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Title: Sulfate Resistance of Fly Ash Concretes--The R-Value

Author(s): Edwin R. Dunstan, Jr.

Publication: Symposium Paper

Volume: 100

Issue:

Appears on pages(s): 2027-2040

Keywords: chemical analysis; concrete durability; expansion; fly ash; mortars (material); sodium sulfate; sulfate resistance; tests; General

DOI: 10.14359/3843

Date: 4/1/1987

Abstract:
In 1973 the Bureau of Reclamation began research on the use of subbituminous and lignite fly ashes in concrete. By 1978 that research had led to the development of the fly ash R-value as an advance indicator of potential sulfate resistance of concretes containing fly ash. The R-value is calculated from results of a chemical analysis of the fly ash as (percent of CaO - 5)/(percent of Fe2O3). This paper is a review after more than 12 years of sulfate resistance testing. Many of the fly ash concretes in this research have failed in sulfate testing over the last 12 years; however, many of these concretes have not failed and are still under test. These sulfate resistance test results indicate that the R-value remains a good indicator of potential sulfate resistance of fly ash concretes. When concrete contains 15 to 25 percent fly ash with an R-value less than 3.0 the sulfate resistance will be equal or better than a concrete with the same cement and no fly ash.