| At present,due to the low price,low dosage and simple injection technology of powdered accelerator,it still occupies the main position in the domestic market.However,with the emergence of many disadvantages of powdered accelerator in dry shotcrete construction,there is an urgent need for a low price liquid accelerator with superior performanceAcrolein is widely used as a common raw material in chemical industry,but in the process of preparing acrolein in industry,a large amount of waste liquid is produced and current treatment with incineration.In this paper,the feasibility of preparing liquid accelerator from waste liquid of acrolein production is discussed from the point of economic benefit and environmental protection benefit.The specific research contents of this paper are as follows:（1）Acrolein tail liquid is a kind of industry waste liquid.The composition of the waste liquid is varied due to its different preparation technology.The properties and components of the waste liquid for the production of acrolein are analyzed and tested.The results show that the waste liquid is a kind of low concentration acrylic acid aqueous solution with similar density to water and strong acid property.It is feasible to use it as raw material for industry production to prepare liquid accelerator.（2）The single factor control variable method is used to investigate the effects of the molar ratio,concentration,reaction temperature and reaction time of raw materials on the stability and setting time of the accelerator.According to the analysis of experimental data,the most suitable preparation conditions are obtained.:molar ratio 1.6,concentration 60%,reaction time1.5h,reaction temperature 90℃.（3）The properties of liquid accelerator prepared from acrolein waste liquid were tested.The results show that the liquid accelerator prepared in this paper can adapt to all kinds of cement.All the indexes can meet the requirements of the national industry,and at the level of 6%,the indexes can meet the requirements of the first class products stipulated by the national industry.（4）Combining the hydration mechanism of cement and using XRD（X-ray diffractometer）modern microscopic analysis method to study the mechanism of promoting coagulation of liquid accelerator,the results are as follows:a)After adding the accelerator,the effective component in the accelerator will react with the gypsum and eliminate the retarding effect of the gypsum on the cement,which will promote the hydration reaction of the calcium aluminate（C3A）and accelerate the solidification hardening of the cement.b)Ca（OH）2 will crystallizes when it is sufficiently generated,while Ca（OH）2 is the hydration product of tricalcium silicate（C3S）,which speeds up the hydration process of tricalcium（C3S）.At the same time,the consumption of gypsum causes the surface of C3A particles in cement to come into contact with aqueous solution again,this also accelerates the hydration rate of tricalcium aluminate（C3A）,and thus accelerates the solidification hardening of cement. |
