Stress Analysis for Concrete Materials under Multiple Freeze-Thaw Cycles

Abstract

Once ice forms in highly saturated concrete material, internal tensile stress will be generated and causes damage to the material, which is a serious problem for concrete structures in cold and wet regions. On one hand, each component (porous body, ice and liquid) should satisfy the compatibility of stress and strain, which has been discussed by the poromechanical theories. On the other hand, if some empty voids exist, the hydraulic pressure will release when liquid water escapes from the expanded area according to Darcy's law. Recent closed freeze-thaw tests on the saturated mortar showed a consistent tendency: as the number of freeze-thaw cycles (FTC) increases, the deformation changes from the expansion to the contraction. In order to make clear the physical and mechanical changes during this process, a more comprehensive hydraulic model is developed, which combines both the mechanisms mentioned above. The estimated strain behavior by this model is in a good agreement with experimental measurements, and also, it has good potential and is more flexible to be applied to different cases such as different saturation degrees and cooling rates. The permeability change can be also considered in this model as a reflection of frost damage level.

Strong Coupling of Freeze-Thaw Cycles and Alkali Silica Reaction - Multi-scale Poro-mechanical Approach to Concrete Damages -

“…Finally, the crystallization and cryosuction pressures only reply on the temperature due to thermodynamic equilibrium (Scherer and Vallenza II 2005). This calculation scheme has also been verified by the mesoscale closed FTC test (Gong et al 2015a) and macroscale open test (Gong et al 2015b).…”

“…3 Calculation scheme of pore pressures during ice formation. (Gong et al 2015a) ready occupied by ASR gel, the ice formation will be delayed and with less amount, and finally result in a smaller frost expansion. However, when the entrained air bubbles are filled by the ASR gel, they may lose their function in preventing the frost damage.…”

“…The FTC induced deformation and damage has also been modelled by the authors (Gong et al 2015a(Gong et al , 2015b. The above studies deal with one or dual impacts of weak coupling, which are rather ideal to predict the real complex deterioration process in real life.…”

“…Once the saturation degree exceeds a critical value (Fagerlund 2002), significant damage in the porous skeleton will occur due to several kinds of pore pressures (Powers 1945;Scherer and Vallenza II 2005;Coussy and Monteiro 2009;Gong et al 2015a). This kind of internal damage will be cumulated during numbers of FTC and result in gradual degradation in material properties (Hasan et al 2004;Gong et al 2013).…”

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

“…However in the closed test of mortar slices (2mm thick) conducted by Sicat et al (2013), there was expansion during first few cycles, and converted to contraction as the number of cycle increases. In order to explain this reversing phenomenon in closed test, the authors developed a physical model to estimate the internal pore pressure quantitatively (Gong et al 2015), by combining Powers' hydraulic model (1949), Coussy and Monterio's poromechanical model (2008;Errata 2009) and Scherer's crystallization/cryosuction model (2005) together. In that model, most of the influential factors can be considered, such as cooling rate, saturation degree, material properties (elastic modulus, void ratio, pore size distribution and so on), and also the damage accumulation (reflected by the permeability change) after each cycle.…”