Influence of Condensed Silica Fume and Fly Ash on the Heat Evolution in Cement Pastes


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Title: Influence of Condensed Silica Fume and Fly Ash on the Heat Evolution in Cement Pastes

Author(s): I. Meland

Publication: Special Publication

Volume: 79


Appears on pages(s): 665-676

Keywords: blended heat of hydration; -- pozzolans; silica. cements; calorimeters, cement lignosulfonate; plasticizers; pastes; fly ash; -- portland cements;

Date: 5/1/1983

Isothermal calorimetry has been used to evaluate the influence of pozzolans on the rate of heat liberation and the total heat of hydration in cement pastes. Normal Portland cement was replaced by 10 or 20% condensed silica fume or fly ash. A water/solid ratio of 0,5 was used and the heat of hydration was followed continuously for 50 hours at 20°C. In one test-series a commercial lignosulphonate was used. It With the exception of the 10% condensed silica fume-blended paste containing lignosulphonate, all the blended cements showed 4 ,~ a decrease in the total heat of hydration compared with Normal Portland cement. A substitution of Normal Portland cement by fly ash retarded II while inducing of condensed silica fume accelerated the rate of heat development. With lignosulphonate the fly-ash blended cements prolonged "the dormant period" and the condensed silica fume blended pastes strongly diminished this period compared with Normal Portland cement paste. When condensed silica fume was present, the retarding effect was reduced.