Studies On The Frost Resistance Of Concretewith Nano-modified Inorganic Coatings

Based on the present situation of freeze-thaw damage of concrete in China,nano modified inorganic coating is used to improve the frost resistance of concrete.Through comparative study,we compared the difference of antifreeze performance improvement of two inorganic coating water glass and cement-based coating,and the difference of antifreeze effect improvement of inorganic coating modified by different content of nano-SiO₂ and TiO₂.At the same time,the freeze-thaw experiment was carried out under the slow freeze-thaw and fast freeze-thaw modes respectively to simulate the air freeze-thaw structure and water freeze-thaw structure in the real environment.At the same time,combining macro detection with micro analysis,the mechanism of anti freezing protection of different nano modified inorganic coating concrete was analyzed through two kinds of micro experiments of SEM and MIP.Finally,the life prediction model was established.The main research results are as follows:1.Different inorganic coatings have different effects on the improvement of the frost resistance of concrete,among which the cement-based coating is better than the water glass coating.The improvement effect of cement-based coating on the frost resistance of concrete is 46⁸0%,while that of water glass coating is about 20%.2.Nano materials can further improve the frost resistance of inorganic coatings.The effect of cement-based coating modified by nano materials can be improved by30%⁴5%,but the effect of different dosage and different kinds of nano materials on the modification of cement-based coating is not obvious,which is very excellent.However,the effect of nano materials on the water glass coating is different in the fast freeze-thaw cycle and the slow freeze-thaw cycle.In the rapid freeze-thaw process,the effect of nano-TiO₂ modified water glass coating is 80%higher than that of unmodified coating,while the effect of Nano-SiO₂ modified water glass is 42%higher.However,in slow freeze-thaw,the modification effect of nano materials is less than20%.3.After microcosmic experiment analysis,it is found that the nano SiO₂ has obvious effect in cement base modification.Through SEM and MIP experiments,it can be observed that nano SiO₂ can promote the formation of a large amount of needle ettringite filling pores inside the permeation zone of cement based coating,and the volcano ash activity of nano SiO₂ can promote the formation of large amount of C-S-H gel in the permeation area,and the effect of the two joint action is obvious.At the same time,SEM observation shows that the surface of the inorganic coating modified by TiO₂ is very dense.The adhesion and agglomeration of TiO₂ can also play a good role in water resistance of inorganic coating,so as to improve the frost resistance.4.In view of the excellent effect of nano modified inorganic coating concrete,the life prediction models are established for practice.For the air freeze-thaw structure,the service life of nano modified cement-based coating concrete can reach22 years,which is 40%longer than that of nano modified water glass coating concrete;for the water freeze-thaw structure,the effect of nano modified water glass and cement-based coating is basically the same,which is maintained at 7⁸ years.