INOVASI SLEEPER BETON BERBASIS SERAT KARET DAUR ULANG

Abstract

This study investigates the effect of substituting coarse aggregate with fiber rubber derived from waste tires on the fresh and mechanical properties of concrete sleepers. The research was conducted experimentally using three mixture variations: 0% (NC), 5% (FR5%), and 10% (FR10%) fiber rubber by volume of coarse aggregate. Cylindrical (Ø150 × 300 mm) and beam (150 × 150 × 600 mm) specimens were tested after 28 days of curing to evaluate slump, unit weight, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity. The results show that the inclusion of fiber rubber increases workability, with slump values rising from 36 mm (NC) to 40 mm (FR5%) and 43 mm (FR10%). However, the unit weight decreases from approximately 2424 kg/m³ (NC) to 2248 kg/m³ (FR5%) and 2118 kg/m³ (FR10%), attributed to the lower density of rubber compared to mineral aggregates. Mechanical properties significantly declined as the fiber rubber content increased: compressive strength decreased from 54.93 MPa to 15.95 MPa and 10.69 MPa, splitting tensile strength from 3.26 MPa to 1.75 MPa and 1.74 MPa, flexural strength from 5.73 MPa to 3.70 MPa and 2.53 MPa, and modulus of elasticity from 37,428 MPa to 18,132 MPa and 14,327 MPa, respectively. These findings indicate that while rubber inclusion enhances workability and ductility potential, it substantially reduces the strength and stiffness of concrete. Therefore, the use of fiber rubber in sleeper applications should be limited or accompanied by surface treatment, mix modification, or hybrid reinforcement to maintain adequate structural performance.