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Questions connected to influence of frost degradation on microstructure and physical properties of water saturated cement mortars and their resistance to cyclic water freezing are the objectives of research. The main aim of the investigation is to analyze the ice-induced deterioration of cement mortars with different water/cement ratios (w/c=0.50 and 0.40) in a accelerated durability tests. The changes of pore size distribution and water absorption coefficient are investigated by means of mercury intrusion porosimetry and capillary absorption test. Additionally, the analysis of the impact of drying temperature (40°C, 60°C, 80°C and 105°C) on the microstructure is introduced.The performed tests enabled to estimate that the destruction of the cement matrix and the range of observed changes depend on the initial pore size distribution and their volume in the cement matrix. It is also established that the increase of transport properties is correlated with the change of pore size distribution. The obtained results allow to conclude a decrease of content of small pores (up to 150nm) and increase of larger pores for mortar with w/c=0.50. Application of superplasticizer, which resulting in reduction of water to cement ratio up to 0.40, allows to obtained resistant to 150 frost cycles cement mortar.

The purpose of the study is to understand how the cyclic water freezing (0, 25, 50, 75, 100 and 150 freeze-thaw cycles) impacts microstructure and transport properties of cement-based materials. Tests were conducted on cement mortars with different water/cement ratios (w/c=0.45 and 0.40) and on two types of cement (CEM I and CEM III) without air-entraining admixtures. The changes of pore size distribution and open porosity were investigated by means of mercury intrusion porosimetry. Additionally, the relationship between intrinsic permeability and the water absorption coefficient of cement mortar samples was analysed. The water absorption coefficient and gas permeability were determined using capillary absorption test and the modified RILEMCembureau method. The evolution of transport coefficients with growing number of freeze-thaw cycles were determined on the same sample. It was also established that change of pore structure (a decrease of small pore volume 100nm) induces an increase of water transport parameters such as permeability and water absorption coefficient. The higher gas permeability corresponds to the higher internal damage. In particular, it is associated with the change of cement mortar microstructure, which indicates damage of narrow channels in the pore structure of cement mortars.

The parameters characterizing the microstructure of cementbased materials, such as porosity or permeability, determine not only durability, but also risk of degradation of the cement matrix due to an aggressive environment. The report presents results of a research on transport properties of cement mortars subjected to cyclic water freezing. Mortars prepared on the basis of two different cements were the object of the research: Portland cement CEM I 42.5R and Portland blast-furnace slag cement CEM III/A 42.5N LH/HSR/NA, with two water-cement ratio (w/c=0.45 and 0.40). The experimental study was carried out in order to determine the relationship between intrinsic permeability and the water absorption coefficient in relation to the number of freeze-thaw cycles. The evolution of transport coefficients was determined using a capillary absorption test and the modified RILEM-Cembureau method. It was established that the degradation processes induced an increase of transport properties. Moreover, the microcracks had a more significant influence on permeability and lesser influence on the water absorption coefficient. The gas permeability of damaged mortar changed very significantly, an increase with several orders of magnitude could be noticed. Moreover, the positive impact of CEM III on ice-induced degradation was also visible.