Experimental study of the effect of elevated temperature on compressive and tensile strength of concrete made with microsilica and polypropylene

The occurrence of fire in structures is a possible phenomenon that can significantly affect the mechanical properties of the materials of structural members. Nowadays, the use of new materials and additives in concrete construction has been considered, and it is necessary to examine the strength of concrete made with these materials during and after fires and to ensure its proper behavior. In this research, microsilica, as a very effective pozzolanic material and polypropylene fibers as a material to improve cracking resistance were used to make concrete. The behavior of concrete specimens with different values of these additives after exposure to high heat was investigated in the form of tensile and compressive strength tests. The control concrete specimen was considered for comparison with other specimens where the compressive strength of this specimen was 30 MPa. In addition to the control specimen mixing design, 11 other mixing designs were made with propylene fibers in the amount of 0.05, 0.075 and 0.1% of the weight of concrete and microsilica in the amount of 5%, 10% and 15% of the weight of cement. The specimens were placed in an oven at 600 ° C for one hour. After cooling, compressive and tensile strength tests were performed on the specimens. The results showed that the combination of polypropylene and microsilica fibers increased the tensile strength, the maximum increase was 82% compared to the control specimen. The maximum increase in compressive strength compared to the control specimen was 63.4%. After exposure to heat, the tensile strength of the proposed sample increased by 44% compared to the control specimen.