The primary objective of this project was to develop a test for measuring the bond strength between pavement layers. The research was also to evaluate tack coat materials and application rates for the Alabama Department of Transportation (ALDOT).
This Technical Brief provides an overview of tack coats and their vital role bonding multiple asphalt layers into one monolithic system. Poor tack coat techniques result in compromised bonding of the asphalt layers. This leads to pavement distresses. Possible slippage cracking and delamination are associated with poor bonding. Additionally, poor bonding can lead to structural distresses, namely fatigue cracking and potholes. Often this lack of sufficient bonding is not recognized as the source of failures.
Find the full report here.
Asphalt tack coat is a light application of asphalt, usually asphalt diluted with water. It is used to ensure a bond between the surface being paved and the overlying course. Normally, hot asphalt cements, emulsified asphalts, or cutback asphalts are used as tack coats. The objective of this study was to evaluate the practice of using tack coats through controlled laboratory simple shear tests and determine the optimum application rate.
See Report Here.
TRB’s National Cooperative Highway Research Program (NCHRP) Report 712: Optimization of Tack Coat for HMA Placement presents proposed test methods for measuring the quality and performance characteristics of tack coat in the laboratory and the field, and includes a training manual presenting proposed construction and testing procedures for tack coat materials.
It is available for Purchase as a PDF from TRB here.
Following damage that appeared on the surface layers (fatigue cracks, peeling, rapid structural fatigue), the IBEF International Bitumen Emulsion Federation launched a survey in 1998. The goal of the survey was to assess the current situation of this technique worldwide by studying the practices, proportions and specifications that exist.
Find full report here.