Construction of LC-HPC Bridge Decks Incorporating New Technology
General Problem Statement and Background:
Bridge decks constructed using low-cracking high-performance concrete (LC-HPC) have performed exceedingly well when compared with bridge decks constructed using conventional procedures. The LC-HPC decks have been constructed using 100% portland cement concretes with low cement paste contents, lower concrete slumps, controlled concrete temperature, minimum finishing, and the early initiation of extended curing. Methods to further minimize cracking, such as internal curing in conjunction with selected supplementary cementitious materials, shrinkage-reducing admixtures, shrinkage-compensating admixtures, and fibers have yet to be applied in conjunction with the LC-HPC approach to bridge-deck construction. Laboratory research and limited field applications have demonstrated that the use of two new technologies, (1) internal curing provided through the use of pre-wetted, fine lightweight aggregate in combination with slag cement, with or without small quantities of silica fume, and (2) shrinkage compensating admixtures, can reduce cracking below values obtained using current LC-HPC specifications. The goal of this project to apply these technologies to new bridge deck construction in Kansas and Minnesota and establish their effectiveness in practice. Additional states may be added as the study progresses.
State departments of transportation expend significant effort and resources on the construction of durable reinforced concrete bridges and bridge decks. Existing data show that the modifications to construction procedures, materials, and design details used in LC-HPC bridge deck construction significantly reduce the degree of cracking and, thus, reduce exposure of reinforcing steel to the corrosive effects of deicing chemicals and decrease freeze-thaw damage. Of the two, corrosion presents the far greater threat to the durability of bridge decks. The goal of the project is to combine knowledge from research and practice to develop a comprehensive strategy for the construction of low-cracking bridge decks. If successful, the result will lead to an improvement in durability and an increase in the useful life of bridges.