PREPARATION: THE KEY TO A SOUND SUBFLOOR
Paul Igo, Technical Director at The Preparation Group, explains the importance of preparing a surface to make for a sound subfloor.
When selecting the correct equipment and methods for a job, consideration must be made for potential problems such as uneven joints, high spots, contaminants, worn coatings, sticky residues, old tiles and friable substrates, which need to be tackled to achieve a clean profiled surface suitable for the application of the specified flooring system.
There is a wide range of surface preparation machines and accessories on the market and a vast array of techniques that can be employed - each producing a different result. The model, size and power requirements of the machine will determine production rates achievable, together with the accessories selected and the type, thickness and composition of the material to be removed. Other important factors to consider are; area size, location and accessibility, the power supply available and, critically, the profile required for the specified material to be applied. It is important to note that surface preparation machines are also designed to work with vacuums or filtration units to minimise dust contamination.
SHOTBLASTING
In the correct conditions, shotblasting is one of the most cost- effective methods of preparation. When concrete is not finished correctly, or if it has been brushed/ tamped, the surface may have a large degree of laitance, commonly termed “fat”. To achieve a sufficient bond for the specified system to be applied, this laitance must be removed and shotblasting is the ideal method. It is also selected to clean and key power-floated concrete and to remove coatings and light surface contaminants.
Shotblasting machines are available in walk-behind 110v single-phase and
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three-phase electric and ride-on versions. The model number usually relates to the operating width of the machine.
The process involves steel shot or abrasive which is propelled at high velocity (by a rotating wheel contained in the body of the machine) onto the background surface to produce the desired profile. The machine reclaims the shot, whilst the debris is removed and collected by a dedicated vacuum/ filtration unit for disposal.
There is a huge array of profiles that can be achieved, each determined by the size or grade of shot selected and the speed at which the machine is propelled.
Surfaces to be shotblasted must be sound/hard. It is not suitable for removing or treating soft compositions or materials in excess of 2mm in thickness. It is important to note that due to the nature of the operation, shotblasting will produce a lining effect, commonly known as tramlining. This can be minimised with operator experience but cannot be eliminated. The process will also highlight surface defects in the background surface.
Shotblasting cannot be applied to wet or damp conditions and, for optimum results, the process requires a smooth even surface otherwise the shot will escape from the machine.
www.tomorrowscontractfloors.com PLANING
You would select planing to remove materials in excess of 2mm in thickness, when there are multiple layers of coatings and when a rippled profile is required. Applications include the removal of old screeds, asphalt, latex and adhesives and for reducing tamped surfaces and levels.
Machines range from small 110v single-phase, to larger three-phase electrically-powered petrol or diesel walk-behind models and ride-on versions for large-scale projects and heavy-duty applications.
The planing operation is based on a drum rotating at high speed within the body of the machine. The profile or texture is created by the accessories fitted to the drum known as flails, or picks in the case of ride on models, which are interchangeable. Once contact is made with the surface being treated, the flail configuration cuts with a downward rotary action.
There are different shapes and sizes of flails and picks available for specific
tasks and they can be arranged on the drum for light cleaning applications through to heavy-duty grooving. Generally, milling flails are for the removal of thermoplastic line markings, bitumous and rubber deposits, TCT flails for cleaning, texturing and roughening concrete and star flails and beam flails for removing soft material compositions. Picks can remove and reduce materials in excess of 2mm and up to 25mm.
It is important to note that hard surfaces may be a problem for smaller planing machines as there is not enough weight to cut into the surface. This can result in the machine malfunctioning and becoming a hazard to the operative.
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