Self hardening property of Botswana fly ash

Abstract

Fly ash is the finely divided mineral residue resulting from the combustion of coal in electric generating plants. It is being produced in huge quantity and most of it is being disposed as a waste. Continuous disposal has raised a very alarming situation globally. In Botswana, it is being produced at the rate of more than 300 t per day at Morupule Power Station. Almost 70% of this production is disposed off as a waste and only 30% is being used in making cement. Few limited studies suggest that a fly ash containing low unburnt carbon (LOI) may exhibit self hardening property even if the calcium content (CaO) is low. Since the Botswana fly ash contains about 2 – 3% of LOI and 10 % of Calcium oxide, it is expected to exhibit self hardening property. In the present investigation, an effort has been made to study the self hardening property of Botswana fly ash by testing penetration resistance of fly ash flowable fills and unconfined compressive strength of 3 soils mixed with fly ash and compacted to their optimum unit weight. It has been found that the strength of both flowable fills and all the soils increases with time and with the amount of fly ash without any cementing material which is normally the case with most of the pozzolanic materials. . This will encourage the use of fly ash economically as a construction material

Keywords: Fly ash, Self hardening, Dynamic cone penetration, unconfined compressive strength, curing period.