Porous Properties of Silica Prepared by Selective Acid Leaching of Heat-Treated Vermiculite

The porous properties of silica prepared from heat-treated Transvaal vermiculite (South Africa) by acid leaching were determined. The effect of temperature on the destruction of the crystal structure of the vermiculite was determined, leading to the adoption of heating conditions of 600 o C for 2 h which produce a fully amorphous sample. The heat-treated samples were leached with 2M hydrochloric acid at 80 o C for 0.5, 2 and 8 h and their porous properties were characterized by measuring their specific surface areas and pore volumes. The highest surface area and pore volume (559 m2/g and 0.51 ml/g) was obtained for the sample leached for 8 h. Thermal amorphisation of vermiculite exerts a negative influence on the porous properties of the mineral

Characterisation of various fly ashes from Australia and Mongolia and their utilisation for preparation of Geopolymers with advanced applications

Fly ashes from different power stations of the Australia (Collie, Eraring, Tarong) and Mongolia (Darkhan, 3rd and 4th thermal power stations, Ulaanbaatar city) have been characterised by different techniques. It was determined that the Australian fly ashes are class F while most of Mongolian fly ash is class C. Due to their chemical and mineralogical differences the fly ashes behave differently when alkali activated to make geopolymers. The influences of various parameters on the preparation of geopolymers have been investigated and established for routine manufacture. The applicability of using fly ash for building structural elements, acid and alkaline resistant products and thermal resistance materials will be presented

Fly ash based geopolymer thin coatings on metal substrates and its thermal evaluation

Class F fly ash based Na-geopolymer formulations have been applied as fire resistant coatings on steel.The main variables for the coating formulations were Si: Al molar and water: cement weight ratios. Wehave determined that the adhesive strength of the coatings strongly depend on geopolymer composition.The ease with which geopolymer can be applied onto metal surfaces and the resultant thickness depend on the water content of the formulation. Adhesive strengths of greater than 3.5MPa have been achieved on mild steel surfaces for compositions with Si:Al of 3.5. Microstructure evolution and thermal properties of the optimised coating formulations show that they have very promising fire resistant characteristics

Characterisation of class F fly ash geopolymer pastes immersed in acid and alkaline solutions

Acid and alkaline resistance of class F fly ash based geopolymer pastes has been investigated. As prepared geopolymers showed high solubility in both strong alkali and acid solutions. Calcination of the fly ash based geopolymers at 600 C resulted in a decrease of amorphous component from 63.4 to 61.6 wt.%. However, the solubility of the Al, Si and Fe ions in 14 M NaOH and 18% HCl after 5 days immersion decreased from 1.3 to 16-fold in comparison to as prepared geopolymer samples. Calcination of the geopolymers also resulted in a 30% reduction in compressive strength. Acid and alkali resistance of the geopolymers investigated strongly depends on mineralogical composition change of the calcined geopolymer. Partial crystallisation of non-reacted fly ash particles in the geopolymer decreases its solubility in acid and alkali solutions