A COMPARATIVE STUDY OF EMULSION AND MODIFIED BITUMEN IN ROAD CONSTRUCTION

Abstract

The use of bitumen emulsions began in the early part of the 20th century. Today 5% to 10% of paving-grade asphalt is used in emulsified form, but the extent of emulsion usage varies widely between countries. Today approximately 3 million tons of emulsions are produced in the United States representing about 5% to 10% of asphalt consumption. More than 8 million tons of emulsions are produced worldwide. Emulsion production varies greatly among countries with the United States, France, Mexico, and Brazil being significant producers. In India, use of bitumen emulsion is about 1.45% of the total bitumen used in highway related applications and is certainly far below the international trends; particularly when it is not a new material and its properties and potentialities are well known. Since last 15 years extensive laboratory studies and research works have been undertaken for development of designs and construction techniques in cold mix technology to suit Indian climatic conditions and construction materials available, under the guidance of IRC, CRRI and MOST. Bitumen, the black-coloured substance coming from the bottom of the vacuum distillation columns in the crude oil refineries, has been employed in the road building for ages. It has been reported that bitumen owes many interesting properties and characteristics, such as impermeability, adhesivity, elasticity and cost, which make it the most suitable material as a binder of mineral aggregates in paving applications. During last decades the properties required to road pavements have become more and more exigent, due to the increasing number of vehicles and load weight of some of them. Modification of natural bitumen with synthetic polymers/rubbers constitutes a route to overcome the new technical demands. Several thermoplastics and elastomers have been mixed with bitumen, usually in proportions below 10%, to improve the properties of the binder employed in roads. Polyethylene and ethylene vinyl acetate EVA copolymer have revealed as good modifiers to improve permanent deformation and thermal cracking. Elastomers, like styrene— butadiene rubber (SBR) and styrene—butadiene— styrene block copolymer (SBS) are very suitable, because besides of improving mechanical properties, ageing is also upgraded.