Mitigation of moisture damage in asphalt concrete: Testing techniques and additives/modifiers effectiveness

Moisture damage is a serious pavement distress that most transportation agencies face. It's complicated mechanisms are dependent on several factors in asphalt pavement. This phenomenon triggers several pavement distresses, thus costing the country billions of dollars in pavement maintenance and rehabilitation. The most traditional technique adopted to mitigate moisture damage is adding selected additives or modifiers to asphalt mixtures. The additives and modifiers are used during construction to improve water resistance in asphalt pavement. However, each additive or modifier performs differently. This study evaluates the effects of two additives and two modifiers on the moisture susceptibility of two asphalt mixes. The additives include a liquid anti-stripping agent and hydrated lime while the modifiers include styrene butadiene styrene (SBS) and polyphosphoric acid (PPA). The effectiveness of the additives and modifiers was evaluated by conducting three mixture tests, including the Lottman AASHTO T283-02 test with five freezing and thawing (FT) cycles, the wheel-tracking test, and a fracture test using semicircular bending (SCB) specimens. The Lottman AASHTO T283-02 showed that adding liquid anti-strip to asphalt binder produced the best moisture resistance for both mixes followed by hydrated lime. The wheel track test showed that hydrated lime and SBS modifiers resulted in the least rut depth when used in both mixes. The results of the fracture test showed that liquid anti-strip and hydrated lime produced the highest fracture resistance. On the other hand, the three above test results indicated that PPA may not control asphalt mixers' moisture susceptibility. (c) 2015 Elsevier Ltd. All rights reserved.