Effect of Freezing Temperature on the Microstructure of Negative Temperature Concrete

The pore size distribution and the microstructure of negative temperature concrete was studied with different temperature, combining with some testing methods, such as MIP and SEM. Moreover, the change of the compressive strength was also studied with different ages. In addition, the relationship between the microstructure and the macro-mechanical properties on negative temperature concrete was explored further with different freezing temperature. It indicated that the lower the early curing temperature, the looser the original structure of cement paste; the total volume of gel pore whose pore size was less than 20nm was decreasing apparently, and the compressive strength declined. When changing to standard curing, the pore size trended to be thinner, the compressive strength was increasing sharply. The concrete was cured from -5°C to standard curing, the volume of pore that was less than 200nm was equal to that of the concrete with the standard curing in the age of 28d, so was the compressive strength. However, the volume of the macro pore of the concrete curing under -10°C and -15°C was greater than the concrete curing the standard condition, the compressive strength was less.