Japan turns geothermal waste into super grout

March 03, 2025

Scientists in Japan have come up with a new way to make soil stronger using waste fluids from geothermal energy plants. This new grout material, called Colloidal Silica Recovered from Geothermal Fluids (CSRGF), is an environmentally friendly alternative to traditional grouting methods and improves soil stability significantly.

Grouting is a construction method where special materials are injected into the ground to make it stronger. This process is commonly used to stabilize buildings, roads, bridges, and tunnels, especially in areas with weak soil. It is particularly important in places that experience earthquakes because it helps prevent liquefaction—a process where the ground becomes unstable due to shaking. 

Liquefaction can cause buildings to tilt, sink, or even collapse, leading to devastating damage and loss of life. However, traditional grouting materials require a lot of energy to produce and release carbon emissions, which contribute to climate change.

To tackle this issue, a team led by Professor Shinya Inazumi from the Shibaura Institute of Technology developed CSRGF. “Geothermal energy production generates large amounts of silica-rich waste fluids, which traditionally pose maintenance and disposal challenges,” elaborated Inazumi.

“By repurposing this waste into a high-performance CSRGF grout, we aimed to establish a circular economy approach, transforming an industrial byproduct into a valuable construction material.” This approach not only reduces industrial waste but also promotes a more sustainable way to reinforce soil in critical infrastructure projects.

More effective in earthquake zones

Tests in the lab showed that CSRGF grout improves liquefaction resistance by 50% compared to traditional grouting materials. This means that structures built on CSRGF-treated soil will be much more resistant to earthquakes and other geological disturbances. 

Additionally, CSRGF has a low viscosity, meaning it flows easily and spreads evenly underground. It takes just the right amount of time to harden, allowing it to reach deep layers of soil without clogging, while still meeting environmental safety standards.

CSRGF isn’t just useful for earthquake-prone areas. It also helps strengthen underground structures like tunnels, subway systems, and building basements, where water seepage can weaken foundations. By providing a strong and stable base, this grout extends the lifespan of these structures and reduces maintenance costs. 

Because of its water-sealing properties, it is also ideal for use in coastal and flood-prone regions, where it helps prevent erosion and protects against rising sea levels. In the future, engineers could use CSRGF to reinforce levees, dams, and sea walls, helping communities become more resilient to climate change.

Furthermore, CSRGF can help in preserving historical buildings and sites. Many older structures are built on weak or shifting soil, and traditional grouting methods may not be suitable due to environmental restrictions. CSRGF provides a safer, more effective way to reinforce these sites without causing additional damage to the surrounding ecosystem.

Building a more sustainable future

This new grout is a big step forward for environmentally friendly construction. Reusing industrial waste reduces pollution and cuts down on the carbon footprint of traditional grouting. It also lowers the demand for energy-intensive materials like cement and chemical-based grouts, which contribute to global CO2 emissions. 

Its production is also affordable and can be scaled up, making it a practical choice for the construction industry. Since geothermal plants already produce silica-rich waste fluids, CSRGF can be made using existing resources, further minimizing its environmental impact.

“By replacing traditional silica-based grouts with our sustainable alternative, the construction industry can advance toward a greener infrastructure development, supporting global efforts to achieve carbon neutrality by 2050,” said Inazumi. If widely adopted, this new material could make a significant contribution to reducing greenhouse gas emissions in the construction sector.

The research team also plans to scale up production and test CSRGF in real-world construction projects. They aim to monitor how well the material performs over time and in different environments.