Evaluation of the effects of polypropylene additive on moisture damage properties of asphalt mixtures

Evaluation of the effects of polypropylene additive on moisture damage properties of asphalt mixtures
abstract:
Different methods are used for reducing the effects of moisture damage in asphalt mixtures. Hydrated lime and amin-materials are conventionally used as anti striping additives. The polymeric materials have basic properties and they might reduce the acidic properties of binders. Hence, the effects of one polymeric material named Polypropylene (PP) additive were investigated on the moisture damage of asphalt mixtures. For this purpose, different asphalt mixtures were fabricated using granite and limestone aggregates as well as 0, 2, 4% PP additives. Indirect tensile strength tests were applied on 1, 3 and 5 freeze–thaw conditioned mixtures based on AASHTO T283 standard method. Also, surface free energy tests were used for determining adhesion properties of base binder, modified binders and aggregates in different conditions. Obtained results showed that PP improves the strength of asphalt mixtures in wet and dry conditions. In general, it seems that the use of PP up to 4 percent decreases the moisture sensitivity of asphalt mixtures. Also, the results of surface free energy tests showed that PP increases the free energy of adhesion. Thus, adhesion properties improve between asphalt binders and aggregates.