Title: Effect of Highly Reactive Rice Husk Ash on Durability of Concrete and Mortar
Author(s): I. Wada, T. Kawano, M. Kawakami, and N. Maeda
Publication: Symposium Paper
Appears on pages(s): 205-222
Keywords: abrasion resistance; acid resistance; alkali-aggregate reaction; compressive strength; freeze-thaw durability; silica fume
The performance of a highly reactive rice husk ash (RHA) as a supplementary cementing material for producing high strength and high durability concrete is reported in this paper. The effects of the specific surface area of FHA, FHA content, and water-cementitious ratio on the compressive strength of mortar are investigated. Some basic properties of the FHA concrete such as acid resistance, abrasion resistance, and alkali-silica expansion are also examined. Furthermore, the properties of the FHA concrete such as freezing and thawing resistance and compressive strength are tested. The pore size distribution and quantitative analysis of CA(OH)2 in the hardened RHA mortar and paste are used in evaluating of the pozzolanic reactivity of the RHA. The compressive strengths of the mortar and concrete are significantly improved by the RHA addition, and are higher than those of the control mortar and concrete. Unlike other pozzolanic materials, the concrete incorporating the RHA shows excellent strength development at early-age even without steam-cure. The acid resistance of the mortar is remarkably improved by the FHA addition. The abrasive coefficient loss of the mortar with FHA is marginally smaller than the control mortar. With increasing RHA content of the mortar, the expansion of the mortar due to alkali silica reaction is decreased. The pore size distribution of the RHA mortar shows a tendency of shifting towards the smaller range of pores compared to the control mortar. After 240 testing cycles, the effect of the RHA addition on the resistance to freezing and thawing cycling of air-entrained concrete in negligible. The Ca(OH)2 contents of the mortar and the paste are decreased with the addition of RHA. Moreover, the RHA pastes show Ca(OH)2 content lower than the silica fume pastes at early-ages.