Laboratory investigation on use of fly ash plastic waste composite in bituminous concrete mixtures

This paper reports the benefits of composite of fly ash and plastic waste in Bituminous Concrete (BC) mixture for construction of flexible pavement. Fly Ash (FA) and Plastic Waste (PW) are two abundantly available waste materials, with several good characteristics, making them suitable for bituminous road construction. The plastic waste will improve some properties of the bituminous mix and also solve environmental problems. Fly ash is the finely divided residue that results from the combustion of pulverized coal. It can be used as cost-effective mineral filler in hot mix asphalt (HMA) paving applications. The Thermal degradation behavior of the plastic waste was investigated by Thermo Gravimetric Analysis (TGA). Samples were prepared using various percentages of plastic content from 0.25% to 1% with 0.25% increment by weight of the total mix. From the tests it was found that the optimum content of plastic is 0.75% and the optimum binder content of bitumen for fly ash as filler is 5.3% and fly ash-plastic waste composite is 5.4%. Samples were prepared using 0.75% plastic content and optimum binder content of bitumen by weight of total mix. The designed BC mixes such as mixture containing fly ash as well as fly ash-plastic waste composite were prepared in a laboratory mixer and are designated as BC A and BC B respectively. The BC mixtures were subjected to performance tests such as indirect tensile strength, indirect tensile strength ratio, static creep and resilient modulus at different temperatures and rutting resistance by wheel tracking test. From the indirect tensile strength ratio (TSR) it is found that, the TSR of BC B was 10.3% higher than the BC A mix indicating better resistance to moisture damage. From the static creep test it is found that the permanent deformation of BC B is higher than the BC A at both the temperatures 35 degrees C and 45 degrees C but percentage of recovery is higher for BC B than the BC A mix. Resilient modulus values of BC B was higher than the BC A at both the temperatures 35 degrees C and 45 degrees C. Higher values of resilient modulus values indicate that they are very high and support to reduce rutting behavior of mixtures. Rut depth of BC B is 15.9% lower than the BC A. These findings indicate that BC containing composite as substitute of traditional filler is an acceptable material for bituminous road construction. (C) 2013 The Authors. Published by Elsevier Ltd.