The influence of Balinese Black Rock Ash on the compressive strength of concrete

Concrete is widely used as a structural material, and it is currently being experimented with to improve its quality. Concrete is made from a mixture of Portland cement or other hydraulic cement, coarse aggregate, fine aggregate, and water with or without the use of additives. Balinese Rock Ash (BRA) has a chemical composition such as SiO2 of 62, 83%, Al2O3 of 13, 59%, CaO of 8, 13%, MgO of 3, 36%, Na2O of 3, 56%, K2O of 2, 39% and Fe2O3 of 5%. BRA stone waste is one of the wastes from the processing of traditional building ornaments. The resulting waste ranges from 2% - 3% of 1 m3 of natural stone. Currently, this waste has not been managed properly and is usually allowed to accumulate around work areas or vacant land, thus potentially causing environmental disturbances. The purpose of this study was to determine the effect of utilizing BRA as a mineral additive on the compressive strength of normal concrete. The results of the regression analysis show that the optimum compressive strength value occurs at the percentage addition of BRA as much as 8.65% resulting in compressive strength of 21, 46 MPa at 14 days of age, the percentage of addition of BRA as much as 7, 50% produces a compressive strength of 22, 08 MPa at 28 days of age, the percentage of addition of BRA of 7, 64% produces a compressive strength of 22, 19 MPa at 42 days of age and the percentage of addition of BRA of 7, 90% produces a compressive strength of 22, 48 MPa at 56 days.