Influences of chemical activators on incinerator bottom ash

This research has applied different chemical activators to mechanically and thermally treated fine fraction (<14 mm) of incinerator bottom ash (IBA), in order to investigate the influences of chemical activators on this new pozzolanic material. IBA has been milled and thermally treated at 800 °C (TIBA). The TIBA produced was blended with Ca(OH)2 and evaluated for setting time, reactivity and compressive strength after the addition of 0.0565 mole of Na2SO4, K2SO4, Na2CO3, K2CO3, NaOH, KOH and CaCl2 into 100 g of binder (TIBA+Ca(OH)2). The microstructures of activated IBA and hydrated samples have been characterized by X-ray diffraction (XRD) and thermogravimetry (TG) analysis. Thermal treatment is found to produce gehlenite (Ca2Al2SiO7), wollastonite (CaSiO3) and mayenite (Ca12Al14O33) phases. The thermally treated IBA samples are significantly more reactive than the milled IBA. The addition of Na2CO3 can increase the compressive strength and calcium hydroxide consumption at 28-day curing ages. However, the addition of Na2SO4, K2SO4, K2CO3, NaOH and KOH reduces the strength and hydration reaction. Moreover, these chemicals produce more porous samples due to increased generation of hydrogen gas. The addition of CaCl2 has a negative effect on the hydration of TIBA samples. Calcium aluminium oxide carbonate sulphide hydrate (Ca4Al2O6(CO3)0.67(SO3)0.33(H2O)11) is the main hydration product in the samples with activated IBA, except for the sample containing CaCl2.