Concrete paths add finishing touches

Press, 13 February 1986, Page 24

Concrete paths add finishing touches

Provided easy directions are carefully followed, anyone with a little or no experience in concrete work can lay concrete paths quite successfully and make the home look more attractive.

If the ground is uneven, cord lines may be used as a guide to levels, and adjustments made by sighting along the lines until the desired gradient is found.

The ground should then be trimmed, and the area excavated so that the finished level of the path

will be about 2.5 cm above general ground level. It is essential that the site be well drained, so as well as removing all turf and top soil, any damp patches should be dug out and filled with sand or fine metal chips and then thoroughly compacted. If the path is on level ground, a cross fall for drainage away from the house 6mm per 300 mm of path width should be provided. This should be allowed for .in excavation and setting up of the side forms.

A rounded top to the edges of the slab will give the path a neat appearance and prevent chipping or other damage to the edges. For the side forms, timber battens, 100 mm by

25mm, with the top or screeding edges and the inside faces dressed are satisfactory, with plywood being used for curved sections.

The side forms are held in position at the required level by nailing to wooden pegs spaced at 800-900 mm intervals and driven well into the ground.

Considerble stress will be put on the formwork by the fluid concrete as it is being placed and compacted, so rigid bracing is necessary to avoid unsightly bulging and misalignment.

To facilitate removal of the forms after the concrete has hardened, the inside should be lightly greased just before placing the concrete. To assist drainage and

to allow unrestrained movement of the hardening concrete relative to the base, a bed of granular material, fine gravel or metal chips, is spread over the site before placing the concrete. The depth of this fill material should be such that its level comes to no less than 75mm below the top of the forms.

As concrete hardens it shrinks slightly, and to eliminate or reduce cracking, ... contraction joints should be provided at 2m intervals.

Usually this is done by inserting thin wooden strips 6mm thick across the path and to the full depth of the concrete. These strips may be left permanently in place or later removed after the concrete has hardened sufficiently to resist tearing.

A better type of contraction joint can be made by using a jointing tool. At the same intervals of 2m, grooves of 20mm deep and 10mm wide are cut into the stiffening concrete by drawing the tool carefully across the path. It is good practice to use a dressed piece of 150 by 25 laid across the path as a guide. To get a neat joint, this should be repeated several times as setting of the concrete progresses

up to the point when final trowelling of the surface takes place.

At the same time as contraction joints are being made or cut in the concrete, an edging tool used to prduce a curved top to the edges of the path should be run backwards and forwards against the top of the side forms.

Rapping the siaes of the forms with a hammer and spading along the edges of the slab will assist the concrete to consolidate. The surface should then be levelled off by moving a straight edge backwards and forwards with a sawlike motion across the top of the forms, always keeping a small amount of concrete ahead of the straight edge to fill any Inw c;nnt<: Before final finishing can be commenced all water must have disappeared from the surface and the water sheen must be starting to fade.

Steps should be taken to prevent damage to the surface of the path while it is still “green” and about 12 hours after finishing the path should be completely covered with damp sacking to ensure progressive hardening of the concrete. This “moist curing” should be continued for one week.