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©
Canadian Standards Association
Precast concrete — Materials and construction
November 2009
23 Protection and curing
23.1 General
23.1.1
Except as specified in
Clause 23.1.2
, curing and protection shall comply with Clause 7.4 of CSA A23.1 and
Clauses 23.1.3
to
23.3
of this Standard.
23.1.2
When the ambient temperature in the plant does not fall below 5 °C and the manufacturing facilities
are protected from wind and the direct rays of the sun, curing and protection shall comply with
Clause 7.4.1.5.3 of CSA A23.1 and
Clauses 23.1.3
to
23.3
of this Standard.
Note:
CSA A23.1 specifies additional curing and protection measures for outside casting. An estimate of the moisture
evaporation can be obtained from Annex D of CSA A23.1.
23.1.3
Immediately after the concrete is placed and consolidated, provisions shall be made for moisture
retention. The concrete shall not be subjected to rapid drying or excessive stresses during the curing cycle.
23.1.4
The curing process shall be well established and controlled and shall continue until the concrete has
attained its specified transfer or handling strength.
23.1.5
Records of concrete strength and temperature shall be maintained during the curing cycle.
23.2 Initial curing
23.2.1 General
23.2.1.1
The minimum concrete strength for stripping precast elements shall comply with CAN/CSA-A23.3.
23.2.1.2
The strength of elements at the time of transfer of prestress and stripping shall be determined by test
cylinders cured under temperature and moisture conditions that simulate as closely as possible the
conditions under which the concrete in the precast forms is cured.
23.2.1.3
The strength of the concrete at transfer of prestress and stripping, as well as the 28 d concrete strength of
precast elements, shall be specified on the shop drawings.
23.2.2 Accelerated curing and heated concrete
23.2.2.1 General
When a combination of accelerated curing and heated concrete is used, the requirements specified in
Clause 23.2.2.3
shall apply.
Notes:
(1)
Concrete is heat treated to accelerate its strength development. Two types of heat treatment are recognized:
(a) accelerated curing, which is heating of the concrete after it has been placed in the forms; and
(b) heated concrete, which is heating of the concrete before it is placed in the forms.
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