What is the asphalt/concrete interface?
How airfield lighting sits in flexible and rigid pavement, and across the joint where the two meet: where cans go, how they are bedded, and what changes when the surface is overlaid.
The asphalt/concrete interface is how AGL equipment sits in the two main pavement types, and across the joint where they meet. Asphalt is flexible: its layers flex under load, soften with heat and are often overlaid. Concrete is rigid: it is laid as slabs with sealed joints that open and close with temperature.
It is a civil interface because those differences decide where a can sits and how it lasts. Cans are kept clear of slab joints and of the transition joint, which move and are resealed, and the bedding, grout and sealant must suit the pavement and be approved for it. Laying asphalt over concrete raises the surface and tends to bring slab joints up as cracks, so fixtures, cans, cable slots and seals need resetting and the circuits retesting afterwards. Agree all of this with the civil designer before the surface is closed or overlaid. Treat any cable as live until it has been isolated, locked out and proved dead, and work to the airport’s permit-to-work.
Layers flex and soften with heat. Often overlaid, so levels and bedding change over time.
Slabs with sealed joints that move. Cans are set clear of the joints.
Frequently Asked Questions
Q1What is the asphalt/concrete interface in airfield ground lighting?
The way AGL equipment sits in, and across, the two main pavement types. Asphalt is a flexible pavement and concrete is a rigid one, and each treats a can, its bedding and its cable route differently. The term also covers the transition where asphalt meets concrete, such as an asphalt shoulder beside a concrete apron or an asphalt overlay on concrete slabs.
Q2How do asphalt and concrete pavements differ for lighting?
Asphalt layers flex under load, soften with heat and are often overlaid, so levels change over the life of the pavement. Concrete is laid as slabs separated by joints that open and close with temperature and are sealed. These differences decide where a can sits, how it is bedded and how often the interface is disturbed.
Q3Why keep cans clear of slab joints?
A slab joint moves and is resealed from time to time. A can that sits on or close to a joint can be loaded by that movement, and its bedding and seals can be damaged. The layout normally sets the clearance, so follow the design drawings and agree any exception with the civil designer.
Q4What happens where asphalt meets concrete?
The two materials have different stiffness and movement, so the joint between them can crack or open. Cans and cable slots are normally kept out of it. The transition joint is kept sealed so water cannot reach the layers and the lighting below.
Q5What happens when asphalt is laid over concrete?
Joints and cracks in the slabs below tend to show up again as cracks in the new surface. The overlay also raises the surface level, so fixtures and cans need resetting, cable slots reinstated, and bedding and seals renewed. Agree this with the civil team before the works and test the circuits afterwards.
Q6Can the same bedding and sealant be used in both pavements?
Not automatically. Bedding, grout and sealant must be compatible with the pavement material and the temperatures it sees, and approved by the manufacturer and the pavement designer. Use the materials the design and the manufacturer's data call for.
Q7Where are the requirements defined?
FAA AC 150/5340-30 covers design and installation of airport visual aids, AC 150/5370-10 covers construction standards, and ICAO Doc 9157 Parts 3 and 5 cover pavements and electrical systems. Confirm against the current edition, the design drawings and the manufacturer's data.
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