Slag-cement concretes that contain complex antifreeze additives and require no heating

Abstract

Investigations were made of slag-portland-cement concretes that harden in subzero temperatures of from -5 to -25 deg. C and require no heating. M 300 slag portland cement, 2 groups of slag binders - grades 300 and 400 respectively, 5-20 mm crushed granite and fine-grained sand were investigated. Calcium nitrate, calcium-nitrite-nitrate, and calcium- nitrate-chloride served as antifreeze additives that accelerated the hardening process. The test results indicate that slag-portland-cement concretes without additives acquire virtually no strength when frozen when subsequently cured for 60 days under normal conditions, the strength of concretes frozen at -5 deg C is approximately 80% of the design strength. Failure of the concrete surface was noted in a number of cases. For slag- portland-cement concretes with antifreeze additives and slag-binder concretes containing chemical activators, a post-freeze strength ranging from 20-50% and 10-35% respectively of the design strength is acquired. The post-thaw hardening rate does not exhibit a well-defined dependence on the freezing point nor on the type of antifreeze additives used. It was noted that an increase in additive concentration contributes to a gain in concrete strength both on curing while frozen, and in the process of continued curing under normal conditions. Comments are also made on the optimum percentage of additives, frost-resistance tests, strength properties, the utility of the slag binders, sulfate resistance, and the corrosive action of antifreeze additives.