Hydrothermal Reactivity of Rice Husk Ash and its Use for Calcium Silicate Products


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Title: Hydrothermal Reactivity of Rice Husk Ash and its Use for Calcium Silicate Products

Author(s): N. Hara, H. Yamada, K. Inoue, N. Inoue, S. Tsunematsu, and H. Noma

Publication: Special Publication

Volume: 114


Appears on pages(s): 499-516

Keywords: calcium silicate hydrates; calcium silicates; durability; hydrothermal reactions; insulation; rice; sands; silica; wastes; Materials Research

Date: 5/1/1989

Usability of rice husk ash was investigated as a siliceous material for calcium silicate products manufactured by hydrothermal reaction. It is concluded that rice husk ash can be used as a superior siliceous material for manufacture of calcium silicate insulating materials with good thermal durability up to 1000 C. Characteristics of rice husk ash, namely, high SiO2 content, reactive silica phase comprising amorphous silica, cristobalite and/or tridymite, and high surface area, are favorable to the formation of well-grown xonotlite which forms bodies of insulating materials. Trial products with bulk densities ranging from 0.11 to 0.41 g/cm3 prepared from rice husk ash using glass fiber for reinforcement not only satisfied all the requirements in the industrial standards (JIS A9510) but also gave 1.4 to 2 times higher bending strength than commercial products prepared from conventional siliceous materials, such as finely ground quartz sand, silica fume, and diatomaceous earth. A variety of rice husk ashes with different crystallinity are usable for manufacture of calcium silicate products, but the hydrothermal reaction condition should be optimized according to the crystallinity or amorphousness of the ash.