical performance.
Buildings may reach the end of their service life due to various reasons such as functional changes, expansion needs, or urban-scale planning decisions. In such cases, reusing existing building components as inputs for new constructions presents a more circular alternative to landfilling or energy-intensive recycling processes. This highlights the importance of considering Design for Disassembly (DfD) in building design. However, the construction industry has high initial investment costs and multiple actors, which may present challenges to the adoption of innovative approaches. Therefore, adapting conventional construction details may provide a practical approach to improving their disassembly potential. This study examines how circular design principles, specifically DfD, can be incorporated into exterior wall details. It analyses existing wall detail practices in both the Netherlands where prefabrication is relatively common, and Türkiye where on-site construction remains dominant, to explore how differences in construction practices are reflected in their design for disassembly. It also examines how bio-based materials can be incorporated into exterior wall details while maintaining their disassembly potential. Based on these analyses, the study proposes redesigned versions of conventional exterior wall details optimized for both disassembly and the use of bio-based materials. These proposals are evaluated in terms of their detachability with the Disassembly Potential Measurement Method and disassembly sequence analysis. Results indicate that the disassembly potential of conventional exterior wall details can be improved through relatively small changes and component or element selection decisions without waiting for major changes in the construction industry.
Lightweight cementitious composites containing copper tailings and limestone powder were prepared by chemical foaming followed by carbonation curing. The three mineral-replacement mixtures exhibited larger cross-sectional carbonation area ratios than the OPC reference, exceeding 80% after 3 days. After 14 days of carbonation curing, C40-C exhibited the highest TG-based net CO 2 uptake among the three blended mixtures, reaching 15.55 wt% on the normalization basis defined in this study. Limestone-associated filler and nucleation effects influenced early hydration and aluminate-related reactions. The MIP results indicated a non-uniform redistribution of the mercury-accessible pore network, consistent with localized carbonate filling and partial pore-throat coarsening. C30L10-C achieved a compressive strength of 27.8 MPa after 14 days and exhibited relatively favorable residual strength retention at 600 °C. However, severe strength deterioration occurred at 900 °C. These results identify composition-dependent differences in carbonation response, strength development, and high-temperature performance within the investigated lightweight cementitious system.
Low-grade clay is a promising supplementary cementitious material for reducing clinker consumption and CO2 emissions in the cement industry. This study systematically compared mechanochemical grinding and thermal activation for enhancing the reactivity of low-grade clay. Grinding progressively promoted partial amorphization of kaolinite and montmorillonite, whereas calcination above 800 °C effectively activated illite through dehydroxylation and structural amorphization. 60-min grinding produced higher dissolved Al and Si dosages and bound water contents (5.3-6.9 wt.%) than calcination, indicating greater pozzolanic reactivity. However, calcination at 800 °C yielded the highest 28-d compressive strength (∼55 MPa), whereas ground clays achieved 41-45 MPa despite more effective pore refinement. Grinding prolonged the induction period, while calcination accelerated cement hydration. From an environmental perspective, mechanochemical activation reduced CO2 emissions and energy consumption by 13-20% compared with calcination, demonstrating its potential as a sustainable low-carbon activation strategy for low-grade clays.
Comprehensive transport hubs, as large-scale public spaces, require comfortable indoor acoustic and vibration environments to ensure high-quality service for passengers. This study examined two comprehensive transport hubs in Shanghai. Field measurements of noise and vibration were spatially matched with questionnaire responses by functional area. The matched data were analyzed using fully adjusted proportional-odds ordinal logistic models. Regression standardization was then used to derive population-average exposure-response relationships and two-parameter logistic surrogates. Representative noise and vibration levels ranged from 55.5 to 70.7 dB(A) and 60.7-68.0 dB, respectively, with metro platforms among the higher-exposure areas. Each 5 dB(A) increase in noise was associated with 2.39 times the cumulative odds of higher annoyance, while vibration showed a positive but uncertain association. Poorer self-rated health was associated with higher noise annoyance. Standardized responses reached 15.0% for noise %HA and 54.7% for vibration %FA. The framework links area-level exposure assignment, multivariable adjustment, population-response characterization, and engineering applications.
