Reducing Drying Shrinkage of Bridge-Deck Concrete

A number of Alabama Department of Transportation (ALDOT) engineers concur that concrete shrinkage is a primary cause of bridge-deck cracking, which is the main cause of premature deck deterioration and reduced durability in Alabama. Because shrinkage-compensating concrete (SCC) substantially reduces shrinkage and thus shrinkage cracking, the ALDOT engineers decided to examine SCC as a candidate material for bridge decks. These engineers also wanted to test new shrinkage-reducing admixtures (SRA) that reduce early drying shrinkage cracking of bridge decks. This article describes a research project conducted for ALDOT that tested the behavior and properties of fresh and hardened SCC and concrete employing SRA. The aim was to improve the durability of bridge decks in Alabama by reducing instances of early bridge-deck cracking. The research was limited to lab tests on fresh and hardened concrete for 4 mixtures.