Page 339 - Handbook of Thermal Analysis of Construction Materials

316 Chapter 8 - Supplementary Cementing Materials

Many massive concrete elements are made from slag cements.
There is a possibility of early age thermal cracking in such structures, hence,
a general hydration model was developed based on conduction calorimetric
studies. [46] In this model, the heat production is calculated as a function of
degree of hydration or temperature. This model enables simulation of the
field temperature in massive concrete elements.
The DTA and X-ray methods have proven useful in the examina-
tion of set supersulfated cements. [47] Thermograms of supersulfated cement
hydrated to different times are plotted in Fig. 18. The cement exhibits an
endothermal effect at 150–170°C that is mainly attributed to ettringite. A
large amount of ettringite is present even at 28 days and is lower at later
periods. The increased strength in cement at 28 days is due mainly to the C-
S-H phase and alumina gel. A quantitative estimation of products of
hydration of supersulfated cement has also been carried out by thermal
methods. [47]

Figure 18. Differential thermograms of supersulfated cement.

Autoclave treatment of slag with lime results in an increased
strength. Kalousek and Chopra [47] studied by DTA the autoclave products
of slag-lime mixes and tried to investigate the causes leading to strength
decreases in certain instances. The increase in strength corresponded to an