Evaluation of Permanent Deformation and Fatigue Using Lime Modified Binder

Abstract

HMA is a common material widely used for paving purpose. Hot mix asphalt (HMA) pavements are subjected to continuously changing traffic wheel loads and environmental conditions. When environmental actions are combined with the imposed stresses from the repeated traffic loads moisture damage can occur and causes a reduction in pavement life due to the formation of “rutting and cracking failures”. To prevent this damage, this research will resort to specifying anti-stripping additive in an attempt to increase adhesion at the aggregate-asphalt interface. Lime is the most common solid anti stripping additive used in Pakistan. Long term performance of HMA pavements treated with lime shows that it is effective in reducing the moisture sensitivity of the mixture. Pavement industry is facing serious problem related to “rutting & fatigue cracking” in HMA pavement. Ever since the start of the use of Hot Mix Asphalt Pavements, rutting & fatigue cracking have been the major problem in the design and performance of these pavements. To help this problem Superpave mix design system was developed in 1993 as an attempt to improve the performance of HMA mixture. . Superpave mix design method was used in this research and the binder is modified with Lime primarily targeting its properties to produce a better mix that improves resistance to fracture growth (i.e. it improves fracture toughness). Superpave gradation is bound by 0.45 power line that is surrounded by restricted zone and control pints 0.45 power line starts from zero to maximum aggregate size. The allowable ratio of the fine sand fraction to the total sand was to help reduce the incidence of moisture susceptible causing rutting. This research will help to evaluate the effect of the Lime Modified Binder on the above mentioned pavement performance measures of Superpave HMA mixtures on the basis of a statistically planned and properly controlled laboratory experiment. In this research the selected gradation will be Superpave 1 (19mm NMAS) as well as Superpave 2 (25mm NMAS). The research will focus on rutting using HWT and fatigue cracking using UTM-25. The gradations are tested using Margalla quarry aggregate and bitumen grade 60/70 of Attock Oil Refinery will be used. The binder is modified with Lime with different percentage of lime with the total weigh of dry aggregate. The optimum asphalt content xiii of the binder has been determined using the superpave mix design method for both gradations, and then volumetric of gyratory sample has been figured out. Moreover, performance testing including Hamburg Wheel Tracker test and Indirect Tensile Fatigue test has been done on the mixes using the optimum content determined earlier. The performance tests were performed on the compacted mixtures and the results showed significant increase in resistance to rutting potential and fatigue cracking using lime as modifier and at the end statistical analysis was conducted on results obtained from Indirect Tensile Fatigue test and temperature was found to be the most significant factor followed by gradation and lime content.