Engineering with geopolymer injection for ground improvement, void filling and structural lifting

This content was presented in a UK webinar on 28th January 2026.

Geopolymer injection is a fast, low-disruption engineering solution for improving weak ground, filling voids, re-establishing slab support, reducing water ingress and lifting structures with precision.

At Geobear, we use specially formulated geopolymers to deliver asset maintenance, stabilisation and remediation across the built environment. The method is suitable for a wide range of projects in highways, rail, utilities, ports, airports, warehouses, commercial buildings and residential properties.

This page explains how geopolymer injection works, how it behaves in different ground conditions, and where it can be used to solve geotechnical and structural challenges.

What is geopolymer injection?

Geopolymer injection is a process in which a two-part expanding polymer is delivered through small injection tubes installed into the ground, beneath slabs, into voids or below foundations.

The material is injected in liquid form and reacts rapidly at the point of delivery. Depending on the formulation and application, it can:

• fill voids
• improve load-bearing ground
• re-establish support beneath slabs
• reduce rocking and flexing
• provide controlled lift to structures
• reduce or stop water ingress pathways

Because the process is delivered through small drilled holes and compact mobile equipment, it is far less invasive than traditional excavation and reconstruction methods.

How geopolymer injection works

The process is straightforward, but the engineering behind it is highly controlled.

Typical installation process

1. Small holes are drilled through the slab, foundation or treatment zone.
2. Narrow injection tubes are installed to the required depth.
3. Geopolymer is injected at the target location.
4. The material expands and reacts according to the surrounding conditions.
5. Movement is monitored in real time where stabilisation or lift is required.
6. Verification testing can be carried out before and after treatment where needed.

Injection holes are typically around 14 mm in diameter, with injection tubes typically around 12 mm. This enables treatment with minimal disturbance to the asset and surrounding area.

Engineering behaviour of geopolymer

One of the key advantages of engineering with geopolymer is that the material behaves differently depending on the application, the ground conditions and the level of confinement.

Behaviour in voids

When geopolymer is injected into an open void, it expands freely to fill the available space. In this condition, it exerts little or no pressure until it comes into contact with the surrounding surfaces.

This makes it highly effective for void filling applications, including inaccessible cavities, washout zones and redundant pipes.

Behaviour under confined conditions

When the material is injected beneath a loaded structure or within confined ground, it can generate significant expansive pressure. This allows it to:

• restore support beneath slabs and foundations
• densify weak ground
• improve bearing capacity
• create controlled lift where required

This confined expansion is what enables Geobear to stabilise and lift heavy assets with millimetre control.

Geopolymer in different soil types

The treatment mechanism varies depending on the soil profile.

Granular soils

In sands and gravels, geopolymer typically forms discrete bulbs within the soil mass. These bulbs interact with the surrounding material and create local densification, improving stiffness and load-bearing behaviour.

This makes geopolymer well suited to ground improvement in granular soils affected by washout, settlement or low density.

Cohesive soils

In clays and other fine-grained soils, geopolymer tends to form lenses or layers. These layers act like in-situ reinforcement planes, improving the behaviour of the ground and reducing compressibility.

This layered response is particularly important when designing ground improvement solutions in cohesive soils.

Material properties of geopolymer

Geobear uses a range of geopolymer formulations selected according to the engineering requirement. Different materials are chosen depending on whether the aim is to fill a void, improve weak ground, support a slab, stem water ingress or lift a structure.

Typical characteristics include:

• rapid reaction times
• expansion ratios of around 3 to 40 times initial liquid volume
• lightweight density compared with concrete
• closed-cell structure
• very low permeability
• strong resistance to chemical exposure
• no requirement for added water on site

Material stiffness and strength increase significantly under confined conditions, which is a key factor in design.

Durability and design life

Geobear’s geopolymer materials have been assessed through laboratory testing, accelerated ageing studies and long-term technical review.

When correctly specified for the application, the material has been assessed as having a design life of up to 120 years.

Long-term creep performance is also considered during design. Material selection is based on expected loading and confinement so that the geopolymer performs as intended over time.

Environmental performance of geopolymer injection

Geopolymer injection is recognised as a lower-carbon alternative to many traditional repair and stabilisation methods because it reduces the need for excavation, reconstruction and heavy material import.

Environmental benefits can include:

• reduced spoil generation
• reduced vehicle movements
• reduced material consumption
• lower embodied carbon than replacement solutions
• shorter site programmes
• minimal disruption to operational assets

The material has also undergone leachate testing, indicating minimal environmental impact on surrounding soils and groundwater when properly applied.

