Effect of type and quantity of binder on rutting characteristics of bituminous mix

Abstract

Rutting is one of the most common types of failure observed on high volume bituminous pavements in India, and Viscosity Grade bitumen (VG 30) is the most common binder used for construction, and these could not provide desirable performance. Modified binders, both polymer and crumb rubber, have also been used in construction, mainly to address rutting failures. Though these binders have shown improved performance over VG 30 binders, the effect of type and amount of modified binder on the performance of mixes is not clearly understood. Although rutting in bituminous mix depends on many factors, such as size, gradation, surface texture of aggregates, type and amount of binder, etc., it is important to find out the role of the binder in the performance of the mixes. Keeping the above in view, performance of three commonly used modified binders were evaluated for binder rheological parameter G*/sin ẟ associated with rutting behaviour using dynamic shear rheometer. Bituminous mixes prepared at 0.5% incremental binder contents either side of the optimum binder content were evaluated to study the effect of type and quantity of binder on rutting performance of the mixes. A mid-point aggregate gradation of a wearing course of Indian highways, bituminous concrete, as per Indian Roads Congress specifications, was considered. Rut tester was used to evaluate the relative rutting susceptibility of the mixes. Correlation between rut depth measured and binder content on air voids for each type of binder was developed. Relative rutting performance of bituminous concrete mix at different binder content for all types of binders was evaluated and presented. Based on the study, it was observed that polymer modified binder (PMB 40) performed better compared to other binders considered in this study. Also with increase in binder content beyond certain limit, rutting susceptibility of the bituminous mixes increased irrespective of type of binder used, but the effect was less in the case of PMB 40 mixes.