Early Opening of Portland Cement Concrete (PCC) Pavements to Traffic

This report presents the results of a detailed stress analysis and a field and laboratory test program which investigated the early-age strength gain for selected portland cement concrete (PCC) paving mixtures used in Wisconsin as well as the effects of early-age loading on doweled pavement joints. A simplified procedure for predicting critical dowel-PCC interface stresses was developed. This procedure was used in conjunction with allowable bearing stresses to establish minimum compressive strength requirements for opening to traffic based on pavement design parameters, including PCC, base, subgrade and dowel material properties. Equations for predicting early-age PCC compressive strength from 7-Day or 28-Day laboratory test results were developed based on maturity readings. The best correlation was observed for estimating the %7-day early-age strength based on maturity readings of field-cured bagged cylinders. Exposed dowel load and deflection tests were used to investigate the effects of early-age loading on the PCC immediately surrounding the dowel. These tests proved inconclusive with no apparent trends in the data. More research in this area is needed to develop appropriate testing protocol and practical guidelines for implementation.