Reducing the Effect of Freezing Temperatures on the Compressive Strength of Concrete with Calcium Chloride and Air Entrainment

摘要

Untreated and unprotected fresh concrete should not be exposed to freezing temperatures. If untreated fresh concrete freezes, it will not gain strength while frozen. It may gain strength upon resumption of normal curing. The ultimate compressive stress of normal concrete is increased with the use of a calcium chloride admixture. Air entrainment offers no advantage as an antifreeze agent. Air entrainment lowers the ultimate compressive stress of concrete. The percentage of air which is entrained in concrete is partially controlled by the mixing time. Calcium chloride is an excellent accelerating admixture when used in concrete which is cured under normal conditions. Use of the admixture increased the ultimate compressive stress of specimens cured in the moist room. The use of calcium chloride as an accelerating admixture permits fresh concrete which is exposed to freezing temperatures to gain some compressive strength. The strength attained is lower than it would be if the fresh concrete were protected from freezing and cured normally. Type III portland cement with a calcium chloride admixture produced the highest percentage of normal compressive stress when the fresh concrete was exposed to freezing temperatures. (Author)