MOISTURE DAMAGE STUDY FOR VARIOUS TYPE OF BITUMINOUS MIXES

Abstract

Flexible pavements with bituminous surfacing are widely used in India. Various factors have been responsible for the early development of distresses like raveling, undulations, rutting and cracking of bituminous surfacing. The detrimental effects of water in asphalt mixtures as distresses in bitumen pavements were first recognized in 1930s and have been studied extensively during the last 35 years. This deterioration process, referred to as moisture damage, is generally defined as the degradation of the mechanical properties of the material due to the presence of moisture in its microstructure. In the recent years, modified bituminous mixes have become more popular in the construction of flexible pavements. These products have gained popularity because of their ability to reduce rutting at warm temperature and reducing the occurrence of thermal cracking at cold temperature. This modification can be done by waste materials which are generally dumped in nearby areas. With time, the amount of waste materials dumping results in wastage of many acres of precious land and having the harmful and non-hygienic impacts on ecological system. That is why, today disposal of the dumps has become a crying necessity, not only to region the vast valuable space occupied by them, but also to reduce the pollution and other hazards. Hence, in the present study efforts have been made to compare the use of CR and waste plastic bag fibres with SBS in modification of bitumen. It will not only bring out significant saving in road material costs but also help towards tackling the problems of disposal of such waste materials, which tend to be hazardous in as much as they can cause pollution of both air and water. This study presents an approach to evaluate the effects of SBS, CR and waste plastic bag fibres modifiers at their selected percentages i.e. 3, 5 and 7% on moisture damage resisting property of a bituminous mix. The basis of laboratory study was ASTM D 1075 -54 & AASHTO T 283 test and it was performed on two types of bituminous mixes which includes BC & SDBC mixes. The study was initially carried out for mixes prepared without the use of modifiers and the same process was repeated with addition of SBS, CR and waste plastic bag fibres modifiers at 3, 5 & 7 percentages. Testing data and analysis demonstrated that all the three mentioned modifiers contributed to improvement in moisture damage resistance which is reflected in its retained stability and tensile strength ratio results. The percentage improvement for different modifier is maximum at their optimum dose which is different for different modifiers. However, SBS modification in both the bituminous mixes has more improvement in moisture damage resistance than CR modification and waste plastics bag fibres modification. This study also concludes that the effect of various modifiers i.e. SBS, CR and waste plastics bag fibres is more pronounced for SDBC mixes in comparison with the BC mixes. Keywords: moisture damage, stripping, bituminous mixes, SBS, CR, waste plastic bag fibres, retained stability, tensile strength ratio. iv