ANALISIS PENGGUNAAN SERAT RAMI TERHADAP KUAT TEKAN DAN MODULUS ELASTISITAS BETON DAN SILICA FUME SEBAGAI BAHAN TAMBAH

Concrete is a widely used construction material because it is relatively inexpensive, easy to shape, and has high compressive strength despite its weakness in tension. The general composition of concrete consists of cement as a binder, fine aggregate, coarse aggregate, and water as a medium for chemical reactions. To increase its tensile strength, one method used is to add fibers to the concrete mixture. This study used ramie fibers (Boehmeria nivea) at 0.5% of the cement weight with a length of 20 mm, as well as variations in silica fume at 0%, 5%, 10%, and 15%. The tests were conducted at 28 days of age using cylindrical test specimens measuring 150×300 mm to determine the effect of mixture variations on the compressive strength and elastic modulus of concrete. The results showed that normal concrete had a compressive strength of 25.46 MPa and an elastic modulus of 27,559 MPa. Concrete with flax fiber without silica fume experienced a decrease in compressive strength to 23.01 MPa and an elastic modulus of 25,896 MPa. This decrease is due to the hygroscopic nature of flax fibers, which absorb water, thereby inhibiting the cement hydration process and resulting in less than optimal bonding. Conversely, the addition of silica fume can improve the performance of flax fiber concrete. With the addition of 5% silica fume, the compressive strength increased to 26.79 MPa and the modulus of elasticity to 31,931 MPa. At 10%, the compressive strength reached 27.16 MPa and the modulus of elasticity was 33,887 MPa, while at 15% the highest values were obtained with a compressive strength of 28.29 MPa and a modulus of elasticity of 34,990 MPa. These results indicate that silica fume plays a role in increasing concrete strength through pozzolanic reactions and micro-pore filling, thereby compensating for the weaknesses caused by the addition of hemp fibers.