| Chemical gypsum is one kind of industry solid waste.Because of its variety and difference sorts and contents of impurities in gypsum,like metallic ion,acid and organic substance,these is few efficient resource utilization method for chemical gypsum during industry production.Chemical gypsum is often dumped in vast stockpiles as waste.Unrecoverable damage is causing to the soil,air as well as the source of water around stacking area.High strength gypsum is a new kind green building material,it could be widely used in construction,medical,military,art and other fields.Compared to the traditional using method,converting chemical gypsum to high strength gypsum by salt solution reaction at atmosphere pressure is a resource utilization method with low cost and high added value.Presently,researches about salt solution method at atmosphere pressure are mainly focused on the influence of electrolyte and crystal modifier on?-HH synthesis reaction.The study about properties of raw material on reaction process and result is insufficient.For the questions above,this article is starting from preparation of the reaction raw material-high strength gypsum precursor,synthesis high strength precursor in different methods,then quantize the micro-properties through modern test equipment.For one thing,finding out the relationship between synthesis method and precursor properties.For another,synthesizing high strength gypsum with different micro-properties and macro-performance.Finally,analyzing the effect of precursor properties on the high strength gypsum synthesis reaction.The work and research results done in this article are as follows:1.Analyzed the high strength gypsum precursor synthesis chemical reaction from the perspective of kinetics and thermodynamics.Explained that synthesis temperature is the key factor influencing the chemical reaction rate,temperature and solution environment are main factors influencing precursor's solubility.Analyzed the high strength gypsum precursor producing process from the perspective of crystal nucleation and growth.Explained that temperature,supersaturation of the solute,crystal average surface energy and frequency factor mainly affect the nucleation process,while temperature and supersaturation of the solute is key factors that affect the growth process.2.FE-SEM,PSA and S230 conductivity meter were used to test and analysis the microstructure,particle size distribution and dissolution property of high strength gypsum precursor which was prepared in different condition.Experimental results show,when precursor synthesis temperature is between 50 and 60?,coalescence and adhesion is apt to happen among crystals.As the synthesis reaction extends,the average crystal size rise,however since the interaction between crystals,obvious growth could only be find after 10h reaction from PSD results.dissolution property is close related to crystal PSD.As the reactant concentration inclined from 0.10mol·L-1to 1.10mol·L-1,precursor's average crystal size decline firstly and then ascends.Besides,precursor dissolute rate rises in acid solution,especially the precursor produced in high reactant concentration.Impurities added to the reaction solution could not only affect chemical reaction process but also nucleation and growth process,thereby the microstructure,PSD and dissolute rate of high strength gypsum precursor are differed.3.Salt solution reaction results at atmosphere pressure shows,precursor's microstructure is related to the microstructure of?-HH,and we found a positive correlation the PSD of precursor and?-HH.Finally,precursor's dissolute rate is a critical factor whether salt solution reaction at atmosphere pressure could occur in the same reaction condition. |
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