THE EFFECT OF BOTTOM ASH AS A MATERIAL FINE AGGREGATE SUBSTITUTION ON THE STRENGTH OF POROUS CONCRETE

Bottom ash is the residual product of coal combustion which can be useful for the utilization of porous concrete mixtures. In this study, bottom ash was used as a substitute for fine aggregate in the manufacture of porous concrete. Bottom ash has a larger and heavier grain size with a characteristic dark gray color. The purpose of this study was to determine the strength of concrete using bottom ash as a fine aggregate substitution material. The percentage of using bottom ash as a fine aggregate substitution material is 0%, 10, 20% and 30%. The research was carried out at the Structure and Materials Laboratory of the Indonesian Muslim University, Makassar, South Sulawesi. The specimens used were 24 cylinders with a diameter of 15 cm and a height of 30 cm. The tests carried out were in the form of compressive strength, split tensile strength and porosity tests with a design concrete quality of 17.5 MPa. From the research results, the results of the compressive strength test obtained the optimum bottom ash composition when using 21.61% bottom ash with a maximum compressive strength of 20.02 MPa at 28 days of age, the split tensile strength test obtained the optimum bottom ash composition when using 21 bottom ash .73% with a maximum split tensile strength of 2.42 MPa at 28 days of age while for the porosity test the optimum bottom ash composition was obtained when using 22.12% bottom ash with a minimum porosity of 17.86%.From the results of the analysis using the exponential statistical method, the relationship between porosity and split tensile strength is obtained by a minimum porosity of 17.86% and a maximum split tensile strength of 2.47 MPa, for compressive strength a minimum porosity of 17.86% and a maximum compressive strength of 20.02 MPa with an optimum bottom ash composition of 21.61%.