Cracking of Fresh Concrete as Related to Reinforcement

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Title: Cracking of Fresh Concrete as Related to Reinforcement

Author(s): Fadh H. Dakhil, Philip D. Cady, and Roger E. Carrier

Publication: Journal Proceedings

Volume: 72

Issue: 8

Appears on pages(s): 421-428

Keywords: bridge decks;corrsion;cover;cracking (fracturing); deicers; deterioration; photoelasticity;reinforced concrete; reinforcing steels.

Date: 8/1/1975

Abstract:
Numerous srudies have shown that corrosion of the top reinforcing steel leads to fracture planes and spalls or "potholes", the most serious form fo deterioration of concrete bridge decks. Those studies also showed that the depth of concrete cover over the top reinforcement is a major determinant of the occurance of deterioration. The research reported here was undertaken to quantify the effect of depth of coverand 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. A photoelastic study was also undetaken 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 sunsidence cracking over the reinforcement leads to corrosion of the reinforcement in the presence of deicing salts. The conclusions from this study were: (1) depth of cover significantly affects subsidence cracking, (2) corrosion potentials are significantly higher for cracked concrete, and (3) tensile stresses over reinforcing bats due to body stresses in fresh concrete increase sharply with decreasing cover.