| The durability of concrete structures in wet and acid corrosive medium has been reduced significantly,which seriously affects the normal use of the structure.How to effectively prevent the acid corrosion medium from invading the concrete structure and ensure its safety and normal use during the service life period.It has become an urgent problem to be solved for concrete structures under corrosion.It is very important to study a kind of coating which is in coordination with concrete structure under variable temperature and effectively protecting the concrete structure from acid corrosive medium,which is critical to meet the normal use and durability of buildings under acidic conditions.However,the existing anticorrosive coating has many problems,such as low adhesive force,insufficient temperature resistance and poor coordination between coating and base temperature.Some foreign products have better performance,but the price is too high to be widely applied.In this paper,waterborne polyurethane modified silicate cementing material is used as a cementitious material to improve the toughness and bond strength of the coating.The special coarse-grained filler is used as the skeleton to improve the temperature resistance,and the composite fine powder is used as the filling material to improve the mechanical properties and water resistance.As a research idea,a new type of temperature-resistant and anti-corrosion coating is prepared.First of all,three types of water-borne polyurethanes are prepared and studied,considering their compatibility with silicates,waterborne polyurethanes with excellent properties are selected.On this basis,taking the mechanical properties of coating as temperature resistance and acid resistance as the basic indicators,the influence of the amount of waterborne polyurethane and the type and amount of filler on the performance of composite coating are studied and the best mixture ratio is obtained:Composite binder and filler mass ratio was 3:5,the composite cementing material of aqueous polyurethane nano silica accounted for 10%,accounting for 4%,the coarse filler accounted for more than 30%,fine quartz powder filler and cast stone powder respectively accounted for 28% and 42%,The flexural and compressive strength of the coating reached 10.00 MPa and 27.9MPa respectively,which increase by 57% and 25.1%compared with that of the unmodified coating,and the temperature resistance,acidresistance and water resistance are stable.The compressive strength of the coatings increased by 34.1%,32.4% and 37.3%,respectively.In addition,the effects of interfacial agents on the adhesive properties of the coating and the base is studied.It is found that the bonding strength of the coating and the base can be increased by 10.7%.By means of SEM,EDS,TG and MIP,the performance improvement mechanism of polymer modified silicate cementitious material and coating is analyzed.The SEM results show that the modified polyurethane coating is well fused with silicate compound to form a dense interpenetrating network structure,and the gap is significantly smaller than that of the blank group.After high temperature and acid corrosion,the structure of organic and inorganic interpenetrating network is not destroyed by high temperature and corrosive substances.But the coating in the blank group has different degrees of corrosion and the gap of the coating increases.EDS analysis showed that after sulfuric acid corrosion,the percentage of sulfur atoms detected in the blank group is 6.73,while that in the modified group is not detected,indicating that the corrosive substances had penetrated into the blank group coating,while the modification group is not corroded by corrosive substances.The analysis of thermal weight loss shows that the weight loss of the modified group before 250 ? is very small,which show that the polyurethane can meet the temperature resistance at 250 ?.The test of mercury pressure show that the most pore sizes of the modified coating and the blank group are 7.12 nm and 11.56 nm respectively,indicating that the pore structure of the modified coating is refined. |
PDF Full Text Request