Abstract
In this investigation, mortar specimens made with two plain cements, Type I and V, and blended cements, made with fly ash, silica fume, and blast furnace slag, were exposed to sodium-sulfate and magnesium-sulfate solutions. The performance of these cements, in both the environments, was evaluated by measuring expansion and determining reduction in compressive strength. The data indicate that while the performance of all blended cements, particularly those made with silica fume, was generally excellent in the sodium-sulfate environment, their performance in the magnesium-sulfate environment was not satisfactory. A similar trend was observed in mortar specimens made with a water-cement ratio of 0.35. The type of cement did not have any significant influence on the performance of either plain or blended cements in both environments. The deterioration of plain and blended cements in sodium-sulfate and magnesium-sulfate environments is attributed to the initial reaction of sodium sulfate and magnesium sulfate with calcium hydroxide. The reduction of calcium hydroxide in blended cements provides an opportunity to magnesium sulfate to react more directly with the primary and secondary calcium silicate hydrate due to the destabilization of these phases by magnesium hydroxide. Comparatively, lower deterioration of blended cements exposed to the sodium-sulfate environment is attributed to the reduced calcium hydroxide, which significantly mitigates the sulfate attack in these cements.
Published Version
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