Use of wastes of the sugar industry as pozzolana in lime-pozzolana binders: study of the reaction

Abstract

Mineralogical studies of different wastes of the sugar industry, mainly sugar cane bagasse ash and sugar cane straw ash, have shown that such by-products are likely to be pozzolanic. Their use in lime-pozzolana binders could become an interesting alternative for developing countries. This paper presents a study that was aimed at monitoring the reaction between lime and wastes of the sugar industry having pozzolanic properties by evaluating 1) content of calcium hydroxide, dependent on time; 2) development of the pore structure, dependent on time; 3) study of the reaction products at different stages; and 4) mechanical properties of hardened pastes. The presence of calcium hydroxide was confirmed by x-ray diffraction analysis and thermogravimetic analysis of powder from samples of hydrated lime-pozzolana pastes. The reaction products in hydrated pastes were observed in a scanning electron microscope, and the pore structure was assessed using a mercury intrusion porosimeter. The results of the study show that sugar cane bagasse ash does not act like a reactive pozzolana, mainly due to the presence of unburned material and carbon, whereas sugar cane straw ash shows good pozzolanic activity comparable to that of rice husk ash.