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©
Canadian Standards Association
Precast concrete — Materials and construction
November 2009
23.2.2.4 Heated concrete
23.2.2.4.1
Heated concrete shall be achieved by
(a) preheating the concrete materials;
(b) heating the concrete mixture using a means such as superheated steam; or
(c) a combination of Items (a) and (b).
Note:
The use of heated concrete can cause premature stiffening of the mix.
23.2.2.4.2
During the heated concrete cycle, concrete surfaces shall be protected from moisture loss as specified in
Clause 23.2.2.3.2
.
23.2.2.4.3
During the heated concrete cycle, concrete surfaces shall not be exposed to combustion gases
(see
Clause 23.2.2.3.3
).
23.2.2.4.4
The heated concrete cycle shall be as specified in
Table 3
.
23.2.2.5 Measuring and recording the heat treatment cycle
23.2.2.5.1
When accelerated curing or heated concrete methods are used, the governing concrete temperatures shall
be those achieved within the concrete elements.
23.2.2.5.2
Temperatures shall be measured by one or more of the following means:
(a) devices, such as expendable thermometers or thermocouples, cast into the concrete; or
(b) temporary measuring devices placed against the concrete surface under a temporary cover of heavy
insulation.
For standard elements, however, temperatures may be measured within the enclosure, in which case the
correlation between the enclosure temperature and temperatures within the concrete shall be determined
and documented and the temperature within the concrete shall be used to govern the cycle.
23.2.2.5.3
Concrete temperatures should be recorded continuously, but the interval between temperature readings
shall not exceed 30 min.
23.2.2.5.4
The times at which concrete temperatures are measured shall be recorded.
23.3 Extended curing
23.3.1
Extended curing, as specified in Clause 7.4.2.1 of CSA A23.1, shall be used where it is important for
durability. The concrete shall be kept in a surface-damp condition.
Note:
For architectural precast concrete panels, additional curing should continue until the hydration of the cement on the
surface is sufficient to prevent unhydrated cement from streaking the panel surfaces or being carried by rainwater to window
glass areas or other surfaces that could be affected.
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