Concrete Mixtures Made with Ternary Blended Cements Containing Fly Ash and Rice-Husk Ash

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Title: Concrete Mixtures Made with Ternary Blended Cements Containing Fly Ash and Rice-Husk Ash

Author(s): N. Bhanumathidas and P. Kumar Mehta

Publication: Special Publication

Volume: 199

Issue:

Appears on pages(s): 379-392

Keywords: blended cements; chloride penetration; compressive strength; durability; fly ash; rice-husk ash; water-cementitious mate-rial ratio

Date: 6/1/2001

Abstract:
Blending fly ash with normal portland cement enhances the durability and service life of concrete structures. Fly ash-based blended portland cements containing 1530% fly ash by mass are being increasingly used worldwide. These cements have been used in high-performance concrete for modem structures such as Petronas Towers, Euro-Tunnel, and Akashi-Kaikyo Bridge. High-volume fly ash concrete is another recent development according to which, large volumes of fly ash, 50-60% by mass of the total cementitious material, can be used in combination with a superplasticizer to overcome the slow rate of strength development in blended portland cements. The chloride permeability of unsuperplasticized, high-volume fly ash concrete at early ages is rather high, but it can be greatly reduced by the incorporation of either silica fume or a highly pozzolanic rice-husk ash. Rice-husk ash is a siliceous material produced by furnaces that use rice-husks as fuel. The rice-husk ash containing amorphous silica in cellular microstructure is a superpozzolan, and has proven to be a valuable material for making highly durable concrete. It also contributes to concrete strength at early ages. This paper describes a preliminary research study on the role of rice-husk ash in enhancing the properties of high-volume fly ash concrete, particularly the early-age strength and chloride impermeability.