Investigation of Cracking in Concrete Bridge Decks at Early Ages

The loads, construction procedures, and material behavior influence the performance of the bridge deck as well as its structural integrity. This paper includes a thorough investigation to identify the probable causes of cracking in reinforced concrete bridge decks, particularly at early ages. The objectives of the study were addressed through a literature review process and a comprehensive nationwide survey. Experiments were performed to establish the magnitude of the modulus of elasticity of concrete at early ages as well as the curvature it can withstand without cracking. A computer program was developed to take into account the loads due to sequence of pours. A compendium was developed to categorize the various causes of cracking to identify appropriate procedures that may control this cracking. The parameters considered in the investigation were age of concrete, stage and sequence of pours, curing procedures, heat of hydration, strength gain, thermal changes, and construction type. Results of the literature review and survey indicated that in most cases, cracking of concrete may be attributed to the high evaporation rate and high magnitude of shrinkage. Other factors include the use of high slump concrete, excessive water in the concrete, insufficient top reinforcement cover, insufficient vibration of the concrete, inadequate reinforcing details of the joint between the new and old deck, sequence of pour, and weight and deflection of the forms. The calculated curvatures for the selected bridges were smaller than the curvatures needed to crack dynamically loaded fresh concrete in a laboratory environment.