Freeze-Thaw Durability of High-Strength Concrete

Abstract

This report presents freeze-thaw durability results of anin vestigation regarding the application ofhigh performance concrete (HPC) to prestressed bridge girders. This study included a total of 30 concrete mixes and more than 130 specimens, with the following variables: aggregate type, round river gravel, partially-crushed gravel, granite, high-absorption limestone, and low-absorption limestone; cementitious material composition, Type III portland cement only, 20 percent fly ash, 7.5 percent silica fume, and combination of 20 percent fly ash with 7.5 percent silica fume replacement by weight of cement; and curing condition heat-cured or seven-day moist-cured. No air-entraining agents were used in the study's initial phase to simulate the production of precast/prestressed bridge girders. Results indicate that it is possible to produce portland cement concrete with high strength and freeze thaw durability without the use of air-entraining agents. Overall, the moist-cured concrete specimens exhibited better freeze-thaw durability than the heat-cured concrete specimens. The reference concrete mixes--containing only portland cement-performed better than the concrete containing pozzolan material of fly ash or silica fume. The low-absorption limestone aggregate concrete mixes exhibited the best freeze-thaw durability performance--in some cases, enduring more than 1,500 freeze-thaw cycles without failing. The study found that the moisture content of the coarse aggregate at the time of mixing had a significant impact on the concrete's freeze-thaw durability.