Pilot Study On Preparation Of Quasi-Sulphaluminate Cement With Electrolytic Manganese Slag

Electrolytic Manganese Slag (EMS) is a kind of industrial solid waste with high water content generated from electrolyzing the manganese carbonate with sulphuric acid. During this process, serious contamination to the environment was caused. As a high-sulphate-content clay-like material, there is always a bad lack of breakthrough in its utilization. What's more, there are lots of misunderstandings of its fundamental properties. According to its chemical compositions, EMS can be used uttely well in preparation of quasi-sulphaluminate cement.The basic properties, especially the states of sulphate of EMS were pilotly studied by various of analytic methods in eye of its utilization as a building material. The quasi-sulphaluminate cement was prepared and its property was primarily studied. Meanwhile, much attention was paid on sulphates decomposing and stablization during incineration.Results showed that: (1) EMS is a kind aluminate-silicate mineral with a high sulphate content (as much as 20%/wt%, in name of SO3 ). Well crystalized quartz,mullite,hematite are the main mineral phases. Gypsum is not the unique pattern of sulphate in EMS as generally reported. The resolvable sulphates consist about 25% of the total, and it contributes priorly to the dissolving behavior of sulphates. Moreover, the fineness of the particles, 80% of which are smaller than 100μm, contributes to a fine dispersion of raw materials when mixing. (2)The cement with the main phases calcium sulphoaluminate,dicalcium silicate,anhydrite can be obtained by rational mixing of raw materials, the introduction of aluminate-bearing material is directly contribute to the formation of calcium aluminate. (3) Various factors may affect the burnability of the raw materials. Results showed a high strength clinker can be obtained when sintered at 1200℃, 30min. (4) The sulphate decomposing ratio of EMS may reach 90%, while with the combination of lime stone and kaolin, it falled to less than 50% due to the formation of sulfate-solidifier. (5) The alkalinity of the material changes widely according to the alkalinity coefficient of material preparation, the pH value of the quasi-sulphaluminate cement may be 2 less than that of OPC at early ages while the 56d alkalinity can be the same.(6) There is a tight relation between the setting time of clinker and raw material proportion. The initial setting time may be about 1h or less than 20min when the alkalinity coefficient of the clinker is 0.66 or more than 0.77 respectively. The optimal incinerating temperature,gypsum dosage should be choosen practically, a cementious material with a compressive strength of 50MPa at 28d can be obtained after a rational preparing of raw materials. The remained free lime mainly contribut to the early expansion of the binder when meets water.The results indicated that a high strength of cementious material can be obtained by sintering large amount of EMS at a relative low temperature, which pave an effective way for handling the environmental problems caused by the residue.