Preparation
The concrete substrate must be a minimum of 28 days old, with a residual maximum moisture content of 75% RH. The substrate should be solid and sound with a minimum compressive strength of 25 N/mm2 and a minimum pull-off strength of 1.5 N/mm2.
Ensure a damp proof membrane has been installed and is functioning properly. If in doubt, test an area first to ensure there is no rising damp. If damp is detected, please contact the Polycote Technical Helpline for further information.
For the maximum adhesion and performance of the screed, thorough preparation of the substrate is essential, and all surfaces must be clean, sound, dry and free of surface laitance. A list of recommended preparation methods, are as follows:
- Powerfloated concrete – use a Vacuum Assisted Shotblaster to remove weak laitance and provide a surface key for the coating. If this is not possible, chemically etch with Polycote Etch IT, then rinse thoroughly and allow to dry.
- Loose paint or rust – remove, using a Vacuum Assisted Shotblaster, Floor Grinder or equivalent method
- Loose or friable concrete – use a Vacuum Assisted Shotblaster. If this is not possible, chemically clean with Polycote Etch IT then rinse thoroughly and allow to dry
- Metal – use a shot-blaster to prepare the surface to SA2.5 (bright steel) and primed with ZP Primer. Deck plates of 4mm or less do not provide a sufficient substrate for Flortex PU Screed, please contact Polycote Technical Helpline for further information.
- Weak Concrete/Holes – weak concrete must be removed and holes should be filled, prior to the installation of the screed. Please contact Polycote Technical Helpline for further information.
Polyurethane screeds tighten as they cure, so a ‘toe-hold’ must be formed at all terminating edges, including perimeter walls, day joints, expansion joints, drains, manholes, inspection lids and door thresholds. This prevents the screed from pulling away from the edges and ensures full bond to the subfloor.
The toe-hold should be cut approximately 150mm from the edge and run continuously along it. Minimum size: 20mm wide x 8mm deep.
Priming
First and foremost, it is essential to establish the correct primer for your floor. This is dependent upon the hardness/porosity of the substrate, the application temperature, the speed of cure required (mostly governed by the amount of downtime allowable) and whether or not there is any damp or oil/contamination present. If in doubt, please consult with one of our technical team before purchasing any material.
Ensure all surfaces are primed as per the application instructions on the specific product data sheet. Make sure the toe-hold grooves are fully primed. It is very important that the primer does not fill the groove and that a minimum depth of 8mm is maintained. Whilst the primer is still wet, broadcast the aggregate (as provided) to provide a suitable ‘key’, thereby ensuring an excellent adherence of the screed to the substrate. Once cured (this is mostly the following day, ensure that any and all unbonded aggregate is removed prior to the application of the screed.
Mixing
Stir the individual components before mixing together. Add Part ‘B’ to Part ‘A’ and thoroughly mix in a rotary drum mixer for at least 1 minute before adding the aggregate. For smaller quantities, a heavy-duty slow speed drill with a mixing paddle may be used. Steadily add the aggregate whilst continuing to mix. Once all the aggregate has been added continue mixing thoroughly for 3 minutes.
Number of parts supplied: 3
Never mix by hand. Furthermore, it is strongly advised not to spilt individual unit quantities. It is essential that the correct (individual part) quantities are used together with thorough mixing. The use of incorrect quantities and/or a lack of thorough mixing WILL result in a poor or non-cure situation.
Application
A constant supply of mixed material must be maintained to ensure a consistent application and to keep a continuous ‘wet edge’. The mixing station should be positioned as close to the application area as practicable. Pour the mixed material immediately onto the prepared and primed substrate and spread evenly with a trowel to the specified thickness, ensuring all toe-hold grooves are fully filled. Each new mix must be blended into the previously applied material, with a wet edge maintained at all times. Installation is recommended only by fully trained and competent tradesmen. A list of approved, nationwide Polycote contractors is available on request, offering reliable and professional installation services.
Application Temperature
The ambient temperature of the substrate as well as the working area should be a minimum of 15°C during the application and curing period. The surface of the substrate should be a minimum of 10°C. If the temperature of the room or substrate be allowed to drop during the application and/or curing process, this will adversely affect both the curing and final strengths/performance of the screed. Should the screed be exposed to damp during the curing process, this may also adversely affect both the colour and appearance of the system. Therefore, the substrate and uncured floor must be kept at least 3°C above the dew point to reduce the risk of condensation or blooming on the surface. The unmixed materials should be a minimum of 10°C prior to mixing/installation.
