Effect of cohesive and adhesive parameters on the moisture resistance of thin friction course (TFC) with varying mix design parameters

Abstract

Thin friction course (TFC), one typical pavement surface treatments (PSTs), is mixed with modified asphalt emulsion, fine aggregate, and cement. Moisture-induced damage is one of the main distresses usually occurring in TFC. To mitigate potential moisture damage, varying TFCs with different combinations of emulsion, SBR latex, and cement dosages were investigated by the wet track abrasion test (WTAT). Then, the adhesive strength and cohesive stiffness of corresponding residue emulsion-cement mastics were estimated based on the binder bond strength (BBS) test and the strain sweep test, respectively. The results indicated that the increased emulsion, SBR latex, and cement dosages are beneficial to the moisture resistance of TFC. The pull-off strength of BBS test shows poor correlation with the aggregate losses and the failure type is cohesion by observation, which means the adhesion strength of the residue mastic-aggregate bond is higher than the cohesive strength based on the limited data. Furthermore, based on the strain sweep test, it was found that the cohesive parameters, including the maximum shear stress and the complex modulus at the strain level of 7% could perfectly correlate with the average aggregate loss with a correlation coefficient of 0.8841 and 0.8678, respectively. Therefore, both SBR and cement modification could enhance the cohesive stiffness of the cement-binder mastics and then improve the moisture resistance of the TFC.