Phase Reconstruction Of Manganese Slag And Research Of Its Cementitious Properties

Ferroalloy has deoxygenation, desulfurization, reduction and alloying effect duringiron and steel smelting industry. In recent years, with the rapid development ofChinese iron and steel industry, the demand of ferroalloy increased greatly, followedby a large number of ferromanganese, silicon manganese ferroalloy slag (referred asto manganese slag) was discharged. Manganese slag is essentially a slag which issimilar to granulated blast furnace slag (GBFS) with potential hydraulic activity.Because of its lower activity, its application in cement and concrete is limited;stacking of manganese slag not only takes up valuable land resources, but will alsocause soil and groundwater pollution, affecting human health. Thus, carrying out theactivity of manganese slag is important to stimulate research and industrialapplications in concrete.As we all known, the hydraulic activity of GGBS is closely related to its glassphase content and the glass network structure. In general, slag with the higher contentof glass phase, its hydration activity will be better than others. As the manganese slagis a kind of slag with high amount of MnO, therefore, the present study attempts toimprove the glass phase content of manganese slag and modify the network structureto improve its activity. By introducing phase modifiers and re-melting the manganeseslag, then cooling it using water quenching method to improve the glass phase contentof manganese slag. In addition, another reason which low activity of manganese slagis lack of the active mineral. Thus, another way to improve its activity is to increasethe active mineral content of manganese slag. Therefore, this study is based on largerdisplacement water quenched manganese slag in Guangxi province, with two thermalactivation methods, namely by increasing the content of the active minerals and glassphase to enhance the activity of manganese slag. In this research, B2O3, Na2CO3wereused as the phase modifier, on the one hand with its fluxing action to reduce themelting point of manganese slag; on the other hand, network structure of themanganese slag can be improved by them, and then improve the glass phase contentof manganese slag, thereby increasing the activity of manganese slag. The way how toenhance the mineral content of manganese slag would be: CaO is applied as anadjustment components, making it occur solid phase reaction with the originalsiliceous materials at a high temperature, prompting the formation of a large numberof belite phase.The results showed that, the glass transition temperature range of manganese slag isbetween850-900°C, after calcination at1100°C, there is significant crystallizationphenomenon, the mainly crystals precipitated is anorthite. Doping with15percent ofB2O3, calcined at1300°C, and holding for one hour, cooled by water quenching, theglass phase content exceeds95%. Its7d activity index is52.1%,28d activity indexreach81.7%, compared with the original manganese slag, the activity index improved16.5%. Mixing with10percent of sodium oxide, after calcination at1400°C,purification for one hour, manganese slag cooled by water quenching treatment has 98.5%of glass phase content, which7d activity index was62.4%,28d activity indexreached88.9%, compared with pre-treatment, the activity index improved23.7%.With the addition of40percent of CaO, calcination at1200°C conditions for one hour,cooled by air, the content of belite phase up to63.2%, its28d activity index was76.1%, compared with the pre-calcination treatment, little change in activity, whichmay be due to C2S has a lower hydration degree before the28day. Rietveldquantitative phase analyze of belite show the content of belite phase reach63.2%.Comparison of the two modified methods, difficult to find, modified manganese withthe method of raising the content of glass phase has a better hydration activity. Thisresearch can provide a theoretical reference for resource utilization manganese slagand other low activity of metallurgical slag.