Determination of the Optimum Lime Content for Asphalt Concrete Using Marshall Mix Design

This study evaluates asphalt concrete with and without hydrated lime using the Marshall mix design method with the aim of determining the optimum amount of lime required to modify the asphalt concrete. The hydrated lime was added by the dry method to the aggregates blend of asphalt mix with different percentages of hydrated lime (1.0 - 8.0 %) and the bitumen content ranged from 5.5% to 7.5%. The optimum binder and lime contents were found to be 6.5 % and 2.0%, respectively. The Marshall stability of the asphalt concrete with hydrated lime at 2% was 8.69 kN, while that of unmodified asphalt was 6.96kN, indicating that introduction of lime results in better performance. Generally, the lime modified asphalt samples had stability in the range of 4.12kN to 8.69kN, while the unmodified asphalt has stability in the range of 5.49 kN and 6.96kN. Both the lime-modified and unmodified forms conform with the General Specification, Road and Bridges. The flow values for the asphalt samples with lime were between 2.0 and 3.5 mm for 5.5% - 6.5% bitumen content, while the unmodified samples have values between 2.5 and 3.5 mm but both did not meet the specifications at higher bitumen content. The study showed that it is a good idea to introduce lime into asphalt, as it will result in production of asphalt mixture.