A COMPARATIVE STUDY ON MODIFIED BITUMINOUS MIXES USING CRUMB RUBBER OF CARS AND TRUCKS

Abstract

The demand for bitumen has increased tremendously in recent years due to rapid urbanization. In India, the annual consumption of bitumen in 1990 was 1.6 million tons. For construction of new roads and maintenance of existing roads, bitumen demand at present is around 4.4 million tons. Requirement of bitumen in the country is met only by imported crude. Bitumen is a scarce material due to limited reserves of crude petroleum in the world. Traditional bituminous binders present various limitations to cope with the excessive overloading and increasingly severe climatic conditions, which lead to premature failure of bituminous surfacing. Beside this, constructions of heavy-duty pavements also require modification of bitumen. So, it is necessary to improve desirable properties of the bitumen by modifying it with different types of modifiers.. The modifiers used in the present study are SBS and crumb rubber (CR) obtained from discarded tyres of Maruti car and trucks. The blends were prepared with different contents of these modifiers and tests for penetration, softening point, elastic recovery, Marshall stability, tensile strength and fatigue testing were conducted. The results show that while penetration value decreases with the content of modifiers, the softening point increases indicating the suitability of the binder in high temperature regions. The elastic recovery of the bitumen modified with different blends of modifiers also gets enhanced. The Marshall stability increases by 1.8 times when 6 percent CR along with 12 percent SBS is added to bitumen. The stability value of the bituminous mix is 2 to 14 percent more by adding crumb rubber from truck tyre than that of Maruti car tyre as modifiers. iii The indirect tensile strength also increases by 1.5 times when 6 percent crumb rubber along with 12 percent SBS is blended with bitumen. There is an increase in fatigue strength also. The number of repetitions to cause failure also increased 2 times approximately.