Performance of Mortar Specimens in Chemical and Accelerated Marine Exposure
V. D. Vanden Bosch
Appears on pages(s):
accelerated tests; blast furnace slag; chemical tests; chlorides; compressive strength; durability; expansion; magnesium; mortars (material); sea water; sodium chloride; sulfate resistance.
Different types of blast furnace slag cement with increasing amounts of slag were tested for sulfate resistance according to the ASTM C 452, the Koch and Steinegger test and the Mehta test; the results were compared with the performances of portland cement under same conditions. The evolution of the strengths as a function of time and of composition of the liquid phase (sea water or salt solution of 5% Na2S04 - 5% MgS04 and 5% MgC12 ) was investigated on mortar bars. The conclusions are that the chemical resistance of the blast furnace slag cement improves with the slag content; a high fineness of grinding improves both the chemical resistance and the mechanical strength. Exemples of marine structures made with blast furnace slag cements in the Netherlands are given. Some of these structures are more than 50 years old and still in an excellent condition. The best chemical resistance is obtained when the slag content of the cement is higher than 65-70%. This is imputable to the fact that, in these conditions, the formation of ettringite is impossible, due to the low content of free calcium hydroxide in the cement paste. A magnesia content of the slag higher than 5% is harmless, because Mg0 is entirely in the glass phase and not present as the expanding periclase variety.