Study On Damage Behavior Of Cement Based Materials Under Frost Attack

In the western region of China,due to the severe weather conditions,frost attack has become one of the important reasons for the damage of cement-based materials.In this paper,through the theoretical analysis of the physical changes in the process of frost damage,quantitative analysis of the damage degree of the material in the process of freeze-thaw cycle,so as to improve its ability to resist freeze-thaw damage.Saturation and bulk modulus are two important parameters affecting the deformation of cement based materials.In this paper,the moisture distribution model is established by characterizing the capillary condensation,adsorption and desorption,and the ink bottle effect.In addition,the mechanical properties of cement based materials with certain aggregate size distribution were characterized based on the multilayer inclusion model.The results show that the multilayer inclusion model has good applicability for the characterization of the bulk modulus of the material.In this paper,the freezing and thawing cycle of the material in the condition of complete saturation is simulated.It is found that when the material is fully filled with water,the density of the material in the pores will change because of the conversion of water into ice.This deformation will cause damage to the material itself.When the material is not full of water,the degree of saturation will directly affect the deformation in the process of freezing and thawing.When the material contains bubbles,the bubble has a significant effect on the internal changes of the cement-based materials.At the same time,the crystallization pressure and hydrostatic pressure are also applied to the analysis of cement-based materials containing bubbles.In this paper,the surface spalling of cement based materials without salt is discussed.It is generally believed that the effect of salt on the surface of cement based materials in the process of freezing and thawing.Through the theory of mechanics of porous media simulation found that even without salt,at lower temperatures,the surface of the material will be quickly frozen,hindering the flow of pore solution,reduce the permeability of the material,so the material surface will form a larger tensile force,prompting surface spalling.Finally,the cracking area of the material is calculated by the strain energy and crack energy.Based on this,the damage degree of the material was quantified.