Utilization of cement kiln dust (CKD) to enhance mine tailings-based geopolymer bricks

This paper studies the feasibility of enhancing the physical and mechanical properties and the durability of copper mine tailings (MT)-based geopolymer bricks with cement kiln dust (CKD). The effects of CKD content (0-10%), sodium hydroxide (NaOH) concentration (10 and 15 M) and initial water content (12-20%) on unconfined compressive strength (UCS), water absorption, and weight and strength losses after immersion in water are studied. To shed light on the mechanism for the contribution of CKD to geopolymerization, microscopic and spectroscopic techniques including scanning electron microscopy/energy- dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy are used to investigate the micro/nanostructure and the elemental and phase composition of geopolymer brick specimens. The results show significant improvement of UCS and durability when CKD is used. Water absorption, however, slightly increases due to the hydration of Ca in the added CKD. The enhancement of UCS and durability is attributed to the improving effect of CKD on dissolution of aluminosilicate species, formation of CaCO₃, and integration of Ca into the geopolymer gel.