Biochar — a carbon-rich material that absorbs and retains water well — is generated from biomass and frequently used in the agricultural industry as soil amendment to improve crop yield. Now the same material could also be used to make buildings stronger.
Researchers from NUS Design and Environment have discovered that incorporating a small amount of dry biochar powder recycled from saw dust into concrete mixture can make concrete structures up to 20 per cent stronger and 50 per cent more impermeable to water.
The strategy makes use of the biochar’s porous and fibrous structure and its good water absorption and retention properties to enhance the concrete’s curing and hardening process, and subsequently improve the strength and permeability properties of concrete structures.
The novel method also promotes wood waste recycling.
In Singapore, over 530,000 tonnes of wood waste was generated in 2016 alone, with a large fraction contributed by saw dust. If unrecycled, this wood waste is incinerated or disposed in landfills, leaving a significant carbon footprint on the environment.
The use of biochar technology in concrete construction therefore offers an innovative approach to store large amounts of carbon in buildings while enhancing the building structures. Using this method, close to 50kg of wood waste can be utilised for each tonne of concrete fabricated. This translates to around six tonnes of wood waste recycled for every home unit with a 100sqm floor area.
“This is a simple and affordable strategy to enhance our building structures, particularly in Singapore, where water leakage from rain and water pipes are common problems. At the same time, we are putting the large amount of wood waste generated in Singapore to good use,” said Associate Professor Kua Harn Wei who led the research team.
The team is already in discussion with a local firm to commercialise the technology. They are concurrently studying the different methods of employing biochar in concrete to develop other types of high performance concrete structures.