Predicting the Freeze-Thaw Durability of Bricks Based on Residual Expansion

摘要

The response of saturated brick masonry units to internal freezing water was studied in an attempt to improve the accuracy of freeze-thaw durability predictions currently described in ASTM C 67. Cryogenic dilatometry was employed to study the change in length, or response, of water-saturated brick during freeze-thaw cycles. In all cases, a permanent, or residual, expansion was observed. Residual expansion varied from approximately 0.01% to 0.08% for different commercially available brick for a single freeze-thaw cycle. No strong correlation was found between residual expansion and physical properties cited in current ASTM specifications. Research on lab-fired extruded brick showed that the amount of residual expansion is related to the "maturity," or amount of "heat work" expended, in firing of the brick. Comparison of lab- and plant-fired brick with similar water adsorption values yielded considerable differences in residual expansion, reflecting a lack of correlation between physical properties and durability. Residual expansion may be a quantitative index reflecting the freeze-thaw durability of brick, and may result in a more definitive and faster test procedure than that described in ASTM C 67.