INVESTIGATION OF THE EFFECT OF AGGREGATE PRETREATMENT WITH ANTISTRIPPING AGENTS ON THE ASPHALT-AGGREGATE BOND

Addition of Chemical antistripping agents (ASA) to asphalt has inheren t disadvantages such as reduction of the effectiveness of ASA in hot a sphalt and formation of relatively weak bond with the aggregate surfac e. To circumvent such problems, a novel approach of aggregate pretreat ment with ASA was investigated in this study. The aggregate was pretre ated with aqueous emulsions/solutions of different organic surface mod ifiers. 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 a nd simplicity. The effect of such variables as pretreatment drying tim e, drying temperature, type of aggregate, pH of boiling water, and con centration of ASA on the bond quality was also examined. The results i ndicated that aggregate pretreatment with organic surface modifier inc reased stripping resistance of asphalt paving mixtures. The excellent stripping resistance shown by iron naphthenate is likely due to the fo rmation of water insoluble salts between the positive iron ions and th e negative polar groups at the asphalt-aggregate interface.