Long-term research at the University of Strathclyde has seen a number of exciting, practical innovations develop, which could change the face of ground engineering forever.
Innovation can come in many forms, whether it’s a new process to improve an aspect of construction, or the latest equipment upgrade that radically changes how a job can be done.
A rich seam of innovation can also be found in materials research. Any construction project will rely heavily on sourcing the most appropriate materials to get the job done safely and efficiently. And with the use of materials in construction set to come under increasing scrutiny following the Grenfell Tower fire, any research into improving them – whatever form that may take – should be welcomed by the industry.
One such research programme is well under way at the University of Strathclyde in Glasgow, which is working closely with Bam Nuttall to tackle a number of problems found in geotechnical engineering.
Academic work is often criticised for being too far removed from practical onsite applications, but this research is already being tested or deployed on Bam Nuttall’s sites, and has the potential to radically improve its business.
Construction News was given an exclusive tour of the laboratories at the University of Strathyclyde to see three of the innovations in action, all working on providing improved solutions for soil grouting.
There are three main areas of research on show: microbially induced calcite precipitation (or in layman’s terms, turning loose sand into sandstone); colloidal silica grout injection; and magnetic detectable grout.
While all relate to soil stabilisation and grouting, all have different applications and the potential to improve different parts of the ground engineering process.
Sand to sandstone
The first experiments we see are the microbially induced calcite precipitation.
Here the team injects loose sand with a naturally occurring soil bacteria, which attaches itself to the surfaces of the sand particles.
A food source, urea, is then injected along with calcium chloride to create a biochemical reaction. This leads to a build-up of calcium carbonate along the contact points between the sand, eventually forming solid sandstone.
“In the natural world, this process takes thousands of years,” explains postdoctoral research fellow James Minto. “Here, we can do it in half an hour.”
A potential application for this technology can be found in nuclear waste disposal.
University of Strathclyde Sand turned into sandstone with biogrout
Currently, nuclear waste tends to be buried hundreds of metres underground in repositories, where it can be safely stored for potentially hundreds of thousands of years. But even the most solid rock contains some fractures, which will contain water flow, and tunnel boring can cause local fracturing of the tunnel wall rock as well.
Traditional cement grouting techniques are fine until ground water comes in contact with it, when it will react and become highly alkaline. This can lead to changes in the swelling properties of the clay barriers that surround the nuclear waste – potentially leading to radioactive particles getting out of the repository.
The microbially induced calcite precipitation doesn’t have this problem, as it doesn’t react with groundwater in this way.
The team are experimenting with injecting the small rock fractures with bacteria to form a thin strip of calcite, as well as filling wider apertures with loose sand and then injecting with bacteria to form a solid.
“A newer application that we’re looking at is whether it could be used in the sealing of, and remediation of, wells,” Dr Minto says.
“At the moment a cement plug is put in the well, but there tends to still be little flow pathways around the edges which are difficult to fill in with cement. We think that calcite could be used, after traditional cement, as a secondary seal.”
Repeated cycles of bacteria and calcium carbonate can be injected to further reduce permeability and increase strength, too, although the material does not cure like concrete. Once formed after each cycle, it is at its maximum strength; each cycle acts to precipitate more calcite in the pore space.
The team has also experimented with multiple injections in a space to build up layers of calcite and create a seal over an area of 3 sq m – “the area we’d need to seal in the field”, Dr Minto says.
Alasdair Henderson is people and culture director at Bam Nuttall, which is helping to fund and support the research. “This could see huge reductions in CO2 emissions, as you wouldn’t need to manufacture cement,” he says.
But how close is to being used out on sites? “We’re just a meaningful field trial away from widespread use,” Dr Minto says.
The second area of research we see is colloidal silica grout injection.
Colloidal means that a solution has microscopic insoluble particles suspended throughout another substance, which in this case refers to micro silica particles in water.
A solution with 40 per cent silica is mixed in front of our eyes with sodium chloride, and as the liquid is poured back and forth from one plastic cup to another, it slowly beings to congeal and become more solid, turning into a gel-like substance.
Another University of Strathclyde postdoctoral research fellow, Matteo Pedrotti, then shows us a cup containing a solution mixed two days ago, which is now a solid. The application here? Soil stabilisation, using entirely natural substances and eliminating the need for cement grout.
University of strathclyde bam nuttall silica grout
When injected into soil, the solution will flow wherever water would flow, ensuring a good spread. Depending on its make-up, the team is also able to control how long it takes to work, allowing them to stabilise soil at much longer distances away than is possible with traditional techniques.
