Experimental Study On Self-repair Of Concrete Crack

Because of its high compressive strength,good stability,easy preparation,and low price,concrete is currently widely used in water conservancy projects,construction,highways and other fields.However,concrete has great brittleness and is affected by external forces or other factors during use,and is prone to micro-cracks or partial damage.If these cracks are not repaired in time,it may affect the durability of concrete and affect the mechanical properties of concrete.Faced with the problems of concrete cracking and crack repair,this study uses self-healing concrete to solve the above problems.Self-healing concrete is an ecological restoration technology that simulates the self-healing of organisms in nature after being injured.In this study,C30 self-compacting concrete was used as the base material,and the repair system composed of the embedded pipe with repair glue and the concrete base material was tested.The main research contents and conclusions are as follows:(1)Based on the theory of composite materials,establish a micro-balance equation to obtain and optimize the shortest length of the glass tube.The test results show that when there are multiple cracks or individual cracks in the matrix of the optimized glass tube,the repair glue can be released more quickly and the cracks can be completely filled,and the damaged parts of the concrete can be repaired in time.(2)In this paper,the fluidity of the repair glue,the flexural strength and the split tensile strength of the concrete after the glue repair are studied through the fluidity test,the flexural strength test and the split tensile strength test.The results show that:the flow of a certain polyurethane glue Good performance,the glue can completely fill the cracks and gradually solidify within 2h;use this glue to bond the section of the test block,the maximum flexural strength is 3.8MPa,the maximum split tensile strength is 2.43MPa,and the strength that meets the requirements of the specification is selected.This glue is used as a self-repairing glue for concrete.(3)Through compressive strength and split tensile strength tests,the maximum amount of glue embedded is studied.The results show that the amount of embedded glue cannot exceed 4%of the volume of the concrete.If the amount is less than 4%,the strength of the concrete will decrease.Slower,the corresponding minimum compressive strength is 34.7MPa,the split tensile strength is 1.89MPa,and the strength meets the requirements;when the content exceeds 4%,the strength drops relatively quickly,which is lower than the specification requirement,that is,4%is the critical blending of the glue.the amount.(4)The effect of different amounts of glue and the arrangement of glue on the self-repair of concrete cracks was studied.The results show that the repair effect of concrete becomes better with the increase of the amount of glue.When the amount of glue exceeds 3%,The repair effect tends to be stable.The repair effect is best when the content is 2%,2.5%,3%,3.5%,and the layout is rhombus,trapezoid,rectangle,and trapezoid.The flexural strength after repair can reach 90%of the original strength,reaching 3.56MPa.Because the repair effect is similar when the dosage is 3%and 3.5%,the best dosage of glue is 2%～3%.(5)The effect of freezing and thawing environment on concrete repairing effect was studied,and the results showed that the repairing effect of concrete was decreasing with the increase of freezing and thawing times.When the amount of glue is 2%～2.5%,after 100 freezing and thawing cycles After that,the flexural strength of concrete decreases faster,the minimum flexural strength is 3.34MPa,and when the amount of glue is 3%,the flexural strength decreases more gently before 150 freeze-thaw cycles;when the number of freeze-thaw cycles is the same,The higher the amount of glue,the better the repair effect of the concrete.The reason is that when there is more glue,a thicker glue layer will be formed around the cracks to better resist damage.(6)The microscopic state of the bonding between different amounts of glue and cracks was studied by electron microscope.The results showed that:when the amount of glue is less than 2%,the bonding effect is poor,and when the amount is 2%to 3.5%,the bonding The effect is better.When the amount of glue is less than 2%,the amount of glue is small,and the cracks cannot be completely filled,and there are more pores at the cracks;when the amount of glue is greater than or equal to 2.5%,the amount of glue is sufficient,making the concrete and glue The liquid looks like a whole and has a higher density.