Developers, public bodies, contractors, and investors are recognising that environmentally friendly, sustainable construction provides not only long-term positive environmental benefits but also immediate financial payoffs as well.

Furthermore with the UK government calling for a reduction in construction excavated material being sent to landfill together with the increase in landfill charges, improvement of existing ground is now high on the sustainable construction agenda, helping to reduce the industry's carbon footprint when it comes to developing sites.

Many companies have in the past used cement as the main binder for soil stabilisation but Deep Soil Mixing is currently working to utilise new recycled binder solutions to make the soil mixing process even more sustainable than it is already.

"We have to be innovative in the way we build to tackle carbon emissions and this means starting with the groundworks," says Robert McGall, MD of Deep Soil Mixing. "UK soil contains about 10 billion tonnes of carbon, roughly equal to 80 years of annual greenhouse gas emissions so it is vital that we don't where possible dig this out and take to landfill. Time and time again we see proposals where contractors are looking to remove poor soil such as peat from developments and this needs to be reviewed when there are solutions such as soil stabilisation which treats peats in-situ changing its geotechnical properties without the need to remove it.

"Soil mixing is by nature of what we do environmentally friendly. By making use of the existing ground on-site and improving it to achieve a specified bearing capacity and shear strength, there is no need to excavate, cart away or dispose of the existing material off-site and then bring in costly and bulky fill materials. It is not just about improving unsuitable ground but aims to turn poor quality soils and fill into acceptable bearing strata for numerous applications.

"This, in turn, reduces the carbon footprint on a site with fewer vehicle movements and you are not moving contaminated or poor-quality ground to landfill. On one site alone following a carbon footprint calculation using soil mixing we reduced the carbon emissions by just over 70 per cent as opposed to excavate and cart away and fill.

"Over the coming year, we will be undertaking R&D at our research facilities in Bedfordshire and Staffordshire including extensive laboratory treatability studies in which a wide range of novel binders and additives will be tested together with a range of soils and contaminants. In parallel, extensive field trials will then follow. Extensive in-situ testing, sampling and groundwater monitoring will then be carried out together with extensive laboratory testing of the site samples and assessment of the field measurements."

Deep Soil Mixing is no stranger to groundbreaking R&D as the company was at the forefront of soil mixing in the UK in 2009 as part of the government-funded Soil Mixed Remediation Technology (SMiRT) initiative with the geotechnical department of Cambridge University.

The company has also been leading the way in improving the plant and equipment used for soil mixing and in 2008 it designed and developed a new double-rotary mixing attachment. The double rotary mixing attachment has proved a great success compared to the industry standard single rotary mixing head as the double rotary forms more consistent homogeneous soil mixed columns, enabling geotechnical engineers to have confidence that the system provides consistent results.

"We are hoping to publish our results in the summer of 2021 and highlight further the importance of sustainability to the construction industry from the ground up.

"In 2020 we should not be removing soil to landfill and effectively moving the problem elsewhere when there is a geotechnical and sustainable solution available. Soil mixing has been widely used across the USA, Europe, Australia and the Far East and the UK should use it more widely. If we are to build three million homes to solve the housing crisis, we should be using more brownfield land and in doing so we should not be removing soil from site," added McGall.

"As a ground remediation solution soil mixing reduces project times, costs and the carbon footprint on construction projects compared to other more traditional ground engineering methods such as various types of piling, excavate and cart away, dynamic compaction, surcharge etc."

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