The chemical composition and mineral structure of fluorgypsum as well as its harm to application in cement were elaborately analyzed. The primary fluorgypsum was modified and its applications in cement＇s production w...The chemical composition and mineral structure of fluorgypsum as well as its harm to application in cement were elaborately analyzed. The primary fluorgypsum was modified and its applications in cement＇s production were studied. The technological flow chart of preparing modified fluorgypsum was given. Experimental results indicate that hydration ratio the modified fluorgypsum through adding compound additive for 14d is about 70%. The modified fluorgypsum as cement retarder has certain stimulation to fly ash and increases the strength of compound cement. In addition, its adding amount is lower than that of natural gypsum. The modified fluorgypsum is a good substitute for natural gypsum.展开更多
The properties and microscopic structure of tailings solidification bodies, the hardening mechanism of the fluorgypsum-based binder material （FBBM） and tailings solidification mechanism were investigated. FBBM consi...The properties and microscopic structure of tailings solidification bodies, the hardening mechanism of the fluorgypsum-based binder material （FBBM） and tailings solidification mechanism were investigated. FBBM consisted of 40% fluorgypsum,25%-50% blast furnace slag,10%-35% ordinary Portland cement clinker（OPCC） and 1% activator, which was good material in binding iron ore tailings.XRD analysis showed that the properties of tailings solidification bodies was related to its ettringite content.SEM and XRD analyses of tailings solidification bodies showed that the chemical reaction was produced between FBBM and tailings in the whole hydration process. The hydration of the resulting gel material covered the surface of the tailings particles and formed a gel structure. A large number of ettringite crystals and the remaining board-like gypsum crystals took each end and constituted the structural skeleton. The filamentous network-like calcium-silicate-hydrate（C-S-H） gel bonded firmly together with ettringite crystals, dehydrated gypsum crystals and granular tailings, and formed an extremely dense whole.展开更多
The mechanism of activator to fluorgypsum and the fluorine solidification were investigated by the performances of composite binding material.Through the setting time testing of fluorgypsum with NaOH,Na2SO4 and NaF,th...The mechanism of activator to fluorgypsum and the fluorine solidification were investigated by the performances of composite binding material.Through the setting time testing of fluorgypsum with NaOH,Na2SO4 and NaF,the least activator dosage were all 1%.And the cementitious material over 80% of fluorgypsum was processed to improve its quality with slag,fly ash and clinker.The maximum compressive strength of composite binding material was over 12.90 MPa in 28 days,and the concentration of fluroride reduced 64.7% which compared with the pure fluorgypsum binding material.Analysis of X-ray diffraction and scanning electron microscopy images showed that ettringite crystals,dihydrate gypsum crystals and C-S-H gel were filled with each other.The unreacted CaF2 crystals were embedded by a great deal of network and filamentous C-S-H gel.It was the main reason that the composite binding material strength improved,water resistance increased and leaching toxicity reduced.展开更多
基金the National Natural Science Foundation of China(No.20471046)
文摘The chemical composition and mineral structure of fluorgypsum as well as its harm to application in cement were elaborately analyzed. The primary fluorgypsum was modified and its applications in cement＇s production were studied. The technological flow chart of preparing modified fluorgypsum was given. Experimental results indicate that hydration ratio the modified fluorgypsum through adding compound additive for 14d is about 70%. The modified fluorgypsum as cement retarder has certain stimulation to fly ash and increases the strength of compound cement. In addition, its adding amount is lower than that of natural gypsum. The modified fluorgypsum is a good substitute for natural gypsum.
基金Funded by the National High Technology Research and Development Program (863 Project) (No.2009AA064004)the Fundamental Research Funds for the Central Universities (No.5082011 and No.1104003)
文摘The properties and microscopic structure of tailings solidification bodies, the hardening mechanism of the fluorgypsum-based binder material （FBBM） and tailings solidification mechanism were investigated. FBBM consisted of 40% fluorgypsum,25%-50% blast furnace slag,10%-35% ordinary Portland cement clinker（OPCC） and 1% activator, which was good material in binding iron ore tailings.XRD analysis showed that the properties of tailings solidification bodies was related to its ettringite content.SEM and XRD analyses of tailings solidification bodies showed that the chemical reaction was produced between FBBM and tailings in the whole hydration process. The hydration of the resulting gel material covered the surface of the tailings particles and formed a gel structure. A large number of ettringite crystals and the remaining board-like gypsum crystals took each end and constituted the structural skeleton. The filamentous network-like calcium-silicate-hydrate（C-S-H） gel bonded firmly together with ettringite crystals, dehydrated gypsum crystals and granular tailings, and formed an extremely dense whole.
基金Funded by National High-Tech Research and Development Program of China (863 Program) (No.2009AA064004)
文摘The mechanism of activator to fluorgypsum and the fluorine solidification were investigated by the performances of composite binding material.Through the setting time testing of fluorgypsum with NaOH,Na2SO4 and NaF,the least activator dosage were all 1%.And the cementitious material over 80% of fluorgypsum was processed to improve its quality with slag,fly ash and clinker.The maximum compressive strength of composite binding material was over 12.90 MPa in 28 days,and the concentration of fluroride reduced 64.7% which compared with the pure fluorgypsum binding material.Analysis of X-ray diffraction and scanning electron microscopy images showed that ettringite crystals,dihydrate gypsum crystals and C-S-H gel were filled with each other.The unreacted CaF2 crystals were embedded by a great deal of network and filamentous C-S-H gel.It was the main reason that the composite binding material strength improved,water resistance increased and leaching toxicity reduced.
