Sulfate Resistance of Combinations of Portland Cement and Ground Granulated Blast Furnace Slag


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Title: Sulfate Resistance of Combinations of Portland Cement and Ground Granulated Blast Furnace Slag

Author(s): John P. H. Frearson

Publication: Special Publication

Volume: 91


Appears on pages(s): 1495-1524

Keywords: Keywords: blast furnace slag; blended cements; expansion; fly ash; mortars (material); portland cements; portland slag cements; sulfate resistance; sulfate-resisting cements.

Date: 2/1/1986

Laboratory test programmes have been carried out to assess the sulphate resistance of various Portland and Portland blast-furnace slag cements and of Portland cements blended with ground granulated blast-furnace slag ('slag'). Slag contents of between 30% and 80% were used. The test method was based upon the German 'Flat Prism' test. Tests were carried out on mortars containing ground slag from two sources, also pulverjsed fuel-ash (pfa - 'fly ash'), and with Portland blast-furnace cements. Control specimens contained either ordinary or sulphate resisting Portland cements. Prisms were tested at water-cement ratios (w/c) ranging from 0.45 to 0.60, using constant cement contents mortars. Supplementary tests used w/c ranging from 0.40 to 0.60 and constant water content mortars. Results are now available for mortars which have been immersed in sodium sulphate solution for periods of up to 3 years. The results confirm the inferior resistance to sulphate attack of ordinary Portland cements and of blends of both ordinary and sulphate resisting Portland cement containing lower slag replacement levels. Sulphate resistance increased as the slag content increased, and the 70% slag content mortars were found to have a superior resistance to those containing sulphate resisting Portland cements alone. The influence of slag content on sulphate resistance was found to be more significant than that of the w/c in the range examined.