Vegetable ashes as Supplementary Cementitious Materials

Approximately 140 billion metric tons of biomass are produced every year in the world from agriculture. The ashes resulting from firing agricultural wastes such as rice husk, sugar cane and others can be used as Supplementary Cementitious Materials (SCM). They can be mixed with lime alone or in ternary mixtures with Portland cement and lime. If fired at temperatures around 600-700 degrees C the agricultural ashes exhibit good reactivity. Despite extensive research work carried out on the use of agricultural ashes as source of SCMs, few success stories are reported on practical applications on an industrial scale. Details of the firing technology should be re-assessed, with special emphasis on the scale at which the technology begins to be economically suitable. Further research is also needed to understand the mechanisms of structural transformation of amorphous silica during calcination, and the impact of the ashes on cement hydration in blended systems.