Study On Coating Protection Of Concrete In Marine Environment

The coaction of load and marine environment could accelerate the corrosion of concrete structure and affect the service life of the building seriously.The coating protection technology is one of the commonly used concrete protective measures.This paper studied the properties and the protective performance changes under the effect of chlorine salt immersion of polyurea coating,epoxy coating and chlorinated rubber coating in the standard experimental condition through both macroscopic and microscopic investigations.As the main part of the study,the change law of glossiness,adhesion and anti-chloride-permeability for coated mortar were investigated under the coaction of bending load and environmental factors.The main conclusions in this paper were as follows:1.The conventional performance results of polyurea coating,epoxy coating and chlorinated rubber coating showed that the tensile strength of polyurea coating 2.5 times as that of epoxy coating and 6.6 times as the chlorinated rubber coating.The elongation at break of polyurea coating was 39.9 times as epoxy coating and 3.6 times as the chlorinated rubber coating.The tear strength of polyurea coatings was 3.1 times as that of the epoxy coating and 13.2 times as the chlorinated rubber coating.There were no cracks in the polyurea coatings when it was in tension.For the drying time,polyurea took the shortest time,followed by chlorinated rubber,and epoxy took the longest time.The low temperature flexibility of the polyurea coating is superior to the epoxy and chlorinated rubber coatings.The solid content of polyurea coating,epoxy coating and chlorinated rubber coating is 99.88%,88.31% and 46.18%,respectively.The drying time of polyurea was least and which of epoxy was longest.The water absorption rates of the three kinds of mortar samples were 0.23%,0.31% and 0.57%,respectively,which was much lower than those of mortar without coating.2.It was shown that the protective performance of the coating under the single factor of chloride salt immersion: Na Cl solution immersion,the order of gloss reduction from high to low was epoxy,chlorinated rubber and polyurea.In Na Cl solution,the adhesion of polyurea coating kept stable.However,the adhesion of epoxy and chlorinated rubber decreased with the immersion time going on.The order of the chloride ion content from high to low was mortar without coating,chlorinated rubbercoated mortar,and epoxy coated mortar and polyurea coated mortar.Compared with the diffusion of chloride ion for mortar without coating,that for polyurea,epoxy and chlorinated rubber decreased by 78.94%,77.66% and 69.36%.3.The combined study of bending load and chlorine salt immersion showed that the glossiness of polyurea decreased slightly as the load went up.Under small load,the adhesive strength kept unchanged,and the adhesive strength got down slightly while the load increased to 30-50%.The chloride ion content of polyurea-coated mortar rose with the increased load.When bearing 0%,15%,30% and 50% bending load,the polyurea-coated mortar showed the diffusion coefficients of chloride ion under2.0×10-12 ? /s.It was shown by microscopic morphology in SEM that the polyurea coating structure inside was compact under loading states,and the sealing effect was outstanding.Polyurea remains good protective property under combined effect of bending load and chlorine salt immersion.4.The combined study of bending load,wet-dry circulation and chloride salt immersion showed that after 90 d,compared to the serious loss of the glossiness of chlorinated rubber and the obvious loss of epoxy,the glossiness of polyurea just experienced slight decrease.Polyurea,epoxy and chlorinated rubber lost 12.24%,24.25% and 47.47% on the adhesive strength respectively.The chloride ion content from high to low were chlorinated rubber coating mortar,mortar,mortar coating epoxy polyurea coating.The diffusion coefficients of chloride ion of above mortars were3.76×10-12?/s,5.36×10-12?/s and 5.46×10-12?/s separately.The electrochemical test showed that the reinforced mortar coating chlorinated rubber internal corroded,the remaining two did not occur corrosion;SEM morphology test showed that the polyurea coating in the role of multi factor coupling internal structure remained dense,and epoxy resin and chlorinated rubber coating surface defects.It can be concluded by above experiments that polyurea coating has the best anti-corrosive performance under the chlorine salt immersion,the co-action of bending load and chlorine salt immersion,the co-action of bending load and chloride salt and the combined effect of bending load,dry-wet circulation and chloride salt and is applicable to protect the marine concrete.