Early age cracking of reinforced concrete bridge decks

Abstract

This paper describes the instrumentation and test results of a reinforced concrete bridge deck constructed on three-span continuous steel girders in Evansville, West Virginia. An instrumentation system consisting of 232 sensors is developed and implemented specifically to measure strains and temperature in concrete deck, strains in longitudinal and transverse rebar, the overall contraction and expansion of concrete deck, and crack openings. Data from all sensors are automatically collected every 30 minutes starting at the time of placing the deck. The results indicated that elevated longitudinal stress due to constrained drying shrinkage is the main factor responsible for crack initiation during the first two days after concrete placement. Several factors contribute to the deterioration of the deck: (1) thermal stresses developed in the deck because of the constraining effects of the stay-in-place forms and shear studs; (2) non-uniform curing of the concrete along the deck; (3) in-plane temperature variations along the deck; (4) slippage of the rebar inside the concrete.