| Iron tailings as the largest solid waste in China,can be used as the main component of building ceramics,to achieve secondary utilization,the use of the concrete made of ceramic particles in mechanical properties and durability compared with ordinary concrete has a big difference,this thesis compares the uniaxial compressive stress-strain curve of ordinary concrete and iron tailings ceramic concrete,and analyzes the curve characteristics and failure characteristics;And compare and analyze the salt frost resistance characteristics of two kinds of concrete in the state of precompressive stress,salt corrosion and freeze-thaw,the main work is:(1)The preparation of iron tailings ceramics with different proportions was studied,the main physical and mechanical properties of ceramics with different proportions were compared,and finally the A6 group with the smallest apparent density was selected,which could meet the requirements of GB/T 17431.1-2010 "Light Aggregate and Test Methods Thereof" for 900-grade artificial ceramics.Iron tailings ceramic concrete with water-to-adhesive ratio of 0.45,0.40 and 0.35 was prepared by combining iron tailings ceramics particles in A6 group,and ordinary concrete with the same water-to-adhesive ratio was prepared as the control group.(2)Establish a database of elastic modulus of lightweight coarse aggregate concrete with domestic and foreign experimental data,calculate the database data through numerical models,and finally establish regression models for elastic modulus,apparent density,and axial compressive strength based on the model specified by the American Concrete Institute(ACI).The results show that both the experimental model and ACI model can be used to calculate the elastic modulus of iron tailings ceramisite concrete in this thesis.(3)Through the uniaxial compressive stress-strain curve test of iron tailings ceramic concrete and ordinary natural crushed stone concrete,the curve characteristic points,strength difference,deformation difference and failure mode of the two concretes were compared,and the ratio relationship between the uniaxial compressive strength(fc)and cubic compressive strength(fcu)of the two concrete was determined,the semi-empirical semi-theoretical constitutive model and parameters most suitable for the two concretes were selected,and the random damage constitutive model of iron tailings ceramic concrete was established through the statistical distributions of Weibull and Lognormal.(4)Analysis of the results of chloride salt salt freezing test after preloading,the salt frost resistance of iron tailings ceramic concrete is higher.Both types of concrete showed positive correlation between salt frost resistance and water-to-adhesive ratio,negatively correlated with freeze-thaw times,and increased and then decreased with stress level.Preloading at 0%～25%stress levels improves the salt frost resistance of concrete.(5)The effects of water-to-adhesive ratio,stress level and number of freeze-thaw cycles on the salt frost resistance of iron tailings ceramic concrete were analyzed in order of the number of freeze-thaw cycles,stress level and water-adhesive ratio,and the influence on the salt frost resistance of ordinary crushed stone concrete was:freeze-thaw cycles,water-glue ratio and stress level.(6)The BP neural network prediction model with four input values and two output values is established by preloading salt freezing test data,and the results show that by analyzing the accuracy of the model,it is found that the model has a high degree of fit,and through the error comparison between the predicted value and the test value,it is found that the prediction error is between 0～8.7%,indicating that the prediction results of the model are effective and can be used to the prediction of the durability performance of preloaded concrete with aggregate changes. |
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