Imprinted Concrete

Weather is a major factor with imprinted concrete and the installation process depends heavily on what the weather throws at us. As the agreed installation date approaches, the trader will generally reconfirm the starting date. They are usually able to carry out the initial steps of the installation process in most weather conditions. However, as they require dry weather on the day concrete is to be poured, the start date may be delayed. Traders will always try their best not to deviate too far from the start date but unfortunately the weather is the main predictor.

Job Site Preparation

Generally, most sites have previously installed paving: brick, tarmac, concrete or slabs. Removal of these will be carried out using suitable plant machinery for the job site. For tight, small areas, hand excavation may be carried out if mini excavators cannot access the area. Preparation usually takes one day, but can take longer if the scale of the work is larger.

The standard foundation construction of using MOT type 1 will be laid to 150mm thick and consolidated in two layers of 75mm thick, using a heavy wacker plate or vibrating roller.

Drainage requirements, addition of linear drains, recess man holes and single point gulleys are addressed and installed at this stage. These are all set at the correct finish levels prior to pouring.

Shuttering to achieve your chosen outside perimeter shape is erected and also set at the correct finish levels. The shutter also denotes the thickness of the concrete surface – typically 125mm thick or 5”.

At this stage, concrete is ready to be installed provided that there are no delays due weather conditions or any other unforeseen factors. Wet weather or an outside ambient temperature of less than +5 centigrade will prevent the concrete pour.

Imprinted Concrete Installation (Pour Day)

On the day of the pour, the contractor will typically arrive on site about an hour before the concrete is due. Usually around 7:30-8:00am.
During this first hour, all the equipment will be prepared and a polythene membrane will be installed to protect walls, windows, doors and any other areas which need protection from concrete splashes, colour surface hardener and release agent.

Concrete is batched and delivered to the site. The mix must be air entrained (AeA) – a specific add mix which is used for concrete intended for outside use. It will typically be of a consistency of 80 to 100 slump, and have a strength rating of C25 or higher. The concrete may have fibres within the mix and additional steel mesh reinforcement may also be installed.

The concrete is poured and levelled to the required predetermined levels and falls, then screeded. A roller or power tamp will be used to bring up the fat which is then trowelled. Generally, it takes two hours to do this on a 50m² pour. This may vary depending on accessibility to the job site and unloading of the concrete.

The concrete is then coloured with the powder colour surface hardener (your main colour of choice). One bag per 10m² is cast out over the wet concrete.

The concrete is then closed, and when the condition of the curing concrete is suitable, the colour powder release agent (your secondary colour of choice) is cast over the closed coloured concrete.

The colour powder release agent prevents the imprinting mats from sticking to the concrete during printing. It also adds a secondary antique colour to the imprint which gives the concrete its natural stone-like effect. As it is hydrophobic by nature, it can repel small quantities of water from the surface and protect the concrete surface during the curing stages.

Once imprinting has been completed, the site is closed off and pets must be kept away in case they wander over the imprinted concrete. The release agent is a very fine dust which you must try to avoid getting on your shoes and bringing into your home until it is power washed after a few days.

Cutting Of Expansion Joints

During summer months, expansion points (control joints) need to be cut within a 24 hour period after the concrete has been poured.

During winter months, this 24 hour period is not as critical as the concrete surface may not have cured enough within the time. In this case, the cutting of control joints is usually delayed by two days or more.

Removal of Powder Release Agent

Once the trader is satisfied that the concrete surface is fully hardened and cured (usually after a few days), the release agent is removed from the surface of the concrete.
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The surface is then treated with a release agent wash. This will break down more surface release agent and remove the majority of the remaining powder.

After that, the surface is power washed to remove both the acid wash and remaining free release agent.

The above steps can be repeated if the trader feels that more removal is required.

Sealing

The pattern imprinted concrete surface must be thoroughly dry before sealing. The sealing process is weather dependent and will need to be done in favourable conditions.

During summer months, sealing may be carried out on the same day as the removal of the release agent – again, depending on the drying conditions.

After sealing, the control joints (expansion joints) are then filled with a bead of silicone filler. This prevents water and dirt getting into the joint and possibly inducing edge spalling (cracking or chipping) in the winter.

Completion of Installation Process

After sealing is completed, aqua drains, gulleys and manhole covers will be checked to ensure that they lift freely and easily.

Any remaining items from the installation process will be removed and the site will be cleaned.