Analytical Study of Pure and Extended Portland Cement Pastes: II, Fly Ash‐ and Slag‐Cement Pastes

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Abstract
A range of pastes of portland cement interground with low‐calcium fly ash or granulated blast furnace slag was studied by X‐ray diffraction, analytical electron microscopy, thermo‐gravimetry, and determinations of CO 2 and of unreacted fly ash or slag. Partial replacement of clinker by fly ash results in increased reaction of the alite from at least as early as 3 d. The amount of Ca(OH) 2 formed from a given weight of clinker increases at 3 d due to the enhanced reaction, but from 28 d onward, it decreases due to the pozzolanic reaction. The mean Ca/SI ratio of the C‐S‐H decreases with time or fly ash content, toward a lower limit of ∼1.4. Partial replacement of clinker by slag also decreases both the amount of Ca(OH) 2 formed from a given weight of clinker and the mean Ca/Si ratio of the C‐S‐H, but to a lesser extent. Using the methods described in Part I of this paper, the results of the experimental methods were tested for mutual consistency, and volume percents of phases, porosities, and related quantities were calculated.
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