Effects of Polymer Modified Asphalt Emulsion (PMAE) on Pavement Reflective Cracking Performance

Hot mix asphalt (HMA) overlay is widely used to restore functional and structural capacity of existing asphalt pavements. In order to ensure that the overlay and the underlying layer act as a uniform composite layer and more effectively transfer and distribute the external load over a large area, a good bond between the overlay and underlying layer is a necessity. Overlay performance greatly depends on both the bond strength along the interface and the cracking resistance across the interface provided by. the interface materials. For example, one way to potentially enhance HMA overlay cracking performance is by using a highly polymer modified asphalt emulsion (PMAE) at the interface to help relieve stress transferred across the interface, as well as to enhance bonding between layers. Consequently, it is necessary to evaluate the effects of the interface conditions on overlay cracking performance. The effects of two types of interface conditions on reflective cracking were evaluated: conventional tack coat and PMAE. Tests were performed on composite specimens with these two different interface conditions using a newly developed Composite Specimen Interface Cracking (CSIC) test. Tests were performed under repeated tensile loading while monitoring the rate of damage development. Results clearly indicated that the PMAE interface can significantly improve reflective cracking resistance. However, these test results need further experimental road test evaluation and verification.