1.1. The slow reaction period
Two quite different hypotheses, discussed in detail in refs. [2,10],
have been proposed to describe the origin of the period of slowreaction
shortly after mixing with water, sometimes called the induction period
or dormant period for portland cement. One hypothesis is that the C3S
dissolution rate decreases abruptly after a small degree of reaction
owing to a change in the mechanism of dissolution [4,11,12]. We will
refer to this as the “etch pit” theory because it is sometimes described
in terms of a transition from etch pit unwinding at high driving forces
to step-flow dissolution at lower driving forces. The other theory proposes
the formation of a protectivemetastable hydrate layer on the surface
of cement that partially seals the cement particle and inhibits
dissolution [13,14].
1.1. The slow reaction periodTwo quite different hypotheses, discussed in detail in refs. [2,10],have been proposed to describe the origin of the period of slowreactionshortly after mixing with water, sometimes called the induction periodor dormant period for portland cement. One hypothesis is that the C3Sdissolution rate decreases abruptly after a small degree of reactionowing to a change in the mechanism of dissolution [4,11,12]. We willrefer to this as the “etch pit” theory because it is sometimes describedin terms of a transition from etch pit unwinding at high driving forcesto step-flow dissolution at lower driving forces. The other theory proposesthe formation of a protectivemetastable hydrate layer on the surfaceof cement that partially seals the cement particle and inhibitsdissolution [13,14].
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