NUS team develop new method to strengthen building structures by mixing wood waste with concrete

(From left) Research assistant Chakradhar Pedapati, PHD student Souradeep Gupta, research assistant Manikandan Jayaraj and associate professor Dr Kua Harn Wei with a biochar and a concrete column containing biochar.
(From left) Research assistant Chakradhar Pedapati, PHD student Souradeep Gupta, research assistant Manikandan Jayaraj and associate professor Dr Kua Harn Wei with a biochar and a concrete column containing biochar. ST PHOTO: NG SOR LUAN

SINGAPORE - Researchers from the National University of Singapore (NUS) have found a way to use wood waste to strengthen building materials.

The new method uses biochar, which is a material produced when heat is used to decompose sawdust.

The researchers from the School of Design and Environment said biochar in powder form is added to concrete in order to increase the material's strength and impermeability, which refers to the ability to prevent water from passing through.

Associate Professor Dr Kua Harn Wei, one of the four involved in the research, explained how biochar works.

The lead researcher said usually, water is added to powdered concrete to create a wet mix in a process called hydration. The problem has been that during the process, water evaporates, weakening the mix.

But the researchers found that when biochar is added, the mix is better at retaining water, which in turn produces stronger concrete.

Biochar in powdered form also plugs gaps that exist within the concrete mix to reduce water seepage through cracks that might form when it is set.The researchers found that adding biochar strengthened the concrete mix by 20 per cent and its impermeability by 50 per cent.

The NUS team conducted experiments and found that a 50 millimetre cube of pure concrete could take about 72.6 kilonewtons (kN) of force before cracking, withstanding the weight of about 119 people whose average weight was 62 kilograms each.

But when biochar was added, it took about 83 kN of force, withstanding the weight of about 137 people.

The researchers said using biochar is also environmentally friendly, by helping to recycle wood waste. In 2016, more than 530,000 tonnes of wood waste was produced in Singapore, mainly from furniture factories, which was previously either incinerated or disposed of.

Dr Kua believes that the new method will help to alleviate some of Singapore's existing structural problems.

For example, Ministry of National Development data show that more than six out of every 10 cases brought to the Strata Titles Board from 2014 to 2016 involved water leakage issues between unit owners.

"This is a simple and affordable strategy to enhance our building structures," said Dr Kua.

"Particularly in Singapore, this will help to reduce the problems of water leakage from rain and water pipes that could potentially seep through our concrete ceilings."

The team from NUS is currently discussing with companies and government agencies to commercialise this technique, as well as researching further on cement composites to serve wider applications.