| Because of great energy consumption of China’s iron and steel industry, now forsaving energy, reducing consumption and recycling the sensible heat of blast furnaceslag with high efficiency, so it is necessery to develop a kind of new process of drygranulating that can substitute the traditional process of water-quenched granulating.Blast furnace slag, a kind of cementing material with latent activity, plays anincreasingly important role in the building materials industry and has become anindispensable functional material in the cement concrete. On the premise of currentchange of blast furnace slag granulation process, the quality and property of blastfurnace slag that made by newprocess of dry granulating has already become the issuethat causes the attention of many building materials researchers.Therefore, this articleaimed to study the quality performance of blast furnace slag which made by drygranulating process.Using the industrial limestone and fly ash as raw materials, the blast furnace slagwas prepared in the simulation condition of the actual slag-making process. Under thedifferent chemical composition of blast furnace slag, the influence on the structureand performance of blast furnace slag was studied with the uniform design method.Through regression analysis, The experimental results indicate that quaternaryalkalinity is the key factor that can affect the glass content of blast furnace slag. Thepriority of impact of three factors on the glass content of blast furnace slag isquaternary alkalinity> ratio of SiO2/Al2O3> ratio of CaO/MgO. Under the currentlaboratory conditions, the optimal composition of blast furnace slag is obtained. For7d and28d activity index regression analysis:7d activity index is mainly influencedby quaternary alkalinity and SiO2/Al2O3ratio, while28d activity index was mainlyaffected by SiO2/Al2O3ratio. Simultaneously, with the combination of XRD,TG-DTA, IR and other analytical tools, the relationship between the structurecharacteristic of the glass content, the degree and type of crystallization, thepolymerization degree of silicon-oxygen tetrahedron of blast furnace slag andhydraulic activity are discussed.Considering the formation process and cooling process of blast furnace slag, theexperiment first selected air-cooled way, then the method of orthogonal experimentwas used to study the influence of four different process conditions including heating rate, temperature of slag discharge, time of heat preservation of melt slag in hearthand cooling rate on the structure and performance of blast furnace slag. Then theinfluence law of each process conditionson on the properties of blast furnace slag wasobtained respectively. The optimum condition parameters of formation process ofblast furnace slag were also obtained. At the same time, the test of phase structure ondifferent technology conditions of blast furnace slag showed that raised thetemperature of slag discharge, speeded up cooling rate and prolonged the time of heatpreservation of melt slag in hearth can reduce the polymerization degree of silicateand aluminum ion of blast furnace slag.Importantly, the study reviews the relationship between glass contents andhydraulic activity of slag, the glass contents and hydraulic activity did not present agood positive correlation, just a right amount of crystallization in blast furnace slag isbeneficial to the hydraulic activity. In addition, combined with the previousexperimental results，phase diagram and TG-DTA analysis, the thermodynamics andproperties of main chemical reactions in blast furnace slag forming process arediscussed. The research provides a theoretical basis for the process and quality controlof blast furnace slag. |
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