Evaluation of the anti-rutting potential of polymer-modified binders by means of creep-recovery shear tests

In the experimental study reported in this paper a creep-recovery shear test method was used to evaluate the anti-rutting potential of different polymer-modified bituminous binders. The effects of several factors related to modification were investigated, such as polymer type (SBS, styrene–butadiene–styrene vs. ethylene–vinyl–acetate), composition (styrene content), structure (linear vs. radial SBS) and dosage (3–6 % by weight of the base bitumen). The effect of short-term aging was also considered by comparing binder response before and after treatment with the rolling thin-film oven test. Following previous work on the development of the test protocol, experimental results were analyzed by referring to shear modulus curves G(t) and to permanent compliance (J _P), obtained by dividing residual strain at the end of the unloading phase by the stress applied during creep loading. Results indicated the effectiveness of the proposed method in discriminating between the behavior of the different polymer-modified binders and in capturing the effects caused by the factors considered in the investigation. Reliable rankings of the binders were established and were explained by referring to the specific behavior of employed modifiers.