Use of Biomass Ash for Development of Engineered Cementitious Binders

Abstract

Using waste agriculture and power plant byproducts to replace materials that are energy-intensive to produce can make these materials more “green”. Improved compressive strength can be obtained when rice husk ash (RHA) partially replaces ordinary Portland cement, a substance potentially hazardous and energy-intensive to make. When RHA is combined with other nanoparticles to replace ordinary Portland cement (OPC), strength can be further enhanced. The microstructure of cement binders with replacement of OPC by combinations of coal fly ash, silica fume, RHA, nanosilica, and metakaolin were investigated using X-ray diffraction, backscattered electron imaging with energy-dispersive spectrum analysis, X-ray photoelectron spectroscopy, and nitrogen sorptiometry. A combination of sustainable, renewable RHA and the waste product coal fly ash was found to synergistically improve cement binder strength. Analyses suggested the enhanced strength was due to RHA increasing amorphous reactive silica and coal fly ash contributing alumina to form calcium–silicate–hydrate (C–S–H) gel along with calcium–aluminum–silicate–hydrate (C–A–S–H). Thus, this work shows the potential benefits of merging residual wastes from the agricultural sector with wastes from coal in combustion-based power plants.