EFFECTS OF LENGTH AND ASPECT RATIO OF ENSET FIBER ADDITIVE ON PERFORMANCE OF HOT AND COLD MIX AC

Abstract

Rutting and cracking are co mmonly appearing types of distress which lead to deteriorations of asphalt pavement. The main reason for these problems is limitation on tensile strength of asphalt binder. Adding strong fibers as additive in asphalt mixture is one of pavement modification techniques. As findings revealed, natural fibers are poorer in their tensile strength than artificial but they can be strengthened by braiding. The main objective of this study is to evaluate the effects of length and aspect ratio of Enset fiber additive in dense grade asphalt mixture and their outcomes on performance indicators such as stability, flow resistance, IDT and TSR of a modified AC comparatively with the unmodified mix. Modified and unmodified Marshall test specimens were prepared and tested for Marshall stability, flow resistance, density, and IDT tests on wet and dry samples. Experimental investigations have been conducted using ASTM test methods and specifications. The effects of of length and aspect ratio on stability and flow values were analyzed using Regreasion model of analysis. Results indicated that a modified CMA (cutback with 14% solvent and cured for 22 days) resulted a 6.4% decrease in density and 49.9 % reduction in SFR (SFR) that of the control CMA. Compared to the unmodified mix Enset fiber additive lowered density by 1.4 % but exhibited enhancement of 6.0 % on stability and 3.8 % on SFR at 0.35 % fiber dosage and 6.8% binder content when length and aspect ratio of the fiber were 15 mm and 197.07 respectively in HMA. It was observed that Stability and flow have quadratic relation with fiber length and linearly related with aspect ratio. From further investigation on HMA it was confirmed that the modification improved IDT and reduced brittleness at failure but tensile strength ratio of the modified HMA reduced. So, it was concluded that Stability, flow and SFR were negatively affected by Enset fibers additive in CMA while they have been enhanced in HMA. At 0.35% content a 15 mm length and 197.07 aspect ratio Enset fibers additive HMA hasbrought remarkable improvement on SFR and IDT but negatively affected resistance to water induced damage.