Building Construction Handbook, Eighth Edition

Concrete Surface Finishes ~ it is not easy to produce a concrete

surface with a smooth finish of uniform colour direct from

the mould or formwork since the colour of the concrete can be

affected by the cement and fine aggregate used. The concrete

surface texture can be affected by the aggregate grading, cement

content, water content, degree of compaction, pin holes caused by

entrapped air and rough patches caused by adhesion to parts of

the formworks. Complete control over the above mentioned causes

is difficult under ideal factory conditions and almost impossible

under normal site conditions. The use of textured and applied

finishes has therefore the primary function of improving the

appearance of the concrete surface and in some cases it will help

to restrict the amount of water which reaches a vertical joint.

Casting ~ concrete components can usually be cast in-situ or

precast in moulds. Obtaining a surface finish to concrete cast in-

situ is usually carried out against a vertical face, whereas precast

concrete components can be cast horizontally and treated on

either upper or lower mould face. Apart from a plain surface

concrete the other main options are:-

1. Textured and profiled surfaces.


2. Tooled finishes.


3. Cast-on finishes. (see next page)


4. Exposed aggregate finishes. (see next page)

Textured and Profiled Surfaces ~ these can be produced on the

upper surface of a horizontal casting by rolling, tamping, brushing

and sawing techniques but variations in colour are difficult to

avoid. Textured and profiled surfaces can be produced on the lower

face of a horizontal casting by using suitable mould linings.

Tooled Finishes ~ the surface of hardened concrete can be tooled

by bush hammering, point tooling and grinding. Bush hammering and

point tooling can be carried out by using an electric or pneumatic

hammer on concrete which is at least three weeks old provided

gravel aggregates have not been used since these tend to shatter

leaving surface pits. Tooling up to the arris could cause spalling

therefore a 10 mm wide edge margin should be left untooled.

Grinding the hardened concrete consists of smoothing the surface

with a rotary carborundum disc which may have an integral water

feed. Grinding is a suitable treatment for concrete containing the

softer aggregates such as limestone.

Concrete Surface Finishes