Characterization of rice husk ash obtained from an industrial source

Chemical, physical and mineralogical characterization of an industrial rice husk ash is reported and the differences with ash typically obtained by laboratory combustion of husks were highlighted. Valorization of industrial ash was targeted by controlling the combustion temperature of rice husks at 600 °C, 650 °C, 700 °C and 750 °C in an atmospheric fluidized bed industrial boiler of a paper mill. The other parameters were ash sampling points (air-preheater, economizer and electrostatic-precipitator) and the ash processing condition (as-received and ground). Irrespective of the burning temperature or sampling point, all ashes had a cellular microstructure with a high specific surface area (25 m2/g − 50 m2/g), silica content was greater than 80% with the amorphous fraction being larger than 90%. Pozzolanic reactivity of ground ash for the entire burning temperature range of 600 °C -750 °C was acceptable and a 15% replacement of cement with the processed ash in blended mortars yielded optimum strength and flow performance.