Pengaruh Pemanfaatan Pra-Kondisi Spent Bleaching Earth dengan Bottom Ash sebagai Material Subtitusi Parsial Semen terhadap Kuat Tekan Beton

Spent Bleaching Earth (SBE) waste is a solid residual material from the palm oil refining industry, while Bottom Ash (BA) is coal combustion residual ash that accumulates at the bottom of power plant furnaces. Both types of waste often trigger environmental pollution problems if simply disposed of, but the silica content and pozzolanic properties within them make these wastes highly promising for recycling as alternative materials in the construction sector. In relation to this, this study aims to analyze the effect of utilizing pre-conditioned SBE and BA waste as partial cement substitution materials on the physical and mechanical characteristics of concrete. The parameters evaluated in this study include the Plasticity Index (PI), slump value, concrete compressive strength (at the age of 7 and 28 days), and shrinkage potential up to 72 hours of observation. The test results showed that the combination of the two wastes produced a low PI value, ranging from 0.46% to 8.21%, which proves that the material becomes more stable against changes in moisture content. In terms of mechanical testing, the substitution variation of 10% SBE and 5% BA proved to be the most optimum composition with a compressive strength achievement of 21.77 MPa at the age of 7 days and 26.53 MPa at the age of 28 days. However, the addition of excessive waste substitution (such as in the variation of 20% SBE and 10% BA) actually resulted in a drastic decrease in compressive strength to 18.10 MPa at the age of 28 days due to a significant reduction in the portion of the binding cement. On the other hand, for the dimensional stability parameter, the variation of 15% SBE and 15% BA provided the best shrinkage resistance with a value of 0.080 at the 72nd hour. This occurred because the cavities in the Bottom Ash are able to absorb and retain water, thus functioning effectively as an internal curing agent. Overall, it can be concluded that the formulation of 10% SBE and 5% BA is highly recommended if the primary target is the achievement of compressive strength, while the formulation of 15% SBE and 15% BA is more appropriately applied to structures susceptible to cracking problems caused by shrinkage.