Studies On Carbonation Resistance Of Concrete With Nano-modified Inorganic Coatings

Carbonation is one of the main reasons that affect the durability of concrete.The corrosion of steel bars caused by it has endangered the safety of concrete structures and attracted people's attention.Inorganic coating can effectively delay the process of concrete carbonation and reduce the rate of carbonation development.It is not only convenient for construction,economical and simple,but also particularly suitable for already built buildings,so it has become an important auxiliary measure for the durability protection of concrete buildings.However,the protective effect of the inorganic coatings is average and needs further improvement.As an emerging material,nano-materials have been applied in various industries and have made good progress.In this paper,two inorganic coatings,water glass?sodium silicate aqueous solution?coating and cement-based permeable crystalline coating,nano SiO₂,nano TiO₂ and nano SiC are selected.The concrete covered by the coating is the research object,The combination of theoretical analysis and experimental research was used to systematically and thoroughly study the influence of inorganic coatings and nano-modified inorganic coatings on the carbonation resistance of concrete.Scanning electron microscope?SEM?and mercury intrusion test?MIP?were used The corresponding mechanism analysis was made from a microscopic perspective,and finally a carbonation depth prediction model of nano-modified inorganic coated concrete was established.The main research results obtained are as follows:?1?The inorganic coating has a very good effect on improving the carbonation resistance of concrete.The cement-based coating is slightly better than the water glass coating,and is affected by the degree of moisture on the surface of the concrete substrate.For the water glass coating:dry<moist<wet.For cement-based coatings:dry<moist<moist.Adding hardener and pickling treatment to the water glass coating has the same protective effect.Increasing the number of brushing passes can effectively improve the anti-carbonation effect of cement-based coated concrete,but it is not obvious for cement-based coating.?2?The protective effect of the three nano-materials on water glass and cement-based coatings is ranked as follows:nano-TiO₂>nano-SiO₂>nano-SiC,nano-SiO₂>nano-TiO₂>nano-SiC.Nano-TiO₂ can effectively improve the micro-morphology of the water glass coating.Nano-SiO₂ can significantly improve the micro-morphology of the cement-based surface and the pore structure of the concrete in the penetration zone of the coating,thereby enhancing the protective effect of the coating.?3?Through the research on the carbonation model of nano-modified inorganic coated concrete,the prediction model of the carbonation depth of the coating equivalent concrete thickness was established based on Fick's first law,and it was reasonably simplified,and the service life of the coated concrete Make predictions.Two inorganic coatings and nano-modified coatings can effectively extend the service life of concrete.The paper has 37 pictures,28 tables,and 97 references.