Scientists from Russia and China develop material to stabilise soil on islands

A team of scientists from South Ural State University (SUSU), a partner of TV BRICS, and Zhejiang University (China) has developed a technology for strengthening calcareous sand using enzymes, coconut fibre and calcium carbonate. The resulting material is up to five times stronger under dynamic loads and is environmentally safe, making it suitable for use in construction on islands and reefs. This was reported on the website of the Russian university.

When building on islands, engineers face a problem: the local calcareous sand is porous and brittle, and crumbles easily even under light loads. Transporting ordinary sand from the mainland is expensive and difficult. Traditional methods of soil stabilisation – such as cementation or chemical resins – are harmful to the environment. To solve this problem, Russian and Chinese scientists have proposed an alternative: adding calcium carbonate to ordinary sand, which is obtained through the enzymatic precipitation of loose building material.

First, the researchers extracted the enzyme urease from soybeans, then mixed it with a solution of urea and calcium chloride. As a result of a chemical reaction that takes place at room temperature and without harmful emissions, calcium carbonate (the same as limestone) was formed, which binds the grains of sand together. To further strengthen the structure, coconut fibre was added to the mixture. This prevents the material from breaking down under impact.

"Coconut fibre plays a key role: it reinforces the material, much like steel reinforcement in concrete. Under dynamic loads – for example, from a wave impact or an aeroplane landing – it prevents the reinforced concrete from breaking apart. Samples without fibre were completely destroyed, whilst those with fibre retained their integrity. This is of fundamental importance for island airfields and jetties," explained Tamara Chernykh, Professor of the Department of Building Materials and Products at South Ural State University.

During the experiments, the best results were achieved with a mixture of reinforced sand containing equal proportions of fine and coarse sand and 0.4 per cent coconut fibre. The samples were tested for static strength (compression) and dynamic strength. The researchers found that the higher the calcium carbonate content, the stronger the material. The optimal mixture demonstrated high resilience even under heavy impact.

The technology can be used to reinforce ground beneath runways, jetties, breakwaters and other structures in coastal and island areas. The researchers emphasise that the development is environmentally friendly, uses local materials and does not require high-temperature firing, unlike cement, and therefore minimises carbon dioxide emissions.