The effects of moisture on the thermal properties of concrete between -80 degrees C and 0 degrees C

Samples of saturated moist-cured micro-concrete and pasta with vv/c ratios between 0.30 and 0.70 have been invest- igated and compared with samples of dry and rewetted paste between -80°C and 0°C. The freezable water in these pastes has been measured from the enthalpy difference between moist-cured and dry samples, and is significantly less than evaporable water contcnt. The NMR spectra of these pastes have been studied at temperatures down to -80°C and suggest that the eva- porable water is adsorbed and not free. Thermal strains of samples with different degrees of saturation between 0°C and -80°C have been measured and the effect of rewetted water also investigated. It is concluded that the physically adsorbed water which causes a large thermal strain in concrete paste comprises 75% of the total evaporable water. The permanent expansion of concrete paste during a thermal cycle only occurred in a rewetted, resoaked, fully moist-cured concrete paste.