Workability, compressive strength & leachability of coal ash concrete

Abstract

One of the essential steps for planning solid waste management towards sustainable development is to reuse solid waste in the construction industry. Coal is one of the world's most important sources of energy, fueling almost 40 % of electricity worldwide. Malaysia is commonly producing electricity through burning millions of tonnes of coal. This process generates around 8.5 Mt of coal ash, which comprised of 80 % Fly Ash (FA), and 20 % Bottom Ash (BA) as waste. The study aims to investigate the workability, compressive strength and leachability of concrete containing BA and FA as replacement of sand and cement. Cement was substituted with 20 % of FA by mass and fine aggregate was replaced with BA at 0, 20, 50, 75 and 100 % in the concrete mix. The results show that the percentage sum of SiO2, Al2O3 and Fe2O3 (the main chemical composition in coal ash) in FA and BA are about 78.82 % and 83.24 %. The leaching test showed that the heavy metal concentrations in leachates are much lower than recommended in the USEPA SW 846. Workability of concrete was reduced by increasing BA content as a sand replacement in the concrete mixture. After 91 d and 180 d curing periods, the compressive strength of both the experimental and control samples of concrete were roughly comparable. It can be concluded that BA and FA can be used as a replacement of sand and cement in normal concrete without any environmental problem.