Influence of silica fume on the pervious concrete with different levels of recycled aggregates

The world nowadays is trying to find alternative approaches to be used in manufacturing instead of consuming raw materials. Using recycled aggregates in new concrete is one of these effective approaches, which in turn reduces the quantity of waste and reduces the required landfills. In this present work, an attempt was made to study the effect of using recycled aggregates as an alternative to raw aggregates in pervious concrete with different levels (0 %, 25 %, 50 %, 75 % and 100 %), in addition to the impact of adding 5 % and 10 % of silica fume as a replacement of cement weight on the pervious recycled aggregate concrete properties. The concerned properties are as follows: fresh and hardened density, fresh and hardened voids content, water permeability, compressive strength, splitting tensile strength, flexural tensile strength, and potential resistance to degradation of the pervious concrete. Additionally, relations between water permeability and other parameters of the pervious concrete were deduced. Experimental results generally showed that by increasing the recycled aggregates' percentages, there was a consequent deterioration in concrete properties. Whereas, the addition of silica fume enhanced the mechanical properties. It was observed that the addition of 5 % silica fume to concrete with 50 % recycled aggregate was subsequently accompanied by 4.2 % and 5.5 % increase in the fresh and hardened pervious concrete density, respectively, while a 17.5 %, 11.7 % and 17.2 % decrease in the hardened concrete voids content, concrete permeability and concrete degradation, respectively. Regarding the strength parameters, the pervious concrete’s 28 days compressive strength, 28 days splitting tensile strength and flexural tensile strength increased by 100 %, 20 % and 20.3 %, respectively, As follows, the addition of silica fume significantly improves the mechanical properties of the pervious concrete, with a slight decrease in the permeability parameters.