Extending the Season for Concrete Construction and Repair—The Next Phase

Abstract

The Phase I study, conducted prior to the work reported herein, developed the tools to design, mix, place, and cure concrete in cold weather made with various combinations of commercial admixtures. The admixtures helped to protect concrete and maintain productivity, even when the temperature of concrete falls to-5°C soon after mixing. Phase II addressed the effect of high doses of the chemical admixtures studied in Phase I. The primary finding from Phase I that led to this study was that admixtures, when used in moderate dosages, seemed to improve the freeze-thaw durability of concrete. Phase II found what appears to be a maximum dosage after which freeze-thaw durability becomes a concern. That is because cement hydration can only create a finite amount of space to absorb these chemicals. Thus, for freeze protection, admixture dosages should be designed according to water content as specified in Phase I, while, for freeze-thaw durability, admixture dosages should be dictated by cement content. When using both considerations, the freeze-protection limit for enhanced freeze-thaw durable concrete can be lower than the-5°C limit set in Phase I. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.

Early Age Performance of OPC-GGBFS-Concretes Containing Belite-CSA Cement Cured at Sub-Zero Temperatures

“…A compressive strength of 3.5 MPa developing at an early age considerably limits frost damage. Nevertheless, to overcome such situations, a number of precautionary measures are recommended when the air temperature falls below 5 • C or is below 10 • C for at least 12 h throughout the day [14][15][16][17]. These include heating the mixing water or aggregates, covering concrete with isolative blankets, or adding heating systems to the formworks [18].…”