N1

N1 is a surface-applied hot pour sealant compliant with BS EN 14188-1, classified as the elastic, high-extension type. Applied molten through a heated boiler, it cures quickly and offers the flexibility needed for surface joints that see constant traffic and seasonal movement. It is suited to standard surface joint sealing on highways and airfield surfaces, including motorway work that we’ve completed such as the M20.

In our experience, N1 works better than N2 on busier surface joints because its higher extension accommodates more slab movement without splitting, whereas N2 is better reserved for stable, low-movement joints. Slots must be dry, sound, clean and free from frost and dust before sealing, with the finished seal recessed below the surface to prevent extrusion under traffic in hot weather.

Applications: Highways, motorways (including the M20), airfield surface joints. Specification: N1 hot applied joint sealant.

N1 is chosen for joints that move a lot, but the width of the joint matters as much as the sealant in it. The same 5mm of movement is a 50% strain in a 10mm joint and only 20% in a 25mm joint, so widening the slot is often a better way to cope with high movement than relying on the sealant alone. Long concrete bays, expansion joints, bridge approaches and sun-exposed aprons are where the movement should be calculated rather than assumed.

The work follows the sequence used on the M20 between junctions 8 and 9: the old sealant ploughed out, the joint sawn, dried, grit blasted and caulked, then sealed hot. Movement figures vary between manufacturers within the N1 class, so they are confirmed against the data sheet for the product being laid.

There is more in N1 sealant for high movement joints explained.