Effect Of Fluorogypsum On Properties Of Sulfoaluminate Cement-based High-water Packing Materials

High-water packing materials（HPM）has the advantages of simple packing process,less packing material consumption,and fast material setting and hardening speed,and are widely used in the coal mining process.In HPM,gypsum accounts for about 40%（mass ratio）of the whole system,and the gypsum in this system can be anhydrite（generally based on natural anhydrite）and dihydrate gypsum.The main component of fluorogypsum is type II Ca SO₄.Studying the application of fluorogypsum in HPM can not only increase the utilization rate of industrial solid waste and reduce the environmental load,but also reduce the consumption of natural gypsum ore and protect the natural resource environment.This paper mainly studies the effects of fluorogypsum content,experimental water temperature（25℃,15℃and 5℃）and water-binder ratio（2:1,3:1 an d 4:1）on HPM single liquid fluidity,setting time,compressive strength and the effect of additives（aluminum sulfate,potassium aluminum sulfate dodecahydrate,calcium carbonate and silica）on the basic properties of HPM mixed with 80%fluorogypsum in B material,through XRD,SEM and TG-DTA.The test method,combined with the relevant theory of the hydration of HPM,was used to analyze the hydration mechanism.Summarizing the experimental results,the following conclusions are drawn:（1）When the experimental water temperature was 25°C and the water-binder ratio was 3,with the increase of the content of F1 and F2,the initial setting time and final setting time of HPM increased.With the increase of F1 content,the compressive strengths of 1 d,7 d and 28 d decreased gradually;with the increase of F2 content,the compressive strengths of 1 d,7 d and 28 d gradually increased.With the increase of fluorogypsum content,the experimental water temperature and water-binder ratio have little effect on the setting time and compressive strength of HPM.When studying the effects of the initial setting time and final setting time of HPM increased gradually content and water-binder ratio on the weathering resistance of HPM,it was found that the fluorogypsum content had little effect on the weathering resistance of HPM,while the water-binder ratio had a greater effect on it.When performing HPM packing in weathered environments,the water-to-binder ratio should not be greater than 3:1.Microscopic analysis found that fluorogypsum mainly affected the hydration rate of HPM and the morphology of AFt.The hydration rate of the F2 group was the fastest,and the surface of the generated AFt was relatively flat and its size was relatively uniform.The size of the AFt formed in the F1 group was not uniform and the surface was relatively rough.（2）When studying the effects of aluminum potassium sulfate dodecahydrate,aluminum sulfate,calcium carbonate and silica on the properties of fluorogypsum-based HPM,it was found that aluminum sulfate and aluminum potassium sulfate dodecahydrate can significantly shorten the setting time of HPM,and aluminum potassium sulfate dodecahydrate can significantly shorten the setting time of HPM.It can also significantly improve the compressive strength of HPM at different ages.Calcium carbonate and silica are beneficial to the development of compressive strength,and the optimal dosage（accounting for the mass ratio of B material）is 1%,2%,3%and 2%,respectively.The microscopic analysis shows that both aluminum potassium sulfate dodecahydrate and aluminum sulfate can promote the formation of AFt in the HPM system.The strength will have adverse effects,and attention should be paid to its dosage.Silica has little effect on the morphology of hydration products,and mainly plays the role of micro-aggregates and the later pozzolanic reaction.It is concluded that at normal temperature,fluorogypsum can replace natural anhydrite in HPM and is widely used in HPM system;at low temperature,adjust the ratio,such as reducing the ratio of gypsum/quick lime,and adding acertain amount of amount of aluminum sulfate or potassium aluminum sulfate dodecahydrate,fluorogypsum can be used in HPM system.