“We first applied this on site seven or eight years ago at Dounereay, and we’ve been using it for temporary works on another site,” Mr Henderson says.
While it doesn’t turn soil into a rock-hard solid, the silica grout can stabilise it to such an extent that it could be used for temporary or even permanent works. This would eliminate the need for some potentially risky temporary works involving sheet piles or other methods on some sites.
The nuclear industry is, again, very interested in this technology, with the Australian Nuclear Science and Technology Organisation – Australia’s nuclear industry regulator – supporting the research.
In particular, the team thinks the grout could be used for in-situ containment or stabilisation of radioactive wastes that have contaminated the ground, rather than excavating and reconditioning the soil.
Rebecca Lunn heads up the centre of ground engineering and energy geosciences at the university, and recently received an MBE for services to science, technology, engineering and maths. She leads the research team and explains why the nuclear industry is so interested.
“On sites the quick and dirty methods don’t work well, as they add to risk and exposure of workers, and it’s not something you’d want to do unless it was absolutely your last resort. You need barriers for long-term containment and durability.
“Nuclear has a need for innovation other than just cost – risk and health are major drivers. That’s why our technologies have developed in the nuclear arena, now we are looking at taking them away from that and into the mainstream construction industry, too.”
The third and final innovation on display is designed to tackle a major problem faced by ground engineering contractors: how to tell whether your cement grouting has truly done what you want it to.
Christopher Reid is a Bam research fellow in construction and innovation at the university, and spends time with Bam’s innovation team as well as in the lab. He works alongside Lindsey Corson, a mathematician and numerical modeller developing the detection software.
The team at Strathclyde is developing a detectable grouting system, dosing grout with needle-shaped synthetic magnetite. The team monitors the background magnetic field before grouting, then takes magnetic readings after grout injection to determine exactly where the grout has gone underground, and in what quantities, building up a 3D image of the injected grout body. The system concept is similar to that used in modern medical scanning to generate internal images of the human body.
“Grouting jobs are traditionally over-designed – this could lead to huge reductions,” Mr Henderson says. “This is about improving the productivity of existing grouting techniques.”
This project is being supported by funding from Innovate UK, with Bam Nuttall conducting field trials now to refine the technology. The early signs are promising, and could be a huge step forward in productivity for contractors if they prove successful.
Necessity: The mother of innovation
The partnership between Bam Nuttall and the University of Strathclyde is clearly proving to be a fruitful one, with the contractor first getting involved with the university five years ago, stepping up activity in the last two to three years.
But what has set Bam apart from other potential construction partners for this particular strand of research? “If I’m being honest, it was about the fact that we just seemed to see things the same way,” Prof Lunn says.
“Alasdair was very interested and engaged in what we were doing. For me [it was] very unusual in that he was willing to think outside the box and consider construction in a different way in what, I think, is quite a conservative industry on the whole.”
She goes further in sounding the clarion call for innovation, saying the construction industry will have “no choice” but to invest more in research and development.
University of Strathclyde Loose sand cemented with calcium carbonate
“Two things probably hinder change here: one is the procurement process; and the other is the way things like British standards are applied, and the difficulty of getting innovation into the industry in the first place,” she says. “There is a lot in the way, but in the end if we don’t overcome these problems the UK construction industry will collapse, because it will happen outside [the country] no matter what we do.”
Mr Henderson shares Prof Lunn’s view that the industry needs to focus more on innovation, adding that materials should not be overlooked. “There’s a lot of focus on the digital agenda, which is absolutely a good thing,” he says. “But materials science seems to have been forgotten a bit at times.”
The striking thing about the research being done here is its practical potential – all three of the strands of research we saw are either on the brink of field trials, being tested, or in use already.
“Lots of academic institutions talk a good game – but it’s only innovation when we can turn it into something on the ground,” Mr Henderson says.
Prof Lunn agrees. “I think there’s a huge difference between being able to demonstrate something on a cubic-centimetre sample in a laboratory to being able to use something at a commercial scale,” she says.
“My mission is to get it out of the lab and into the mainstream construction – and it’s been great to find a partner that’s enthusiastic about doing it.”
The partnership looks set to go from strength to strength, with both sides benefiting from the arrangement and actively seeking more funding to support the research.
In the context of last year’s Modernise or Die report, and the government industrial strategy’s plans to support R&D, programmes like this show what can be achieved with targeted support for practical innovations that can make a difference.