Laboratory Evaluation of Stone Mastic Asphalt using Crumb Rubber and Munjin Fiber

Abstract

In Pakistan most of the pavements are made up of hot mix asphalt as this is the most available and economical material and it is also suitable for climate here. However hot mix asphaltic pavements normally require frequent maintenance and rehabilitation because they are damaged due to intense loadings. Thus increasing the agency’s estimated cost and making it uneconomical. To make the asphaltic pavement economically efficient and effective, several alternatives should be designed. One of the alternatives to minimize the damages of pavement, reduce agency cost and to prolong the service life is use of modified asphalt pavements i.e. Stone Matrix Asphalt Pavement. The Stone matrix asphalt is a gap graded mix having higher coarser content, high asphalt content and fiber as a stabilizer. In this study an attempt has been made to study the use of Munjin Fiber and Crumb rubber as a stabilizing agent in Stone matrix asphalt SMA-25. Munjin Fiber is non- conventional natural fiber. Crumb rubber is a waste material of rubber tires; wet process was opted for incorporating crumb into mix. The research was conducted to optimize crumb rubber for Volumetrics and Performance properties of mix. Crumb Rubber was incorporated at 2%, 4%, 6%, 8%, 10% and 12% by weight of optimum bitumen content. In term of performance parameters Moisture sensitivity and Fatigue life of the mix were evaluated using UTM 25. Indirect Tensile Test for moisture sensitivity was conducted on Marshal compacted samples. For Indirect Tensile Fatigue Test Gyratory compacted samples were prepared and tested for fatigue life (Cycles to failure). An average optimized crumb rubber content was determined from Marshal Test, ITS, ITFT. Study concluded that mix showed excellent behavior in terms of volumetrics at 5.8% optimum bitumen content and 4.95% Crumb Rubber content. Further it was found that on addition of 5% crumb rubber mix displayed maximum moisture resistivity. It was observed that fatigue life of the mix increased abruptly on addition of crumb rubber but to certain level after that it decreased. Average optimized crumb rubber content was found to be 4.6% and it was found that on average optimized crumb rubber content Marshal stability and Moisture resistivity was improved by 38% and fatigue life was increased 79% as compared to Control mix.