The tack coat bond is known to affect the longevity of asphalt pavements. Proper interlayer bonding prevents successive pavement layers from acting independently of one another and creating non-uniform stress and strain profiles in the pavement structure. Poor bonding between pavement layers can result in various pavement failures such as slippage cracking, debonding and early fatigue cracking, all of which contribute to a reduced pavement fatigue life. Tack coat application rate and uniformity (that can be achieved by uniform tack coat application and by avoiding/minimizing tracking) are two major factors that control the performance of the tack coat bonding and longevity of the pavement structure.
In this study, a wireless scale system (OreTackRate) that can be controlled from a tablet computer was developed to measure tack coat application rate accuracy and uniformity. The developed wireless scale system was recommended to be implemented during construction to validate application rate accuracy and uniformity. In addition, a distributor truck certification process was developed and presented in this study. The developed scale system can also be used to determine whether the applied tack coat is cured at any time point during construction. Residual tack coat application rate can also be measured using OreTackRate during construction. A construction surface cleanliness test (OreTackClean) and a test procedure were also developed in this study to reduce tracking and achieve more uniform tack coat distributions that will ultimately improve long-term tack coat performance.
Additionally, this study focuses on developing and implementing a more robust set of specifications and quality control (QC) provisions for quantification of tack coat bond quality in laboratory or field settings. By improving upon and implementing the OreTackBond (formerly known as Oregon Field Torque Tester [OFTT]), a rigorous in-situ test for tack coat quality is validated for large-scale implementation as part of the highway construction inspection process. In this study, a construction QC process for tack coat bond performance was proposed. Results of field and laboratory OreTackBond tests showed that developed in-situ QC control process can be effectively used to improve the in-situ tack coat bond performance. Implementation of all these tests, procedures, and technologies are expected to improve the tack coat uniformity during construction and improve the overall longevity of the pavement structures.