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 5 pH 5 14.71) and alkaline-earth hydroxides of Ca, Sr, and Ba (12.47 5 pH 5 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),AH,,, and minor amounts of Ca(OH), and C,ASH, (stratlingite). 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 ~1 4 . 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), with time; Mg behaved similarly. The effect of the charge or ionic radius of the activator cation was insignificant.

A salt-saturated concrete proportioned with Class H oilwell cement, Class F fly ash, and a shrinkage compensating component was developed to meet performance requirements for mass placement as seal components at the Waste Isolation Pilot Plant. Target properties of the concrete included 8-in. slump 3 hr after mixing, no aggregate segregation, heat rise of <25°F 4 hr after mixing, compressive strength of 4,500 psi at 180 days, minimal volume change, and probable geochemical stability for repository conditions. Thermal and mechanical properties of promising candidate concrete mixtures were measured. Modulus of elasticity and creep behavior were similar to those of ordinary portland cement mass concretes. Thermal expansion for the salt-saturated concrete developed here was typical of ordinary concrete with similar silicate aggregates. Thermal conductivity, diffusivity, and specific heat approximated values measured for other mass concretes and were similar to values of the host salt rock.

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