FUNDAMENTAL PRINCIPLES OF AIRCRAFT HANGAR FLOOR COATING DESIGN

The aircraft hangar floor coating process begins with on-site concrete design. Before concrete placement, soil investigation, groundwater level, drainage conditions, and soil compaction must be evaluated. Concrete is poured in accordance with structural design, leveled using vibrating screeds, and finished with power trowels (helicopter trowel). Expansion and control joints are designed according to the project requirements.

Concrete must cure for a minimum of 28 days, achieve sufficient strength, and have a low moisture content before any coating is applied. Moisture rising from the substrate must be checked, and suitable ambient and surface conditions must be ensured.

Subgrade and Concrete Design

Hangar floor coating design starts with field concrete design. Before concrete pouring, geotechnical and foundation reports are reviewed to determine the groundwater level and soil void ratio. A suitable drainage system is then designed and the soil is compacted. Depending on the site location and soil conditions, appropriate waterproofing systems are planned beneath the foundation in compliance with relevant standards.

According to the structural design, the concrete thickness and class are defined and the slab is cast in compliance with standards.

Concrete Placement and Joint Design

During concrete placement, leveling must be carried out using vibrating screeds, followed by power trowel finishing. Expansion joints and control joints must be designed according to the structural layout. Otherwise, subsequent coatings may crack or fail as the concrete moves.

Control joints must be cut at least 1/3 of the slab thickness after a minimum of 24 hours following casting. In a properly designed system, floor coating should only begin after at least 28 days of curing.

Concrete must reach a minimum compressive strength of 25 N/mm² (C20 class) and a minimum tensile strength of 1.5 N/mm. Moisture content at 2 cm depth must be below 4%.

Test methods: C-Aquameter, CM Device, Darr Method.



Moisture Control

There must be no rising moisture from either new or existing concrete substrates. Groundwater may rise through capillary action, causing floor coatings to blister and delaminate.

This condition can be detected with a simple polyethylene sheet test. A transparent polyethylene sheet is sealed to the concrete surface using polyurethane mastic. If moisture droplets form under the sheet, the floor must not be coated. If no moisture is observed after 24 hours, the surface is suitable for coating.

Environmental Conditions

The hangar roof, walls, doors, and windows must be completed. Ambient and surface temperatures must be between +10°C and +30°C.

In cold conditions, products should be stored at +20/+25°C before use. Rain, dust, wind, animals, and insects must be prevented from entering the building while the coating is fresh.

In resin-based systems, pot life and curing time are affected by ambient temperature, substrate temperature, and humidity.

Low temperatures slow curing and extend working time.

High temperatures accelerate curing and shorten working time.

The temperature must not fall below the minimum limits specified by the manufacturer until full curing is completed. After application, the coating must be protected from direct water contact for at least 24 hours.

If water contact occurs, softening and blistering may appear, and the coating must be completely removed and reapplied.

Application Procedure

When selecting coatings for aircraft hangars, the most suitable system should be chosen among epoxy, polyurethane, and polyurethane concrete coatings, considering substrate conditions, traffic loads, temperature and pressure variations.

In terms of performance, polyurethane concrete coating systems are generally preferred because they provide greater thickness, higher resistance to heavy loads, superior thermal stability, and excellent chemical resistance. Therefore, this article focuses on polyurethane concrete coating design.



Surface Preparation

Concrete substrates must be prepared using abrasive equipment (shot blasting, milling, diamond grinding, etc.) to remove laitance and obtain an open-pore surface. Weak concrete must be removed, voids and holes fully opened, and dust cleaned using an industrial vacuum.

Cracks, voids, and damaged areas must be repaired. For surface repairs and leveling, 60–70 AFS (0.1–0.3 mm) quartz sand should be mixed with special polyurethane concrete primer depending on site conditions.

Because polyurethane concrete may generate internal tensile stress, 8–10 mm wide joints must be created along columns and across the floor (every 4–5 meters). These joints must be cleaned and then filled with polyurethane concrete after primer application.

Primer Application

Polyurethane concrete primer is a solvent-free, three-component system, specially formulated for industrial flooring using modified polyurethane resins.

Because it is three-component, thorough mixing is essential. Use a mechanical mixer (e.g., Collomix CX 22).

Pour Component A into a mixing container.

Add Component B completely and mix for 1 minute until homogeneous.

Add Component C and mix for 3 minutes until homogeneous.

Avoid excessive mixing to minimize air entrapment.

Apply the prepared primer at 300–500 g/m² using a roller, trowel, or notched trowel.

Ensure the surface is fully and uniformly coated without voids.