Preparation of Geopolymer by Red Mud-slag-superfine Calcium Oxide and Its Mechanical Properties
In order to improve the utilization rate of red mud,slag and other solid waste resources,geopolymer cementing materials(C-R-S geopolymer)with red mud,slag and superfine calcium oxide as main raw materials was prepared.The effects of calcium oxide content,red mud content,activator(sodium silicate)modulus,activator(sodium silicate)content,water-binder ratio and curing temperature on the properties of geopolymer were studied.The microstructure and polymerization mechanism were analyzed by scanning electron microscope(SEM),three-dimensional CT,thermoactive microcalorimetry,X-ray diffraction(XRD)and Fourier transform infrared spectrometer(FTIR).The results showed that the mechanical properties of C-R-S geopolymer were enhanced by the addition of ultrafine CaO.When the content of red mud is 40%,the content of ultrafine calcium oxide is 5%,the modulus of activator is 1.25,the content of activator is 20%,and the water-binder ratio is 0.45,its mechanical properties are the best,with a compressive strength of 71.4 MPa and a flexural strength of 9.2 MPa.High temperature curing can improve the mechanical properties of C-R-S polymer.The microscopic morphology of C-R-S geopolymer is a lamellar structure with nanoholes,and the holes and cracks are small under three-dimensional CT.The analysis of heat flow evolution shows that the addition of ultrafine CaO can advance the heat release of hydration and accelerate the polymerization of the system.XRD and FTIR showed that the C-R-S geoplymer mainly existed in the form of calcite,suolunite,hematite,calcium nephelite,C2S,C3S.Many hydration products of C-S-H were formed in the hydration process.
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