Page 251 - Handbook of Thermal Analysis of Construction Materials

Section 2.0 - Lignosulfonates 233

An addition of 0.1% CLS may extend the initial and final setting
times of cement mortar by two and three hours, respectively. The influence
[8]
of 0.3% CLS on the hydration of cement is shown in Fig. 9. Thermograms
indicate that the reference cement containing no admixture exhibits a broad
endothermal peak below 200°C, representing the formation of both ettringite
and C-S-H phase. These peaks increase in intensity as the hydration period
is increased. The effect between 450 and 500°C is caused by the dehydra-
tion of Ca(OH) andits intensity indicates the extent to which the hydration
2,

of the C S component has progressed. The cement hydration, in the
3
presence of lignosulfonate, is retarded as seen by the lower intensity of the
Ca(OH) decomposition peak. The low temperature effect below 300°C in
2
the presence of CLS is not sharp as that obtained in the reference sample.

Figure 9. DTA of cement hydrated in the presence of lignosulfonates.