Characterisation of granulometric composition of a Mongolian fly ash and its application for value added products

In Mongolia coal fired thermal power stations are producing over 90% of the country´s electricity. The 4th thermal power station uses Baganuur and Shivee-ovoo coals for firing and annually disposes over 300 thousand tonnes of coal firing by-products such as fly ash. However, in Mongolia utilisation rate of the coal firing by product is negligible and seems to be caused little knowledge of the mineralogical and physical-chemical properties. Granulometric characterization of the Baganuur and Shivee ovoo fly ashes have been performed. Specific surface area of both fly ashes varied from 1.04 to 2.75m²/g. The >74 μm fraction of Shivee ovoo fly ash comprised around 17% of the total weight while for Baganuur fly ash it was equal to 7%. The crystalline part of the >74 μm fraction of Baganuur fly ash was mostly quartz while in Shivee ovoo fly ash it was a mixture of quartz, diopside and akermanite. Raw and fine fractions of the Baganuur and Shivee ovoo fly ashes have been used for preparation of a geopolymer type binder. Raw and fine fractions of both fly ashes have been activated with 10 M NaON solution and cured at 70°C for 24h. Geopolymer type pastes based on Shivee ovoo and Baganuur fly ashes exhibited compressive strengths of over 20 and 30 MPa, respectively. Compressive strength of the geopolymer pastes based on fine fraction showed negligible change. Comprehensive characterizations of Baganuur and Shivee ovoo fly ashes and geopolymer pastes were performed using XRD, XRF, SEM, BET methods..