Study On Preparation Of Calcium Silicate Hydrate From Fly Ash Aluminum Residue And Study On The Properties Of Calcium Silicate Hydrate Test Block

Coal is a rich primary energy in China.The large-scale industrial construction in China has led to the rapid development of the thermal power industry,followed by increasing emissions of fly ash.The accumulation of fly ash not only occupies land,but also causes many environmental problems.With the progress of science and technology and the improvement of people’s awareness of environmental protection,fly ash has been widely used.Among them,the progress of extracting alumina from fly ash has been made,and a lot of waste residue has been produced after the fly ash is extracted from aluminum.Under this background,this paper proposes to prepare amorphous hydrated calcium silicate from this residue.The aluminum extraction residue in this paper is the product of aluminum extraction by acid method.Through particle size,N₂ adsorption and desorption,XRD,XRF and SEM analysis,it is found that the content of silica in the residue is 52%,and the residue is mesoporous with large pores.Phase analysis showed that more than 90%of the residue was amorphous,and the surface roughness of the residue was found by sem.Therefore,white mud（fly ash aluminum residue）has high activity and is a good siliceous material which can be used to synthesize hydrated calcium silicate.The aluminum extraction residue of fly ash in this paper is derived from the aluminum extraction by acid method.Phase,chemical composition,surface morphology and particle size analysis of the residue were conducted by N₂ adsorption and desorption,XRD,XRF and SEM.It was found that the residue was mesoporous and rich in macropores.Amorphous hydrated calcium silicate was prepared by dynamic hydrothermal method with fly ash aluminum residue as siliceous material and calcium hydroxide as calcareous material.The experiment adopted the orthogonal experiment method,and the synthesis parameters of calcium-silicon ratio,water-solid ratio,reaction temperature and reaction time were four factors,each factor had three levels.The synthesized powder was pressed into shape under the pressure of 20～40MPa to determine the apparent density,strength and water resistance of the specimen.Based on the range analysis of orthogonal experimental results,it is concluded that the best combination conditions of softening coefficient are calcium silicon ratio 0.6,water-solid ratio 5%,reaction time 2h,reaction temperature 100℃.The water resistance of the test block was improved by adding calcium stearate and organosilicate hydrophobic agent into the hydrated calcium silicate powder.The effects of the grinding time,the content of calcium stearate and the content of organic silicone on the water resistance of the test block were investigated.The water resistance of the test block was improved by adding organic silicone,but the change of water resistance was not significant.When calcium stearate is added,the water resistance is the best when the dosage is 3%grinding for 30min,and the 1d softening coefficient can reach 0.93.When silicone is added,the water resistance is the best when the content is 0.3%,and the 1d softening coefficient is 0.86.