Use of Waste to Energy Bottom Ash as an Aggregate in Portland Cement Concrete: Impacts of Size Fractionation and Carbonation

The use of alternatives, especially recycled materials, as substitute to naturally mined aggregates in concrete is an issue that is garnering more consideration with respect to the construction industry. This research contribution presents work in which bottom ash from a waste to energy facility was used as a partial aggregate replacement in Portland cement concrete (PCC). Compressive strength testing of specimens demonstrated a decrease in strength with increasing ash replacement percentages. This effect was significantly larger for the samples containing <9.5 mm ash fraction, this was attributed to the reactivity of the aluminum in the ash. The effect of aging the ash on concrete properties was assessed through an accelerated carbonation experiment. Carbonation was found to have little effect on the strength and durability properties of ash-amended PCC. Ash-amended concrete containing the larger ash size fraction was able to meet set design strengths at low replacement percentages (25 %).