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
Hydrided Mg-3Ni-2MnO2 composite powders were fabricated by reactive ball milling with hydrogen, and accumulative hydrogenation kinetics and temperature field of reaction bed with various porosities (0.37, 0.53 and 0.6...Hydrided Mg-3Ni-2MnO2 composite powders were fabricated by reactive ball milling with hydrogen, and accumulative hydrogenation kinetics and temperature field of reaction bed with various porosities (0.37, 0.53 and 0.63) were measured. The results show that the accumulative hydrogenation kinetics of Mg-3Ni-2MnO2 powder reaction bed depends strongly on the effect of heat transfer, mass transfer and intrinsic reaction together. The reaction bed with the porosity of 0.53 exhibits the largest hydrogenation rate. During the hydrogenation process, the temperature of reaction bed rises quickly due to the fast release of heat, and the temperature difference between center and wall with 0.53 porosity can keep high even for a long time, which promotes fast heat transfer. The further analysis indicates that more emphases should be put on heat transfer rate rather than the only improvement of the effective thermal conductivity.展开更多
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.
基金Projects(2006126, 2006130 and 2008GG10007004) supported by the Science & Technology Plan of Shandong Province, China
文摘Hydrided Mg-3Ni-2MnO2 composite powders were fabricated by reactive ball milling with hydrogen, and accumulative hydrogenation kinetics and temperature field of reaction bed with various porosities (0.37, 0.53 and 0.63) were measured. The results show that the accumulative hydrogenation kinetics of Mg-3Ni-2MnO2 powder reaction bed depends strongly on the effect of heat transfer, mass transfer and intrinsic reaction together. The reaction bed with the porosity of 0.53 exhibits the largest hydrogenation rate. During the hydrogenation process, the temperature of reaction bed rises quickly due to the fast release of heat, and the temperature difference between center and wall with 0.53 porosity can keep high even for a long time, which promotes fast heat transfer. The further analysis indicates that more emphases should be put on heat transfer rate rather than the only improvement of the effective thermal conductivity.
