Experimental investigation of frost induced damage of cement mortar

Abstract

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 influence of cyclic water freezing on gas permeability of non-air-entrained concrete

“…Drying might result in a structural and physical collapse of hydrates, which could damage the microstructure of the cement matrix (12). The infl uence of drying temperature on the microstructure and transport properties of cementitious materials was also discussed in (13). It was assumed that the drying did not induce further damage, since the reasonable temperature gradients were presented across the sample.…”

“…Directly before the gas permeability test, the samples were placed inside the desiccators for 24 h at 20 o C. w fazach ettringitu i żelu cementowego (12). Wpływ temperatury suszenia na mikrostrukturę oraz własności transportowe kompozytów cementowych analizowano również we wcześniejszej pracy autorów (13).…”