Performance of High-volume Carbide Lime Mortar Under Accelerated CO2 Curing Followed by Postconditioning Treatments

This study explores the potential of using calcium hydroxide (Ca(OH)₂) derived from Carbide Lime Waste (CLW) as a high-volume cement replacement (40%–70% by volume) in mortar. The mortar was subjected to accelerated carbon dioxide (CO₂) curing to enhance carbonation capture while maintaining the desired strength, promoting more sustainable construction practices. The optimum high-volume mortar was further analysed to examine its long-term properties under various postconditioning treatments, including water, wet gunny, and air curing, in terms of calcium carbonate (CaCO3) formation and late-age strength. The physical properties, such as water absorption and mechanical properties, including compressive, flexural, and splitting tensile strengths, were evaluated. CO2 capture performance was assessed through carbonation depth testing, and microstructural analysis was performed using Thermogravimetric analysis (TGA) and X-ray diffraction (XRD). Results showed that CLW70 exhibited the best mix design, achieving 100% carbonation depth and 70% CaCO3 formation within 7 days of accelerated CO2 curing. Compressive strength increased from 2.62 MPa on day 1 to 17.01 MPa on day 7. XRD analysis indicated that air curing was the most effective postconditioning treatment, resulting in the highest CaCO3 peaks. Accelerated CO2 curing also reduced water absorption, and mechanical strength improved with curing age, demonstrating that the CaCO3 formed during the carbonation process densified the CLW mortar after 7 days of curing.