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How to level cement screeds

How to level cement screeds

Applying leveling screed to a concrete base is a popular building practice in SA. This provides a strong, smooth surface to install flooring over.  Consult a contractor before screeding a large area, installing a thin floor (< 2mm / 0.08″) over the screed, or installing screed over underfloor heating.

If you are not installing new flooring and just want to level an old concrete floor use fast track self-levelling compound pumpable (SLC P) fast-track self-levelling screed.

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GOOD TO KNOW:

For fast track refurbishment and new construction where finishes such as carpets, ceramic tiles, vinyl, wood block or cork need to be applied quickly.

HERE’S HOW:

Preparation

  • The base slab or screed should be sound with a minimum thickness of 40 mm and with a minimum compressive strength of 25 MPa.
  • The surface must also provide a minimum tensile adhesion strength of 1.5 MPa.
  • All surfaces must be clean, mechanically sound and free of laitance, dust, grease and oil. Vacuum abrasive blast cleaning is the preferred method of surface preparation.
  • Wet grinding followed by vacuuming may also be used.

Bonding / Priming

  • Concrete surfaces should be primed with abe.®prime SLC acrylic primer.
  • Apply the abe.®prime SLC acrylic primer (refer to data sheet for additional information ) onto the floor surface by means of a brush and leave it to dry before applying abe.®screed SLC P.
  • Priming improves the adhesion of the abe.®screed SLC P to concrete, prevents formation of air bubbles and reduces water absorption into the sub floor.

Mixing

  • Correct mixing and proportioning of the abe.®screed SLC P, is essential for good results.
  • It is imperative to carry out the “flow ring” test on each new batch to ensure that the product performance properties are obtained and to provide ease of application.
  • Refer to the “Method statement abe.®screed SLC P” for additional information.
  • Add 5.0 L of clean potable water to the mixing vessel and whilst slowly stirring, slowly add the 25 kg of powder and mix for 1 minute. Once all the powder has been added mix for a further 4 to 5 minutes at a medium speed until the products consistency is obtained and is lump free and homogeneous. Avoid mixing at high speeds as this may entrap air.
  • The mix must be applied immediately after mixing, if the mix is left to stand the flow properties will be reduced due to the hydration process and impair the finish.
  • Excess water may lead to a friable surface and will reduce the strength of the abe.®screed SLC P.
  • Do not mix more abe.®screed SLC P than can be applied in 10 minutes.

Coverage (Powder)

  • 1.7 kg/m2 per mm thickness
  • 34 kg/m2 at 20 mm thick

Application

  • Pump or pour the mix over the concrete surface. For pumped application, ensure the continuity of electricity and water supplied is secured. Pump or pour the abe.® screed SLC P onto the floor in a continuous operation, feeding fresh material into a wet edge.
  • abe.® screed SLC P will level out to a smooth, even finish. Where necessary, release small air bubbles from the newly laid screed with a trowel, spiked roller or a tee-bar. This practice must be adopted within 5 minutes of application to avoid interfering with the final levelling properties.
  • Any lumps found in the product are to be removed before placing the product.

Refer to the “Method statement abe.®screed SLC P” for the application process.

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