Compound Square Waterproofing
In 2018 the roofs and the irrigation tanks at Compound Square were waterproofed with hot-sprayed pure polyurea. Krypton Chemical makes the resin. The crew on site sprays it.
Overview
Compound Square is a residential compound: low blocks, planted courts, and the roads that loop between them. Water on a job like this has two addresses. It falls on the roofs, and it sits in the irrigation tanks that feed the landscape.
In 2018 both were lined with the same family of membrane. Hot-spray pure polyurea. One film on the decks, one film inside the tanks. Krypton Chemical supplies Polyurea Rayston for that duty.
| Project | Compound Square, Egypt |
|---|---|
| Year | 2018 |
| Roofs | Hot-spray pure polyurea |
| Irrigation tanks | Hot-spray pure polyurea |
| Membrane | Polyurea Rayston |
Challenge
A compound roof is a field of small decks, not one heroic slab. Each block has its own upstands, its own outlets, and its own afternoon in the sun. Water does not fail in the middle of a roof. It fails at the parapet, where the film is thinnest and the movement is greatest.
The irrigation tanks are the other half. They hold water for the gardens through a long season. A lining that is sound on the floor and weak at the outlet will lose level into the slab, and the first sign is a wet ceiling in a room that has nothing to do with irrigation.
Doing both with one resin is only sensible if that resin can take immersion and can take UV-driven movement. The detailing still changes. A roof outlet is not a tank flange. The gun has to know which one it is standing in.
Solution
Polyurea Rayston is a two-component pure polyurea, hot-sprayed. It gels in about 4 seconds at 25 degrees C, so dust on an open roof does not get a long wet film to land in, and a tank corner stays where it was sprayed. The typical build is 1.5 to 2.0 kg per square metre, about 1.5 to 2 mm.
Elongation is about 324 percent and tensile strength about 16.2 MPa, with tear strength of 69 N/mm. Liquid water permeability is 0.002 kg per square metre per square-root hour. On a roof that elongation is the daily swing of the concrete. In a tank it is the bond that has to live underwater at the cove.
The resin is aromatic. On a roof the colour can shift in the sun without the strength following it. An aliphatic topcoat holds the shade where the deck stays exposed. Inside a tank the sun is not the question. The outlets are.
Application
Concrete first. Pull-off at least 1.4 N/mm2, moisture under 4 percent, surface between 10 and 40 degrees C. Open the pore by grinding, repair cracks before the spray, knock sharp edges off the upstands, and vacuum the dust. A compound roof collects grit between blocks. A tank that has already held water can look clean and still carry laitance.
If damp is suspected from below, the datasheet calls for two coats of epoxy primer, the second blinded with quartz. Metal outlets and tank flanges are cleaned and primed with the polyurethane primer. Then the machine: components preconditioned around 25 to 30 degrees C, the amine side stirred and pigmented.
Spray at 65 degrees C on the amine, 75 degrees C on the isocyanate, 65 degrees C in the hose, and at least 140 bar. Watch the build so 1.5 to 2 mm lands on the field and on the detail. On the roofs the pass includes the parapet and every outlet. In the tanks the pass includes the cove and every flange. Gel in four seconds means the detail is sprayed and left. It is not brushed out later.
The roof can be walked once the film has hardened through the first hours. The tank is accepted with a water test: fill it, hold it, and look at the outlets if the level moves. Hardness on the datasheet is tracked from five minutes through four days at 25 degrees C. The calendar is the same resin. The acceptance is not.
Results
Compound Square, 2018: roofs and irrigation tanks in hot-spray pure polyurea. The roofs take the sun and the movement. The tanks take permanent water. Both get a film that is one piece, at the thickness the datasheet sets, with the outlets in the same pass as the field.
Crack bridging reaches class A5 at minus 10 degrees C and class B4.2 at working temperature and in the cold. Egypt will use the movement, not the frost. Shore hardness of 87A and 35D leaves a lining that maintenance can walk, on a roof or in a drained tank.
Products
Polyurea Rayston
Hot-spray pure polyurea for the roofs and the irrigation tanks. Typical 1.5 to 2 mm. Elongation about 324 percent. Gel about 4 seconds at 25 degrees C.
FAQ
Why one membrane for roofs and for irrigation tanks?
Both stay wet in their own way. A roof takes sun and a daily temperature swing. An irrigation tank holds water all season, with outlets and a floor-to-wall corner. Polyurea Rayston is sprayed for both: about 1.5 to 2 mm, elongation about 324 percent, gel in about 4 seconds at 25 degrees C.
How thick is the film?
The typical rate is 1.5 to 2.0 kg per square metre, which builds about 1.5 to 2 mm. That is datasheet data, not a core from Compound Square.
What does the concrete need first?
Pull-off at least 1.4 N/mm2, moisture under 4 percent, and a surface between 10 and 40 degrees C. Open the pore, repair cracks, and vacuum the dust. A tank flange is primed metal, not bare steel.
Can the roof move in the sun?
Elongation is about 324 percent. A villa roof in Egypt swings between noon and night. The film has to follow the deck and the upstand, or the water finds the parapet.
When can an irrigation tank take water?
The polyurea is touch-dry in minutes. The tank should still be checked at the outlets and the corners, then filled as a water test, before it is handed to the irrigation system.
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