Experimental Study On Mechanical Properties Of Single Crystal Ice And Its Effect On Compressive Strength Of Lightweight Aggregate Concrete

The working environment of artificial freezing method is generally-5℃～-15℃.in this environment,some free water in the internal pores of concrete will form capillary ice crystals,thus affecting the mechanical properties of concrete.In order to investigate the influence of pore ice crystals in shale ceramsite aggregate and concrete matrix on the mechanical properties of concrete,In this paper,the compressive strength test and Brazilian splitting test of single crystal icicle and single crystal icicle bundle under different material constraints were carried out respectively.The effects of loading rate,size effect and constraint effect on mechanical properties of different types of icicle were analyzed.Then the influence of capillary ice crystals on the mechanical properties of lightweight aggregate concrete is analyzed by the volume ratio of pore ice crystals in different types of concrete.The main research contents are as follows:(1)The macroscopic single crystal icicle and single crystal icicle bundle formed by freezing tap water at-8℃ for 4d were taken as research objects,The effects of loading rate and section size on compressive strength were analyzed through uniaxial compression tests under different loading rates.The results show that both the macroscopic single crystal icicle and the single crystal icicle bundle have significant size effect.(2)By Brazilian splitting test of macroscopic single crystal icicle with different cross section sizes,The size effect of icicle splitting strength is analyzed.The results show that the splitting stress of macroscopic single crystal icicle decreases with increasing diameter.(3)PVC tube,brown paper and A4 paper were used as the restraint wall of macroscopic single crystal icicle and single crystal icicle bundle respectively.The compressive strength and failure pattern of icicle with different restrained materials were analyzed.The results show that the compressive strength of icicle can be improved and the failure mode of icicle can be completely changed by different restrained materials,and the restrained effect increases with the increase of elastic modulus of restrained materials.(4)After standard curing for 28 days,different lightweight aggregate concrete is dried and soaked in water,take it out during different periods of immersion,and frozen at-8℃ for 4d.the influence of different ice crystal volume ratio on mechanical properties of lightweight aggregate concrete was analyzed.The results show that the compressive strength of concrete increases with the increase of ice crystal volume ratio.