Phase I, FHWA pooled-fund project TPF-5(003), demonstrated the practicality of using commercially available admixtures as antifreeze admixtures for concrete. Eight admixture formulations, developed under laboratory conditions, were successfully demonstrated in the field. The concrete made with these admixtures fully cured at internal temperatures of ¿5°C, was as durable as normal concrete, and was less expensive than conventional concrete because no additional heat was required to keep the antifreeze concrete warm. The project report, released in February 2004, provided the first-ever tools in North America to design, mix, place, and cure concrete in below-freezing weather. Phase II, TPF-5(075), is investigating the potential that admixtures may enhance the freeze-thaw durability of concrete. Preliminary test results demonstrate that the Phase I admixtures increase the freeze-thaw durability of concrete, at least at moderate dosages, possibly by actively depressing the freezing point of pore water in hardened concrete. In support of this finding, a recent condition survey of the West Lebanon bridge repairs made two seasons ago during Phase I showed that the antifreeze concrete repairs were performing better than were the conventional concrete repairs (see photos on proposal cover). Phase II, originally scheduled to end in October 2005, is expected to lead to guidance for enhanced service life of concrete in northern climates.

Develop admixture dosage guidance. It is envisioned that this guidance will be in the form of a series of tables based on max/min expected air temperatures, boundary conditions, mixture proportions and temperature, and concrete mass. This guidance will complete the field guide drafted in Phase I.

Phase III will develop design guidance for specifying admixture dosage rates to match given job site weather conditions. Current guidance provides for one capability: ¿5°C concrete. Experience has shown that this capability is often more than necessary. What is needed is a guide for tailoring admixture dosages to a given situation, based on mix design, weather conditions, and element size.

Phase I was conducted under TPF-5(003) and Phase II is being conducted under TPF-5(075).