The Influence of Polypropylene Fiber and Silica Fume on the Mechanical Properties of No-Fine Concrete with Recycled Aggregate

Civil Engineering Department, University of Baghdad, Baghdad, Iraq

^a* Corresponding author Ruaa.hassan2001M@coeng.uobaghdad.edu.iq
^b hadeel.kalid@coeng.uobaghdad.edu.iq

Abstract

No-Fines Concrete is a type of concrete produced without fine aggregate or sand. Because of its high porosity, it allows rainwater to seep into the ground, directly replenishing the groundwater aquifer. With a design load of three tons, no-fine concrete can be utilized as pavement for rural roads. Additionally, this type of concrete can be utilized as a sub-base material in both flexible and rigid pavements. Aside from No-Fines Concrete's permeability properties, asphalt overlays are another option. This research studied the impact of silica fume and polypropylene fiber on the properties of no-fine concrete with recycled aggregate. The ratios of cement to aggregate and water to cement were 1:4 and 0.3, respectively. The recycled aggregate was demolished reactive powder concrete used in percentages of 10, 20, and 30% as a substitution for coarse aggregate by volume. The recycled aggregate percentage of 10% was the optimal percentage as it showed the least adverse effect on the no-fine concrete mixes. The polypropylene fiber was then added to the no-fine concrete mixes with 10% recycled aggregate in the percentages of 0.5, 1, and 1.5% by volume. The optimum percentage of polypropylene fiber was 0.5%, which improved the mechanical properties of no-fine concrete. Silica fume was used as a partial substitution for cement at a percentage of 10% and added to no-fine concrete mix with 10% recycled aggregate. The results show that using 10% silica fume and 0.5% polypropylene fiber with 10% recycled aggregate increased the splitting tensile strength, flexural strength, compressive strength, and modulus of elasticity by (22.54 and 40.32%), (22.22 and 35%), (21 and 35.37%), and (22 and 38.19%) compared to reference mix (NC) and the no-fine concrete mix with 10% recycled aggregate (RNC10), respectively. In comparison, the dry density was higher by (1.34%) than RNC10 and lower by (0.68%) than NC.