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Waterproofing of a closed concrete drinking water tank


0) Introduction

This is the system for the waterproofing of a closed concrete drinking water tank with a seamless thick elastomeric membrane, liquid applied (cold), able to bridge over fissures and also to resist continuous contact with water. The sistem is valid for a new concrete tank, in order to prevent the occurrence of leaks in the future and also for the refurbishment for an old tank with already some leaks that should be repaired.

1) Advantages of the polyurethane coating over the traditional acrylic cement coating

Boths systems are liquid applied and once they get cured form a seamless and
continuous coating. IMPERMAX AQUA 2K coating is flexible and elastic with an
outstanding ability to bridge over fissures. However a cementitious-acrylic
coating is just a very slight flexible, but not elastic, it has a the capacity to adapt
itself to a small movements of the concrete surface, however it has not the
capacity to bridge over medium or large fissures. The result is that normally
some leaks appear relatively shortly after the application of an acryliccementitious
coating, mainly if it is a new tank that is still setting on the ground.

2) Description of the materials

Epoxy 100 Primer is a two component epoxy resin, that even it has no solvents
it has got very low viscosity. It should be applied over a well dry surface.
Humidity primer is a two component epoxy resin, water based that could be
applied over a surface with small remain of moisture. When it is applied it has
got a milky appearance, once it gets dry, it becomes clear. The curing time
could be accelerated (low temperatures, closed area) with the Accelerator IH.
IMPERMAX AQUA 2K is a two component polyurethane resin, totally free of
solvents, roller applied. It has got quite low thixotropy, so over a vertical surface
should be additivated with the Thickening Additive (powder form). It has got a
drinking water certificate, following European specifications.

3) Description of the application process

The Impermax Aqua 2K, the Humidity Primer and the Epoxy 100 Primer could
be applied with a roller. The surface must be smooth, dry, free from oils, greases, waxes, silicones…If it is new concrete, it should be well-cured and dry and free from laitance.
0- Repair the cracks, holes, remove part of the surface that is not well adhered..

1- Primer
1.1: If it is new concrete water tank, well-cured and well dry: 1 coat of about 0,3
kg/m2 of Epoxy 100 Primer. 2 component Epoxy resin, 100% solids.

1.2: If it is a water tank filled with water in the past, with remains of moisture
inside the surface: 1 coat of about 0,3 kg/m2 of Humidity Primer, two
component Epoxy resin, water-based. In order to help the resin get cured in a
closed area (and help the water evaporate from the resin) forced ventilation is
advisable. In a closed area Accelerant IH is also advisable.

2- Reinforcement of singular points: cracks, joints, corners…Apply a first thin
coat of Impermax Aqua 2K and reinforce it with the non woven geotextile
GEOMAX. The self adhesive strip Butyl Tex could also be used.

3- Apply one coating of approximate. 1,5 kg/m2 of IMPERMAX AQUA 2K with a
roller (2 component elastic PU resin, 100% solids with no solvents). Over the
vertical surface the Thickening Additive must be used to avoid the sagging of
the resin (1-3% of additive in the resin). The vertical surface is coated firstly and
afterwards the horizontal surface.

4) Remarks

Let the material dry about 10 days before filling the tank with water. Rinse the water tank with water and mild detergent before fill it with drinking water.