Evaluation of Probing versus Coring for Determination of Portland Cement Concrete Pavement Thickness

Abstract

The Wisconsin Department of Transportation (DOT) has used contractor probing measurement of fresh portland cement concrete pavement to determine pavement thickness since 1998. Before that, the Wisconsin DOT used coring to measure thickness and determine payment for pavement. The probing method is nondestructive and has financial advantages for the Wisconsin DOT because it eliminates the costs of coring and reduces the expenses of contract administration. Probing also provides the contractor with immediate feedback on the depth of the pavement being constructed. A study was conducted to verify the reliability of probing measurement for determining pavement thickness and verifying contractors’ compliance with design requirements. To determine whether probing was still a viable method for use by the Wisconsin DOT in construction contract administration, core depths were compared with field-measured probe depths for 12 projects constructed between 2006 and 2008 across the state of Wisconsin. Sample means were compared, statistically calculated estimates of differences were examined, and a statistical analysis at the 95% confidence interval was carried out. According to these analyses, probing does provide an acceptable measure of pavement thickness. All contractor probe measurements and more than 80% of the Wisconsin DOT core samples showed that constructed pavement thickness exceeded the design thickness.