The Sulphate Resistance of Portland and Blast Furnace Slag Cement Concretes


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Title: The Sulphate Resistance of Portland and Blast Furnace Slag Cement Concretes

Author(s): G. J. Osborne

Publication: Special Publication

Volume: 126


Appears on pages(s): 1047-1072

Keywords: blast furnace slag; blended cements; concretes; curing; durability; mortars; portland cement; strength; sulfate attack; sulfate resistance; tests; Materials Research

Date: 8/1/1991

Laboratory tank tests were used to assess the sulfate resistance of a series of portland and blast furnace slag cement concretes. Following different early curing regimes, 100 mm concrete cubes were stored in tanks of sodium and magnesium sulfate solutions for 5 years. The concrete cubes were photographed, and their sulfate attack ratings and compressive strengths measured at 1, 2, and 5 years. The results showed that concretes made with ground granulated or pelletized blast furnace slag and portland cement generally had good sulfate-resisting properties when the slag content was 70 percent and above. The significance of the precuring regime, the tricalcium aluminate (C3A) content of the portland cement, and alumina level of the slag on the sulfate resistance of concrete are discussed. A degree of carbonation of the concrete prior to storage in the sulfate solutions was found extremely beneficial in the prevention of sulfate attack. Sulfate-resisting portland cement (SRPC) of low tricalcium aluminate content and combinations of high tricalcium aluminate ordinary portland cement (OPC) with low alumina slags were shown very resistant after 5 years in high-strength sulfate solutions. The concrete cube results were compared with data previously obtained using the same series of cements in small-scale accelerated methods of test, and a reasonable correspondence was found. Recommendations are made for an acceptance test for determining the sulfate resistance of cements and for maintaining good concrete performance in sulfate conditions. The BRE tank test is a severe test, and its relevance to the ultimate behavior of concretes in the field is discussed.