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9525
Shepherd and Sons Contracting LTD
9525
9525, written properly as 95/25, is a grade of oxidised bitumen rather than a proprietary sealant. The numbers are its properties: a softening point around 95 degrees and a penetration around 25. It is unmodified, carrying no polymer or rubber, but it is air-blown in manufacture rather than raw. That makes it hard and rigid where N1 and N2 are designed to move, which is why its place is below the surface rather than on it. Our main use for it is sealing cable chases carrying airfield ground lighting cable, where a runway is being resurfaced and the chase will be buried under the new asphalt.
In our experience, 9525 works better than a surface-grade sealant for AGL chases because its rigidity and bitumen content protect the cable run through the full depth of the construction, where a flexible surface sealant would not hold up between layers.
Applications: sub-surface and inter-layer cable chases, AGL cable sealing, below-surface joints. A note on specifying it: 95/25 is a grade of oxidised bitumen, so there is no such standard as BS EN 9525. Oxidised bitumens sit under BS EN 13304, while hot applied joint sealants such as N1 and N2 sit under BS EN 14188-1.
Sealing a chase that will be buried
The order of work matters as much as the material. The chase is cut to width and depth and cleaned out, because debris left in the slot stops the bitumen bonding to the sides. The 95/25 is heated in a boiler, hotter than a surface sealant needs, and run in over the cable. It is filled to the level the new asphalt will sit on and no higher, since anything standing proud becomes a bump under the paver.
Once the overlay goes down the seal cannot be reached again for the life of the surfacing, so it is inspected before the asphalt arrives rather than after. On a live airfield all of this happens inside the possession, with the pavement handed back serviceable before the first movement.
Where a chase stays at the surface rather than being overlaid, an N grade hot applied sealant is the right material instead. More in what is 9525 sealant? and what is a cable chase?
Shepherd and Sons Contracting LTD
