Publication: Effectiveness of bottom ash in geopolymer concrete
Date
2017
Authors
Ahmad Safwan Kamal Nasharuddin
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Abstract
In Malaysia, 8.5 million tons of coal ash, which is produced of waste material Bottom ash and Fly ash in seven power plants. Product combustion of coal ash is deposited in a dry landfill and a pond which is causing another environmental problem to the community surrounding. Besides that, it is very expensive for a power plant to dispose of bottom ash and fly ash. Hence, a significant amount of research has conducted and explored a potential of coal bottom ash and fly ash to be used in industry. Other than that, the rapid growth of cement production generates large amounts of Carbon dioxide (CO2) which leads to global warming. Hereby, the utilization of coal ash in producing geopolymer offers an alternative to replace a cementitious material. Coal bottom ash widely used as a partial or total replacement to aggregate in Ordinary Portland Cement (OPC) concrete. Since there are limited studies on using bottom ash as fly-ash based geopolymer concrete, this study will be focusing on effectiveness of bottom ash in geopolymer concrete with the inclusion of bottom ash. Sodium hydroxide (NaOH) and Sodium Silicate (NaSiO) were used as chemical activator. One control mix using 100% fly and 0% bottom ash as binder material was prepared as a comparison. The amount of for bottom ash and fly used in mixtures will be a major factor effect on compressive strength, water absorption and weight loss test were performed at 3,7 and 28 days of curing age.
Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solution 5M with ratio 1:2 were kept constant for all mixtures. All mixtures were prepared using 50 mm x 50 mm x 50 mm cube size and cured in the oven at temperature of 90°C for 24+1 hours after demoulded. The cube samples were kept at room temperature until the testing days. All mixture shown an increased in strength when the curing age increased. The mixture containing 15% of bottom ash shown significant increases over curing age from 7 days to 28 days of curing age about 169% increment. Besides, the mixture containing 5% of bottom ash shown a good characteristic of geopolymer concrete in water absorption and weight loss test because it is comparable to the control mixtures. The optimum amount of bottom ash in geopolymer concrete was M1, 5% of bottom ash, which produced 18.3 MPa of compressive strength at 28 days, 7.2% of the water absorption percentage and 3.6% weight loss rate after 28 days of curing age.
Description
TA455.A63 A35 2017
Keywords
Coal ash , Concrete