EFFECT OF ADDITIVES ON PROPERTIES OF BITUMEN

Abstract

Bitumen is derived from crude petroleum oil, the price of which has risen dramatically since the early 1970's. Consequently, the users seek either alternative material or means of extending the life of asphalt / bitumen by mixing certain additives. It was estimated that approximately 100-120 million tonnes of asphalt / bitumen are used World wide each year. In india,the requirement of asphalt / bitumen is of the order of 18 to 20 million tonnes per annum. The bitumen is mainly used in bituminous road construction. The performance related properties of paving bitumens can be suitably modified by incorporation of additives. In the present work, a study has been conducted on bitumen with certain additives. The additives used in this study are agriculture based additive (ABA), lime processed product (HL), natural mineral processed additive (NMPA), polypropylene wax (PPW) a bye product of IPCL, Baroda , Gujarat, polypropylene plant, styrene-butadiene -styrene block copolymer (SBS) a synthetic polymer, waste rubber processed product (WTR) and sulphur. The results indicate that the surface deformation caused due to higher temperature and brittleness (cracking) at low temperature can be prevented by the use of additives. The SBS, PPW and WTR are found most effective. The brittleness at low temperature can be reduced by SECS PPW and Sulphur as their glass paint values are quite low. The compatibility of additives with bitumen is an important factor. The techniques such as Scanning Electron Micrography (SEM) and Reflective Optical Micrography (ROM) are presently used to study reinforcement behaviour of additives in bitumen. The dispersion of PPW, SBS and HL is found to be homogenous and iv uniform at 4% level. The cracking of bituminous surfacing as a result of contraction and expansion of base and sub base materials during temperature variations may be checked by use of additive like SBS, WTR and PPW as their elastic recovery values are very high am compared to bitumen without additives. The thermal decomposition behaviour of additives is investigated by Thermogravimetry Analysis (TGA)/ Differential Thermal Analysis (DTA) studies.The products are stable to thermal decomposition at mixing temperatures. Initial Decomposition Temeprature (IDT) values can be taken as maximum limiting application temperatures. A number of test stretches were laid using WTR-Bitumen blends for sealing of cracks at Delhi-Nitipass Road, SH-45 on a badly cracked surface to study the performance of additives with bitumen. Performance of a test, stretch laid in June, 1990 was monitored through visual observations in Apri1,1991. The sealing layer is found to be intact and there are no signs of reflection cracking. To arrive at the final conclusion and making complete and exhaustive recommendations to use these additives, further detailed field studies are to be carried out and have been incorporated in the thesis in recommendations for further study.