Effectiveness of Hydrated Lime Modified Bituminous Mixes in Pakistan

Abstract

Road network in Pakistan has been deteriorating steadily for the past couple of decades. Some of the major factors attributing to this decline are increase in road traffic, improper construction and maintenance practices and lack of maintenance funds. To alleviate this process, several measures may be effective, such as, improved traffic management, securing additional funds for timely maintenance, improved and innovative roadway design, use of better quality of materials and the use of cost-effective construction methods. One of the innovative methods being used around the world for improving road networks is use of Hydrated Lime in asphalt mix as a modifier. With this perspective, this research project aimed at exploring the potential prospects of Hydrated Lime to enhance asphalt mix properties as an additive. Objectives of this project was to inquire the benefits of Hydrated Lime in term of properties it improves and comparing the effectiveness and performance of conventional asphalt mix and asphalt mix modified by crumb rubber (CRMB), high density polyethylene (HDPE) i.e., waste plastic bottles and low density polyethylene (LDPE) i.e., waste plastic bags and Hydrated Lime. Hydrated Lime was shredded to powder form and then used in preparing modified asphalt mix. Dry Method was employed to add the Hydrated Lime (by weight of Mix). Marshall Mix design was used, first to determine the optimum binder content and then further to test the modified mixture properties. In total 30 samples were prepared of which 10 samples were used to determine the optimum asphalt binder content, 3 samples were tested for Marshall Stability and Flow, 10 samples were made to determine optimum lime content, 3 modified samples were tested for Marshall Stability and Flow, 2 samples (1 controlled, 1 Modified) was made for wheel tracking test and 2 samples for Skid resistance test respectfully. The optimum asphalt content was found out to be 4.5%. Five proportions of powdered Hydrated Lime by weight of the Mix was selected to be tested (i.e. 0.5, 1, 2, 3, 4%). The tests include the determination of bulk density, stability and flow. The optimum proportion of the modifier is found to be 2% by the weight of the Mix. All the results of this study were compared to that of previous studies which explored the prospects of adding HDPE, LDPE and CRMB in the asphalt mix. Rutting is the major cause of road failure in Pakistan due to violation of axle load limits, improper design practices and exposure to high tire pressure and high temperatures. Rutting test