19 September 2013 — Researchers from the Niels Bohr Institute in Copenhagen have shown that cement made with waste ash from sugar production is stronger than ordinary cement.
The research, published in Scientific Reports, shows that ash helps to bind water in the cement so that it is stronger, can withstand higher pressure and crumbles less. Energy is also saved and pollution from cement production reduced.
In some countries where sugar cane is grown, such as Brazil, agricultural waste product from sugar production has been added to cement for years.
“I have been studying cement using quasi-elastic neutron scattering for several years and researchers from Brazil asked whether I wanted to analyse samples of cement mixed with waste products in the form of sugar cane ash,” said Niels Bohr Institute nanophysics researcher Heloisa Bordallo.
“I decided to say yes to the project, which aimed to investigate the properties on a nano-scale and map the mobility of water in the cement.
“The quality and strength of cement is directly related to how much of the water is chemically bonded. The more the water can move around, the worse it is for the strength and durability.”
The experiments showed that cement mixed with around 20 per cent ash was stronger, could withstand higher pressure and would crumble less. The researchers said ordinary cement was generally stronger during the first few months, but after a year the ash cement became stronger.
The researchers said the research could lead to better environmental outcomes in the construction industry.
“The cement industry is huge and if they are to adopt a new idea, they need to have proof that it works,” said Ms Bordallo. “Using quasi-elastic neutron scattering we have now studied cement mixed with ash and shown what is happening and why it is stronger.
“Cement production uses a lot of energy and emits large amounts of CO2, because it needs to be heated up to very high temperatures. Cement production accounts for five per cent of global CO2 emissions. If you replace 20 per cent of the content with ash, you are saving both CO2 emissions and raw materials.”