Mechanical Properties and Hydration Characteristics of Red Mud-metakaolin Composite Cement Mortar.

This research uses Bayer red mud, metakaolin and cement as raw materials. In order to analyze the influence of Bayer red mud and metakaolin admixture on the mechanical properties of cement mortar, cement mortar is prepared by Bayer process red mud and metakaolin in different mixing ratios. The composite cement mortar were characterized the phase composition and micro morphology by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR) and scanning electron microscopy (SEM). The results show that the 28 d compressive strength of cement mortar reaches 47.38 MPa when the content of red mud is 10% and metakaolin is 10%. As the active SiO₂ and Al₂O₃ in the red mud and metakaolin are mixed into the excess Ca(OH)₂, the secondary hydration reaction will generate C-S-H and gismondine (CaAl₂Si₂O8·4H₂O) to fill the internal voids, increasing the structural compactness, which improves the compactness of the structure and is beneficial to the mechanics of the composite cement mortar. [ABSTRACT FROM AUTHOR]