The thermal decomposition of 3Mg（OH）2·MgCl2·8H2O （318MHCH） nanowires synthesized from agglom- erated Mg（OH）2 microspheres was investigated. The influence of heating rate and temperature on the composition and morphology of the products was investigated. Thermogravimetric-differential scan- ning calorimetry, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction showed that increasing the heating rate from I to 20 ℃/min promoted the escape of crystalline water from the 318MHCH nanowires. 318MHCH nanowires were dehydrated stepwise to 310MHCH porous nanowires from room temperature to 320℃, and then to MgO cubic nanoparticles from 420 to 700 ℃. The nanowires retained their one-dimensional morphology, until the phase changed to MgO. The immediate collapse of the one-dimensional structure was attributed to the presence of Mg-O/Cl chains.
Air quenched basic oxygen furnace steel slag （BOF-SS） is processed at very high cooling rate, which is expected to have different cementitious properties from conventional slowly cooled BOF-SS. For this purpose, the strength activity indexes of air quenched and slowly cooled BOF-SS are investigated. The results reveal that, under the specific surface area （S） of 490 m^2/kg, the compressive strength activity index reaches 1.24 after 28 days with replacement of 15% air quenched BOF-SS and reaches 1.05 after 28 days with replacement of 20% air quenched BOF-SS and 30%granulated blast furnace slag （GBFS）. The cementitious activity of air quenched BOF-SS is obviously higher than that of slowly cooled BOF-SS, mainly because it contains more C3 S and glassy phases.
Lei GANHai-feng WANGXiu-ping LIYuan-hong QIChun-xia ZHANG
