Page 264 - Handbook of Thermal Analysis of Construction Materials

Section 7.0 - Conduction Calorimetric Assessment of Retarders 245

The relative effects of phosphonates can be evaluated by compar-
ing the time at which the induction period is terminated at different dosages
of a chemical. In Fig. 17, the time of termination of the induction period is
plotted as a function of dosage. [30] Among the acids, the most efficient
retarder is DTPMP which requires 0.05% for an induction period of 21
hours, compared to periods of 13 and 10 hours respectively for acids ATMP
and HEDP at the same dosage. Among the salts, Na DTMP is the most
6
effective retarder.

Figure 17. The effect of various concentrations of phosphonate compounds on the
induction period of portland cement.

7.0 CONDUCTION CALORIMETRIC
ASSESSMENT OF RETARDERS

Several techniques have been applied to obtain an understanding of
the rate of hydration, types of products, complex formation, inter-conversions,