Study on the pozzolanic activity of sugar cane straw ash produced using different pretreatments

摘要

This work systematically describes a laboratory study on different pretreatments of sugar cane straw to produce pozzolanic ash. Two procedures were used to accelerate the hydrolysis of celluloses and hemicelluloses and remove metallic impurities present in significant levels in sugar cane straw: hot water washing and acid leaching. Proximate analysis by thermogravimetry was carried out to cover volatile matter, fixed carbon, and ash content of the different straws. Detailed measurements of X-ray diffraction, oxide percentages, loss on ignition, and BET specific surface area were performed to compare hot water washed, acid leached, and non-pretreated ashes, after controlled processes of burning and grinding. The pozzolanic activity of the ashes was evaluated from the modified Chapelle and electrical conductivity methods. The results revealed that ashes with a high content of amorphous silica were produced, in spite of the straw pretreatments. However, both straw pretreatments induced a significant increase in pozzolanic activity, mainly associated with the removal of impurities, especially CaO, SO3, K2O, and carbon compounds. The effect of the hot water washing treatment was relatively small in relation to the acid leaching, but the hot washed ash was significantly more pozzolanic than non-treated ash.