Research On Concrete Durability Test And Intelligent Optimization Of Mixture Ratio In Complex Environment

The aging and premature damage caused by the durability of concrete structures have become one of the severe challenges faced by the construction industry.Common durability problems,including salt-alkali corrosion,freeze-thaw damage,carbonation corrosion and other factors,will lead to the rapid deterioration of the durability of concrete structure.Based on the project of Songyuan-Tongyu section of the Tieke Expressway,this paper aims at the concrete service conditions of compound salt erosion,long-term freeze-thaw cycle and strong wind carbonization,and studies the deterioration mechanism of concrete durability between environmental and raw material factors,and carries out multi-objective prediction and mix proportion optimization of concrete durability under severe environment.In order to connect the test results with the actual service condition of the structure,the multiple and interactive deterioration mechanisms are considered in the deterioration law test of concrete durability.The degradation mechanism of salt invasion,freeze-thaw cycle,carbonation alternation and their coupling effects were studied by accelerated laboratory test.The coupling effects of multi factors on the degradation mechanism of concrete durability were studied,including the evaluation of freeze-thaw damage caused by spacetime environment,composition,composite salt erosion,strength failure and carbonation erosion.It provides support for revealing the synergistic effect of complex coupling conditions on the deterioration of concrete durability.In order to improve the durability of concrete in actual service stage from the configuration stage,it is necessary to simultaneously control the mass loss change rate,relative dynamic elastic modulus,chloride diffusion coefficient,compressive strength and carbonation depth under the highly nonlinear constraints.Based on the water,cement,aggregate,chemical admixture and mineral admixture,the Random Forest prediction algorithm and NSGA-III multi-objective optimization algorithm are developed to study the prediction of concrete durability and multi-objective optimization of concrete mix ratio under the complex conditions of multi factor coupling.The results show that the method is feasible and effective,and provides a new method for the design of concrete mix ratio.