Resistance to Repeated Freeze–Thaw Cycles

For the freeze–thaw test, cube specimens with sides of 100 mm were used, according to the SR 3518:2009 [35] standard. Before the start of the 50 freeze–thaw cycles, 6 specimens for each composition were immersed in water. The water had a temperature of 20 ± 5 ◦C. The immersion was prepared gradually, the water level being raised every 24 h, first up to 1 <sup>4</sup> of their height, then up to <sup>1</sup> <sup>2</sup> , then up to <sup>3</sup> <sup>4</sup> , and finally to the total immersion. After the water immersion, three of the six specimens were kept in a water bath, whereas the other three were tested in 50 freeze–thaw cycles. During the freeze–thaw cycle of 8 h, for the first 4 h, the specimens were frozen in a cold room at the temperature of −17 ± 2 ◦C, and then for next 4 h, they were introduced in water with a temperature of 20 ± 5 ◦C.

After 50 cycles, the specimens subjected to freeze–thaw and those kept only in water were tested for compressive strength, in accordance with EN 12390-3:2019 [32] stipulations. The evaluation was conducted through the difference between the average compressive strength of the three specimens kept in water and the average compressive strength of the three specimens tested in 50 freeze–thaw cycles.
