Moisture is always considered as one of the factors causing stripping of asphalt. One of most common issues in asphalt mixtures is eradication or reduction of the effects of moisture on bituminous hot mix asphalt and the best method to achieve this is to use additives and to change the structure of asphalt aggregating. Change in the type of aggregate is due to the changing in the rate of optimized asphalt, and actually the increasing in the rate of optimized asphalt could significantly affect the reduction of water in filtration in concrete aggregate and finally reduces the moisture sensitivity. The grading used in this study is related to the gap and stone matrix asphalt. In the mixtures, due to using high amount bituminous materials, the phenomenon of drain down happens, it might decrease the thickness of bituminous around aggregate and causes water infiltration and reduces inter adhesiveness of bitumen and aggregate. Therefore, in order to fix the stone matrix asphalt mixtures, fiber or modifying polymer are used. Thermoplastic elastomers polymers are those that simultaneously have the properties of elastomer and plastomer and in this research the moisture sensitivity of improved stone matrix asphalt mixtures with two kinds of these polymers called Lucobit and WKR-2 with deferent percentages have been studied and compared to 5% SBS in resilient modulus experiment, indirect tensile strength, Marshall stability. The result showed that by increasing these polymers percentages, the increase in resilient modulus and its ratio and the amount of ITS and TSR as well as Marshall stability and its ratio of wetness to dryness will be increased and they also showed better results in high percentages in comparison to 5% SBS.
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