Development of a standard for accelerated determination of frost resistance of autoclaved aerated concrete

Introduction

The “Introduction” analyses the mechanisms of concrete frost damage and describes standard methods for determining the frost resistance of lightweight and cellular concrete.

Research methods

The frost resistance at different freezing temperatures was carried out on samples of autoclaved cellular concrete of D400 to D600 density. Specimens with dimensions of 100 × 100 × 100 mm were cut from prefabricated parts in accordance with EN 771‐4. During the experiment, frost resistance of ААС samples was determined at a standard temperature of −18 ± 2°C, as well as at temperatures from −5°C to −40°C4.

Results and discussion

In the paper, frost resistance of concrete at various freezing temperatures was evaluated by the experimental‐analytical method, which is based on the assumption that frost resistance, expressed in the number of cycles (F) should be inversely proportional to the volume of frozen water at this temperature.

The frost resistance of concrete was evaluated experimentally and analytically at different freezing temperatures, assuming that the frost resistance (F), expressed in the number of cycles, should be inversely proportional to the volume of frozen water at that temperature V(t).

Determination of the rate of ice spreading front and moisture diffusion in building materials by conductometric method during one‐sided freezing allows a more detailed study of the mechanisms of frost failure of building materials.

Conclusions

The proposed experimental‐analytical method for evaluating AAC frost resistance at different freezing temperatures allows, with a small expenditure of time, to obtain more complete information on the material behavior in freezing temperatures than it is provided by the existing standard methods. The analysis of the dependence of freezing resistance on temperature also allows revealing the regions of temperature where it changes most strongly, and to shift, if necessary, these regions towards lower or higher temperatures by adjusting the composition and technology of AAC production.

The developed combined method of independent measurements of moisture diffusion kinetics and ice content makes it possible to determine the speed of diffusion of ice formation front and moisture conductivity depending on the composition (capillary‐porous structure) of samples and their initial storage conditions. This information can give a more reliable picture of the behaviour of AAC under alternating temperature loading under varying initial moisture conditions.