Preparation Of Phase Change Antifreeze Concrete And Evaluation Of Frost Resistance Effect

Buildings in cold regions of our country have been in the harsh environment of freeze-thaw alternation for a long time.Many buildings are damaged by freeze-thaw soon after they are built.Maintenance is not only difficult,but also consumes a lot of manpower and material resources.The phase change material(PCM)is encapsulated by hollow steel ball in macro encapsulation way,which makes up for the defect of phase change material easy to leak.The preparation of phase change antifreeze concrete is of great significance if it is used in practical engineering.(1)The mass of absorbed phase change material accounts for 63%of the mass of phase change steel ball,which improves the occupancy rate of phase change material in concrete,and the encapsulated phase change material is not easy to leak,and the encapsulation effect is good.(2)Steel ball concrete with 25%,50%,75%and 100%steel ball content is prepared by using steel ball poured into mortar as coarse aggregate.Metal repair agent is applied on the surface of steel ball to make the bond between steel ball surface and cement paste more firm.When the content of rough steel ball concrete is 75%,the compressive strength of steel ball concrete decreases by 5.31%.When the content of steel ball is 100%,the splitting tensile property of steel ball concrete is better,which increases by 61.83%.(3)Under the premise of good mechanical properties,phase change concrete with 75%phase change steel ball was prepared.Using the relative dynamic elastic modulus and mass loss rate as the evaluation indexes of frost resistance,the relative dynamic elastic modulus of phase change concrete and ordinary concrete are 88.69%and 82.12%,respectively,and the mass loss rates are 0.88%and 1.06%,respectively.After 150 freeze-thaw cycles,the relative dynamic elastic modulus of phase change concrete and ordinary concrete are78.24%and 74.90%,respectively The loss rates are 3.65%and 4.25%respectively.The indexes of the two kinds of concrete have been significantly reduced,and the phase change concrete shows good frost resistance.(4)The frost resistance of phase change concrete was evaluated by cube compressive strength loss and splitting tensile strength loss after different freeze-thaw cycles.After 50freeze-thaw cycles,the compressive strength of phase change concrete is 1.07 MPa lower than that of ordinary concrete,but the compressive strength loss rate of phase change concrete is 1.52%lower than that of ordinary concrete.After 100 freeze-thaw cycles,the compressive strength of phase change concrete is 2.45mpa higher than that of ordinary concrete,and the compressive strength loss rate is 10.63%lower.After 200 freeze-thaw cycles,the compressive strength of phase change concrete is still better than that of ordinary concrete.The splitting tensile strength of phase change concrete is always higher than that of ordinary concrete.After 100 freeze-thaw cycles,the loss rate of splitting tensile strength of phase change concrete is 1.48%higher than that of ordinary concrete,but the splitting tensile strength of phase change concrete at this time is 0.02MPa higher than that of ordinary concrete.After 150 freeze-thaw cycles,the splitting tensile strength of phase change concrete is 0.12 MPa higher than that of ordinary concrete,and the loss rate of splitting tensile strength is 3.58%lower.(5)Based on the research of concrete damage mechanism by CT scanning.After 200freeze-thaw cycles,the porosity of phase change concrete increases by 1.23%,which is0.97%lower than that of ordinary concrete.During the whole freeze-thaw process,the proportion of void volume<0.01mm3 fluctuates little.The proportion of pore volume of0.01-0.1mm~3of ordinary concrete has been decreased,and the proportion of pore volume of1-10mm~3has been increasing;the proportion of void volume of 0.1-1mm~3and 1-10mm~3of phase change concrete increases first and then decreases.The proportion of pore volume of0.01-0.1mm~3and>10mm~3first decreased and then increased.