Anming She

Ultra-high-performance concrete (UHPC) matrix faces critical challenges of high carbon footprint and significant autogenous shrinkage. Supersulfated cement (SSC), a potentially lower-carbon binder comprising ground granulated blast-furnace slag and gypsum, offers a promising alternative. This study systematically investigated the effect of gypsum type—phosphogypsum (PG), dihydrate gypsum (DH), and anhydrite (AH)—on the early hydration and shrinkage behavior of UHPC matrix incorporating 30% SSC as Portland cement replacement. A multi-technique approach, including mechanical testing, isothermal calorimetry, XRD, TG-DSC, SEM, LF-NMR, and autogenous shrinkage measurements, was employed. Results demonstrate that gypsum type critically governs sulfate dissolution kinetics, thereby dictating phase assemblage and microstructural evolution. DH provides relatively rapid sulfate dissolution, promoting earlier AFt and gel formation, which is associated with the highest early strengths and a marked reduction in autogenous shrinkage. AH shows a slower but sustained sulfate supply, resulting in comparable 28-day strength with moderate shrinkage reduction. PG yielded the lowest autogenous shrinkage (374 μm/m at 7 d), but it also suffered from severe early-age retardation due to soluble phosphate impurities, as evidenced by the delayed hydration peak and lowest 3 d strength. This behavior is mainly related to strong early-age retardation, delayed hydration, delayed setting, and a prolonged low-stiffness state. These findings suggest that appropriate gypsum selection in SSC enables tailored early-age performance and improved volume stability in the UHPC matrix, offering guidance for utilizing industrial by-products such as phosphogypsum in sustainable high-performance concrete design.

Vibration energy harvesting devices are intrinsically linked to environmental vibration intensity in practical applications. This study proposes a composite negative Poisson’s ratio piezoelectric energy harvester inspired by I-beam structures, designed to achieve high energy conversion efficiency under low-frequency vibration conditions. Surface functional zoning is achieved through optimized structures and shapes, causing significant changes in the distribution and magnitude of surface displacement during bending deformation, thereby effectively unifying low resonance frequency, high output power, and excellent durability. Concurrently, the key piezoelectric properties of the composite model were also analyzed through finite element simulation. An overview of the vibration testing, impact testing, and continuous vibration testing at resonance frequency reveals that the optimal model exhibits a 36% improvement in impact electrical response compared to uniform Poisson’s ratio piezoelectric energy harvesters, and the overall power output per unit area increased by 145%. The long-term output voltage variation curve under resonant frequency reveals its outstanding durability performance and repeatable excitation characteristics, with an effective cycle count of up to 50 000 times. This research offers configuration approaches for low-frequency energy harvesting, with the potential to realize vibration energy collection in fields such as roads and bridges.

Alkali–silica–reaction (ASR) in concrete has always been a significant hidden threat, which could cause the expansion and lead to internal stress, ultimately resulting in extensive damage to infrastructure. This study proposes a novel approach to investigate the potential of waste dolomite powder (WDP) as an inert material in mortar to mitigate ASR. The accelerated mortar bar test demonstrated that incorporating WDP at a constant water-to-cement ratio effectively reduced ASR expansion of mortar by up to 18.17%. Additionally, the results indicated that the mortar prepared by WDP had an evident increase of compressive strength (3.05 – 12.95%), and a decrease of water absorption (3.54 – 22.85%). Pore structure analysis revealed a reduction in porosity by up to 24.55%, attributed to the nucleation and filling effects of WDP during cement hydration. In addition, the dilution effect of WDP in mortar decreased the cement content, reducing the formation of alkaline products and decreasing the pH value of pore solution. X – ray diffraction and thermogravimetry analyses confirmed that the amount of alkaline hydration product (Ca(OH) ₂ ) were reduced by 17.96 – 46.11%. Microstructural analysis was performed by using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy techniques, which further demonstrated that WDP significantly enhanced the compactness of matrix and minimized the formation of cracks, which contributed to the reduced ASR expansion. Notably, the use of WDP significantly reduced the overall embodied CO ₂ footprint, energy consumption and economic cost of the mixes. These findings demonstrate the potential of WDP in improving the performance and sustainability of cement-based materials, providing valuable insights for future development of emerging low-carbon and durable building materials.

Life cycle assessment (LCA) is an excellent tool for developing energy saving and emission reduction strategies. However, inconsistencies in the summary calculation methods in LCA can significantly affect the reliability of LCA reports, such as the allocation of environmental loads related to solid waste. Essentially, allocation methods are used to allocate responsibility for environmental loads in situations where boundaries are unclear, and therefore, they are susceptible to regional, industry, and regulatory influences. For a long time, there has been controversy over the selection of allocation methods. This study is based on actual production data from a typical cement plant in South China. Multiple parallel LCA cases were carried out using different allocation methods, and different allocation methods were analyzed. Concepts such as driving force, active/passive environmental load, Valorized Solid Waste (VSW), and Non-Valorized Solid Waste (NVSW) were introduced. Analysis shows that the choice of allocation method directly affects the effectiveness of energy saving and emission reduction plans in the LCA report. For VSW, the economic allocation method has been proven to have high universality, effectively capturing the driving forces of economic factors. For NVSW, based on the “polluter pays principle” and active/passive environmental load, we introduced the Collaborative Disposal Allocation Method (CD method). In this study, the environmental benefits of domestic waste collaborative disposal were calculated using the CD method, resulting in a 2.25% reduction in global warming potential (GWP) and a 45.39% reduction in respiratory inorganics (RIs).