Study of Drying Shrinkage Mitigating Concrete Using Scaled Bridge Bays

Cracks reduce the durability and service life of bridge decks and they usually form as a result of tension induced from restrained shrinkage of concrete. There are several mixture design technologies that can be used to reduce concrete shrinkage and subsequent cracking. The main focus of this study is to evaluate the effectiveness of three such technologies to limit restrained shrinkage cracking in a scaled laboratory bridge deck. The first mixture evaluated shrinkage compensating cement (Type-K) as a partial replacement of Portland cement, the second mixture evaluated pre-wetted lightweight fine aggregate as a partial replacement of fine aggregate to promote internal curing (IC), and finally, the third evaluated a mixture incorporating shrinkage reducing admixture (SRA). Strain of the deck reinforcement was monitored during and after placement of the concrete for a period of 6 months. All of the data was compared with similar measurements from a control deck containing a standard concrete mixture used by the Illinois Department of Transportation. The results showed that, the experimental deck containing Type-K cement exhibited around 100% higher expansion compared to control mixture during the curing period. The IC mixture showed approximately 50% less expansion at 7 days but exhibited 10% less shrinkage at the end of drying period compared to the control mixture. The initial expansion of SRA mixture showed similar peak value compared to control mixture but at the end of the drying period, the shrinkage of SRA mixture was around 75% less than the deck cast with control mixture.