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Can geopolymer injection strengthen the ground beneath building foundations to help fix England’s crumbling school estate

Geopolymer injection technology is designed to strengthen the soil strata beneath building foundations, as demonstrated when Mainmark’s Teretek® resin injection technology was used to provide foundation support and successfully treat subsidence at Dulverton School in Kent.

The nursery building at the school, constructed in the 1960s, displayed signs of cracks both internally and externally. A survey revealed that these cracks were evidence of subsidence caused by shrinkage of the clay soil beneath the foundations. This was due to the long and dry summer of 2022, compounded further by trees extracting moisture from the ground. Kent council initially considered traditional underpinning; however, they ultimately chose geopolymer injection due to its shorter treatment timeline and minimal disruption to the school premises.

A feature by Building Magazine titled ‘How do we fix England’s crumbling school estate?’ shows that the challenges Dulverton school was faced with are by no means an isolated incident. It was reported that ‘700,000 pupils are now being taught in buildings that require major rebuilding or refurbishment’. According to figures from the National Audit Office (NAO) the UK’s independent public spending watchdog, there are over 10,000 school buildings dating back to the 1940s that are continuing to deteriorate. It is estimated that, across the whole school estate of 64,000 buildings, a concerning 38% are past their estimated design life.

The NAO report also included details about reinforced autoclaved aerated concrete (RAAC) that has shown the huge impact that untreated construction issues can have on the education system. The report stated that the ‘DfE (Department for Education) had identified 572 schools that may contain RAAC. By May 2023, specialists had completed 196 assessments and confirmed the presence of RACC in 65 schools of which 24 required immediate action.

Whilst £5.3bn of funding was recommended by the Department for Education (DfE), for long-term maintenance between 2016-17 and 2022-23, only £2.3bn was spent by the DfE for school rebuilding, maintenance, or repair. According to the NAO, reasons for the slow progress include suppliers not taking up contracts due to the instability of the construction sector.

What benefits does the use of geopolymer injection bring from a school’s perspective?

From a school’s perspective, construction works can disrupt pupils. Ideally, these projects are planned during the summer holidays. However, this can create scheduling challenges and make it more difficult to find available contractors during the brief six-week break. Geopolymer injection offers a faster process than traditional underpinning eliminating the need to coordinate heavy machinery and different teams of contractors. The geopolymer injection process is all carried out by one team using specialist handheld equipment. This allows rapid turnaround times to fit in with the schedule of the school rather than the school having to work around the contractor’s timelines.

Schools also need to plan their maintenance and improvement projects. As can be seen from the issues identified in the NAO report, many will need further refurbishment to upgrade structures including walls and roofs. Such refurbishments will add extra weight to the foundations and the use of geopolymer resin injection can strengthen the ground to increase its load bearing capacity. Whether a school requires treatment for existing subsidence or wishes to find a way to strengthen the ground to guard against future subsidence geopolymer injection can provide the solution required.

What benefits does the use of geopolymer injection to treat subsidence bring to the school estate?

Utilising geopolymer injection technology for subsidence treatment in school buildings can be achieved with minimal disruption. Unlike traditional underpinning, it doesn’t require excavation of trenches or the presence of heavy machinery on-site. Trained technicians use handheld equipment to inject geopolymer resin into the ground. The school building’s interior and exterior are typically left undisturbed. In some cases, minor clearing work may be necessary if vegetation covers external injection points. Inside the building, technicians can drill through concrete slabs with smaller diameter holes and deliver the resin without the need to clear large areas before treatment.

Geopolymer injection technology is a fast, efficient and cost-effective process that can take place during the shorter half-term breaks or can even be carried out in phases over the weekends, making scheduling of the work for the school much easier. The treatment at Dulverton school using Teretek® geopolymer injection technology took just two days during the first week of the summer holidays.

When geopolymer injection is employed to treat subsidence, it follows a precise process involving the controlled injection of expanding geopolymer resin into the soil beneath the foundations. This process can be executed both from the outside and inside the building. After being injected through tubes, usually 16mm in diameter at pre-determined depths and positions, the resin expands and rapidly hardens to compact the existing soil and fill any voids. This enhances the ground’s load bearing capacity beneath the foundations effectively mitigating subsidence and providing a stronger base in case additional loads are introduced during future refurbishments.

How can I find out if geopolymer injection technology is suitable for my school suffering from subsidence?

If you are concerned that your school is suffering from the effects of subsidence or would like to take steps to improve the ground bearing capacity of the school estate contact our team at Mainmark. Our experienced technicians can evaluate any existing ground inspection reports and we are able to carry out our own survey to determine the cause and best options for treatment.

For instances where sections of walls are subsiding, such as with Dulverton school, Teretek® resin injection technology can provide targeted foundation support to arrest subsidence and increase the ground loadbearing capacity.

However, if you believe that the entire school building is being affected by subsidence, a more appropriate option may be our JOG Computer Controlled Grouting technology. This multi-point cementitious grouting allows the foundations of the whole building to be supported, and lifted, to return the school to its former level.

Whatever subsidence needs to be addressed, get in touch with us and we discuss the best treatment solution tailored to your schools’ individual requirements.

Hossein Khansari
Dr Hossein Khansari is a Technical Lead at Mainmark in the United Kingdom. He holds a PhD in Geotechnical Engineering and possesses extensive expertise in the field, boasting over 25 years of valuable experience within the geotechnical industry.
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