Study On Mechanical Properties And Damage Mechanism Of Polypropylene Fiber Lightweight Aggregate Concrete After High Temperature

Concrete will often show different degrees of cracking after a certain period of service,affecting its mechanical properties and durability,and even lead to structural damage and collapse of buildings.Failure to repair cracks in a timely manner will result in serious economic losses and,in some cases,other disasters.The cement-based permeable crystalline waterproof material is a rigid waterproof material prepared by mixing active chemical substances with ordinary Portland cement,quartz sand and the like as a base material.The material not only forms an effective waterproof coating on the surface of the substrate,but also contains active chemicals that can penetrate into the concrete under the action of osmotic pressure,and re-hydrate with the moisture inside the concrete and the material that is not completely hydrated in the cement.The role is to form insoluble crystals.These crystals are combined with concrete to adhere to the concrete surface,so that water and other liquids in any direction are blocked and compacted to achieve permanent waterproofing,moisture resistance,protection of steel bars and reinforcement of concrete structural strength.effect.The cement-based permeable crystalline waterproof material is a kind of intelligent self-repairing material,which not only has good waterproof and impermeability,but also is a green and environmentally-friendly anti-seepage material.At present,China's research and development work on cement-based permeable crystalline waterproof materials is still far behind engineering applications.There is still a lack of experimental data support and theoretical analysis on its mechanism of action and function,and its expensive price seriously hinders the The promotion of materials in China.In order to better apply and play the role of cement-based permeable crystalline waterproofing material,this paper carried out the compressive strength recovery rate,tensile strength recovery rate and secondary impermeability pressure of cement-based permeable crystalline waterproof material concrete.Determination,in order to characterize the effect of cement-based permeable crystalline waterproof material on the repair effect of concrete cracks.The variables involved in the test include: the amount of cement-based permeable crystalline waterproof material,water-cement ratio,curing conditions,and curing time.Through the comparison of the crack repair effect of cement-based permeable crystalline waterproof material concrete and blank sample,combined with the existing research results and related theories,the mechanism of repairing cracks in cement-based permeable crystalline waterproof material is analyzed;Test phenomena and results,determine the most beneficial to the cement-based permeable crystalline waterproof material to play its repairing role,water-cement ratio,curing conditions and curing time,provide reference for practical engineering applications;application of scanning electron microscopy,X-ray diffractometer,The microscopic means such as spectrometer are used to observe the internal microstructure of the concrete and determine the morphology,quantity and chemical form of the active substance.The results show that:(1)Under the proper conditions,the self-healing properties of concrete with cement-based permeable crystalline waterproof material are obviously better than those of blank group,and the mechanical properties and impermeability after repair exceed the initial value of concrete..(2)The strength of concrete with cement-based permeable crystalline waterproof material has greater sensitivity to the amount of cement-based permeable crystalline waterproofing material.With the change of the amount of cement-based permeable crystalline waterproofing material,the mechanical properties fluctuate.Larger.(3)Under the compounding ratio,the cement-based permeable crystalline waterproofing material is 0.7%,which is most beneficial to improve the self-healing ability of concrete;when the water-cement ratio is 0.5,the cement-based permeable crystalline waterproofing Material concrete has the best self-healing effect.(4)The test results show that the curing method has a great influence on the repairing effect of the cement-based permeable crystalline waterproof material concrete after cracking,and the standard curing and repairing effect is the best;when the curing is carried out until 56 d,the cement-based infiltration crystallization is carried out.The self-healing effect of concrete cracks in concrete materials tends to be stable and meets the conditions for continued service.(5)X-ray diffraction analysis,energy dispersive spectroscopy and scanning electron microscopy(SEM)results show that a lot of needle-shaped crystals are formed inside the concrete filled with cement-based permeable crystalline waterproof material.The main component may be calciumcarbonate;the formation of these crystals is concrete.The root cause of the crack being repaired.