Title: Properties of Concrete Containing Ultra-Fine Fly Ash

Author(s): Karthik H. Obla, Russell L. Hill, Michael D. A. Thomas, Surali G. Shashiprakash, and Olga Perebatova

Publication: Materials Journal

Volume: 100

Issue: 5

Appears on pages(s): 426-433

Keywords: alkali-silica reaction; cracking; durability; fly ash; shrinkage; sulfate attack; workability.

DOI: 10.14359/12819

Date: 9/1/2003

Abstract:
Fly ash and silica fume are two pozzolans that have been widely used for improved concrete strength and durability. Silica fume displays a greater pozzolanic reactivity than fly ash primarily due to its finer particle size. The reactivity of fly ash can be improved by reducing its particle size distribution. This paper discusses the fresh and hardened properties of concrete made with an ultra-fine fly ash (UFFA) produced by air classification. Durability testing for chloride diffusivity, rapid chloride permeability, alkali-silica reaction (ASR), and sulfate attack was also conducted. It was found that at a given workability and water content, concrete containing UFFA could be produced with only 50% of the high-range water-reducer dosage required for comparable silica fume concrete. Similar early strengths and durability measures as silica fume concrete were observed when a slightly higher dosage of UFFA was used with a small reduction (10%) in water content.