Effect of drying and wetting cycles on frost resistance of concrete was evaluated by the ASTM C666 A and the GIF. Both methods showed that drying and wetting cycles deteriorated the frost resistance of non-AE high performance concrete. Though the micro cracks were observed, the effect on the frost damage was not proven. Change in microstructure of hardening cement paste by drying and wetting cycles was also studied by means of mercury intrusion porosimetry and NMR. Micro pores around 50-100nm in diameter increased. The NMR spectra identified to Q_0 and Q_1 decreased, while Q_2 increased, showing the condensation of silicate anion structure.
