Study On Preparation Of Geopolymers With Kaolin And Steel Slags

Geopolymer is a new sort of inorganic and environmental friendly binding material withthree dimension network structure composed of SiO4and AlO4. It’s superior to Portland cementin many respects, and has broad application prospects.Kaolin was thermally activated with the addition of sodium hydroxide through solidreactions to form Si and Al precursors. Kaolin based geopolymers were synthesised byhydration of the formed precursors, and geopolymeric materials based on steel slags and kaolinwere prepared by hydration of a mixture of the precursors and steel slags. The surface bonding,mineralogy, and microstructure and morphology of the raw material, activated products andsynthesized geopolymers were fully characterized by using Fourier Transform InfraredSpectroscopy (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM).Kaolin was melted with100%NaOH (mass ratio referring to kaolin) at950°C for35minand then pulverized after cooling in the air. The formed precursors were moulded after wateraddition, and cured at100%moisture, forming geopolymers with sound compressive strength.The bonding information shows that the ordered kaolin structure collapsed during thermalactivation with NaOH, generating less ordered Al and Si precursors. Reacting with water, the Aland Si precursors polymerized to form more ordered geopolymers of continuous threedimensional–Si-O-Si(Al) structures.5wt.%Si and Al precursors (formed by thermally activated of kaolin with the addition ofNaOH at mass ratio of1:1) with95wt.%steel slags were mixed. The mixture was molded bypressing after water addition, and cured at100%moisture, forming geopolymeric materialswith better compressive strength. The compressive strength at3d,7d and28d were20MPa,30MPa and31.4MPa, respectively. And the compressive strength at28d reached the nonbearingwall material level MU30.The bonding information shows that three dimensional Si(Al)-Ostructures of geopolymer were generated during the hydration reaction; calcium silicate in thesteel slags was alkali-activated to form C-S-H structures and the other substance as fillingmaterials well increased the compressive strength.