STRENGTH PROPERTIES OF POLYPROPYLENE FIBER REINFORCED HIGH STRENGTH CONCRETE

An experimental program was carried out in this research to investigate the behavior of high strength concrete with polypropylene fibers addition. Two types of concrete mixtures were studied, one containing 0.22% polypropylene fibers and the other 0.30% polypropylene fibers in volume fraction. The concrete class determined at 28 days was C70/85. Mechanical properties such as compressive strength, splitting tensile strength, flexural strength, modulus of elasticity and energy absorption were determined on high strength polypropylene fibers reinforced concrete. High strength fiber reinforced concrete properties were determined at 1, 3, 7, 28 and 56 days. The influence of polypropylene fibers addition on the spalling phenomenon and residual strengths of concrete after exposure to high temperature was also determined at 56 days of concrete. After analyzing the results of the experimental program we concluded that the addition of polypropylene fibers to the high strength concrete composition hasn't a positive influence on the compressive and flexural strength of high strength concrete, but it has for sure a negative impact towards splitting tensile strength of high strength concrete. However, the modulus of elasticity and the energy absorption of the high strength concrete with polypropylene fibers addition are higher than of the high strength concrete without fibers addition. Referring to the residual strength of high strength polypropylene finer reinforced concrete it was observed that regardless the presence of the polypropylene fibers, the residual strength (compressive and splitting tensile) drops continuously under rising temperatures, reaching after exposure to 900 degrees C to 30% of their initial strength.