Innovative New Crack Sealing Method Inspired by Fossilisation

One of the most common ways to handle hazardous material waste and keep it from causing more harm is to store it deep below the ground. This method is also one of the available ways to remove carbon dioxide from the atmosphere until it can be reused or disposed of in a different way.

But, underground storage is not without its problems. For one, the shafts and investigatory boreholes need to be sealed to ensure the material stays put. Plus, rocks and bedrock are likely to crack and fracture under high pressures, or because of environmental shifts caused during natural disasters – like earthquakes. These factors have the potential to cause catastrophic leaks, allowing dangerous or unwanted compounds to escape into the environment.

Unfortunately, current cement blends are not sufficient to seal these openings for long enough, and can also be disrupted by chemical imbalance and high-pressure weather events.

Japan for instance, is one of the earthquake-prone countries that this would affect – which has led to experts searching for a new solution. One such expert is Hidekazu Yoshida from the Nagoya University Museum. With a background expertise in fossilisation, Yoshida ‘realised that well-preserved fossils in concretions had withstood weathering and the like for tens to hundreds of thousands of years in the natural environment’. It’s this that inspired the current research into concretion as a method of sealing cracks and holes in rocks.

Fossil concretion is a natural geological function in which minerals precipitate (release) from a solution and accumulate into a larger mass around an organic material. For example, calcite is lost from groundwater and forms a seal around a fossil, helping to preserve it by binding surrounding rock sediment. 

Using this process as a starting point, the researchers were able to mix compounds that create calcite into a concretion-forming resin, which could be applied to necessary areas like flow shafts in rocks – a lot faster than the natural concretion process could.

The team were even able to get some unexpected phenomena during testing to truly put their resin through its paces. Initially, the plan was to apply the resin to flow-paths found in the rock from a laboratory 350 metres underground in Hokkaido, Japan. Whilst their testing was being conducted, the area experienced six earthquakes over two days, including one measuring in at a 5.4 magnitude. Incredibly, the cracks with applied resin stayed sealed, and the resin even exhibited crystal reformation, which resealed open cracks.

Yoshida explains that whilst the earthquakes were an obvious coincidence, they were a great opportunity to see how their invention would perform in real-life situations – with very positive preliminary results. ‘Such a fast-acting and sustained sealing effect of rock fractures, including post-earthquake crack repair, has never been reported before’.

With results like these, it’s unsurprising that the group is working even more to achieve commercial viability for their resin. The team even anticipates that the resin could be beneficial to a broad range of industrial applications, including road and building safety, long-term underground material storage and much more.

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