Abstract
AbstractRecycling of red mud (RM) has attracted more attention in recent years due to severe environmental problems caused by landfilling. The effect of composition optimization and Nano-strengthening on the properties of a binder based on RM was studied in this paper. Results showed that modifying ratios of main oxides and adding Nano-SiO2could obviously affect the mechanical properties and microstructure of the binder. Specimens with high SiO2/Al2O3molar ratio (S/A) displayed considerable increase in compressive strength, while decreasing Na2O/Al2O3molar ratio (N/A) improved the workability of the fresh mix. The compressive strength was developed significantly to be 45 MPa at 28 days by adding Nano-SiO2with 0.4 wt.% of RM. Phase transformation and microstructure change at different stages of RM decomposition and binder geopolyerization were investigated by X-ray diffraction (XRD), Fourier transformation infrared (FTIR) and Scanning electron microscopy (SEM). The results of this study may provide a prospective method to use RM more widely in construction applications.
Highlights
red mud (RM) is the main by-product for extracting alumina from bauxite ore using Bayer process
Phase transformation and microstructure change at different stages of RM decomposition and binder geopolyerization were investigated by X-ray diffraction (XRD), Fourier transformation infrared (FTIR) and Scanning electron microscopy (SEM)
Alkali Thermal Activation process was applied on raw RM to help improve its properties [42, 43, 49], and the chemical compositions of the mix were modified to get the optimum ratios for producing the binder
Summary
RM is the main by-product for extracting alumina from bauxite ore using Bayer process. The effect of RM characteristics on geopolymer is not satisfactory, as the mechanical properties of the binder deteriorated when the ratio between RM and other materials increased [44]. Alkali Thermal Activation process was applied on raw RM to help improve its properties [42, 43, 49], and the chemical compositions of the mix were modified to get the optimum ratios for producing the binder. In this research the Nano-SiO2 was added to suitable composition mix to augment the compressive strength. The early compressive strength of concrete made by a high volume of fly ash-cement mix has been influenced positively by adding Nano-SiO2 [58, 59]. Compressive strength test, XRD, FTIR and SEM were conducted to study the transformation in the structure of geopolymeric binder
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