Challenge
Concrete pavement slabs on the A55 westbound between J35 and J34 had settled due to sub‑base washout, requiring rapid stabilisation without extended closures on this strategic North Wales route.
Solution
Geobear delivered targeted geopolymer injection beneath affected slabs to fill voids, re‑compact the sub‑base and re‑level the carriageway during overnight closures, enabling rapid return to service.
Strategic trunk road section treated
Delivered within traffic management windows
Rapid strength gain after injection
The A55 is a key strategic trunk road serving North Wales and connecting major ports and regional centres. A section of westbound carriageway between Junction 35 and Junction 34 experienced slab settlement linked to loss of support beneath the concrete pavement.
Water ingress through joints had contributed to sub‑base washout, leading to void formation and differential movement. The resulting uneven surface reduced ride quality and increased maintenance requirements.
Given the A55’s importance as a high‑volume transport corridor, extended closures for traditional break‑out and reconstruction were not desirable. Excavation would have required significant traffic management, longer construction periods and greater environmental impact.
A solution was needed that addressed the underlying ground instability, restored slab support and maintained traffic flow through controlled, short‑duration working windows.
Geobear implemented a precision geopolymer injection programme designed to stabilise and re‑support the affected slabs. Small‑diameter injection holes were drilled through the concrete surface at defined centres.
The two‑component geopolymer was injected beneath the slabs where it expanded to fill voids, bind loose sub‑base material and increase bearing capacity. Controlled expansion enabled accurate slab re‑levelling, monitored in real time to ensure movement remained within specification tolerances.
Works were undertaken during planned overnight closures. The rapid curing properties of the geopolymer allowed treated areas to be reopened to traffic shortly after completion, supporting programme efficiency and minimising user disruption.
The intervention reinstated slab support and corrected differential settlement without full excavation. Ride quality improved and the risk associated with continued movement was mitigated.
Delivery within overnight traffic management windows reduced disruption on this strategic route while providing a technically robust, engineered stabilisation outcome aligned with asset management objectives.
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