Research On Salt-Freeze Resistance Of Glass-Doped Concrete Under Complex Erosion Environment

Under the influence of special climatic and hydrological conditions,hydraulic concrete structures such as dams,aqueducts and tunnels in northwest China are inevitably damaged and destroyed by the erosion of wetting and drying cycles,corrosive salt ions and freeze-thaw cycles.Scholars at home and abroad are committed to improving the durability of concrete in complex environments,among which the saltfreeze resistance of concrete is the key to durability research,which has gradually become a hot and difficult research topic at home and abroad.In view of this,this thesis takes glass-powder concrete as the research object,and obtains the optimal mix ratio of glass-powder concrete meeting the uniaxial strength requirements through the orthogonal test of three levels and four factors(glass powder content,admixture content,water-binder ratio and sand rate).Based on this mix ratio,the mechanical properties and impermeability tests of PO-0 group,GP-10 group,GP-20 group and FA-10 group of concrete(0,10%,20% glass powder and 10% fly ash),composite salt erosion tests,composite salt freeze-thaw tests and CT scanning tests were carried out respectively.The main research results are as follows:(1)Through the analysis of orthogonal test results,the water-binder ratio,glass powder content and water reducing agent content are negatively correlated with the strength of glass powder concrete,and the strength of glass powder concrete firstly increases and then decreases with the increase of sand rate.The mixture ratio of glass powder concrete is considered as follows: water-binder ratio 0.4,glass powder content10%,sand rate 37%,water reducing agent content 2%.The concrete of PO-0 group,GP-10 group,GP-20 group and FA-10 group based on this mix ratio were tested for compressive strength,tensile strength,water absorption and electric flux at different curing ages,respectively.The results show that,with the delay of curing age,the mechanical properties of glass powder concrete approach or even exceed ordinary concrete,and the mechanical properties of glass powder concrete are always higher than those of fly ash concrete at 10% glass powder content.With the delay of curing,the water absorption rate and electric flux value of glass concrete decrease greatly,and the impermeability of glass concrete is better than ordinary concrete and fly ash concrete(2)Composite salt erosion test,water freeze-thaw test and compound salt freezethaw test were carried out respectively on the concrete of PO-0 group,GP-10 group,GP-20 group and FA-10 group,and the macro-property deterioration was analyzed and the one-element quadratic damage equation was fitted.Finally,a life prediction model based on Weibull probability distribution was established for four groups of concrete in salt-frozen environment.The test results show that in the composite salt erosion test,the incorporation of glass powder and fly ash can resist the composite salt erosion well,and the anti-erosion ability of glass powder is stronger,so GP-20 group concrete is preferred.In clear water freeze-thaw,PO-0 group has the best freeze-thaw resistance,while in compound salt freeze-thaw,GP-10 group has the strongest salt-freeze resistance.Glass powder concrete is more suitable for salt-freeze environment,so GP-10 group concrete is preferred.The reliability prediction model based on Weibull distribution can effectively reflect the degradation law of glass powder concrete under the action of freeze-thaw in clear water and freeze-thaw in composite salt,and has high reference value for engineering.(3)Laboratory CT scanning tests were conducted on PO-0 group,GP-10 group,GP-20 group and FA-10 group concrete before and after salt freezing,respectively.The test results show that the number of pores,pore volume,pore diameter,surface area and porosity of the internal pores of concrete increase continuously under the effect of salt freezing,and the porosity sphericity is reduced,and the distribution of pore heterogeneity is intensified.The addition of admixture can change the pore structure of concrete,and 10% glass powder can effectively improve the pore structure.Based on the grey correlation theory,the grey correlation analysis model is established.The pore structure characteristic parameters(average pore volume,average surface area,average pore diameter,average sphericity and porosity)show strong correlation with the macroscopic freeze-thaw properties(mass and dynamic elastic modulus).