Study on the effect of thermal activation temperature on Bayer method red mud-cement based composite mortar
In order to improve the utilization of Bayer red mud in cementitious materials,it modified the phase composition and dissolved alkali capacity of Bayer red mud by high-temperature thermal activation,and investigated the effect law of incorporation of thermally activated modified red mud at different temperatures on the mechanical strength,mineral phase composition and microscopic morphology of red mud-cement composite mortar.The results showed that the decomposition of mineral phases such as calcium chalcocite and calcite in Bayer method red mud after thermal activation treatment from 500 ℃ to 800 ℃ helped to promote the dissolution of free alkali Na+and increased the leachate pH from 11.13 to 11.59.When the admixture of 20％Bayer red mud was added,the working performance of the composite mortar decreased with the increase of the thermal activation temperature of Bayer red mud,and the 28 d compressive strength showed a trend of first increasing and then decreasing.Among them,the 28 d compressive strength of the composite mortar specimens mixed with 700 ℃ thermally activated red mud was the highest,reaching 46.5 MPa,which increased by 15.38％compared with that of the composite mortar mixed with non-thermally activated red mud.It is mainly because the hard alumina in red mud is decomposed into more active amorphous alumina by high temperature thermal activation,and the increased alkaline ion content in red mud can better stimulate the hydration reaction of active minerals in the slurry,and the reaction generates more AFt and C-S-H gels,which makes the microstructure of the specimen more dense and more conducive to the development of mechanical strength at a later stage.
heat activationBayer red mudcomposite mortarworkabilitymechanical properties
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