Strength of sustainable non-bearing masonry units manufactured from calcium carbide residue and fly ash

• Calcium Carbide Residue (CCR) and fly ash (FA) as cementing agent.
• Sustainable CCR–FA non-bearing masonry units.
• Role of water/binder ratio, CCR/FA ratio and curing time on strength.
• Cost analysis for manufacture of CCR–FA masonry units.

This paper aims to study the viability of using Calcium Carbide Residue (CCR) and fly ash (FA) as a cementing agent (binder) for the manufacture of non-bearing masonry units without Portland Cement (PC). CCR and FA are waste products from acetylene gas factories and power plants, respectively. The test samples were made up at a binder to stone dust ratio of 1:8 by weight. The studied water to binder (W/B) ratios were 0.50, 0.75 and 1.00, and the CCR/FA ratios were 80:20, 60:40 and 40:60. The W/B ratio of 0.75 and CCR/FA ratio of 40:60 were found to be an optimal mix proportion providing the highest both unit weight and strength. The higher CCR/FA ratios provide lower strength values because the silica and alumina in FA are insufficient to react with abundant Ca(OH)2 in the CCR for the pozzolanic reaction. The optimal mix proportion provides the strength of the CCR–FA based material greater than 20 MPa, which is acceptable for non-bearing masonry unit. The cost analysis showed that the material costs of the CCR–FA masonry unit were 40% lower than those of the PC masonry unit. Besides the cost effectiveness, the outcome of this research would divert significant quantity of CCR from landfills and considerably reduce carbon emissions due to PC production.