Imprinted Concrete

Imprinted Concrete

Imprinted concrete, or more accurately, patterned imprinted concrete, is a specialised method of providing hard standing areas for car parks and driveways. It is a multi-process technique, involving the removal of any existing material – concrete, block paving, tarmac etc, and replacing it with a sub-base of dolomite or MOT Type 1, compacted to a suitable depth (150mm on firm ground), laid over a non-woven geotextile membrane, all stages being very similar to getting ready for block paving (see Block Paving).

This work may involve establishing firm edges to the area, adjusting inspection covers and any drains or metal hardware within the precincts of the project, in preparation for the next step, which is laying a bed of high strength fibre reinforced concrete to a even depth over the designated area, ensuring a uniform layer of wet concrete to a minimum depth of 100mm.

Once graded to running levels and falls, ensuring no low points remain where water can collect, the concrete is finished with a float. A colour hardener is then applied by hand, to suit the customers choice, spread with a steel float, then allowed to harden to a critical point, which will depend on the temperature at the time of laying.

A ‘release powder’ is then applied in preparation for the imprinting process. There are a very wide range of patterned moulds available, usually 600mm x 600mm, made from latex or rubber, which are then carefully placed on to the concrete, ensuring an even and equal pattern across the work, to achieve a uniform finish to the desired pattern. (Fish-scale, granite setts, curves, arcs, random rectangular paving slabs, cobblestones, circles – almost any pattern you can think of – subject to availability of the moulds.)

Once hardened, stress relief cuts are made to a depth of between 30 and 50mm deep into the concrete, following a line in the pattern to disguise the cut. These relief cuts are essential to prevent the mass of concrete from cracking through thermal movement, and are made right across the area, at approximately three metre centres across the project where stress or tension is most likely to occur. (Or maximum 20 sq m of area.)

The area is then pressure washed to ensure no dust or detritus remains on the surface before a final coating of acrylic sealer is applied to both enhance the colour, and make the surface impervious to oil and stains.

Although each part of the process is relatively simple, and pattern pads may be hired for use, it is important to understand the relevance of each stage, as without full knowledge of the art, you may be left with a concrete surface that will not accept the imprinting moulds, with results less than impressive, and only a shadow of a pattern for your efforts.

It is good practice to attach polythene or similar sheeting to buildings etc with duct tape to prevent cement stains and dyes from discolouring the brickwork during working operations.