Home » Projects » A55 Slab Stabilisation


Geobear was contracted by Tarmac to deliver concrete slab stabilisation work on a section of the A55.

A GPR survey revealed voiding across 193 slabs on a section of the road between junction 34-35. The voiding was a result of general wear and tear from almost 40 years of axle loads and more recently the greater loads carried by larger HGV’s have increased the wear on the route to and from Holyhead port.

The full works programme on the section included some full bay replacement and joint sealing together with the geopolymer injection work performed by Geobear and re-surfacing.


Customer Alternatives

The options available to the client were either full bay replacement, a stabilisation scheme or the slabs could be left unrepaired. Of those options, the bay replacement would have been too time-consuming to complete and was not a feasible option.  To leave the slabs could have led to reflective cracking which would have allowed water to seep into the subgrade causing washout and rocking slabs. 

Using a Geoebar geopolymer solution was the most effective method for the client, and would have minimal delays to road users.


Our solution

The Geobear geopolymer stabilisation works involved using a specialist premium grade geopolymer designed for use on roads with high axle loads.  For each slab, there were 12 injection locations where the expansive geopolymer material was injected beneath the pavement foundation.

The original construction used a granular fill, which over time had micro voiding, the expansion forces of the geopolymer material compacted the sub-base and filled the voids resulting in a solid base for the slabs.  Stabilising concrete slabs using the geopolymer method leads to a life extension of up to 15 years. 

Moreover, with a Geobear solution, the amount of emitted carbon is 73% less than a bay replacement, figures verified in a report by Carbon Footprint Ltd.



Geobear was the most cost-effective option for the client – the geopolymer could fill the voids as well as strengthen the sub-base to withstand additional loads.

The project was delivered quickly with only overnight road closures required, and Geobear completed the works within the programme. 

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