Freeze-Thaw Durablity Versus Freezing Rates
Michel Piaeon. Jacaues P&ost, and Jean-Marc Simard
Appears on pages(s):
air-entrained concretes; air entrainment; concretes; freeze-thaw durability; freezing; measurement; microcracking; pore water pressure; water-cement
Non-air-entrained and air-entrained concretes with varying air-void systems were submitted to-300 freeze-thaw cycles in air at 100 percent relative humidity at freezing rates of 4 and 6 C/h. Length change and pulse velocity variation were used as indicators of concrete deterioration. For a water-cement ratio of 0.5, the critical air-void spacing factor (the value below which concrete will be minimally damaged at 300 freeze-thaw cycles) was determined to be 630 ,urn for a freezing rate of 4 C/h and 450 ,am for 6 C/h. Considering previously published data by the first author for a freezing rate of 2 C/h, the relationship between critical air-void spacing factor and rate of freezing was established. It shows that the freezing rate has a significant influence on freeze-thaw durability. The change in the value of the critical air-void spacing factor from 680 ,um at 2 C/h to 450 pm at 6 C/h is in agreement with the equations from Powers’ hydraulic pressure theory. In the tests described, almost no scaling was observed. Deterioration was always in the form of internal cracking. For a good number of specimens, length changes of more than 1 percent were measured.