Preparation And Properties Of Cement-based Permeable Crystalline Waterproofing Coating

Cement-based permeable crystalline waterproof coating has the advantages of simple construction operation,easy maintenance,low cost,good performance and so on.It is a kind of rigid waterproof material with excellent performance.Firstly,the active substances were screened.XRD,SEM-EDS,nano indentation and other testing methods were used to investigate the effects of active substances and coatings on cement mortar matrix,and the mechanism was analyzed.Then the mix ratio of waterproof coating was explored.Finally,a kind of waterproof coating with low cost,excellent waterproof performance and environmental friendliness was prepared.The results are as follows:(1)Six kinds of active substances were screened by measuring water absorption and flexural and compressive strength.Sodium sulfate and sodium hexametaphosphate had better waterproof performance,with water absorption of48.24% and 49.69% in 48 h,respectively.The mechanical properties of sodium sulfate are better,and the flexural strength and compressive strength are 9.40 MPa and 55.76 MPa respectively.Ethyl orthosilicate has a certain effect on the environment.After comprehensive consideration,sodium silicate,sodium carbonate,sodium sulfate,sodium hexametaphosphate and hydroxypropyl methyl cellulose were finally determined to be added to the coating as active substances.(2)After the cement permeable crystalline waterproof coating is applied to the substrate,the self-healing rate is 109.76%,increasing by 24.04%.The selfhealing ability is good.The active substance in the coating penetrates into the cement mortar matrix.It participates in and influences the hydration process of cement and improves the micro-morphology of hydration products.The resulting crystals plug the micropores,reducing the size of the pores and reducing the volume of the harmful pores.The purpose of "permeation" in the permeating crystalline waterproof coating is achieved.(3)The best ratio of cement-based permeable crystalline waterproof coating is: the mass ratio of cement,ultrafine quartz sand,slag and silica fume is100:50:20:4.Sodium silicate,sodium carbonate,sodium sulfate,sodium hexametaphosphate,hydroxypropyl methyl cellulose,rubber powder,water reducing agent accounted for 2%,5%,1%,0.3%,0.1%,0.25%,0.5% of the total cement,respectively.Its water-material ratio is 0.3.The impermeability pressure ratio of removing coating and with coating is respectively 275% and 325%.And the flexural and compressive strength of coatings for 28 d are 9.57 MPa and64.17 MPa respectively.Its various properties are better than the requirements in "cement-based permeable crystalline waterproof material"(GB18445-2012).The cost is about 535 yuan/ton.There are 28 figures,24 tables and 103 references.