C-S-H series are synthesized at different temperatures and ages by pozzolanic reaction.The change of particle size distribution,phase composition,morphology and nanostructure of C-S-H with temperatures and ages,and th...C-S-H series are synthesized at different temperatures and ages by pozzolanic reaction.The change of particle size distribution,phase composition,morphology and nanostructure of C-S-H with temperatures and ages,and the effects of C-S-H seeds and seeds parameters on the hydration behavior and mechanical properties development of cement were investigated by DLS,XRD,SEM,^(29)Si NMR,TAM-air isothermal calorimeter and mechanical properties test.The results show that the particle size,crystallinity,basal spacing and Q^(2)/Q^(1) ratio of C-S-H increases with the increase of synthesis temperature and age.The addition of synthesized C-S-H seeds to cement pastes results in the strong acceleration effect on cement hydration and significant improvement of the early strength of cement paste and mortar.The 1 day-C-S-H seeds synthesized at room temperature can increase the strength of cement paste by about 30 MPa at 12 h.The effect does not show a very regular change with the increase of the temperature and age of seeds synthesis.Considering the effect of C-S-H seeds on the hydration and mechanical properties of cement,and economy and short cycle of seeds synthesis,the C-S-H seeds synthesized at room temperature for 1 day or 55 ℃ water bath for 12 hours is recommended..展开更多
Calcium silicate hydrate（C-S-H） with Ca/Si ratio 1.0 was prepared via precipitation in solution and heated at various temperatures to investigate its dehydration behavior. The dehydration, structural collapse and re...Calcium silicate hydrate（C-S-H） with Ca/Si ratio 1.0 was prepared via precipitation in solution and heated at various temperatures to investigate its dehydration behavior. The dehydration, structural collapse and recrystallization characteristics of C-S-H and its microstructural change during heating process were investigated by XRD, SEM, Raman and TG-DSC techniques. C-S-H gradually lost non-evaporable water upon heating, about 50% and 80% non-evaporable water was removed below 200 and 400 ℃, respectively, and the rest was removed up to about 1 000 ℃. At 400 ℃, dehydrated C-S-H exhibited the increasing disordering of calcium/silicon environment and the decreasing symmetrical bending vibration of Si-O-Si of Q^2 silicate chains. At 650 ℃ non-bridging oxygen atoms（O（non）） attached to silicon were almost removed, and significant structural change occurred, and at 815 ℃ C-S-H dehydrated to wollastonite.展开更多
Characteristics of the Kelvin-Helmholtz （KH） instability of the interfaces formed by two semi-infinitely distributed fluids and one interlayer were studied. It was found that the coupling effects between theinterfac...Characteristics of the Kelvin-Helmholtz （KH） instability of the interfaces formed by two semi-infinitely distributed fluids and one interlayer were studied. It was found that the coupling effects between theinterfaces should be considered if the interlayer thickness was less than 0. 5 times of the disturbation wave-length. And the degenerate modes could be produced in the situation with proper parameters.展开更多
基金Funded by National Key R&D Program of China(No.2017YFB0310001)the National Natural Science Foundation of China(Nos.51772226,51972249,51872216)。
文摘C-S-H series are synthesized at different temperatures and ages by pozzolanic reaction.The change of particle size distribution,phase composition,morphology and nanostructure of C-S-H with temperatures and ages,and the effects of C-S-H seeds and seeds parameters on the hydration behavior and mechanical properties development of cement were investigated by DLS,XRD,SEM,^(29)Si NMR,TAM-air isothermal calorimeter and mechanical properties test.The results show that the particle size,crystallinity,basal spacing and Q^(2)/Q^(1) ratio of C-S-H increases with the increase of synthesis temperature and age.The addition of synthesized C-S-H seeds to cement pastes results in the strong acceleration effect on cement hydration and significant improvement of the early strength of cement paste and mortar.The 1 day-C-S-H seeds synthesized at room temperature can increase the strength of cement paste by about 30 MPa at 12 h.The effect does not show a very regular change with the increase of the temperature and age of seeds synthesis.Considering the effect of C-S-H seeds on the hydration and mechanical properties of cement,and economy and short cycle of seeds synthesis,the C-S-H seeds synthesized at room temperature for 1 day or 55 ℃ water bath for 12 hours is recommended..
基金Funded by National Key R&D Program of China(No.2017YFB0310001)the National Natural Science Foundation of China(Nos.51772226,51272193,51072150)
文摘Calcium silicate hydrate（C-S-H） with Ca/Si ratio 1.0 was prepared via precipitation in solution and heated at various temperatures to investigate its dehydration behavior. The dehydration, structural collapse and recrystallization characteristics of C-S-H and its microstructural change during heating process were investigated by XRD, SEM, Raman and TG-DSC techniques. C-S-H gradually lost non-evaporable water upon heating, about 50% and 80% non-evaporable water was removed below 200 and 400 ℃, respectively, and the rest was removed up to about 1 000 ℃. At 400 ℃, dehydrated C-S-H exhibited the increasing disordering of calcium/silicon environment and the decreasing symmetrical bending vibration of Si-O-Si of Q^2 silicate chains. At 650 ℃ non-bridging oxygen atoms（O（non）） attached to silicon were almost removed, and significant structural change occurred, and at 815 ℃ C-S-H dehydrated to wollastonite.
文摘Characteristics of the Kelvin-Helmholtz （KH） instability of the interfaces formed by two semi-infinitely distributed fluids and one interlayer were studied. It was found that the coupling effects between theinterfaces should be considered if the interlayer thickness was less than 0. 5 times of the disturbation wave-length. And the degenerate modes could be produced in the situation with proper parameters.
