Page 292 - Handbook of Thermal Analysis of Construction Materials

Section 4.0 - Tricalcium Silicate 271

Table 2. Amount of Lime Formed in the Hydration of C S containing SMF
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Hydration Time, Days 0% SMF 0.32% SMF 1% SMF

1 13.0 11.0 1.4
3 16.5 17.2 17.2
7 19.9 21.0 20.9
28 21.9 22.0 22.3

The effect of sodium SNF of different polycondensation degrees
(n) on C S hydration has been examined by the microcalorimetric tech-
3
nique. Typical results are shown in Table 3. [17] The first peak refers to that
occurring during the pre-induction period and the second to that occurring
during the acceleratory period. The rate of heat development (dQ/dt) (1st
peak) is increased at n > 2. The second peak is of lower intensity and appears
at longer times as n is increased. This retardation is due to the adsorption
effect of the superplasticizer. The minimal effect for the first peak is
attributed to the ineffectiveness of SNF towards the rate of interaction
between C S and water. Although there is significant retardation in the
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appearance of the second peak, the total heat corresponding to this peak is
higher in all samples with n>2. The DTG results confirm those of the
calorimeter.

Table 3. Effect of Condensation Degree of SNF on the Thermal Character-
istics of C S Hydration
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Rate of Heat Time for the Heat Developed
n (dQ/dt) Max Peak Effect (Main Peak) kJ/kg
1st Peak 2nd Peak (Hrs)

1 1.7 4.3 18 71
2 1.6 4.7 15 51
5 4.3 2.9 155 127
7 4.3 1.25 278 180

17 4.5 0.72 350 317