Khalda Petroleum Waterproofing, Abu Gharadig

02 · The challenge

What did this structure ask of the membrane?

Tiled roofs already have a thousand joints. An evaporation pond holds process water in the open desert. Villa roofs take foot traffic and sun. One product cannot pretend those are the same job, so the build-up changes with the exposure.

04 · Application

How is this system built?

Concrete is prepared before any resin goes down. Polyurea Rayston, Krypton’s hot-spray pure polyurea, wants a support that is flat, compact and cohesive. Pull-off strength should be at least 1.4 N/mm2. Cracks are cut out and filled first. High-pressure sand or abrasion opens the pores, and the dust is vacuumed off. Moisture in the concrete must sit under 4 percent. Concrete temperature belongs between 10 and 40 degrees C, and the air should be under 85 percent relative humidity. If damp is suspected behind the slab, two coats of epoxy primer go on, the second one blinded with quartz sand. Metal is cleaned and primed with a polyurethane primer. That bond is what stops a blister when the structure heats up.

An Egyptian roof takes full sun, a wide swing of temperature between afternoon and night, and dust on the wind. The membrane has to stay elastic while the slab moves, and an aromatic film left bare will fade even if it keeps its strength.

Spraying is hot and fast. Both components are brought to about 25 to 30 degrees C before they are loaded. In the machine they run hotter: about 65 degrees C on the resin, 75 degrees C on the isocyanate, and 65 degrees C in the hose. Pressure at the gun is at least 140 bar. The usual build is 1.5 to 2.0 kg/m2, which leaves a film about 1.5 to 2 mm thick. Gel time is about 4 seconds at 25 degrees C. The surface is tack-free in a matter of seconds, not hours. Hardness climbs from roughly 28 Shore A at five minutes to about 88 Shore A after four days. One pass should make the thickness. Where a corner needs a second pass, it should follow within about two hours.

Speed is the practical gift on a crowded site. Upstands, outlets and internal corners can be closed before the next trade arrives. The film itself is elastic. Typical elongation is 324 percent and tensile strength is 16.2 MPa, with tear strength around 69 N/mm. It bridges cracks instead of snapping when concrete moves.

Polyurea Rayston is aromatic. Sunlight will change the colour. Strength does not follow the colour. An exposed face is finished with an aliphatic polyurethane such as Colodur or Impertrans when appearance matters. A buried planter or the inside of a tank does not need that coat to keep its strength. Root resistance is tested to CEN/TS 14416, which is the whole point beside shrubs and wet soil. Water uptake is very low, about 0.002 kg/m2 per square-root hour. Chemical testing puts the film in class II against 25 percent salt and class III against hydrogen sulphide and 10 percent sulphuric acid. Drinking-water migration tests and a WRAS material approval are on the same datasheet, which matters when a tank holds water people will use. The product carries CE marking to EN 1504-2 and European Technical Assessment 16/0148. Those are assessments of the product, not a measurement taken on this job.

Polyurea Rayston technical data sheet

After the spray, the job is in the details you can no longer see. Outlets must be part of the film, not a ring of mastic added later. Vertical turns need the same thickness as the floor. Soil, water or foot traffic should wait until the hardness has climbed, which for this polyurea is a matter of hours for light contact and days for full cure. An exposed aromatic film wants its aliphatic coat before the first hard summer. A buried one wants its protection board and drainage before the backfill. That is ordinary site discipline, and it is what lets a fast membrane still be there in twenty years.

06 · Products

Which products carry this duty?