Page 221 - Handbook of Thermal Analysis of Construction Materials

204 Chapter 5 - Accelerating Admixtures

the sample containing TEA. At 10 and 30 minutes, the ettringite peak
occurring between 150 and 200°C is more intense in the sample with TEA.
It appears that the formation of ettringite is accelerated between 5 and 10
minutes in the presence of TEA whereas in the untreated sample ettringite
is detected between 10 and 30 minutes. The accelerating effect of TEA in
the C A + gypsum mixture is also reflected in a greater amount of heat
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developed at earlier times in conduction calorimetric curves. Scanning
electron microscopic investigation has indicated the formation of more
densified ettringite needles in samples with TEA.

Figure 11. Hydration of C A + 25% gypsum with triethanolamine.
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