Artikel - Design of Coal Wastes Processing Unit And Their Utilization as Cement Replacement on Manufacturing of Building Materials To Control the Environmental Pollution - Retno Tri Nalarsih

Coal waste in solid waste from industry causing a negative impact, because of SOx and NOx compounds in the form of gas into the air and react with water vapor to form H2SO4 and HNO3, resulting acid rain harmful to the environment and health problems. The purpose of this study is to utilize waste coal becomes fly ash and bottom ash where the fly ash is used as an alternative material in the manufacture of cementitious concrete block and cementitious concrete brick to have the better physical and mechanical properties and the higher value. Experimental method is applied to produce samples at the factory.
Independent variables used in this study were: the composition of fly ash (20% and 40%); composition of sand: cement (8:0.75 and 10:1), time of mixture (4 minutes and 8 minutes). The dependent variable used is the compressive strength and porosity of the concrete blocks and concrete bricks. Data from testing the compressive strength and porosity were analyzed by Taguchi method to obtain the most optimum composition. The result showed that the composition of fly ash, the composition of sand: cement; and stirring contribution to contribute to the compressive strength of concrete blocks, each for 38,969%, 20.336% and 73.61%. While the percent contribution of the compressive strength of concrete blocks, each for 49.976%, 7.861%, and 15.169%. Percent contribution of each variable on the porosity of concrete block is 33.379%, 14.76% and 23.275%. While the
concrete brick porosity of 35.567%, 94.47% and 9.04%. Output in this study is the composition of material for concrete blocks and concrete bricks containing coal waste (fly ash). It is found that in order to obtain concrete block and concrete brick quality in terms of compressive strength and porosity, it can be done by varying the composition of 20% fly ash, sand composition: cement 8:0.75 and stirring time of 4 minutes.
Keywords : Fly ash, compressive strength, porosity, concrete blocks, concrete bricks, Taguchi