Cracking in Concrete Pavements

Abstract

Several theories explaining the mechanisms and intervals of cracking of portland cement concrete pavements are reviewed. For plain and jointed pavements, the cracking interval was found to be approximately twice (when expressed in feet) the strength (when expressed in psi) of the concrete. For new concrete with a 30-psi (0.2-MPa) tensile strength after only a few hours, the drying-shrinkage or cooling crack interval is approx 60 ft (18 m). This is a basis for sawing joints at approx 50 ft (15 m) intervals before the concrete is 16 hrs old. For concrete with a compressive strength of 4,500 psi (31 MPa) and sawed joints, the interval between blowups or crushed joints would be about 1 mile (1.6 km). This is the basis for spacing expansion joints approx 0.5 mile to 1 mile (0.8 km to 1.6 km) apart. A theory of differential temperature expansion-contraction between concrete and steel explains the ultimate crack interval of continuously reinforced concrete pavements between 2 ft and 6 ft (0.6 m and 2 m). This interval was verified by field observations.