28th JULY 2011
TECHNICAL SPECIFICATION AND METHOD STATEMENT OF
ARDEX A 37 SCREEDING
SUBMITTED TO:
PROPOSED BY:
ARDEX ENDURA (INDIA) PVT., LTD, BANGALORE

System Recommendations

This document is proposal for the follwing applications:-

1.Bonded screed using A 37 in ratio of 1:5 at minimum 25mm thickonwards with necessary bonding agent.

1.1.Products Involved:

P51:A concentrated, blue, synthetic, water-based, solvent-free multi-purpose primer with a wide range of applications which, after drying, helps to inhibit the penetration of water from subsequently applied materials.

A 37: Cement based polymerized screeding cement with rapid dry formula, produce rapid usable screed.

Aggregate - Sand:

  • The quality of sand, i.e. its concrete making properties, has a large influence on the quality of resulting screed and it should be concrete sand –not plaster sand.
  • Ideally to be used is river sand, if available. Crushed stone is possible to be used if grading is maintained as per chart below.
  • ARDEX could supply the sand from a known and certified source and provide QC on site if awarded the contract for screeding works.
  • To produce a mix that is easy to finish to a smooth surface, it may be necessary to blend two or more sands.

Retention on 8mm – 0.6%

Retention on 4mm – 14.7%

Retention on 2mm – 26.4%

Retention on 1mm – 38.4%

Retention on 0.5mm – 67.3%

Retention on 0.25mm – 95.4%

Retention on 0.125mm – 99.4%

Retention on 0.063mm - 100.0

1.2.Application Procedure

1.2.1.Substrate inspections;

Before starting actual installation, ensure that the following parameters should be inspected:

  • Substrate or base screed should be laid at least 28 days old or as per installer’s specification and recommendation, so the setting process is completed to avoid shrinkage cracks.
  • Flatness of the base should be checked for level to ensure that the specified thickness of screed can be applied over the whole area.
  • The substrate or base screed should be fully compacted and laid to the tolerances (+10/-3 mm) within given limits.
  • All expansion and movement joints shall be properly cut and maintained for terminations as per structural drawing.
  • The area must be handed over to ARDEX Endura and/or its partner company cleaned by broom, eventual debris of other work steps must be removed by the responsible agency or the client prior application of the screed

1.2.2. Bonding agent:

  • P51 shall be mixed with clean water in 1:1 ratio followed by mixing of A37 and sand (0-4mm) sand as fine aggregates in 1:1 in dry condition, thus mixed A37 and sand shall be added with then mixed P51 and water to obtain required consistent slurry.
  • Thus obtained slurry shall be spread over the substrate where A 37 screed is expected. Note: The slurry shall be prepared simultaneously while the A37 mix is being ready. The A 37 screed shall be applied whilst the P 51 bonding slurry is wet. Any dried slurry is again recoated with P 51 slurry.

1.2.3.Mixing of A 37

  • A 37 is mixed with sand as in fine aggregates of 0-8mm in ratio of 1:5 using standard forced action mixers or using screed pump.
  • The quantity of water used in A37 screed should be kept to the minimum consistent with the need to compact the screed material fully. Approximately 6-11 litres per 25 kg bag depending on moisture content of the sand. Every batch of mix shall be checked with the squeeze ball test to indicate ideal water content being achieved.
  • Note: The working time for mixed A37 screed is approximately 1 hour. However the working time may shorten in higher temperature care needs to be taken in such case to finish the mixed materials within the set time

1.2.4.Installation of A 37

  • Install A 37 screed 40mm (or required) thickness over a wet P51 bonding slurry.
  • Compact the screed thoroughly using necessary power floater to the required levels with uniform finish making it ready to receive subsequent waterproofing layers.
  • The finished surface should be free from excessive friability.
  • No water/cement slurry or additional cement may be used during power floating as it will form a weak layer due to inadequate cement/water ratio.
  • Slightly rough and porous surface is acceptable and even preferred for subsequent tiling/natural stone fixing, because a mechanical key will be achieved, not solely a chemical adhesion.
  • The mixed material is supposed to be installed in such a manner and speed, that at any time the wet edge is maintained

1.2.5.Protection of Green Screed

  • Freshly laid levelling screed surface should be given adequate protection against damage or wear during subsequent building operations and until the final flooring is laid.
  • Immediately after finishing of the screed, protect with barricading to give adequate protection against damage or wear during subsequent construction operations until the final flooring is laid.
  • Direct sunlight should be avoided during initial drying period.