Partial Replacement of Cement with Cinchona Industrial waste Ash in the Production of Concrete Blocks

Abstract

The research focused on investigation of suitability of the cinchona industrial waste ash as partial replacement of cement in concrete. The biomass ash, ordinary Portland cement and pozzolana cement were analyzed for chemical composition for comparison purpose. Concrete blocks were produced by partial replacement cement with Cinchona biomass ash where ash content varied between 0 and 100% at an interval of 20%. C32.5 and C42.5 from two companies were investigated with ratios of cement to crushed rock sand varying between: 1:2 and 1:8. Compressed solid blocks of size 140mm x 160mm x 290mm were produced at a compression pressure of 0.015N/mm2 and tested for physical and mechanical properties after curing. Wall panels measuring 1.20m length,0.14m thick and 1.00m height were constructed with the cinchona concrete blocks and machine cut stones and tested for structural properties. The percentage of water required for standard consistency increased with increase in ash content, with water content requirement for standard consistency being 111% for pure Cinchona ash while the same varied between 36 and 39% OPC and Pozzolanic cements. Replacement of 20% cement with cinchona ash reduced the initial setting time to between 10 and 24 minutes. C42.5 from company B had the lowest initial setting time of 3 hours while C32.5 from the same company had an initial setting time of 3 hours 40min. C32.5 from company A had an initial setting time of 4 hours 36 minutes. Pure ash had the longest initial setting time of 7 hours 30minutes on average. Replacement of cement with Cinchona biomass ash reduced the final setting time initially after which setting time increased with cement replacement. Specific gravity of the Cinchona ash blended Cement reduced with the ash content. The ultra-pulse velocity values for concrete blocks produced with cinchona bark ash and Ndarugu stones varied between 1.34 and 1.84Km/s. Wall Panels made from Cinchona ash blended Cement had higher values of compressive strength and modulus of elasticity as compared to Ndarugu machine cut stones. It is therefore concluded that load bearing concrete blocks can be produced with a maximum of 70% ash content for some cements while non-load bearing concrete blocks can be produced within a range of 70 to 85% cinchona ash content.