The bioactive α-Ca3（ PO4 ）2 bone cement was studied by XRD , SEM and isothermal calorimetric measurements. The results showed that a mixed pattern of TCP and hydroxylapatite were obtained after hydration and harden...The bioactive α-Ca3（ PO4 ）2 bone cement was studied by XRD , SEM and isothermal calorimetric measurements. The results showed that a mixed pattern of TCP and hydroxylapatite were obtained after hydration and hardening. The mechanism of hydration and hardening of the α-Ca3 （ PO4）2 was dissolution-precipitation, （ NH4 ） 112 PO4 was the best set accelerator to the α-Ca3 （ PO4）2 cement, and the HAP powers and the （ NH4）H2 PO4 concentration had a great effect on the hydration rate of a-Ca3（ PO4）2.展开更多
Setting time and strength of sulphoaluminate rapid hardening cement （SAC） incorporated in the presence and absence of silica fume （SF） were determined. Combined with the techniques of＂ isothermal calorimeter, XRD...Setting time and strength of sulphoaluminate rapid hardening cement （SAC） incorporated in the presence and absence of silica fume （SF） were determined. Combined with the techniques of＂ isothermal calorimeter, XRD and FSEM, the hydration kinetics of the two systems and the effect mechanism of SF on SAC were investigated. The experimental results showed that SF was proved to be beneficial for SAC system, in terms of setting time and late strength gain. Evidence of accelerator effect of silica fume was found during the first 8 hours of hydration. The formation of AFt was accelerated and the microstructure of the hydration products grew denser with incorporation of SF. SF was proved to play the role of dispersion and setting control at early age and had a greater contribution to later strength due to the increment of crystal nucleation point and the pozzolanic activity. Therefore, SF can be used to not only control the hydration kinetics of SAC, but also develop the late strength and improve the microstructure.展开更多
This scientific paper gives consideration to the information on the contemporary structure of binary systems and three-component CaO-Al_2O_3-ZrO_2 system required to select rational parameters for the synthesis of cem...This scientific paper gives consideration to the information on the contemporary structure of binary systems and three-component CaO-Al_2O_3-ZrO_2 system required to select rational parameters for the synthesis of cementing agents.The production process of experimental clinker that has a Ca_7Al_6ZrO_（18） composition has been described.The data of X-ray phase analysis and petrographic analysis of the experimental composition of special cement have been given and the reasons for availability of inappropriate phases have been analyzed.The processes of hydration hardening of the cement stone have been studied and the data of differential thermal analysis were used for the establishment of the hydration mechanism for basic crystal phases in the cement clinker composition.The differences in the hydration processes of experimental special cement were analyzed in comparison with known mechanisms.A possibility of the exploitation of special binder in contact with ZrO_2（CaO-stabilized）was tested using the specimens of fine concrete that were subjected to thermal treatment in different modes.The physical and mechanical properties of specimens and the mineralogical composition of concretes were given based on the data of X-ray analysis and the petrographic analysis.The cement additive was selected and its amount in the concrete composition was defined to slow-down the hardening and the mixture plasticization time.The relationships of physical and mechanical characteristics of concrete specimens were defined experimentally as a function of granulometric composition of the filler and thermal treatment temperature.The investigation data of corrosion resistance obtained using the static method were used to find out if experimental concretes can operate in contact with the steel-smelting alkaline slag.展开更多
文摘The bioactive α-Ca3（ PO4 ）2 bone cement was studied by XRD , SEM and isothermal calorimetric measurements. The results showed that a mixed pattern of TCP and hydroxylapatite were obtained after hydration and hardening. The mechanism of hydration and hardening of the α-Ca3 （ PO4）2 was dissolution-precipitation, （ NH4 ） 112 PO4 was the best set accelerator to the α-Ca3 （ PO4）2 cement, and the HAP powers and the （ NH4）H2 PO4 concentration had a great effect on the hydration rate of a-Ca3（ PO4）2.
基金Funded by the National Natural Science Foundation of China(Nos.51379163 and 51372184)the National Key Research Program(973 Program)(No.2013CB035901)
文摘Setting time and strength of sulphoaluminate rapid hardening cement （SAC） incorporated in the presence and absence of silica fume （SF） were determined. Combined with the techniques of＂ isothermal calorimeter, XRD and FSEM, the hydration kinetics of the two systems and the effect mechanism of SF on SAC were investigated. The experimental results showed that SF was proved to be beneficial for SAC system, in terms of setting time and late strength gain. Evidence of accelerator effect of silica fume was found during the first 8 hours of hydration. The formation of AFt was accelerated and the microstructure of the hydration products grew denser with incorporation of SF. SF was proved to play the role of dispersion and setting control at early age and had a greater contribution to later strength due to the increment of crystal nucleation point and the pozzolanic activity. Therefore, SF can be used to not only control the hydration kinetics of SAC, but also develop the late strength and improve the microstructure.
文摘This scientific paper gives consideration to the information on the contemporary structure of binary systems and three-component CaO-Al_2O_3-ZrO_2 system required to select rational parameters for the synthesis of cementing agents.The production process of experimental clinker that has a Ca_7Al_6ZrO_（18） composition has been described.The data of X-ray phase analysis and petrographic analysis of the experimental composition of special cement have been given and the reasons for availability of inappropriate phases have been analyzed.The processes of hydration hardening of the cement stone have been studied and the data of differential thermal analysis were used for the establishment of the hydration mechanism for basic crystal phases in the cement clinker composition.The differences in the hydration processes of experimental special cement were analyzed in comparison with known mechanisms.A possibility of the exploitation of special binder in contact with ZrO_2（CaO-stabilized）was tested using the specimens of fine concrete that were subjected to thermal treatment in different modes.The physical and mechanical properties of specimens and the mineralogical composition of concretes were given based on the data of X-ray analysis and the petrographic analysis.The cement additive was selected and its amount in the concrete composition was defined to slow-down the hardening and the mixture plasticization time.The relationships of physical and mechanical characteristics of concrete specimens were defined experimentally as a function of granulometric composition of the filler and thermal treatment temperature.The investigation data of corrosion resistance obtained using the static method were used to find out if experimental concretes can operate in contact with the steel-smelting alkaline slag.
