Page 304 - Handbook of Thermal Analysis of Construction Materials

Section 5.0 - Cement 281

The rate of hydration of cement also depends on the particle size of
cement. The effect of SNF on the hydration of Type III cement has been
studied. [31] Three fractions of cement, viz., 72–30 µm (coarse), 30–4 µm
(medium), and 4 µm (fine) were hydrated in the presence of SNF. Heat
evolution occurring at different times is compared in Fig. 14. The reference
sample exhibits a hump at about 12 hours, but, in the presence of SNF, it is
shifted to about 20 hours. The fine fraction evolving the most heat is the
least retarding of all the samples. Only minimal heat is evolved by the
coarse fraction. The presence of higher amounts of alkali and SO in the
3
finer fraction explains why it shows the least retardation. The alkali
content in the medium fraction is 0.86% and that in the fine fraction is
1.01%. The SO contents in the fine and medium fractions are 12.3 and
3
2.6% respectively.

Figure 14. Calorimetric curves of cements of different fractions in the presence of SNF
superplasticizer.