Page 173 - Handbook of Thermal Analysis of Construction Materials

Section 2.0 - Accelerators 157

Figure 7. Influence of calcium formate on the strength development in C S mortars.
2

In the hydration of portland cement, although initially larger
amounts of heat are developed in the presence of Ca formate, at later stages
the heat may be slightly lower or equal to that of the reference material. In
the early hydration periods, cement produces more ettringite in the presence
of Ca formate than in the presence of CaCl . [52] However, the amount of
2
C-S-H is higher in the presence of CaCl .
2
Ca formate accelerates the setting time of concrete, but compara-
tively a higher dosage is required to impart the same level of acceleration
as that by CaCl . Table 3 compares the initial and final setting times of
2
cement containing 2% CaCl and Ca formate. [52] The effectiveness of Ca
2
formate is also observed at different temperatures. [45]

Table 3. Setting Characteristics of Portland Cement Containing Calcium
Chloride or Calcium Formate (2%)

Admixture Initial Setting Final Setting
(minutes) (minutes)

None 185 225
Calcium chloride 65 75
Calcium formate 80 90