Evaluating Some Mechanical Characteristics of Asphalt Mixtures Containing Recycled Concrete Aggregate and Modified by Polyphosphoric Acid

Abstract

Sustainable waste management aims to reduce the consumption of raw materials by reusing as many RCA materials as possible. This research aims to evaluate the influence treated and untreated recycling coarse aggregate on the hot asphalt mixture’s properties using asphalt grade (40-50) modified with 3% Polyphosphoric Acid (PPA). RCA was used in different proportions (25%, 50%, 75%, and 100%) as a substitute for raw coarse aggregate; the effect of treatment on improving the RCA’s quality was tested. Volumetric properties associated with the Marshall test for asphalt concrete were tested. Tensile strength ratio (TSR) and index of retained strength (IRS) measurements were used to assess the moisture effect. The study findings indicated that 25% RCA is the maximum amount of RCA from concrete that should be added to asphalt mixtures. This percentage recorded the highest values for TSR and IRS, with the ideal modified asphalt content of 4.86%. Based on the results of this study, asphalt concrete's durability will generally grow with RCA use, while its susceptibility to moisture will increase. However, treated RCA improved the results compared to untreated RCA. Using asphalt modified with polyphosphoric acid remarkably improved the asphalt mixtures’ performance and reduced the asphalt consumption rate.