Concrete slabs on runways often break across their corners. This is because the inter-slab sealant weakens over time, allowing ingress of water. When this happens, the sub-base &/or soil underneath the inter-slab joint gets wet and the movement of aircraft over the top of the slab begins to compress the wet soil, pumping it bit by bit up the now unsealed inter-slab space. As time goes by, quite large bodies of soil can be removed in this manner from under the slab,

while still more soil will be washed into lower layers of the sub-base, if proper compression of the soil was not undertaken before the slab was constructed.

Ultimately a large void is formed around the area and concrete slabs, if not already broken, can be felt to move as a load passes over them.

Sooner or later, if not maintained, the slabs will then break at this point. Often one corner can be seen to be broken, but the broken corner indicates that the associated slabs are in danger and Invariably they will all have a void under them.

The expense and inconvenience of replacement can be avoided if the Uretek Slab Maintenance Program is employed to overview the work site. Using Ground Penetrating Radar, Uretek can identify the locations of voids, before they show on the surface as damaged, cracked concrete slabs.

Once a void is identified, Uretek drills 16mm holes through the concrete of the effected area, and investigates the soil strength below. Depending on what we find, we will either underseal the concrete – compressing the surrounding soil, filling any nearby voids and lifting the slab back into place — OR—we will Deep Inject, perhaps as deep as 2 metres to strengthen weak ground, and then underseal as required.

Uretek uses Laser levelling equipment during the process, confirming the progress of the job with string lines and dial gauges. In most cases, a near perfect level can be obtained. Occasionally as concrete slabs rise, they bind against each other, and at this point additional work may be required to achieve a perfect result.

Of course, this work is only the start of the story. Once the slab has been re-levelled, it is vital to ensure that any cracks and inter-slab joints are sealed against further water ingress.

Note that Uretek can also manufacture replacement concrete slabs off site, and then replace and re-level a life expired slab in one night’s work, ensuring that traffic flows are not effected by otherwise extensive replacement works.