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A23.4-09
©
Canadian Standards Association
November 2009
5.2 Colouring materials
Pigment used in the concrete mix or as a surface colourant shall have a proven history of colourfastness
and shall not reduce the durability of the concrete.
Notes:
(1)
Suitable tests or performance records are used to establish colour stability in the actual concrete mix and compatibility
with possible retarders and finish treatments.
(2)
Except for exposed surfaces, dark pigments should be avoided.
(3)
The effect of colouring agents on air content, mixing water requirements, and water absorption of the face mix should
be established before use.
6 Water
Water for use in precast concrete and curing shall comply with Clause 4.2.2 of CSA A23.1.
Water for architectural concrete mixtures and curing shall be free of impurities or colour that could
affect the concrete finishes.
7 Aggregates
7.1 General
Aggregates for use in precast concrete shall comply with Clause 4.2.3 of CSA A23.1 and
Clause 7.2
of this
Standard.
7.2 Special aggregate
Special aggregate for architectural concrete (e.g., ceramics, glass, and plastics) shall not be used unless
tests have proved, to the satisfaction of the owner, that they are acceptable with respect to strength,
density, durability, and appearance for a minimum of 5 years.
Notes:
(1)
Investigation of special aggregates should cover the material itself and its interaction with the concrete materials and
any other materials with which it could come in contact in service.
(2)
Where elements have exposed aggregate finishes, care should be taken in selecting the aggregate so that it can
withstand the environment to which it will be exposed.
7.3 Fine aggregate
7.3.1 General
Fine aggregate for architectural concrete shall comply with
Clauses 7.3.2
to
7.3.4
.
Note:
When fine aggregate is likely to be a major colouring agent in architectural concrete, it should be controlled even
more closely by using manufactured one-size fine aggregate.
7.3.2 Grading
To control the uniformity of the appearance of architectural concrete, the amount of material passing a
160 μm sieve shall be limited to a maximum of 2% or maintained within ±1% of the amount established
in the mix design.
Note:
For low absorption, the percentage of aggregate passing a
315 μm
sieve, when tested in accordance with Test
Method A23.2-2A in CSA A23.2, might need to be lower than the limit specified in CSA A23.1.
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