FINISHING

Finishing is the last stage in concrete construction. After casting of a concrete, the concrete does not offer a pleasant architectural appearance. In some cases like beams, finishing may not be needed. For a residential building, airport or road pavement and culvert and bridges, finishing is a must. Now-a-days, the centering materials are so made such that the concrete exhibit a pleasant surface finish. Many of the prefabricated concrete units are made in such a way to give an attractive architectural effect.

Different types of finishes have been in use now-a-days. Surface finishes may be grouped as under.

1. Formwork finishes
2. Surface treatment
3. Applied finishes

8.9.1 Formwork Finishes

Concrete maintains the shape of formwork, i.e., centering work. Thus, keeping the required shape through formwork, viz., undulated fashionable shapes, V-shaped finishes, plain surfaces, etc., any pleasing surface can be obtained. The imaginative ideas of architects may be implemented by a careful formation of concrete surface.

A properly made out formwork can give a very smooth surface using the right proportioning of materials better than that made by the best mason. Because of increasing cost of labour, self-finishing concrete surfaces are preferred.

8.9.2 Surface Treatment

This is a commonly used method of surface finishing. It is important for a residential floor to be smooth. To obtain a smooth finish, first the proportioning of mix should be appropriate. The finishing of surface should be at the same rate as that of placing of concrete. Attention must be paid to the extent and time of transportation. Careful attention should be paid to the non-formation of laitance, that excess mortar does not remain and excess water is not accumulated on the surface. A poor and dissatisfactory surface is formed due to hurried completion.

Rough finishes are required on concrete pavement slabs, air-field pavements, on roads, etc. In such cases, the concrete is brought to the plane level surface, and then lightly raked, broomed, textured or scratched to create a rough surface. Other finishes are to give good look like exposed aggregate finish.

8.9.3 Applied Finish

Applied finish is the exterior application of rendering made on concrete structures. In this case the concrete surface is finished and kept wet after which mortar (1:3) is applied. The desired finish is then given to the mortar.

Sometimes the rendering applied on a wall is pressed with a sponge. On repeating this process, the sand is exposed and the surface obtains a finish which is known as sand facing. Another type of finish known as Rough Cast Finish is also done. In this type, a wet plastic mix (three parts of cement, one part of lime, six parts of sand and four parts of about 5-mm-size peagravel aggregate) is dashed on the wall surface using a scoop or plasterer’s trowel.

Other finishes under this category are non-slip finish, coloured finish, wear-resistant floor finish, craziness finish, etc.