Cement-silica fume pastes calcium hydroxide

Mitchell, Hinczak, 1., and Day, R.A. (1998) Interaction of silica fume with calcium hydroxide solutions and hydrated cement pastes. Cement and Concrete Research 28, 1571-1584. 

Figure 8 shows the amount of calcium hydroxide formed in cement-silica fume pastes. At all curing periods, lime content is less in portland cement pastes incorporating silica fume. Extrapolation of the curve shows that, at about 24% silica, no lime would be left in the pastes. This figure may vary depending on the materials and method of estimation. 

Figure 8. Amount of calcium hydroxide formed in cement-silica fume pastes hydrated for different times.

Brouwers, 1998). In the presence of these additives the dissolved calcium hydroxide tends to react with the residual non-reacted fly ash, yielding additional amounts of C-S-H, and thus reducing the permeability of the paste. The optimum amounts of these additives to be interblended with Portland cement were found to be around 35 mass% of fly ash and about 8 mass% of silica fume (van Eijk and Brouwers, 1998). However, cement combined with 70 mass% of granulated blast furnace slag behaves not too differently from a cement that contains just Portland clinker alone (Faucon et al., 1996). 

Richardson, I. G. 2004. Tobermorite/jennite- and tobermorite/calcium hydroxide-based models for the structure of C-S-H applicability to hardened pastes of tricalcium silicate, p-dicalcium silicate, Portland cement, and blends of Portland cement with blast-furnace slag, metakaolin, or silica fume . Cement and Concrete Research 34 (9) 1733-1777. 

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