Mu Song

From a View of Alkali Solution: Alkali Concentration to Determine Hydration Process of Alkali Activating Metakaolin

With increasing concerns on concept of sustainability from the world, alkali activating binder materials has gained lots of concerns from academy and industry. However, hydration mechanism of alkali activating metakaolin is still not clearly understood. As a key component of alkali activating binder material, role of alkali solution and its action mechanism on hydration of alkali activating metakaolin are reported rarely. The present research studied influence of alkali concentration on hydration process and microstructure formation of alkali activating metakaolin. Penetration resistance, setting time, compressive strength, hydration heat, and scanning electron microscope, were adopted to reveal the hydration process influenced by concentration of alkali solution. Results show that high concentration of alkali solution accelerated hydration process of metakaolin, but over high concentration was resulted in a decreasing trend of compressive strength in the entire age of 60 days.

Experimental Study on Utilization of Quartz Mill Tailings as a Filler to Prepare Geopolymer

ABSTRACT Quartz mill tailings are produced in a huge amount per year in China. Therefore, now there is an urgent demand for utilization of the quartz mill. In the present research, the quartz mill tailings were used as a filler for metakaolin-based geopolymer to restraint the shrinkage and improve mechanical property. This work studied the influence of quartz mill tailings on the properties of geopolymer prepared by alkali-activated metakaolin. Performance of geopolymer incorporated with quartz mill tailings were addressed in terms of workability, compressive and flexural strength, and drying shrinkage at different ages. Further, X-ray Diffraction, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Mercury Intrusion Porosimetry (MIP) were applied to investigate the relevant microstructure. The results indicated that addition of quartz mill tailings increased the viscosity of the paste, and meanwhile decreased the flowability of geopolymer. Up to 20% of the tailings can replaces metakaolin to prepare geopolymer without a negative effect on the mechanical property. Up to 30% of quartz mill tailings had a role to decrease the drying shrinkage. Besides, weight loss ratio of geopolymer decreased gradually with increasing dosage of the quartz mill tailings. Addition of the quartz mill tailings did not change the mineral composition of alkali-activated metakaolin, and meanwhile the amorphous or semi-crystalline phase has been found. MIP and FTIR results showed that moderate addition of quartz mill tailings optimized the microstructure of geopolymer. Therefore, quartz mill tailings can replace metakaolin up to 20% to prepare geopolymer.