This presentation will review the fundamentals of internal curing and discuss how this technology has been extended to structures in service to improve the durability of reinforced concrete. A series of experimental results will be shown to demonstrate that internal curing through the use of prewetted lightweight aggregates consistently reduces the potential for restrained shrinkage cracking. The implementation of internal curing in a new class of high-performance concrete for use in bridge decks in the state of Indiana will be discussed. These mixtures were designed to achieve an increased service life by both reducing the ionic transport and cracking potential of the concrete. This was achieved through the use of a ternary blended cementitious system with a moderate water-to-cementitious materials (w/cm) ratio of less than 0.43 and internal curing using prewetted fine lightweight aggregates. The corrosion-based service life of these commercially produced internally cured, high performance concretes (IC HPCs) was evaluated using a simulation of the extended Nernst-Einstein diffusion equation with inputs from migration cell testing and permeability measurements. The results indicate that the IC HPCs that were tested have the potential to triple the service life when compared to a conventional bridge deck concrete. Field inspections of these IC HPC bridge decks in service found no evidence of shrinkage cracking typical of traditional high-performance concretes, indicating that the internal curing has effectively reduced the potential for cracking, leading to an overall increase in the durability of the structures.
Courtesy of American Concrete Institute