Page 170 - Handbook of Thermal Analysis of Construction Materials

Section 2.0 - Accelerators 153

The Soviet literature contains references to the use of many
complex admixtures containing CaCl . [38] A study suggests that, of the
2
chlorides of Ca, Ba, Mg, and Fe, 1.6% BaCl gives a one day strength
2
equivalent to that obtained with 2% CaCl . [39]
2
Calcium chloride also has an effect on the hydration of various
other cementitious systems such as pozzolanic cements, slag cements,
expansive cements, high alumina cement, gypsum, rapid hardening cement,
etc. (See, for example, Refs. 1 and 40.)
One of the limitations to the wider use of calcium chloride in
reinforced concrete is that, if present in larger amounts, it promotes
corrosion of the reinforcement unless suitable precautions are taken. There
is, hence, a continuing attempt to find an alternative to calcium chloride,
one equally effective and economical, but without its limitations. A number
of organic and inorganic compounds including aluminates, sulfates, for-
mates, thiosulfates, nitrates, silicates, alkali hydroxides, carbonates, ha-
lides, nitrites, calcium salts of acetic acid, propionic acid, butyric acid,
oxalic acid and lactic acid, urea, glyoxal, triethanolamine, and formalde-
hyde have been suggested. However, practical experience and research on
most of these admixtures is limited.

2.5 Triethanolamine (TEA)

Triethanolamine of formula N(C H OH) is an oily water-soluble
4
2
3
liquid having a fishy odor and is produced by reacting ammonia with
ethylene oxide. Normally it is used in combination with other chemicals in
admixture formulations. Its first use was reported in 1936, and the formu-
lation containing TEA interground with calcium lignosulfonate was used to
increase early strengths. [41]
Ramachandran followed the hydration of C A (with and without
3
gypsum) containing triethanolamine. [42] It was found that TEA accelerated
the hydration of C A to the hexagonal aluminate hydrate and its conversion
3
to the cubic aluminate hydrate. The formation of ettringite was also
accelerated in the C A-gypsum-H O system.
2
3
In a study of the effect of 0, 0.1, 0.5, and 1.0% triethanolamine on
the hydration of C S and C S, Ramachandran concluded that there was an
2
3
initial retardation of hydration. [43] At one day, acceleration of hydration
took place, thus TEA can be construed as a delayed accelerator.