Case studies
Southampton - Repairs without disruption
When Southampton City Council, Halcrow and Colas needed to stabilise slabs on the busiest approach to the city's docks this summer, they opted for a solution that would complete the job quickly, and allow the road to remain open.
"About 1500 lorries use this road in a 24-hour period, so as you can imagine it's not the sort of thing you can shut down," says Colas' Vic Collier. "If we'd had to rip out all the slabs, we'd have been looking at between eight and eleven months, and that's without reconstruction of kerbs and a roundabout."
So Uretek UK, specialists in polymer resin injection, were brought in to fill voids under the roadway and stabilise the slabs without need for excavations.
Over a five week period, Uretek completed repairs to eight and a half thousand square metres of carriageway with minimal disruption. The road remained open throughout, and there were no delays to traffic.
"With Uretek we've taken seven months off the job, and the Port Authority haven't had one complaint about how we've done it ," says Collier.
Speed and lack of disruption are keynote benefits which have enabled Uretek to gain a significant foothold in the repair market over the past two decades. Widely used as a rapid treatment for subsidence and sunken flooring slabs, the processes are now coming into their own for carriageway repairs. The polymer material is ideal for road use, as it functions best where there is a high load expected in one direction and very little in the other. It's also lightweight, adding little burden to distressed subgrades. And the process is unaffected by temperatures ranging from 0*C to 100*C, allowing work in colder seasons.
Uretek's method originated in Finland 30 years ago, and is nowadays used throughout the world. It involves injecting expanding polymer resins through a series of very small-diameter holes, drilled at 1 to 1.5m centres. The holes are small enough to cause no slab breakout at the base of the concrete and no overall slab weakening. Once injected the material expands up to 30 times its volume, providing a strong vertical lift if needed.
Importantly, the process is highly controllable. This is partly because of the very rapid curing time of the material, and partly because the Uretek method does not depend on pumping pressure to lift the slab - it's an all-in-one process, both consolidating ground and lifting the slab to tolerances of +/- 5mm, a result which is carefully monitored by laser level. This precision also makes it possible to stabilise only, without any lift.
Very little equipment is required on the road - a hose from the self-contained Uretek truck, a laser level, a drill - and this means a very fast clear-up. With rapid curing of the polymer resins, Uretek teams can deal with problem areas between rush hours and be off the road quickly.
The speed and ease of the repair can come as a surprise. Phil Nicholls, Area Project Engineer for Exeter, was one of the first pioneers in the use of the Uretek process. Nicholls is astounded that "you can just pump stuff like that in and it just jacks the whole road up and it stays jacked up!" Yet, he reports, "that's what happened. It's such a simple idea and yet it works so absolutely perfectly and it's long-lasting. It's 12 or 13 years ago that the first work was done, and that same slab now is still exactly the same, and that really is amazing."
At first, polymer injection's environmental credentials were not a significant factor in winning work. Yet with the 'greening of the supply chain', the advantage that no road material needs to discarded, and no new material brought in has made Uretek's process a very attractive option.
Apart from the process itself, Uretek's specialist teams of operatives are also gaining compliments, not an unimportant factor in work that often involves interaction with the public and with other contractors. With many years experience in applying resin technologies to road stabilisation Uretek's technicians now bring extensive expertise to every job, and have a good reputation for their on- site skills.
Says Vic Collier: "We very rarely get contractors who come to site who take as much care, and as much pride in their work, and be as neat and tidy behind them as we've seen with Uretek. I can't praise them too much."
Geopolymer injection looks set to achieve a higher profile. Uretek is confident that the speed and lack of disruption achieved on a smaller scale over the past fifteen years on Britain's roads will be rolled out on larger contracts, and that the technology will come to be a standard part of road maintenance best practice.
