INVESTIGATIONS ON CHARACTERISTICS OF MASTIC ASPHALT CONCRETE USING DIFFERENT TYPES OF FILLERS

Abstract

Ever increasing traffic and axle loads have resulted in excessive damage to pavement surfaces. Commonly used wearing surfaces such as surface dressing, dense bituminous macadam, pre-mix carpet, semi dense carpet, and bituminous concrete have been subjected to frequent damages and maintenance agencies are continuously struggling to cope up with deteriorating road surface conditions. Problem is more acute on highways carrying heavy traffic with large proportion of heavy axle commercial vehicles (much more than legal axle load' of 10.2 Ton) and urban streets. Specific locations such as flyovers slopes, bridges, curves, bus stops, intersections, rotaries etc. are subjected to excessive stresses and get damaged very frequently necessiating regular repairs which result in traffic disruptions and inconvenience to commuters. Highway engineers and researchers have been working to over come this problem. Research efforts to produce modified binders to give strong and durable wearing courses have been made uccessfully but economical considerations prohibit their use on large scale. Mastic asphalt concrete offers ideal solution to this problem as it provides hard, tough, stable and durable wearing surface, capable of withstanding very heavy loads including stresses generated by tracked vehicles. Mastic asphalt concrete has an advantage that it does not require any compactive effort. Imperviousness and self crack healing properties of the mastic asphalt concrete makes it most suitable material as strong and durable wearing surface. Although filler content in mastic asphalt concrete is four to five times greater than that of conventional bituminous mixes and has more pronounced effect on strength and rheol.ogical behaviour of mastic asphalt, very little work has been done to investigate effect of various types of fillers and filler contents on characteristics of mastic asphalt concrete. Most of specifications in India and abroad have recommended limestone dust as filler material for mastic asphalt preparation. In the present study different types of fillers including flyash with varying percentages have been used to study the effect of various types of fillers and their relative proportion in the mix in order to access suitability of various filler materials for preparation of mastic asphalt concrete.