Mitigation of Cracking in Cast-In-Place Reinforced Concrete Box Culverts in Alabama
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Significant cracking was observed in Alabama Department of Transportation (ALDOT) cast-in-place (CIP) reinforced concrete box culverts in the Anniston East Bypass (AEB) project in Anniston, AL. Numerous wide, transverse cracks were observed inside the culvert barrels, and cracking was also observed in the culvert wingwalls. Because of the cracking problems in the AEB project, crack condition surveys were done of other CIP reinforced concrete box culverts throughout Alabama to investigate the distress. An instrumentation and testing plan was also developed for a CIP reinforced concrete box culvert under construction in order to evaluate the stress, strain, and temperature development as well as other properties. The amount of temperature and shrinkage reinforcement required to produce acceptable average crack widths in CIP reinforced concrete box culverts was investigated as well. It was concluded that the transverse cracking was most likely a result of restrained thermal and drying shrinkage deformations in the concrete. Transverse contraction joints in the culvert barrel and vertical wingwall joints were proposed to control the occurrence of these cracks. The amount of longitudinal temperature and shrinkage reinforcement was also recommended to be increased to control the crack widths to 0.012 in. (0.30 mm).