The effect of size and shape of pores on the prediction model of compressive strength of foamed concrete

The Balshin's model is the most well-known of the models used to predict the compressive strength of aerated concrete. Among the pore characteristics such as the amount of porosity, the size of the pores, and their shape, Only the amount of porosity is placed as a specific parameter in the Balshin's model. The impact of the other two characteristics, on the other hand, is included in the power value of the Balshin's equation. Compressive strength tests and identifying the characteristics of air voids using microscopic imaging were performed on the mixtures produced in this study, which had weight ratios of sand to the cement of 1, 1.5, and 2, and the percentage of foam volumes of 0, 15, 25 and 35. In this study, a review of some of the factors influencing the change in the pore characteristics was performed, including the porosity of the foamed mixture and the size of sand used, in addition to the effect of the pore characteristics such as size and shape on the compressive strength of the foamed mixture. This study aims to conduct a comparative analysis of the models introduced in previous research to determine the effect of the pore characteristics of semi-structural and structural foamed mixtures (with sand) caused by mixture porosity and the sand size on the Balshin's model. Among the types of relationships presented for the Balshin's model, the relationship based on the paste fraction porosity was used. According to the findings of this study, foam porosity is the most important factor influencing pore size change, followed by sand size. The increase in the size of the pores and their non-sphericality decreased the relative compressive strength and, as a conse-quence, increased the power of the Balshin's model because the maximum level of stress concentration was created adjacent to the middle diameter of the pores at the period of concrete rupture.