Freeze–Thaw Cycles

The B-Series were subjected to five freeze–thaw cycles between 38 and −33 ◦C. These temperatures have been chosen because 38 ◦C is approximately ten degrees higher than the summer air temperature average in Santander (Spain), and −33 ◦C is ten degrees lower than the freezing point of water with 5.0% salt content.

The temperature was measured by introducing a thermo-sensor inside the specimens at the time of manufacturing the mixture (Figure 1). With these thermo-sensors, it is possible to determine the internal temperature of the specimens (logging interval one minute). Knowing this, the time of each freeze–thaw cycle is established so that both phases, hot and cold, have enough time to reach the defined temperatures. Each freeze–thaw cycle requires 48 h to be completed, 24 h for the hot time period and 24 h for the cold time period (Figure 2).

**Figure 1.** Thermo-sensor inside the specimens.

**Figure 2.** Freeze–thaw cycle.

The time that each submerged series remained in frozen water was defined by the steps of solid–liquid and liquid–solid changes. In the case of the B1 series, the time submerged in frozen water is 22 h, and in the B2 series, it is approximately 15 h.
