Damage Model Of Nano Concrete Under Freeze-Thaw Cycles

The freeze-thaw damage of concrete structures has always been one of the focuses of attention.Its structural deterioration is caused by the internal forces produced by alternating positive and negative temperature differences within the material.Because of its poor frost resistance,ordinary concrete has been subjected to freezing and thawing in cold weather,and its service life has been greatly reduced,durability does not meet the requirements of use.Nano concrete can inhibit the occurrence and development of micro cracks in the material,the frost resistance of nano concrete is the focus of this paper.In the basic case,there is initial damage in the material,the destruction of materials under freezing and thawing conditions is the expansion of these microcracks and the formation of macroscopic cracks,eventually the material loses its carrying capacity and destroys it.Damage mechanics can help us analyze and reason the formation and propagation of microcracks in materials and the process and laws of fracture.Therefore,the damage mechanics method is used to study the freeze-thaw process and frost resistance of nano concrete.In this paper,freeze thawing experiments of nano concrete with different nano materials and different dosages are carried out,The mass fraction of the doped nanomaterials is 0.5%,1%,1.5%,2%.When the number of freeze-thaw cycles was50,75,100,150,200,250 and 300,the quality of specimens with different nano materials and different dosages were measured,freeze the elastic modulus and compressive strength.The comparative analysis of different nano materials and different amount of concrete is carried out to study the attenuation law of nano concrete during freeze-thaw cycles.In this paper,the research status of damage mechanics is summarized,and the research of damage mechanics in domestic and overseas scholars is summarized,And a typical concrete damage model is introduced.The mechanism of material damage and its strengthening mechanism are analyzed.Through freeze-thaw tests,it is found that it is similar to fatigue damage,random,and the damage obeys a certain probability distribution as a variable.In this paper,the Weibull distribution model is used to establish the constitutive relation,and the damage model of nano concrete is established,to find out the attenuation law of mechanical properties of nano concrete.The results show that the optimum dosage is 1.5% nm SiO2 and the optimum dosage is 1% nm.CaCO3 has the strongest freeze-thaw resistance,Its compressive capacity is the strongest relative to plain concrete.In general,the addition of nano materials improved the frost resistance of concrete.