A process developed by two Australian scientists in effect creates rock from sediment in days rather than aeons.
The calcite in-situ precipitation system (CIPS) involves combining two water-based, non-particulate and non-toxic solutions and injecting or permeating the mixture into a porous material such as sand, soil or rock.
The solutions react on mixing to produce calcite or calcium carbonate crystals that precipitate on grains, forming a rind and creating bridges between adjacent grains, cementing the material together and increasing mechanical strength and stiffness.
And because pore spaces and throats essentially remain open, porosity and permeability, and hence the material's drainage characteristics, are maintained.
This allows repeated applications of CIPS to achieve the required strength.
The technique is now being marketed worldwide by Edward Kucharski and Graham Price, and another researcher Bob Middleton, working as Lithic Technology.
In Australia, original research focused on improving ground around offshore foundations, Kucharski explains. Since then, work has been carried out on other applications, including underpinning, ground improvement and the restoration of historic structures. Recent projects include work on the 19th century Whalers Tunnel in Perth, where CIPS solution was sprayed on to the crumbling limestone walls to improve strength and stability by replacing calcite cement, reducing the risk of collapse.
'For building restoration, small volumes of CIPS can create a big impact, ' says Professor Peter Vaughan from Imperial College, London. 'For example, in flint and lime mortar walls - used in many UK churches - the solution reverses mortar damage caused by acid rain.'
But while the material is known to work in a lime environment, more research is needed into other chemical environments before its use can become more widespread he adds.
The method is novel, it is unobtrusive, non-toxic and it is very powerful, Vaughan adds. 'It is not in any way a grout - it does not solidify in place and the ground still has free water.'
Vaughan's involvement follows Imperial College research into embankment stability for London Underground in 1993.
Work showed there was often substantial movement in the ash side slopes of these structures, causing significant effect on the tracks.
'I was keeping eye out for something that would stabilise the material, ' Vaughan says.
'John Burland [also from Imperial] had heard about a new technique that had been proposed to stabilise the Leaning Tower of Pisa. Through him I contacted Graham Price in Australia and the team offered to come over to the UK to run a trial.'
The first attempt was, however, 'a bit of a disaster', Vaughan admits. This was mainly due to lack of experience with the UK material which has higher permeability and higher pH than Australian ash, and also the temperature difference between the UK and Australia, which affected the performance of the CIPS solution.
Not to be defeated, a quantity of ash was shipped to Perth, where further tests were carried out and an appropriate CIPS formulation developed in a cold store. Between October 1998 and February 1999, the team carried out an indoor trial on a large model embankment at Chattenden in Kent, which showed that 22 hours after applying CIPS there was a fourfold increase in ash stiffness. Tunnels and overhangs were formed in the stable material to prove the material had developed substantial cohesive strength.
The latest trial, on former London Underground Line aimed to look at ways in which CIPS could be used to improve track and ash embankment stability in a real environment.
Two application techniques were tested. The first was a sprayer, that could, Kucharski says, be adapted to be towed by a track-based trolley. Pipes placed at 90infinity to the track sprayed the liquid between the sleepers.
The other system was semipermanent pipework that could be installed beneath a track during possession and used for repeated treatment application.
The CIPS solutions were prepared in a small compound 150m from the track. Most chemicals were supplied as powders and one in liquid form. The solutions were pumped down two separate lines by a single pump, and mixed at a trackside y-junction.
Repeated Falling Weight Deflectometer tests were carried out on every second sleeper to assess performance of the treated embankment under dynamic loading - to simulate the loads of passing trains.
Results are now being analysed.