| Steel slag has the similar composition with cement, which its primary oxide compositions are SiO2, CaO; hydraulic binding materials are C2S, C3S, and C3A. The application value from hydration heat point was researched when steel slag was used as cementitious material; hydration control mechanism from kinetics point was discussed; in order to improve the content of steel slag in gel materials, the improved methods of volumetric stability and early strength were studied in this paper.Hydration heat emission rate curve of complex binder with steel slag from Xinyu and cement was similar with the cement's, which involved pre-induction period, induction period, acceleratory period, deceleration period and stabilization period. When adding quantities of steel slag were 20%, 30%,40%, in the early hydration stage, steel slag had inhibiting effect to the early hydration of cement. When the content of steel slag was 0-40%, with the increase of steel slag, hydration heat emission rate of acceleratory period reduced, hydration heat reduced. Steel slag could reduce the hydration heat, thermal stress and probability of crack appearance. The strength of composition binder would be reduced when the content of steel slag was too high. When the content of steel slag was 0-40%, with the increase of steel slag, the density of paste reduced when it had hydrated for 12 h. While paste sample of cement-based composite binder mixed with 40% steel slag still could not harden into shape. When the amounts of steel slag were 0%,20%, 30%, the order of the hydration approach was nucleation and crystal growth(NG)?interactions at phase boundaries(?)?diffusion(D). The hydration process did not meet Krstulovic-Dabic kinetic model when the steel slag content was 40%. When 0%?30% cements was replaced by steel slag, the reaction rate constant KNG, KI, KD of composite binder all reduced.When the water-binder ratios were 0.35,0.45,0.55,0.65, the early hydration heat emission of complex binder with steel slag from 25% Xinyu and 75% cement reduced with the increase of water-binder ratio, and the gap decreased on the late stage. It had hydrated fully when the water-binder ratio was 0.35. The order of the hydration approach was nucleation and crystal growth(NG)?interactions at phase boundaries(?)?diffusion(D), when the water-binder ratios were 0.35,0.45,0.55,0.65. The reaction rate constant KNG, KI, KD of composite binder all reduced, and the structure of the paste were gradually loosened with the increase of water-binder ratio.The expansion rate of steel slag-cement complex binder could be reduced by increasing specific surface area of refining slag from Shagang. Compared with the steel slag whose specific surface area was 454.99 m2·kg-1, the expansion rate after boiling decreased by 72.14% and autoclave expansion rate reduced by 51.40% when specific surface area of steel slag was 598.43 m2·kg-1 and the same content of steel slag was 10%. The structure of paste was more compact in the SEM microtopography when increasing the specific surface area of steel slag. According to the grey correlation degree analysis, when the hydration condition was boiling and autoclaved test, the grey correlation degree about expansion and content of steel slag were 0.7027 and 0.8225, while the grey correlation degree concerning expansion and specific surface area of steel slag were 0.6081 and 0.5536, which indicated that the content of steel slag had the greater influences on expansion.When vibrating time was 160 s,3 d,7 d compressive strength of mortar with 30% steel slag from Jiujiang and 70% cement complex binder obtained maximum. The compressive strength and flexural strength decreased with the increase of water-binder ratio when the water-binder ratios were 0.40,0.45, 0.50 and 0.55. According to the grey correlation degree analysis, water-binder ratio had a greater influence on the compressive strength and flexural strength compared with the vibrating time. Under the premise of reducing water-to-binder ratios, selecting the appropriate vibrating time could increase the content of steel slag. |
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