Short/long term assessment of precast concrete block waste as a supplementary cementitious material: mechanical performance, hydration, and microstructure evolution
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Date
2025
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Abstract
The massive production of cement and concrete is projected to grow significantly, with cement alone accounting for 7 %–8 % of global CO2 emissions. Reducing the environmental impact of the cement industry is critical, and low-carbon cement blends incorporating supplementary cementitious materials (SCMs) valorized from industrial wastes are a promising near-term solution. Precast concrete block waste (PCBW), an industrial waste from precast concrete plants and masonry demolition, offers potential as an SCM. This study evaluates the effects of PCBW replacement (0 %, 10 %, 20 %, and 50 % by volume) in cement paste mixtures (CPMs) on hydration and mechanical performance over short (3 days) and long (90 days) terms. The evaluation included isothermal calorimetry, compressive strength, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential thermogravimetric (DTG) analysis, and field-emission scanning electron microscopy. Predictive models using polynomial regression and support vector regression (SVR) were developed to estimate CPM compressive strength based on PCBW replacement levels and curing ages. Results showed that a 10 % PCBW replacement did not statistically affect CPM compressive strength, while 20 % replacement reduced it by 12 % at 90 days. XRD and FTIR analyses revealed high quartz and calcite content in PCBW, consistent with its chemical composition. DTG confirmed the low pozzolanic activity of PCBW compared to other SCMs. The predictive models demonstrated accuracy through 5-fold cross-validation. Using PCBW as an SCM up to 10 % is recommended to reduce environmental impacts without compromising mechanical performance.
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Keywords
Precast concrete block waste, Compressive strength, Filler, Supplementary cementitious material, Sustainability