Beneficiation of Sugarcane Bagasse Ash: Pozzolanic Activity and Leaching Behavior

The annual production of sugarcane in Brazil is estimated at around 646 million tons and contributes around $US 43.8 billion of gross domestic product. Around 80% of Brazil's biomass electricity is generated from sugarcane bagasse. However, the process of generating energy from bagasse using calcination leads to a by-product residue, sugarcane bagasse ash (SCBA), which requires disposal. A simple beneficiation protocol for sugarcane bagasse ash (SCBA) consisting of adequate calcination, grinding and density separation was explored in this study. SCBA was collected from industrial boilers in Brazil and treated to produce three different ashes, including the original untreated ash and two ashes collected from the top and bottom of a water-washing density separation process. Portland cement pastes incorporating 20% SCBA partial replacement for cement were made. Upon controlled burning and grinding, electrical conductivity and Chapelle tests indicated that SCBA had significant pozzolanic activity, with the top separated ash yielding best results. Mercury intrusion porosimetry showed that SCBA cement pastes had more refined porosity compared to that of the control paste. Fine SCBA particles ensured heterogeneous nucleation and promoted pore size refinement. Inductive coupled plasma testing indicated low levels of heavy metals leaching. Results demonstrate that SCBA can be beneficiated to provide an effective pozzolanic material, without harmful leachates released to the environment. [GRAPHICS] .