Study On Preparation And Properties Of Alkali Activated Slag-iron Tailings Concrete

In recent years,with the continuous development of China’s industrial production,at the same time,the number of industrial solid waste is also increasing,of which mining,metallurgy,thermal power generation and other industries are the most serious,and the accumulation of common industrial solid waste such as slag,iron tailings powder is increasing year by year.Reasonable utilization of industrial solid waste is an important part of strategic emerging industry of energy saving and ecological environment protection,which provides strong guarantee for rapid and high-quality development of national economy,and is also the fundamental way to solve environmental pollution and safety risk caused by improper disposal and piling of industrial solid waste.In view of this,this thesis proposes to comprehensively utilize slag and iron tailings powder to prepare alkali activated slag-iron tailings powder cementitious material,and to add coarse and fine aggregates to prepare alkali activated slag-iron tailings powder concrete,which is suitable for road engineering application,in order to expand the application of industrial solid waste.The main research contents and conclusions of this thesis are as follows:(1)The cementitious material is prepared by using water glass activated iron tailings and slag,and the mix ratio of cementitious material is designed and optimized by response surface method.Taking water cement ratio,alkali content,iron tailings powder content and water glass modulus as test factors,the BBD response surface analysis with four factors and three levels was carried out with the response values of compressive strength,bending tensile strength and setting time of cementitious materials at all ages.The analysis results show that there is a significant relationship between the test variables and the response values,and the model fits well with the actual situation.The optimal mix proportion of the cementing material optimized by the model is 0.34 water cement ratio,5.38% alkali content,22.07% iron tailings powder content,and 1.22 sodium silicate modulus.The error between the measured value and the predicted value is small.(2)By means of XRD,SEM and EDS,the microstructure and hydration mechanism of the cementitious material with the best mix ratio were analyzed to explore the relationship between its microstructure and performance.The results show that iron tailings powder and slag have a synergistic effect,alkali activated slag-iron tailings powder cementitious material hydration reaction is rapid,and a large number of zeolite minerals and C-(A)-S-H gel are generated in the hydration process;In the process of hydration,the reaction products gradually changed from flocculated N-A-S-H gel to more orderly C-A-S-H gel until completely disappeared.The sample structure is gradually compact and smooth,and the strength is continuously improved.(3)Based on the response surface model of cementitious materials,the composition design method of alkali activated slag-iron tailings concrete is proposed.Firstly,the water cement ratio,iron tailings content,alkali content and sodium silicate modulus of cementitious materials in concrete are determined according to the design strength of concrete and the regression equation model;Then,the unit water consumption and concrete sand ratio are selected by referring to the mix proportion design of ordinary concrete;Finally,the mass method is used to calculate the amount of coarse and fine aggregates in concrete,and finally the mix proportion of alkali activated concrete meeting the design requirements is obtained.(4)The mechanical properties,abrasion resistance,frost resistance,sulfate corrosion resistance and dry shrinkage of alkali activated slag iron tailings concrete are investigated.The results show that the strength of alkali activated slag-iron tailings powder concrete increases rapidly and steadily,and it has excellent abrasion resistance,frost resistance and sulfate corrosion resistance.Due to the addition of iron tailing powder,the hydration rate of cementitious material is restrained to a certain extent,and its drying shrinkage property is improved.