Application of Anti-Stripping Agents for Increasing Moisture Resistance of WMA Mixes Produced with Different Methods

WMA mixes, compared with HMA mixes, are environmental friendly mixes that produce little air pollutants and greenhouse gases. Their high energy saving costs resulted in their extensive use in construction projects. However, these warm mixes recognized to be susceptible to moisture damage that results in stripping distress in pavements. In this research, WMA mixtures were prepared applying two different methods; namely, application of an organic additive (Sasobit) and adoption of foam bitumen technique. In this latter, small amount of water is inserted together with high pressure air into Wirtgen, WLB-10 machine One of the methods of solving moisture damages is to use anti-stripping additives to increase adhesion properties between bitumen and aggregate particles. In this research, two types of additives; namely, hydrated lime (at 1.5, 2 and %2.5 by weight of aggregates) and Zycotherm (at 0.1, 0.2 and %0.3 by weight of bitumen), were used to reduce moisture sensitivity of Warm Mix Asphalt (WMA). To evaluate moisture susceptibility of WMA mixes, Indirect Tensile Test, boiling water, and Pull Off testing were preformed. The experimental results showed positive effects of hydrated lime and zycotherm anti-stripping additive in reducing moisture sensitivity of WMA mixes. The testing results showed that WMA mixtures that were prepared applying foam bitumen techniqe were more sensitive to moisture damage than WMA mixtures that were prepared by organic additive (Sasobit). As conclusion, results indicated that the mixes containing %2.5 hydrated lime (by weight of aggregates) and %0.3 zycotherm (by weight of bitumen) are the optimum contents of addetives for reducing moisture sensitivity. Moreover, the results indicate that zycotherm additive has a greater effects on redusing moisture sensitivity compared to hydrated lime.