Aone+, the Asset Support Contractor for Area 12, contacted Geobear regarding a section of the A180 near Immingham. Over a 4 km stretch of the westbound carriageway concrete road slabs, some of which were up to 40 years old were suffering serious problems with settlement. Visual inspections highlighted 56 sinking slabs of up to 30mm in places.
The slabs, all of which were on the nearside lane of the dual carriageway had suffered from washout of the fill material. This occurs over time where rainwater ingresses through the joints and washes away fines within the sub-base. As a consequence of heavy and frequent axle loads on the busy route, the slabs had and continued to settle into the voided ground below.
As a consequence of this the ride quality was very noticeable and, critically, the safety of the road was compromised, particularly for motorcycle use.
There are a few options available to rectify the situation. Break out and replace is the traditional method, however this is very time consuming, causes significant disruption to road users and is environmentally unfriendly. As the A180 is one of the main routes out of the ports of Immingham and Grimsby, lengthy closures were not a viable option. Replacement would require at least one if not both westbound lanes to be closed
The favoured option was Geobear’s geopolymer injection method. Our fast non-disruptive solution enabled the route to remain fully open during the day as the quick curing time of the geopolymer means that treated slabs are fully trafficable within 15 minutes of injection.
Geobear’s geopolymer is a two-part material which is injected as a liquid beneath the slab. When the two components mix at the point of injection, they react and expand into a solid mass. Subject to site conditions we select a suitable material that will expand beneath the slab, thereby filling the microvoids, binding the existing fill material and re-compacting the compromised ground. This forms an impermeable base for the slab and the expansive force of the geopolymer enables the managed lifting of the slabs back to their as built datum levels.
Our mobile injection unit worked overnight for 11 shifts treating 56 concrete slabs, each measuring 5m x 4.5m. The benefits of a fast curing solution and the need for minimal plant meant that the unit could traverse the site treating five slabs per night, with some of them being over one hundred metres apart.
Aone+ stated that they wouldn’t hesitate in asking Geobear to tender future projects for them. The work that was delivered was very good and was a good learning curve for them to trial new and innovative solutions.
For further information please contact:
Darren Scott, Area manager Highways: [email protected]