Applications of geopolymer injection

Geopolymer injection can be used across a wide range of geotechnical and structural applications.

Ground improvement

Geopolymer can improve weak, softened or poorly performing ground where additional load-bearing capacity or reduced deformation is needed.

Typical uses include:

• softened subgrades
• ground affected by washout
• weak soils below slabs
• support improvement around buried structures
• pre-construction ground improvement for new build projects

Verification may be carried out using DCP testing, SPT comparison, TRL probing or plate load testing, depending on the site and specification.

Slab stabilisation and slab lifting

Where a slab has lost support, begun rocking or settled unevenly, geopolymer can be injected beneath it to fill voids, restore contact and lift the slab where necessary.

This is commonly used in:

• warehouses
• logistics facilities
• industrial floors
• transport infrastructure
• commercial buildings

Where lift is required, work is carried out in controlled passes and monitored using laser levels or survey control.

Void filling

Geobear uses several geopolymer types for void filling, from lightweight fillers for non-structural applications through to structural fills capable of reinstating support beneath loaded assets.

Typical void filling applications include:

• washout voids
• inaccessible underground cavities
• redundant pipes and ducts
• voids beneath transition slabs
• embankment voids
• animal burrows

Water sealing

Fast-setting geopolymer can be used to stem water ingress and reduce flow paths in underground or retaining structures.

Typical applications include:

• leaking retaining walls
• cofferdams
• tunnel works
• sheet pile structures
• localised underground seepage

Because the material reacts quickly, it can be effective even where inflow rates are significant.

Structural lifting

Geopolymer can be used to lift foundations, slabs and structures affected by settlement or subsidence.

This is useful where the objective is to:

• recover levels
• restore serviceability
• reduce trip hazards
• close or reduce cracks where appropriate
• avoid major excavation or rebuild works

Structural lifting is carefully managed in small increments to avoid inducing unnecessary stresses into the structure.

Sectors where geopolymer engineering is used

Geobear delivers geopolymer solutions across the built environment, including:

• highways
• rail
• ports and harbours
• airports
• utilities
• energy infrastructure
• warehouses and logistics parks
• commercial buildings
• residential properties

Because the injection equipment is mobile and hose-fed, treatment can often be delivered in constrained or difficult-to-access locations without major site disruption.

Project examples

Rail level crossing stabilisation

A level crossing affected by drainage-related washout was re-levelled and stabilised using geopolymer injection on a 1.5 m by 1.5 m grid. The works were completed within two 12-hour possessions, avoiding a more disruptive replacement solution.

Slab track performance improvement

At a slab track site, geopolymer was used to improve deteriorated ground and restore support beneath the slab. Vertical movement under passing trains was reduced significantly, improving track performance.

Sewer stabilisation in softened ground

Around a large diameter sewer affected by washout and settlement, geopolymer injection was used to densify surrounding sands and improve support. Pre- and post-treatment testing showed strong correlation with the design predictions.

Water sealing in a cofferdam

At a sheet pile cofferdam where declutched piles allowed significant water ingress, fast-setting geopolymer was used to reduce inflows and create workable conditions inside the excavation.

Embankment void filling

Geopolymer was used to fill multiple badger set voids within a rail embankment during possession periods, demonstrating how quickly the method can be deployed in sensitive infrastructure settings.

Road subgrade improvement

On highway sites affected by weak subgrade and surface deformation, geopolymer was injected at shallow depth to improve the supporting ground. Testing showed clear increases in equivalent CBR following treatment.

House lifting

At a residential project in London, geopolymer injection was used from within a basement to lift the outer wall of a house towards target level, achieving controlled recovery with repeated injection passes.

Key technical considerations

Every geopolymer project must be designed around the actual site conditions. Important considerations include:

• soil type and stratigraphy
• depth and extent of weak ground or voiding
• buried utilities and drainage condition
• structural loading
• access constraints
• required improvement or lift target
• need for verification testing
• groundwater or environmental requirements

This is why geopolymer engineering should always be supported by appropriate site information, engineering review and project-specific design.

Speak to our engineering team

If you are assessing a project involving weak ground, voiding, settlement, slab movement, leakage or difficult access constraints, Geobear can help review the site and advise on whether geopolymer injection is suitable.

Talk to our team about your project
Request a technical review
Ask for project references or technical data

Common technical questions