Bridge Decks: Mitigation of Cracking and Increased Durability

Abstract

This report discusses the application of expansive cements (Type K and Type G) and shrinkage-reducing admixtures (SRAs) in reducing the cracking due to drying shrinkage. The Type K expansive cement contained portland cement and calcium sulfoaluminate-based component whereas the Type G expansive system was made of portland cement and CaO-based component. The restrained expansion test in accordance with ASTM C 878 demonstrated that Type K and Type G concretes had minimal shrinkage at the end of 100 days. The Type K bridge deck model also exhibited a reduction in tensile strain on the order of 40-50 microstrains and reduction in excess shrinkage potential which showed its effectiveness in reducing the tensile stress due to drying shrinkage. The effect of mineral admixtures on expansion characteristics of Type K and Type G system is also discussed. The effectiveness of SRA was assessed using ASTM C 1581 that clearly showed the delay in cracking time due to addition of an SRA. The increase in SRA dosage reduced the drying shrinkage, but also resulted in reduction of compressive strength.