SULFATE RESISTANCE OF FLY ASH CONCRETES - THE R-VALUE. CONCRETE DURABILITY. KATHERINE AND BRYANT MATHER INTERNATIONAL CONFERENCE, HELD AT ATLANTA, GEORGIA, USA, 27 APRIL-MAY 1987

In 1973 the bureau of reclamation began research on the use of subbituminous and lignite fly ashes in concrete. By 1978 that research had lead 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 (%cao-5)/%fe2o3. This paper is a review (another look at the r-value) 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 15-25% 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. (Author/TRRL)