Protection of outdoor sports court with aliphatic polyurethane paint

Descripción sistema

With the passage of time and the changing habits of an increasingly healthy society, we are faced with the need to find areas where we can practice outdoor sports. Due to the use and inclement weather, these types of facilities must be kept in perfect conditions of use.

In the following technical article we present the refurbishment of a 850m2 multi-sports court located in Sant Joan Despí (Barcelona).

Reason for the intervention

The sports court had an old paint coating that was badly worn and cracked and needed to be replaced to restore the functionality of the equipment.

Challenges and constraints

“Remove old coating and degraded parts.
“Choice of a protection and coating product with high resistance to weathering and UV rays to ensure maximum durability of the sports facility.

Molins Solution

“Preparation of the substrate and application of BETOPOX® PRIMER epoxy primer.
“Application of BETOPOL® aliphatic polyurethane protective paint.

Execution

“1. Preparation of the substrate
The concrete slab that makes up the sports court had a very degraded old resin-based coating that was completely removed by a thorough diamond grinding of the entire surface.
Dust and loose particles were then vacuumed away to ensure that the surface was completely clean and free of dust in the pores that could hinder or prevent the coating from adhering.
Diamond grinding provided a sound, rough, open-pored substrate to ensure proper penetration and adhesion of the epoxy primer. It was also ensured that the tensile strength of the concrete was greater than 1 N/mm2 by means of a tensile adhesion test in accordance with EN 1542, and that the humidity of the substrate was less than 4%, since the epoxy and polyurethane resin-based coatings that were to be applied do not harden correctly in the presence of humidity in the substrate.

“Application of the primer
BETOPOX® PRIMER is a two-component, low viscosity, 100% solids, clear epoxy primer, which was applied to the freshly prepared and clean substrate by short nap roller. At the time of application, it was ensured that the substrate temperature was not below 10ºC and not above 30ºC.
BETOPOX® PRIMER is supplied in pre-dosed 2-component sets. Partial mixing is never recommended as the mixing ratio is strict. For mixing, the contents of component B (hardener) were poured into the container of component A (resin) and both components were mixed with the aid of a low speed mechanical stirrer (<400rpm) ensuring that the stirrer reached the sides and bottom of the container and taking care not to incorporate air into the mixture, until both components were completely homogenised.
The pot life of the mixture in the container is approx. 30 min, so the sets were mixed as they were applied.
During the application of the primer, care was taken to promote the penetration of the product into the substrate with the help of the roller itself, in order to ensure the formation of a continuous, pore-free layer.
The consumption of BETOPOX® PRIMER was 250 g per m2.
To ensure that the primer performs its functions correctly (see technical note) it is important to respect the waiting times before applying the coating, which are a minimum of 12 hours and a maximum of 48 hours. The primer must be dry to the touch when the paint is applied.

“3. Application of the protective paint
After 24 hours from the application of the primer and after ensuring that it was completely dry to the touch, BETOPOL aliphatic polyurethane two-component paint, classified as class SR-AR1-B1,5-IR4 according to UNE-EN 13813, was applied in two coats.
BETOPOL is also supplied in pre-dosed two-component sets and the mixing process was carried out in the same way as for the primer.
The application was carried out with a short nap roller in two coats. The second coat was applied the following day, when the first coat was dry to the touch.
BETOPOL is sensitive to the alkalinity of the substrate, so in this case it was essential to use the primer beforehand.
Unlike coatings based on epoxy resins or non-aliphatic polyurethanes, BETOPOL has a high resistance to UV rays and therefore does not yellow outdoors, and this was the reason for its choice for this outdoor application.

Technical note

Functions of primers in floor screeds
Resin-based primers (generally epoxy) have several important functions in the application of floor coatings:
“Reinforcement and hardening of the surface layer of the substrate.
The impregnation of the substrate by resin-based primers contributes to improve the characteristics of the substrate. The resin, pure or with solvent, penetrates the substrate and hardens inside the pores of the surface layer, reinforcing it.

“Increasing the adhesion of coatings
Priming always improves adhesion but especially in the case of application of coatings with high filler content, as it improves the “wetting” effect between substrate and coating.

“Pore sealing
This is perhaps the most important function of primers. The primer fills the pores of the substrate by displacing the air they contain, thus preventing the appearance of bubbles and craters in the final coating and also avoids excessive absorption of material by the substrate, regulating its absorption.

“Protection of the coating against the alkalinity of the concrete
Some coatings, such as BETOPOL, are sensitive to the alkalinity of concrete, i.e. if they are applied directly on a high pH substrate such as concrete, they do not harden properly and do not form a film. In these cases, the use of a primer is essential.