MECHANICAL ACTIVATION OF FLY ASH FOR MAKING HIGH VOLUME FLY ASH CONCRETE

Fly ash - waste product from industrial process - seldom receives proper attention during the production stage, and thus its chemical composition and other properties are varied. Quality of fly ash is determined by the efficiency of combustion and the type of coal used. It can be detected also from the value of Lost on Ignition (LOI). This paper evaluates changes on fly ash after undergone grinding using rod mill, and determines its suitability to be used in making high volume fly ash (HVFA) concrete. Samples of fly ashes were taken from four different sources, i.e. two samples from a power plant, and one each from textile factory and paper mill. Samples taken from power plant have low Loss on Ignition (LOI), while the other have very high LOIs. Fly ash samples were ground using a rod mill to evaluate the changes in the properties of fly ash
and HVFA mortar. The workability of HVFA mortar was controlled by adjusting the superplasticizer content to obtain the target slump with constant water to cementitious ratio. The results shows that the specific gravity of fly ash increases after grinding. Utilizing ground fly
ash ends up with more significant strength increase of HVFA mortar, especially with those of high LOI values. The strength increase of HVFA mortar utilizing ground fly ash shows that milling of the fly ash is an excellent method for beneficiation of fly ash, especially to the one with high LOI value and low specific gravity.