Challenge
Decades‑old A180 concrete slabs were sinking due to sub‑base washout and heavy traffic, degrading ride quality and compromising safety; a fast, low‑disruption stabilisation was required without lengthy closures.
Solution
Geobear injected expansive geopolymer beneath slabs to fill voids, re‑compact compromised ground and lift slabs back to design level, restoring road safety with minimal disruption and rapid traffic return.
Section of westbound A180 treated
Slabs with up to 30 mm settlement
Night‑shift injection programme
Aone+, the Asset Support Contractor for Area 12, identified a 4 km stretch of the westbound A180 near Immingham where concrete carriageway slabs up to 40 years old were suffering settlement. Visual inspection showed 56 slabs had sunk up to 30 mm due to rainwater ingress that had washed fines out of the sub‑base, leaving voids. Heavy and frequent axle loads on this key freight route exacerbated the problem, noticeably degrading ride quality and posing a safety risk, particularly for motorcyclists.
The A180 is a primary route connecting ports at Immingham and Grimsby. Traditional remedial options such as slab break‑out and replacement were time‑consuming, environmentally intensive and required lane closures that were not viable given traffic volumes and the route’s economic importance. A solution was needed that stabilised the sub‑base and reinstated slab levels while keeping lanes open, limiting disruption to traffic and the surrounding community.
Geobear’s geopolymer injection method was selected for its rapid cure time and minimal footprint. A two‑part geopolymer liquid was injected beneath each affected slab. Upon mixing at depth, the material expanded to fill micro‑voids, bind existing fill material and re‑compact compromised ground. The expansive reaction also provided controlled slab lifting back to original datum levels. The mobile injection unit operated overnight across 11 shifts, treating 56 slabs each measuring approximately 5 m × 4.5 m. Due to the quick strength gain of the geopolymer formulation, treated slabs were trafficable within about 15 minutes, allowing the road to remain open during the day with no long closures.
The geopolymer injection successfully stabilised the sub‑base and restored slab levels, improving ride quality and addressing the safety concerns without requiring westbound lane closures. The multi‑night approach allowed the A180 to remain fully operational with minimal disruption to road users. Aone+ noted satisfaction with the solution and indicated a willingness to involve Geobear in future projects, reflecting confidence in the engineered delivery and performance of the method.
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