'Biocement' could help build underground structures in Singapore

Eileen Poh Channel NewsAsia 2 Nov 13;

SINGAPORE: Building structures underground in Singapore may be made easier if a study to strengthen weak rocks below ground is successful.

It is one of four projects under the Ministry of National Development's S$8 million Sustainable Urban Living R&D Programme which seeks solutions in expanding Singapore's land space.

The projects touch on areas such as underground space utilisation, land reclamation technology and space optimisation.

Underground construction poses several challenges -- cracks in rocks is one of them. Such cracks can cause instability and water seepage problems.

However, this may soon be resolved with a new material called 'biocement', which is simply bacteria with chemicals in water.

The solution will act as a glue to seal cracks in rocks or bond sand particles.

Water containing bacteria, urea and calcium ions are injected into cracks in the rocks. The bacteria breaks down urea and forms calcite and after about two weeks, the calcite deposits harden and fill the cracks.

This method, if successful, can replace the current use of cement to fill the cracks at half the cost.

Associate Professor Tan Soon Keat from the School of Civil and Environmental Engineering at Nanyang Technological University (NTU), said: "It is almost like a liquid, like water itself. So where water can flow, (the biocement) can also flow there. So even if it is a hairline crack, it will follow through."

Assoc Prof Tan and his team at NTU have shown that biocement works under lab conditions.

Assoc Prof Tan added: "We have done the laboratory-scale test and it has worked out. But it has actually not been done in the real-scale. The proof is to do it in... the actual application, that is when we have a test site."

That is what the professor and his team will be focusing on next in a project funded by the Ministry of National Development. The testing stage of the project will take a few years.

- CNA/ac