The failure modes of three laboratory freeze-thaw procedures are compared with field failures. Sets of fifteen plant-fired brick were selected. Five brick from each set were subjected to each procedure.

Two omni-directional procedures were used: The Standard Method as set forth in ASTM C67, Standard Methods of Sampling and Testing Brick and Structural Clay Tile (with a 4-h cold water saturation), and a modified ASTM (with a 5-h boil saturation).

One uni-directional method was used: The Face Freeze-Thaw Procedure. This procedure was developed in the Acme Brick Company Research Laboratory, Denton, Texas, and utilizes the 5-h boil saturation. After each freeze cycle, only the face of the brick is thawed while the body remains frozen. The test specimens are withdrawn after 100 cycles, or when a specimen has failed. A sample is considered to have failed when a laminar crack develops parallel to the brick face. The crack usually develops 10–15 cycles before the face comes off.