Extreme Cold Mechanical Properties of Concrete with Additive-Based Freeze Protection System

Abstract

Concrete can be cast and cured at freezing temperatures when additive-based freeze protection (ABFP) is included in the concrete mixture. However, the effects of extremely cold temperatures on the mechanical properties of concrete with ABFP have not been studied. In addition, the impact of cold temperatures on shear strength and modulus of rupture of concrete with or without ABFP have not been measured. The present study measures the effects of decreasing temperatures on the compressive strength, modulus of elasticity, shear strength, and modulus of rupture of concrete with and without ABFP. Different types of aggregates and ABFP systems were used to manufacture conventional concrete (without ABFP) and concrete with ABFP. Concrete with ABFP is mixed, cast, and cured at −5°C and conventional concrete, at 20°C. Specimens are conditioned at 20°C, −5°C, −20°C, −40°C, or −60°C for 24 h and then tested. Generally, it was found that the mechanical properties of both types of concretes increased as the test temperature decreased. However, ABFP lowers the pore solution’s freezing point and lowers the relative compressive strength increase rate compared with conventional concrete. Concrete with ABFP can have a higher rate of increase in relative elastic modulus than conventional concrete. This is due to the two-phase system of an ABFP pore solution at low temperatures, where ice fills voids, and the unfrozen concentrated pore solution continues to fill capillary voids and wet calcium silicate hydrate. The increase in shear strength from the aggregates and hydration products is greater than the contributions of the pore solution’s frozen properties. Finally, the rise in rupture strength is attributed to the increase in the strength of concrete materials because there is no significant change in the tensile strength of ice with decreasing temperature.