| Chloride ion erosion is the main factor affecting the durability of reinforced concrete structures,when the free chloride ion concentration in the pore solution inside the structure reaches the corrosion concentration threshold,it will cause the steel to corrode,the swelling stress that appears during the corrosion process causes great damage to the stability and compactness of the structure.It is not enough to rely on cement itself to absorb and solidify free chloride ions to reduce steel corrosion,therefore,the preparation of an economical and simple auxiliary material to promote the curing of chloride ions in the concrete has very important engineering practical significance.In this paper,the high-energy ball milling method is used to process the mixture of calcium nitrite,alumina,and calcium oxide to prepare calcium-aluminum composite materials.The physical and chemical properties are analyzed by XRD,FT-IR and SEM;Quantitatively evaluate its adsorption capacity for chloride ions in salt solution through orthogonal experiments,and obtain the best adsorption conditions for calcium-aluminum composite materials;Add the cement paste by admixture and measure its chloride ion curing rate,The compressive strength of the cement-based slurry cured by the adsorbent was tested,and the adsorption products were characterized by XRD,TGA and MIP,and the adsorption mechanism of the calcium-aluminum composite material in cement was proposed.The research results obtained in this paper show that:(1)There is no chemical reaction between the different raw materials after ball milling,but the ball milling process refines the product crystal size and increases the specific surface area of the composite material,adding absolute ethanol as a process control agent in the ball milling process can significantly improve the efficiency of ball milling.(2)The calcium-aluminum composite prepared by ball milling has good chloride ion adsorption performance in NaCl solution,the adsorption equilibrium state is reached when the adsorption time is 120mins,at this time,the chlorine ion adsorption per unit mass material reached 71.892 mg/g.(3)Through orthogonal experiments,the four factors of adsorption temperature,adsorbent content,adsorption pH value,and chloride ion concentration were investigated for the influence of calcium-aluminum composite materials on the adsorption performance of chloride ions in NaCl solution.The order of the four factors affecting the chloride ion adsorption performance of the material is as follows:Adsorption temperature,adsorbent content,adsorption PH value,chloride ion concentration.The optimal adsorption conditions at this time are:adsorption temperature 30℃,adsorbent content 12g,chloride ion concentration 0.5mol/L,adsorption PH value 6,and the adsorption capacity at this time is 114.47mg/g.(4)Calcium-aluminum composite material has good chloride ion curing performance in cement paste and cement mortar,the curing rate of chloride ions is positively correlated with the amount of adsorbent added and the curing age,negatively correlated with chloride ion concentration.Compared with mortar,cement paste has better chloride ion curing effect,when the pure pulp curing age is 28d,the chloride ion concentration is 0.25mol/L and the adsorbent addition amount is 48g,the chloride ion curing rate reaches 80%.The addition of adsorbents will adversely affect the strength of cement-based materials.After the raw material is ball milled,the chloride ion curing performance in the cement-based material is better.(5)The microscopic results show:The calcium-aluminum composite material is added to cement-based materials to adsorb chloride ions mainly by promoting the formation of stable chloroaluminate from tricalcium aluminate and free chloride ions in cement-based materials,improved its chemical adsorption capacity.At the same time,it can significantly improve the pore structure of the material and improve the resistance to chloride ion penetration of cement-based materials. |
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