Performance Assessment of Unbonded Concrete Overlays of Concrete Pavements in Ohio: A Forensic Practice

Abstract

Unbonded concrete overlay (UBCO) is a widely used rehabilitation technique for deteriorated pavements, which is accomplished by placing concrete overlay on top of existing pavement with a sandwiched bond breaker layer between them. This technique is commonly used in Ohio and is proven to be practical in extending the service life of aged concrete pavements. The structural capacity of UBCO over concrete pavement is significantly high due to its two layers of Portland cement concrete (PCC). The objective of this study is to assess the performance of several UBCO pavements in Ohio and to identify causes of early failures. A comprehensive forensic investigation was conducted following the National Cooperative Highway Research Program (NCHRP) guide, including nondestructive testing, destructive testing, lab testing, and computer analyses. It was found that the causes of failure are different for each UBCO project but that they share some commonality. Water damage and poor construction quality control were identified as two major factors in causing the failure of UBCOs. This paper summarizes the performance assessment of UBCO pavements in Ohio. The findings contribute to the understanding of failure modes of UBCO pavements as well as forensic practice.