Cracking Tendency of Lightweight Aggregate Bridge Deck Concrete

Early-age cracking in bridge decks is a severe problem that may reduce the functional life of the structure. In this project, the effect of using lightweight aggregate on the cracking tendency of bridge deck concrete was evaluated using testing frames that restrain movement due to volume change effects from placement to cracking. Expanded shale, clay, and slate lightweight coarse and fine aggregates were used to produce internal curing, sand-lightweight, and all-lightweight concretes to compare their behavior relative to a normalweight concrete in bridge deck applications. Specimens were tested under temperature conditions that simulate summer and fall placement scenarios. Increasing the amount of pre-wetted lightweight aggregate in the concrete systematically decreased the density, modulus of elasticity, and coefficient of thermal expansion of the concrete. When compared to a normalweight concrete, the use of lightweight aggregates in concrete effectively delays the occurrence of early-age cracking in bridge deck applications.