This study investigated the effect of temperature and time at temperatures lower than 0 °C on mortar mixed with antifreezing admixture to determine the temperature–time function with the aim of expressing the effect universally. As a result, the maturity equation for temperatures lower than 0 °C proposed in previous studies was verified to be applicable to type-B blast furnace slag cement. The applicability of this equation at temperatures lower than 0 °C had not been investigated hitherto. The strength development attributable to the effect of the antifreezing admixture can be expressed as the reference temperature, and the reduction in the chemical potential of water chemical potential reduction was found to depend on the reaction rate. A new maturity equation for temperatures lower than 0 °C was proposed considering the effect of the antifreezing admixture.

This paper presents the results of an experimental investigation on the material properties and self-healing ability of a blended cement mortar incorporating blast furnace slag (BFS). The effect of different types and Blaine fineness of BFS on the material properties and self-healing was investigated. Thirteen cement mixtures with BFS of different types and degrees of Blaine fineness are tested to evaluate the mechanical properties, namely compressive strength, bending strength, freeze–thaw, and accelerated carbonation. The pore structure is examined by means of mercury intrusion porosimetry. Seven blended mortar mixtures incorporating BFS for cement are used to evaluate the mechanical properties after applying freeze–thaw cycles until the relative dynamic modulus of elasticity reached 60%. The experimental results reveal that incorporating BFS improves the mechanical properties and self-healing ability. In the investigation of self-healing, smaller particle and high replacement ratios of BFS contribute to increasing the relative dynamic modulus of elasticity and decreasing the carbonation coefficient in the mortar after re-water curing. Moreover, BFS’s larger particles and high replacement ratio are found to provide better self-healing ability. A regression equation is created to predict the relative dynamic modulus of elasticity in mortar considering the Blaine fineness, BFS replacement ratio, and curing conditions.

We have clarified that external insulation reduces the probability of reinforcement corrosion in reinforced concrete buildings in cold snowy districts by 45–78%. Renovation of external insulation is one of the effective methods for improving the insulation performance and durability of reinforced concrete buildings, but there are almost no data that demonstrate durability. Therefore, the carbonation depth and the cover depth were investigated for six medium-rise-wall type reinforced concrete buildings in Hokkaido, Japan, which had been refurbished for external insulation. As a result, it was clarified that the external insulation suppressed the carbonation depth by 30% or more, even when the bonding method of the external insulation was different. In addition, it was clarified that the external insulation further suppressed carbonation in walls where the carbonation depth tended to increase in snowy cold districts. Specifically, external insulation reduced carbonation by up to 35% on surfaces that tend to dry out due to sunlight, and by 49% on surfaces that are affected by water that deteriorates the concrete surface layer.