Potential use of carbide lime waste in construction: a comprehensive analysis

The growing interest in repurposing industrial alkaline wastes for construction has driven research toward sustainable practices, aiming to address environmental
concerns and circular economy principles. This study focuses on the utilization of carbide lime waste, a by-product of acetylene gas production, in construction materials. The current large amounts of calcium carbide produced worldwide, leading to carbide lime waste, underscore the urgency of finding alternative uses for this material. Carbide lime waste is typically discarded in ponds, a disposal method that poses significant environmental threats. Recycling carbide lime in construction not only addresses waste management issues but also offers a sustainable solution for capturing greenhouse gases via its carbonation. Here we present a comprehensive analysis of carbide lime properties, comparing them with traditional calcitic limes. For this task, we used X-ray diffraction, porosimetry, thermogravimetric analysis, and electron microscopy. Carbide lime, primarily composed of calcium hydroxide, demonstrates unique features, including micro and nanoscale portlandite particles, and compatibility with various building constituents. Our study highlights the challenge posed by impurities in waste carbide lime (i.e., sulfides and heavy metals) and underscores the need for optimal process control. Notably, we unveil the remarkable carbonation dynamics and kinetics of carbide lime, which outperforms traditional calcitic limes. Key developments and findings include the purification and optimization of carbide limes, morphological distinctions in carbonated lime crystals, pore characteristics, and (enhanced) reactivity, as compared with industrial hydrated lime.