Sustainable Grout from Geothermal Fluids

A study published in Case Studies in Construction Materials details how Japanese scientists developed a carbon-neutral grout using waste fluids from geothermal energy harvesting devices.

Grouting is a widely used construction technique that involves injecting stabilizing materials into the soil to maintain structural stability, especially in areas with poor ground conditions or those prone to earthquakes.

This technique is crucial in strengthening underground structures, securing foundations, and preventing soil erosion, ensuring that infrastructure can withstand geological and environmental challenges.

However, traditional grouting methods, which rely on silica-based chemical grouts and energy-intensive processes, have significant environmental drawbacks, including high carbon dioxide (CO₂) emissions. As a result, finding sustainable alternatives has become a top priority for engineers and scientists.

In response, a research team from Japan's Shibaura Institute of Technology, led by Professor Shinya Inazumi of the College of Engineering, has developed a novel grouting technique.

The team created Colloidal Silica Recovered from Geothermal Fluids (CSRGF), a carbon-neutral grout that improves soil stabilization while reducing the environmental impact of both geothermal energy harvesting and construction.

Geothermal energy production generates large amounts of silica-rich waste fluids, which traditionally pose maintenance and disposal challenges. 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.

Shinya Inazumi, Professor, College of Engineering, Shibaura Institute of Technology

The new grout addresses two major issues: reducing the carbon footprint of traditional grout production and preventing waste fluids with high silica from damaging geothermal equipment.

Extensive lab tests show that this grout performs exceptionally well, with 50 % more resistance to liquefaction than conventional materials. Its low viscosity and controlled gelling time allow for deep soil penetration while meeting environmental safety standards.

This grout is especially beneficial in earthquake-prone areas, where stabilizing soil is crucial to prevent structural damage during seismic events.

Beyond earthquake prevention, the grout’s excellent water-sealing properties make it ideal for underground construction projects like basements, subways, and tunnels, where water intrusion can threaten structural integrity. It can also help prevent soil erosion and mitigate issues related to rising sea levels in coastal and flood-prone areas.

CSRGF grout marks a significant step in the construction industry's shift toward carbon neutrality. This innovation demonstrates how circular economy principles can lead to more sustainable construction by reducing waste and recycling industrial by-products.

Its scalable, cost-effective production also helps reduce CO₂ emissions in the building sector, setting new standards for environmentally conscious soil stabilization and supporting global sustainability goals.

“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,” added Inazumi.

To confirm the material’s effectiveness in real-world conditions, the research team plans to scale up production and conduct field tests. This invention shows how creative thinking can solve technical problems sustainably, which is crucial as the construction industry strives to balance sustainability with high performance.

Journal Reference:

Terui, T. et. al. (2025) Development and application of geothermally derived silica grout for carbon-neutral soil stabilization. Case Studies in Construction Materials. doi.org/10.1016/j.cscm.2025.e04297