Chloride ion transport in bridge deck concrete under different curing durations
The durability of concrete is usually measured by the number of years of maintenance- free service it provides. If a correct prediction has been made of the environmental conditions to which the concrete will be subjected to, concrete can be made to last for its intended service life. The durability of concrete is closely related to its permeability. The permeability dictates the rate at which aggressive agents can penetrate the concrete and attack the steel reinforcement.
During winter, ice accumulates on the top surface of concrete slabs and bridge decks. For the purpose of removing the snow and ice, de-icing agents, such as sodium chloride and calcium chloride, are applied. These salts migrate down to the reinforcing steel through small pores in the concrete. Over time, the chlorides in these salts can react with the reinforcing steel, breaking down the passive layer and causing the steel to corrode.
In Texas, the specification requirement for wet-mat curing is 8 days for decks with Type I and III cements and 10 days for decks with Type II and I/II cements and for mix designs with fly ash. Once the concrete is cured sufficiently, the deck is allowed to dry for one day. An additional day is typically allowed for any required surface treatment. The main objective of the research is to explore the possibility of opening the bridge decks earlier than 10 to 12 days by decreasing the number of wet mat curing days. For this reason, concrete mixtures typically used in Texas bridge deck were evaluated using numerous tests such as the Ponding test, the Rapid Chloride permeability Test, and the Abrasion Test.
This research focuses on the effect of curing on the chloride ion permeability of different mix design. It is expected that the knowledge gained through this work can be used to optimize the number of curing days and age required before full traffic can be allowed on bridge decks in Texas.