Study On Cementitious Capillary Crystalline Rigid Self-waterproof Materials

The problem of concrete impermeability has always been the focus of research in the field of concrete materials.The cause of concrete leakage is mostly caused by the occurrence of concrete cracks and the formation of infiltration channels.The traditional waterproof material has a short service life,poor waterproof durability,and high repair cost in engineering applications.The osmotic crystalline waterproof material can be divided into a permeable crystalline waterproof coating and a permeable crystalline rigid self-waterproof material.At present,there are many researches on the external coating of permeable crystalline waterproof materials,and the products have been put into use in various markets,and good waterproof and impermeability effects have been obtained,but there is not much research on permeable crystalline rigid self-waterproof materials.The two methods of use have different requirements on the composition and content of the waterproof material,and are not universal.The osmotic crystalline rigid self-waterproof material is different from the traditional waterproof material used in the market.The active chemical substance is transported by water and transported in the pores of the concrete by osmosis,filling and promoting the incomplete water in the concrete,forming insoluble crystals and compacting pores.The permeable crystalline waterproof coating is like putting a"raincoat"on the concrete,which is a"treatment",and the permeable crystalline rigid self-waterproof material is"the root cause",which has a longer-term significance for waterproofing and impermeability of concrete.Therefore,the research group developed a permeable crystalline rigid self-waterproof material,which made its mechanical properties and impermeability meet the relevant requirements,and carried out microscopic analysis to explore its waterproof mechanism,providing a theoretical basis for better application of practical engineering.The research team conducted a preliminary experiment to explore several active substances through a large number of literatures,and used a single factor optimization test to test the mechanical properties and water absorption properties of each active substance added to cement mortar,and initially determined the dosage range and performance characteristics of active substances.Orthogonal design test was used to optimize the single-factor optimized active material by orthogonal test.The compressive strength was used as the mechanical property index,and the water absorption rate was used as the waterproof performance index.The preliminary analysis of the permeable crystalline rigid self-waterproof material was determined by visual analysis.According to the requirements of GB18445-2012"cement-based permeable crystalline waterproof material",the waterproof materials obtained by orthogonal design test are tested to meet the relevant national standards.The cement mortar test piece with the osmotic crystalline rigid self-waterproof material is subjected to chloride ion resistance test and water penetration resistance test,and the concrete test piece to which the waterproof material is added is subjected to water penetration resistance test for impermeability.Finally,the microscopic analysis of the phase by XRD and the microscopic analysis of the surface microscopic morphology by scanning electron microscopy,to further explore the waterproof mechanism of the infiltrated crystalline waterproof material.The test results show that the preliminary mixing ratio of the osmotic crystalline rigid self-waterproof material optimized by orthogonal test and satisfying the construction performance is:sodium silicate 0.5%,sodium sulfate 0.2%,magnesium calcium carbonate 0.3%,methyl silicate Sodium is 0.1%and the calcium formate is0.8%.For the water absorption rate,the influence of each active substance is from large to small:sodium methyl silicate>sodium sulfate>calcium magnesium carbonate>sodium silicate.The appearance,moisture content,fineness,chloride ion content,water reduction rate,condensation time difference and compressive strength ratio of the waterproof material can meet the requirements of national regulations.The28d impermeability pressure ratio of mortar specimens with osmotic crystalline rigid self-waterproof material is 275%,which meets the national standard of 200%;the 56d impermeability pressure ratio is 175%,which meets the national standard of 150%.The electric flux of the mortar specimens with the osmotic crystalline rigid self-waterproof material is reduced by about 10%compared with the blank reference mortar.The anti-seepage pressure ratio of the concrete specimen 28d with osmotic crystalline rigid self-waterproof material is 213%,which meets the requirements of200%of the national standard.Finally,by scanning electron microscopy analysis of the cement paste test piece,it is found that more crystals are formed in the image of the paste sample with the osmotic crystalline rigid self-waterproof material,and the structure is more compact,combined with XRD phase analysis.The active material in the water-repellent material reduces the amount of Ca?OH?₂ to form more hydrated calcium silicate crystals.