Current Research in Sulfate Resistance at the Waterways Experiment Station
Appears on pages(s):
alkali-aggregate reactions; concretes; fly ash;
pozzolans; sulfate attack; sulfate resistance; tests; weathering.
Two studies relating to sulfate resistance are being carried out under the direction of the author. One of these, a cooperative program in ASTM Committee C-l, is to develop a performance test for sulfate resistance of cements that treats blended cements fairly. The other, a Corps of Engineers Civil Works Research Unit, is to evaluate substitutes for sulfate resisting cements. In the latter study, data have been developed showing that some pozzolans are very effective in preventing sul-fate attack expansion of mortars made with non-sulfate resisting cements. The most effective pozzolans appear to be those of high fineness, high silica content, and a high degree of amorphousness of the silica, characteristics that were shown previously to be possessed by pozzolans that are effective in reducing expansion due to the alkali-silica reaction. Other pozzolans, notably some fly ashes, were found to increase the rate of deterioration of mortar bars made with non-sulfate-resisting cements exposed to sulfate solution when used as cement replacements at the30 percent level. These were fly ashes derived from combustion of lignite.