The use of geopolymers to manage settlement and poor ground conditions within the construction and building maintenance industries has grown significantly over 40 years. Geobear have been at the forefront of this technology for almost 40 years, working with our dedicated supply chain partners to create 29 bespoke geopolymers to provide solutions for all situations. This report summarises the environmental benefits of this technology compared to traditional construction solutions and provides data and references to confirm the benefits detailed
Excessive settlement or subsidence of underlying soils can, if untreated, lead to damage to infrastructure and buildings and services that are subject to movement. The settlement can occur rapidly or can take years or decades to occur, depending on the underlying soil conditions and cause of the movement.
The Traditional Solutions
In residential and commercial building subsidence applications grouting has traditionally been used to address ground movement. Grouting techniques generally use a mixture of cement, water and pulverised fuel ash (PFA). The cementitious ratio is usually 20:1 PFA:cement.
The grouting efficiency of conventional grouting techniques is generally around 25%. In addition, the grout has a long setting time which means that grout can be ‘lost’ in fissures, thereby increasing the volume of grout required to stabilise the surface. In applications where grout must be installed below existing structures it is generally necessary to construct a large diameter access shaft, from which small diameter, horizontal grouting holes can be drilled.
The Geobear Solutions
Geobear geopolymer injection is a non-disruptive, alternative to conventional underpinning and piling which Geobear has advanced through over 40 years of research and development. The implementation of the Geobear geopolymer injection system can be utilised for the remediation of subsidence and geotechnical settlement.
The grouting efficiency of geopolymer stabilisation is between 500% and 700%, which means that small quantities of material are required for each stabilisation scheme compared to a traditional grout solution (1 tonne of geopolymer compared to circa 65 tonnes of conventional grout).
The 2-part geopolymer is mixed at the project site and injected through pre-drilled holes into the ground. The geopolymer sets within 1 to 5 minutes, the short setting time ensures that fissures in the ground are quickly filled enabling a more targeted and controllable application.
Once cured the geopolymer matrix is resistant to a wide range of chemicals including fuels, weak acids and alkalis it is also hydro-insensitive. The matrix is sensitive to photooxidation through UV radiation however as the polymer is installed below the ground the risk of UV degradation is removed.
The design life of the geopolymer is in excess of 120 years and therefore replacement is not required during the life of the overlying structure. Following removal of the overlying structure the material can be left in-situ or disposed of as non-hazardous waste
Environmental Impact of Traditional Solutions
Traditional cementitious grout solutions whilst non-hazardous following curing have a number of significant environmental disadvantages during manufacture and installation. These are detailed below:
Grouting techniques utilise a mixture of cement, water and pulverised fuel ash (PFA), which is a by-product from coal fired power plants and is reliant on the burning of fossil fuels which are a limited resource and create a significant impact on climate change through the release of carbon dioxide and other greenhouse gases previously locked within the fossil fuels.
The production of cement is carried out through the production of Portland clinker; this process creates significant quantities of Carbon Dioxide which are released into the atmosphere. The heating of the limestone to create cement is generally achieved through the burning of fossil fuels adding an additional 40% to Carbon Dioxide emissions from the process. Each tonne of cement produced generates up to a tonne of carbon dioxide dependent on the process used.
It is an offence within the UK to contaminate “Controlled Waters”, these include watercourses, lakes, coastal waters and underground water sources. Uncured cementitious grout has a high pH and slow curing period which means that the grout presents a significant risk to adjacent aquatic environments and ground water sources. Breakout of the material through fissures and voids can lead to contamination of the environment. Where this contamination enters a watercourse the increase in pH has a corrosive effect on wildlife and causes a reduction in levels of dissolved oxygen and an increase in suspended solids within the water. These effects combine to have serious long and short term impacts on aquatic ecosystems.
Environmental Impact of Geobear Solutions
Whilst the manufacture of Geobear geopolymers is relatively carbon intensive the grouting efficiency of polymer stabilisation is between 500% and 700%, which means that relatively small quantities of material are required for each stabilisation scheme compared to traditional construction solutions (1 tonne of geopolymer compared to circa 65 tonnes of conventional grout). This efficiency means that in comparison to a traditional grouted solution Geobear geopolymers can create a saving of circa 46% in carbon footprint.
Once cured the geopolymer matrix is resistant to a wide range of chemicals including fuels, weak acids and alkalis it is also hydro-insensitive. Extensive testing of crushed samples of Geobear’s geopolymers by ALS Life Sciences Ltd as part of Environment Agency licencing requirements has established that our geopolymers have no impact on groundwater and water sources.
As with all two-part resins the chemical reaction which creates the geopolymer matrix generates small quantities of gases which have a distinctive smell. These gases are released in extremely small volumes, well below any notifiable threshold, and dissipate quickly once the reaction is complete. They pose no threat to people or wildlife and require no special control measures.
The design life of the geopolymer is in excess of 120 years and therefore replacement is not required during the life of the overlying building. Following removal of the overlying structure the material can be left in-situ or disposed of as non-hazardous waste
The analysis and testing of the Geobear Geopolymers demonstrate a range of sustainability benefits of the system over traditional grout stabilisation. In summary Geobear offers a 40 to 50-fold reduction in the quantity of materials required, when compared to a conventional grout solution and a circa 46% reduction in carbon emissions.