Chloride Transport and Service Life in Internally Cured Concrete

Concrete bridge decks are susceptible to premature cracking and to the corrosion of reinforcing steel. Many agencies have shifted to using higher strength concrete as an attempt to improve the long term durability of bridge decks. Unfortunately, higher strength concretes have not completely solved the problem and in many cases this has exacerbated the problem of early-age cracking. Bridge deck concrete should be designed to minimize the potential for cracking while providing a dense microstructure that reduces the potential for chloride ingress. Concrete mixtures can be designed using a concept called internal curing. Internal curing minimizes cracking while reducing chloride ingress. The work will describe how internal curing, through increased cement hydration and ITZ depercolation, reduces chloride penetration. The impact on chloride ingress and corrosion will be described through a series of experimental measurements. The paper reports results from several transport tests on reference and internal cured concrete for several bridges that have recently been constructed in the state of New York and Indiana.