Effects of rice husk ash and fiber on mechanical properties of pervious concrete pavement

The use of pervious concrete pavement is significantly increasing due to reduction of road runoff and absorption of noise. However, this type of pavement cannot be used for heavy traffic due to a high amount of voids and consequently low strength of pervious concrete. In this paper, rice husk ash (RHA) was used in order to strengthen pozzolanic cement paste and the effect of 0%, 2%, 4%, 6%, 8%, 10% and 12% weight percentages as a cement replacement in concrete mixtures on the mechanical properties was studied. Moreover, 0.2% Vf of glass (where Vf is the proportion of fiber volume to total volume of concrete), 0.5% Vf of steel and 0.3% Vf of polyphenylene sulfide (PPS) fibers were used to improve the mechanical properties of the pervious concrete. Also, several water to cement (w/c) ratios were made and then, physical and mechanical properties of hardened concrete including porosity, permeability, compressive strength, tensile strength and flexural strength were investigated. The results indicated a significant increase in compressive, tensile and flexural strengths. Also, in all of w/c ratios, a similar trend was observed in the compressive, tensile and flexural strengths of concrete containing RHA and fibers but the optimum percentage of RHA was different so that, it increases rapidly to the optimization point but gradually decreases after this point. The w/c ratio of 0.33 significantly increased the mechanical properties of the pervious concrete and reduces the amounts of voids and its permeability.