BACKGROUND

The M42 motorway serves the UK’s second largest city, Birmingham, and other towns where a lot of people live and do business. It’s important that it’s kept open and running – since road congestion costs the UK billions of pounds a year. Cars and lorries barrel down the M42 day and night, often with windscreen wipers on, since this isn’t the driest part of Europe. Unlike vehicles, the slabs of a motorway have no way to keep off the water. It seeps through the joints in the slabs, causing the ground underneath to move. This creates voids (spaces) in the soil. Traffic moving along the road pushes water in voids under the slabs up to the road surface. It’s called a pumping slab, and the M42 had 100 of them, running north and south around busy junction 9. The only way to keep the M42 running was to do the repairs quickly overnight. And the best way to do that was call Geobear.

SOLUTION

The customer had the option to completely replace the slabs. The builders could finish one per night. The work would cost about £750,000. Alternatively, the customer could have five slabs stabilized in a night for less than a third of the price using Geobear’s geopolymer solution. Workshops were held to plan the safe and timely delivery of the project. After close collaboration between Geobear, LaFarge, Tarmac (CRH) and on-site design teams, the geopolymer liquid was injected through 16mm holes in the slabs. It then solidifies, fills voids, pushes out water and compacts the soil. Laser monitors measuring slab movement showed when the area had been stabilized.

RESULT

Within just 15 minutes of treatment, the slabs were finished. And overnight, they were completely repaired and stabilized. They were ready for traffic. And that meant that the customer saved money. Two work teams took 20 days to finish the project, compared with the 80 or so the normal builders would need. The customer saved over £500,000 by using Geobear. Unlike normal building work to replace the slabs, the Geobear solution was not affected by bad weather conditions. We got the traffic running again along this important motorway in the quickest, cheapest and most efficient way. And by doing so, we saved the economy over £3 million.