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Canadian Standards Association
Precast concrete — Materials and construction
November 2009
26 Finishing of formed surfaces
26.1 General
26.1.1
The finish of formed surfaces shall be specified by the owner, in accordance with
Clause 26.2
, and shall be
detailed on the shop drawings.
26.1.2
The finish shall be established from an assessment of previous production or from samples, as specified in
Clause 26.2
.
26.2 Finish grades
26.2.1 Reference sample
After the contract is awarded, a reference sample shall be cast using formwork, reinforcement, concrete,
and vibration typical for the project. The reference sample shall be viewed from a distance of 6 m. Once
accepted, the reference sample shall be identified and used for comparison in assessing compliance with
the specified finish grade.
26.2.2 Commercial grade
For this finish, concrete may be cast in forms that impart a texture to the surface, but fins shall be removed
and large surface voids exceeding 12 mm in diameter shall be filled. Faces exposed to view shall have
well-defined outlines and all sharp edges visible in the finished structure shall be softened by sanding or
grinding.
26.2.3 Standard grade
The finish shall be as specified in
Clause 26.2.2
, except that the forms shall not impart a pronounced
texture to the finished concrete.
26.2.4 Finish Grade B
This finish shall be as specified in
Clause 26.2.3
, except that all surface blemishes shall be finished to
provide a smooth surface of uniform appearance if painted. Form-release or other agents shall not leave a
paint-rejecting coating or leave a caulking/sealant rejecting coating on the concrete.
26.2.5 Finish Grade A
This finish shall be as specified in
Clause 26.2.4
, except that repairs that are exposed to view shall be
colour-matched within practical limits.
Note:
Because variations in cement, curing conditions, and other production procedures can influence the final colour, it is
not reasonable to expect a uniform colour finish in large prestressed concrete elements. The purpose of this finish is to
provide a smooth finish. Repairs and filling of surface defects to produce an acceptable finish should be established from an
assessment of previous production or from representative samples.
27 Surface sealers and joint sealants
27.1
Compatibility between surface sealers and joint sealants shall be established.
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