Activation of Ground Blast-Furnace Slag by Alkali-Metal and Alkaline-Earth Hydroxides |
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| Authors: | Amitava Roy Paul J. Schilling Harvill C. Eaton Philip G. Malone W. Newell Brabston Lillian D. Wakeley |
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| Affiliation: | College of Engineering, Louisiana State University, Baton Rouge, Louisiana 70803;U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg, Mississippi 39180 |
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| Abstract: | The effects of pH, time, valence, and radius of the activator cation on the reaction products and microstructure of ground granulated iron blast-furnace slag were studied by thermogravimetry and derivative thermogravimetry, X-ray diffractometry, scanning electron microscopy, and energy dispersive X-ray microanalysis. Blast-furnace slag was activated by alkali-metal hydroxides of Li, Na, and K (12.34 pH 14.71) and alkaline-earth hydroxides of Ca, Sr, and Ba(12.47 pH 13.53) using a water/slag ratio of 0.4 and curing for 1 day to 26 months. Reactivity of the slag was more strongly dependent on pH than on time. The reaction products were mainly varieties of C─S─H, (C,M)4AH13, and minor amounts of Ca(OH)2 and C2ASH8 (strätlingite). The nature of C─S─H was dependent on pH. A 1.2-nm peak appeared in X-ray diffractograms only when the activation pH was ⌣14.7. Water was present in the C─S─H in a way similar to water in tobermorite and synthetic C─S─H. Leached Ca from unreacted blast-furnace slag was present around the glass particles as an amorphous layer which crystallized into Ca(OH)2 with time; Mg behaved similarly. The effect of the charge or ionic radius of the activator cation was insignificant. |
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