Interface bond strength of engineered cementitious composites (ECC) in pavement applications.

Ultrathin whitetopping (UTW) is a rehabilitation technique that consists of pouring a thin layer of concrete on top of distressed asphalt pavement. UTW has shown satisfactory performance in the field; however, due to the brittleness of concrete, early pavement failure has been reported. Engineered cementitious composites (ECC) have been considered for UTW applications due to its superior tensile ductility, flexural performance, and fatigue resistance in order to serve as an alternative to concrete. To investigate this application, an ECC-UTW was constructed at the Pavement Research Facility (PRF) in Port Allen, Louisiana. A critical factor that contributes to the performance of UTWs is the bond strength with the existing asphalt concrete (AC) layer. Therefore, prior to loading, a series of laboratory bond tests were conducted on drilled core specimens to characterize the strength of ECC/AC and concrete/AC interfaces. Two existing AC surface conditions were considered: milled and unmilled. ECC/AC and concrete/AC specimens were prepared and subjected to direct shear in accordance with AASHTO TP 114. Furthermore, the tensile bond strength was assessed through the pull-off test by ASTM C1583. Results showed that concrete had a superior bond strength with AC compared to ECC under the direct shear condition. In addition, the pull-off tests carried out in the UTW also indicated that concrete had a superior bond in tension with the AC substrate compared to ECC. Interfaces were analyzed by scanning electron microscopy–electron dispersive X-ray spectroscopy (SEM–EDS), and findings indicated a lack of hydration products at the ECC/AC interface. [ABSTRACT FROM AUTHOR]