Guidance for Optimizing Admixture Dosage Rates for Cold Weather Admixture Systems

摘要

The practicality of using commercially available off-the-shelf chemical admixtures to produce antifreeze concrete formulations has been shown to be cost and energy effective compared to conventional cold weather concreting. Three phases of work have been completed thus far. The first phase developed eight antifreeze concrete mixtures in the laboratory and demonstrated these formulations in five full-scale field projects using standard construction equipment, mixing, and placement operations. The second phase developed technical specifications to facilitate integrating the antifreeze concrete technology into standard practice. In this phase antifreeze concrete formulations are able to fully resist freezing down to -5 °C, yet, not all winter conditions require this level of freeze protection. Thus, the ability to exactly tailor the admixture dosage to weather conditions specific to the intended job site would provide flexibility not only for designing antifreeze dosages but for achieving economical concrete mixtures. The third phase developed a guidance manual for designing specific admixture dosages to resist the steady-state weather condition at any job location. Various steady-state scenarios were evaluated using a one-dimensional thermal model based on heat transfer principles and the interaction of the concrete structure within the winter environment that it is placed. Work continues to develop this technology to where it will soon be possible to design specific admixture dosages that will allow concrete mixtures to fully cure under the constantly changing weather conditions that are typical to construction sites.