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
We experimentally studied the interaction between pozzolanic material（fly ash） and dehydrated autoclaved aerated concrete（DAAC）. The DAAC powder was obtained by grinding aerated concrete waste to particles fi ner ...We experimentally studied the interaction between pozzolanic material（fly ash） and dehydrated autoclaved aerated concrete（DAAC）. The DAAC powder was obtained by grinding aerated concrete waste to particles fi ner than 75μm and was then heated to temperatures up to 900 ℃. New cementitious material was prepared by proportioning fly ash and DAAC, named as AF. X-ray diffraction（XRD） was employed to identify the crystalline phases of DAAC before and after rehydration. The hydration process of AF was analyzed by the heat of hydration and non-evaporable water content（Wn）. The experimental results show that the highest reactivity of DAAC can be obtained by calcining the powder at 700 ℃ and the dehydrated products are mainly β-C2 S and CaO. The cumulative heat of hydration and Wn was found to be strongly dependent on the replacement level of fl y ash, increasing the replacement level of fl y ash lowered them in AF. The strength contribution rates on pozzolanic effect of fl y ash in AF are always negative, showing a contrary tendency of that of cement-fl y ash system.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.51772226,51272193,51072150)
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.
基金Funded by the"863"National High-tech Research and Development Program of China(No.2012AA06A112)
文摘We experimentally studied the interaction between pozzolanic material（fly ash） and dehydrated autoclaved aerated concrete（DAAC）. The DAAC powder was obtained by grinding aerated concrete waste to particles fi ner than 75μm and was then heated to temperatures up to 900 ℃. New cementitious material was prepared by proportioning fly ash and DAAC, named as AF. X-ray diffraction（XRD） was employed to identify the crystalline phases of DAAC before and after rehydration. The hydration process of AF was analyzed by the heat of hydration and non-evaporable water content（Wn）. The experimental results show that the highest reactivity of DAAC can be obtained by calcining the powder at 700 ℃ and the dehydrated products are mainly β-C2 S and CaO. The cumulative heat of hydration and Wn was found to be strongly dependent on the replacement level of fl y ash, increasing the replacement level of fl y ash lowered them in AF. The strength contribution rates on pozzolanic effect of fl y ash in AF are always negative, showing a contrary tendency of that of cement-fl y ash system.
