Optimising The Performance of Carbide Lime Waste Mortar: The Role of Temperature in Accelerated CO2 Curing

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This study examined the effects of elevated temperatures higher than ambient temperature on the physical, mechanical, and CO2 (carbon dioxide) capturing performance of Carbide Lime Waste (CLW) mortars with 20% cement replacement at early curing ages (1, 3 and 7 days). The CLW mortars cured under accelerated CO2 curing (CLW20acc) were compared with the control samples under ambient curing (CLW20). The temperatures were set at 30°C, 40°C and 60°C with fixed 20% CO2 concentration. Key assessments include density, compressive and flexural strengths, carbonation depth, and microstructural analyses using Thermogravimetric analysis (TGA). Results revealed that mortar densities decreased with increased temperature, but higher curing temperatures significantly enhanced the performance of CLW20acc mortars over control samples. At 60°C, carbonation depth reached 8.50%, 36.18%, and 86.25% after 1, 3, and 7 days, respectively, while compressive strength increased by 51.5% at day 7 compared to day 1. TGA results demonstrated progressive CaCO3 (calcium carbonate) precipitation from 26.6% on day 1 to 58.5% on day 7, indicating calcium silicate and portlandite conversion into carbonates. XRD study showed calcite as the main phase and vaterite to aragonite as curing temperature and age arose. Ambient curing reduced mechanical strength and carbonation performance in all control samples. These findings demonstrate that elevated temperatures expedite carbonation and enhance the mechanical properties of CLW mortars, validating the potential of accelerated CO2 curing as a sustainable strategy for optimising lime-based materials. This approach offers a dual benefit: reducing CO2 emissions while leveraging elevated CO2 levels to improve construction material performance.