A Study on the Use of CRMB and LDPE in Semi Dense Bituminous Concrete

Abstract

Bituminous surfaced flexible pavements comprise of majority of the roads. Distress symptoms, such as cracking, rutting, etc., are being increasingly caused earlier by high traffic intensity, over loading of vehicles and significant variations in daily and seasonal temperature of the pavement. Investigations have revealed that modifiers can be used to improve rheological properties of bitumen and bituminous mixes to make it more suitable for road construction. Bituminous-mix design involves mixing various aggregate sizes and bitumen contents in optimum proportions. For a given aggregate gradation, the optimum bitumen content is estimated by satisfying a number of mix design parameters. Badly compacted bituminous mixtures develop low stiffness, bad fatigue resistance, bad durability, etc. which are undesirable characteristics for a good pavement. Modified Bitumen is one of the important construction materials for flexible pavements. Use of plastic waste (LDPE) and Crumb Rubber in the construction of flexible pavement is gaining importance. The modified bitumen show better properties for road construction.It is also worth mentioning that, the modifier raw-material has been sourced from disposed waste plastic and crumb rubber. This not only allows us to collect modifier raw-material at low cost, but also provides a solution towards ecological menace posed by increased use of plastics (nonbiodegradable).In the present study, an attempt has been made to use waste plastic (LDPE or Low Density Poly Ethylene) and Crumb Rubber Modified Bitumen (CRMB), blended using dry process for LDPE and wet process for CRMB. The waste plastic bags (for LDPE) was heated to 160-180ºC and added to the aggregate, while crumb rubber from scrap tier was powdered and added to bitumen (60/70) at 120-140 ºC. The LDPE-aggregate mix and CRMBbitumen mix were then combined to get the sample for semi dense bituminous concrete (SDBC). A number of samples were prepared for testing by varying percentage of LDPE and CRMB by weight of bitumen in such a given manner: Physical properties of 60/70 grade bitumen and also the bituminous mix of Semi Dense Bituminous Concrete (SDBC) was prepared for all the 3%, 6%, and 9% of LDPE. Physical properties of 60/70 grade bitumen and also the bituminous mix of Semi dense bituminous concrete (SDBC) was prepared for all the 8%, 10%, 12% of CRMB.