Pengaruh pemanfaatan limbah marmer sebagai bahan substitusi fly ash pada campuran beton geopolimer terhadap sifat mekanik

Abstract

The demand for environmentally friendly construction materials has become increasingly critical due to rising carbon emissions from the cement industry. Geopolymer concrete offers a sustainable alternative by eliminating Portland cement and employing fly ash with alkaline activators. This study investigates the effect of marble waste substitution on the mechanical properties of geopolymer concrete—namely compressive strength, split tensile strength, and modulus of elasticity—and aims to determine the optimal substitution level within the 15% to 30% range. The research was conducted experimentally using cylindrical specimens (15 cm × 30 cm) with marble waste replacing binder mass at 0%, 15%, 20%, 25%, and 30%. The activator solution comprised Na₂SiO₃ and 10 M NaOH in a 4:2 ratio. Normal concrete was designed with a target compressive strength of 25 MPa as a performance benchmark. All specimens were tested at 28 days following SNI and ASTM standards. Data were analyzed descriptively and comparatively to assess performance across variations. Results indicated that marble waste substitution significantly enhanced mechanical properties, with the 15% level achieving the best performance: a compressive strength of 44.3 MPa versus 26.2 MPa for normal concrete, a split tensile strength of 3.252 MPa versus 2.817 MPa, and a modulus of elasticity of 24,881 MPa, closely aligning with predictions from ASTM C-469-94 and Tempest (2010). Substitution above 15% led to decreased performance due to increased porosity and disrupted interparticle bonds. Thus, incorporating 15% marble waste is recommended as the optimal proportion to improve the mechanical performance of geopolymer concrete while advancing sustainable construction practices.