Investigation of the effect of aggregate pretreatment with antistripping agents on the asphalt-aggregate bond

Addition of Chemical antistripping agents (ASA) to asphalt has inherent disadvantages such as reduction of the effectiveness of ASA in hot asphalt and formation of relatively weak bond with the aggregate surface. To circumvent such problems, a novel approach of aggregate pretreatment with ASA was investigated in this study. The aggregate was pretreated with aqueous emulsions/solutions of different organic surface modifiers. The effectiveness of this aggregate pretreatment procedure was evaluated to ascertain the asphalt-aggregate bond strength using the boiling water test. Boiling water test was selected for its rapidity and simplicity. The effect of such variables as pretreatment drying time, drying temperature, type of aggregate, pH of boiling water, and concentration of ASA on the bond quality was also examined. The results indicated that aggregate pretreatment with organic surface modifier increased stripping resistance of asphalt paving mixtures. The excellent stripping resistance shown by iron naphthenate is likely due to the formation of water insoluble salts between the positive iron ions and the negative polar groups at the asphalt-aggregate interface.