Laboratory investigations of dense bituminous macadam (grade 1) mix using different types of additives

Abstract

India has a road network of over 4,236,000 kilometres, the third largest in the world. The road transport carries close to 85% of passenger traffic and 70% of freight transport. The properties of bitumen and bituminous mixes can be improved to meet requirements of any pavement with the incorporation of certain additives or a blend of additives. Bituminous mixes can be prepared and used in a pavement section for a bituminous binder course using different types of additives such as Polymers, Crumb Rubber and waste materials like discarded tube tyres, plastic bottles and rice husk ash. Modified bituminous mixes are expected to give higher life of surfacing depending upon degree of modification and type of additives used. The consumption of plastics is increasing day by day. Nearly 50 to 60% of the total plastics are consumed for packing. Once used plastic materials are generally thrown out as they do not undergo bio-decomposition. Hence, they are either land filled or incinerated. Both are not eco-friendly processes as they pollute the land and the air. Similarly, waste tyres in India are categorized as solid hazardous waste. It is estimated that about 60% of waste tyres are disposed via unknown routes in the urban as well as rural areas. The hazards of waste tyres include- air pollution associated with open burning of tyres, aesthetic pollution caused by waste tyre stockpiles and illegal waste tyre collecting and other impacts such as alterations in hydrological regimes when gullies and watercourses become waste sites. The present study aims at developing bituminous mixes for the Dense Bituminous Macadam (DBM) Grade 1 incorporating the plastic wastes, waste tyre tubes and rice husk ash as partial replacement of the bitumen content. Also the study focuses on the DBM Grade 1 mixes with different blends by using Crumb Rubber Modified Bitumen (CRMB) and Polymer Modified Bitumen (PMB). In this study, the Stability-Flow analysis for the various DBM Grade 1 mixtures with modified binders and with different percentage replacement of bitumen with plastic wastes, waste tyre tubes and rice husk ash are reported. It is found that of the three materials used, replacement of OBC by 10% discarded tyre tube has the highest stability value. The optimum content of CRMB and PMB for use in DBM Grade 1 mix is 5%. Also the bituminous mixes of DBM Grade 1 with 5% PMB having 40% stone dust shows the maximum stability value and the bituminous mixes of DBM Grade 1 with 5% CRMB having 44% stone dust shows the maximum stability value.