AIR-ENTRAINING AND ANTIFREEZE ADMIXTURES IN NORMAL-WEIGHT CONCRETE FOR SHARPLY CONTINENTAL CLIMATES: A REVIEW

Abstract

This paper reviews research on the effect of air-entraining and antifreeze admixtures on the frost resistance and physical-mechanical properties of normal-weight concrete. Fundamental studies, recent peer-reviewed experimental and review papers, and the standards in force in Kazakhstan were analysed. The review covers the mechanisms of frost damage (hydraulic pressure, osmotic pressure and the critical degree of saturation), the parameters of the entrained air-void system, the classification and limitations of antifreeze admixtures, and the available data on their combined use. Air entrainment is effective when the spacing factor does not exceed 0.20 mm, at the cost of roughly 5 % compressive strength loss per 1 % of entrained air; a recent meta-analysis found no correlation between the chemistry of the air-entraining agent and air-void parameters, which shifts the emphasis to construction practice. Antifreeze admixtures allow strength gain at temperatures down to −15…−25 °C, and chloride-free compositions are now preferred. In laboratory studies calcium nitrate (6 % by mass of cement) reduced the strength loss of fresh concrete after 28 freeze–thaw cycles from 72 % to 27.8 %. The available evidence on combined use is limited: chloride-free antifreeze admixtures were found compatible with air entrainment, but sodium salts alter the air-void structure in opposite directions depending on the salt. Four research gaps are identified, and an experimental programme is proposed for the sharply continental climate of Kazakhstan