Behavior of Shrinkage-Compensating Concretes Suitable for Use in Bridge Decks.

摘要

The object of this research was to determine if the use of shrinkage-compensating concrete in bridge decks minimizes cracking and the subsequent spalling caused by rusting of the steel reinforcing. The magnitude of expansion is influenced significantly by length of and methods of storing the shrinkage-compensating cement,choice of admixtures,mixing time,curing procedures and degree of restraint. The magnitude of expansion is approximately the same in specimens 3-in. (75-mm) to 8-in. (200-mm) thick if the restraint is the same and if good curing procedures are followed. The simulated bridge deck specimens made with shrinkage-compensating cements did not crack,or had only a few cracks when compared to the specimens made with Type 1cement. The rate of corrosion of the reinforcing was about the same for both of the concretes but was greater at cracked sections than at uncracked sections. The porosity of the shrinkage-compensating concrete was found to be about 20percent greater than that of the Type 1concrete,but the chloride ion concentration was approximately the same at a given depth. The elimination of cracks by using shrinkage-compensating cement concrete will prevent the rapid corrosion of the reinforcement and subsequent spalling in a bridge that occurs at a crack,and extend the life of the deck before repairs are needed.