A Model for Mechanism of Frost Damage of Cementitious Material

Direct Observation of Supercooled Water in Mortar Materials by Quasi-elastic Neutron Scattering

“…Here, we define the SCW-to-FW 282K ratio as the supercooled water index (SCWI), that is, Figure 4 shows the SCWI as a function of T. It was found that the amount of the supercooled water occupies about 70% for that of the ice crystal even at 272 K (i.e., at around the freezing point of water) in the freeze cycle. Apparently, the amount of the supercooled water is strongly associated with the distribution for the size of the capillary pores [1]. In addition, the SCWI(T) curve had a hysteresis; the amount of the supercooled water in the freeze cycle was 1.2-1.4 times larger than that in the thaw cycle at the same temperature.…”

“…According to the literature data for the thermo mechanical analysis (TMA) measurement of a mortar sample with w/c = 0.5, there is a hysteresis in a temperature-strain curve at temperatures between ~273 K and ~228 K [1]. In the freeze cycle, the strain for the mortar rises instantly from 0 to ~3×10 -4 at around 268 K, and then increases gradually up to ~13×10 -4 from ~258 K to ~228 K. On the other hand, in the thaw cycle, the strain for the mortar remains stable at around ~13×10 -4 from ~228 K to ~243 K, and then decreases gradually until ~3×10 -4 from ~243 K to ~273 K. Interestingly, this behavior of the strain for the mortar is quite similar to that of the SCWI curve for the LHPC mortar.…”

“…In the freeze cycle, some of the supercooled water in capillary pores instantly freezes with the volume expansion of ~9%, which allows the surrounding supercooled water to flow more rapidly. The unfrozen water pressure in the capillary pores is considered to be the trigger inducing the growth of the cracks as well as the drastic volume expansion by changing the supercooled water into the ice crystal [1]. Thus, it is very important to clarify the state of supercooled water (or ice crystal) in the concrete materials in freeze-thaw cycles for understanding the mechanism of the frost damage.…”

Mesoscale Simulation of Deformation for Mortar and Concrete under Cyclic Freezing and Thawing Stress

“…(23)) does not consider the supercooling effect, which was also thought as an important damage mechanism (Katsura et al 1999;2000). It is because that the damage is evaluated by the residual strain and maximum tensile strain in RBSM, and the current mechanical model is a time-independent model, which means the loading history does not affect the maximum deformation, but only the maximum freezing stress at the lowest temperature does.…”

“…Katsura et al (1999) proposed a mechanism considering the dynamic hydraulic pressure due to instantaneous volume expansion as a result of supercooling, and a damage model was also developed based on this mechanism (Katsura et al 2000). Kaufmann (2002) developed a qualitative sequential damage model, separating a freeze/thaw cycle (FTC) into five phases and discussed in detail.…”