Cracking of Fresh Concrete as Related to Reinforcement

The research reported here was undertaken to quantify the effect of depth of cover and two other variables, concrete slump and reinforcement bar size, on the tendency to produce the subsidence cracks over the reinforcement that lead to corrosion of the reinforcement in concrete bridge decks. A photoelastic study was also undertaken to determine the magnitudes of the tensile stresses above the reinforcement as a function of depth of cover. Finally, a corrosion study was carried out to verify that subsidence cracking over the reinforcement leads to corrosion of the reinforcement in the presence of deicing salts. The conclusions from this study were: depth of cover significantly affects subsidence cracking, corrosion potentials are significantly higher for cracked concrete, and tensile stresses over reinforcing bars due to body stresses in fresh concrete increase sharply with decreasing cover.