ANTIFREEZE ADMIXTURES FOR CONCRETE

Abstract : The goal of this project was to develop a chemical admixture that would reduce the need for wintertime thermal protection of freshly placed concrete. Chemicals were investigated for their ability to promote strength gain in concrete cured below 0 deg C. The project was carried out in five phases. Phase 1 evaluated existing and new admixtures. Phase 2 measured the effect of promising chemicals on concrete properties. Phases 3 and 4 tested the practicality of using the new technology/admixture in the field. Phase 5 disseminated the findings through an Army conference and through the development of this report, in addition to normal W.R. Grace advertising channels. Laboratory strength tests established that two prototype admixtures were capable of protecting concrete down to -5 deg C. Results from other laboratory tests show that the chemicals pose no harm to the concrete or embedded ferrous metals. Concrete containing the prototype admixtures passes standard freeze-thaw tests, does not shrink unusually, does not contain harmful alkalis, and does not produce irregular hydration products. Field tests clearly demonstrated that working with these new admixtures requires no new skills. The concrete can be mixed at lower temperatures, saving energy. The admixtures are easily dosed into the mixing trucks, as is normal practice today, and concrete is finished in the usual manner. Estimates show that the two prototype admixtures can extend the construction season by as much as three months in the contiguous United States. The prototype has proved that low-temperature admixtures are possible. The industry partner sees the need to develop admixtures that will work to -10 deg C before going commercial with this technology.