Performance Evaluation of Porous Asphalt Mixtures Modified with Crumb Rubber

Abstract

The objective of this study was to evaluate the mechanical and hydraulic behavior of porous asphalt containing crumb rubber (CR) as a dry-process replacement for the filler. Using 40–50 penetration-grade binders from Lanaz (Source A) in Erbil city and Phonix (Source B) in Slemani city, a constant asphalt content of 4.5%, and CR contents of 0%, 1.5%, 3%, and 4.5%, the mixtures were prepared. The laboratory program included falling-head permeability, Marshall stability and flow, volumetric analysis and indirect tensile strength at 25 and 60°C. With the CR content, the Marshall stability increased for both binders. Stability was 7.3 and 6.9 KN for sources A and B respectively at 4.5% CR compared with 5.4 and 3.5 kN for the controls. Nevertheless, the permeability of Source A decreased from approximately 0.41 to 0.11 cm/s, while Source B decreased from 0.50 to 0.08 cm/s.

Additionally, Marshall flow was approximately 5.0–5.1 mm at the highest dosage. Tensile strength at 60°C was increased by 35.3% and 69.1% at 4.5% CR, but tensile strength at 25°C was decreased by 11.4% and 17.4% for Sources A and B, respectively. This led to a reduction in the reported temperature-susceptibility index of about 25.8% and 34.1%. Overall, CR improved Marshall stability and high-temperature tensile strength while decreasing permeability and tensile strength at 25°C at the maximum dosage, altering the mechanical and hydraulic characteristics of porous asphalt.