Influence of Pore-Size Distribution on the Resistance of Clay Brick to Freeze-Thaw Cycles.

This study examines the influence of raw material characteristics, methods of shaping and of parameters of firing process of clay bricks, on pore-size distribution and on resistance to freeze-thaw cycles (with particular emphasis on the retention time of the specimens at the maximum achieved temperature). Pore-size distribution was measured by mercury-intrusion porosimetry, while the resistance to freeze-thaw cycles was assessed by exposing the bricks to freeze-thaw cycles (HRN B.D8.011 standard) monitoring the appearance of surface changes, decrease of compressive strength as well as the Maage factor. A correlation was set up between the Maage factor and the ratio of the compressive strength before and after freezing as a quantitative indicator of bricks resistance to frost. By using this correlation for all the examined bricks, regardless of their raw material and shaping procedure, a low coefficient of correlation (R2 = 0.26) was obtained. When processed separately, machine-made bricks had a significantly higher correlation coefficient value (R2 = 0.60) than the hand-made bricks (R2 = 0.28).