THE RESISTANCE OF HIGH STRENGTH CONCRETE WITH POLYPROPYLENE FIBER USING DIATOMACEOUS EARTH AS A CEMENT SUBSTITUTE AT HIGH TEMPERATURES

High-strength concrete generally requires a large amount of cement to achieve high compressive strength. This study investigates the use of diatomaceous earth, which contains a high level of silica, as a partial replacement for cement, along with the addition of polypropylene fiber to improve the fire resistance of high-strength concrete. Concrete specimens were prepared with a 10% substitution of diatomaceous earth by weight of cement, 1.5% superplasticizer by weight of cement, and varying polypropylene fiber contents of 0.2%, 0.4%, 0.6%, and 0.8% by volume of concrete. The diatomaceous earth was calcined at 600°C for five hours before use. Concrete cubes measuring 5x5x5 cm were cured for 28 days and then exposed to elevated temperatures of 400°C, 500°C, and 600°C for 5 hours using a furnace in the Materials Laboratory of the Mechanical Engineering Department, Faculty of Engineering, Syiah Kuala University. Compressive strength was measured before and after heating. The results of the compressive strength showed that high-strength concrete with 10% diatomaceous earth substitution had the smallest decrease in compressive strength for each temperature variation and the variation of fiber addition with the largest residual compressive strength was obtained at a temperature variation of 400℃ without the addition of fiber, which was 98,34% of the initial compressive strength. Meanwhile, the greatest residual compressive strength of high-strength concrete without diatomaceous earth substitution was obtained by concrete burned at a temperature of 400℃ with 0,4% addition of polypropylene fiber, which was 81,01% of the initial compressive strength. Concrete with diatomaceous earth and polypropylene fibers better resisted high temperatures than concrete without diatomaceous earth.