Top Tips On Stripping, Grinding & Shotblasting
Tracey Glew, group md, The Preparation Group, explains why preparation is key to create a sound background surface for the successful application and durability of screeds, resins and coatings:
WHEN selecting equipment and methods, always consider potential problems such as uneven joints, high spots, contaminants, worn coatings, sticky residues, old tiles and friable substrates, which must be tackled to achieve a clean profiled surface suitable for the application of the specified screed.
There is a huge range of surface preparation equipment available and a vast array of techniques, each producing a different result. The model, size and power requirements will determine production rates achievable, together with accessories, and the type, thickness and composition of the material to be removed.
Other important factors are: Area size, location and accessibility, power supply available and critically, the profile required for the screed to be applied. Surface preparation machines are designed to work with a filtration unit to minimise dust contamination.
When concrete is not finished correctly or if it has been brushed/tamped, the surface may have a large amount of laitance, commonly termed ‘fat’. To achieve a sufficient bond for the specified material to be applied, this laitance must be removed.
n Multi-stripping: This method is used to remove material from the background surface or to clean it and is often selected when there are no other effective options. There are 110v hand operated, walk behind machines for clearing small areas and large ride-on three-phase electrical or propane powered machines for clearing large areas.
Blades or picks are attached to the front of the machine and their type, weight and position affects the removal of the designated surface. Select a flat blade to scrape off tiles, latex, adhesives and elastomeric systems, whilst you can choose a curved blade to cut material into manageable lengths as it strips, or to lift up carpet and sheet vinyl.
Use picks to break up hard materials such as ceramics and terrazzo tiles.
Having stripped the floor, additional techniques for floor preparation are often specified to provide a suitable background surface for applying the screed or resin.
n Planing: Select planing to remove materials in excess of 2mm thick, when there are multiple layers and if a rippled profile is required. Applications include removing old screeds, asphalt, latex and adhesives and 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 profile or texture is created by the flails fitted to the drum, or picks in the case of ride-on models, which are interchangeable. Generally, milling flails are for removing 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.
n Grinding: Select grinding when a flat, level and smooth concrete profile is required. It removes surface contaminants, adhesives, paint, sealers and coatings and cleans. Grinding models are available in single-phase or three-phase electric and in single-head, double-head, and multi-head versions. There are also diesel and petrol powered alternatives and variable speed models which can be fitted with provision for wet grinding and polishing applications.
The grinding principle is achieved by diamond, tungsten or resin-bonded plates or discs secured to the single or multiple rotating heads for removing adhesives and coatings and for grinding, smoothing and polishing decorative screeds and concrete screed.
As a general rule hard compositions require a soft bond diamond and soft compositions a hard bond. Selection is important, otherwise the machine will simply glaze over the surface without creating the profile or will ‘wear out’ extremely quickly in the initial stages of the operation.
Grinding is not recommend if the surface is uneven or on ‘tamped’ concrete.
n Shotblasting: In the correct conditions, Shotblasting is one of the most cost effective methods of preparation, selected to clean and key power-floated concrete, to remove laitance, coatings, light surface contaminants and for steel preparation. Surfaces must be sound/hard. Shotblasting is not suitable for removing or treating soft compositions or materials in excess of 2mm in thickness.
Shotblasting machines are available in walk-behind 110v single-phase and three-phase electric and ride-on versions. The model number usually relates to the operating width.
The process involves propelling steel abrasive onto the surface, the desired profile determined by the grade and speed of the machine. The debris is collected in a vacuum/filtration unit, for disposal and the shot recycled.
It is important to note that shotblasting will produce tramlining. This can be minimised with operator experience, but not eliminated. Shotblasting will also highlight 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.
This article has been reproduced from the Contract Flooring Journal website. You can find them at www.contractflooringjournal.co.uk.