Bendable concrete without cement

Materials World magazine
9 Mar 2020
Inventor holding a slab of bendable concrete

A robust yet flexible concrete that contains industrial waste and no cement can reduce carbon footprints. 

A new type of composite concrete made from industrial waste but no cement could help reduce the overall carbon footprint of construction projects.

The concrete has a high tensile strength and, unlike conventional concrete which has no stretch and is brittle under stress, it has a very high ductility that allows it to flex under a strong load. 

Researchers at Swinburne University of Technology, Australia, patented the new geopolymer composite concrete. They believe it will be suitable for use in construction projects in regions prone to earthquakes and hurricanes, as well as protecting structures from heavy blasts or impact. 

Making it work 

The composite concrete is made with fly-ash obtained from the waste of coal-fired power stations. This ingredient removes the need to use cement, the most energy-intensive element in traditional concretes. 

It also contains short polymeric fibres and these enable the set material to withstand high tensions, bending and even multiple hairline cracks without breaking down. 

Adding to the environmental aspects, it was designed to be a dry mix material that would not require heat curing, to minimise the energy and carbon consumption. 

Lead researcher for the work, Swinburne University Centre for Smart Infrastructure and Digital Construction, Dr Behzad Nematollahi, said ‘Our laboratory test results showed that this novel concrete is about 400-times more bendable than normal concrete, yet has similar strength.’

Greening concrete 

The impetus behind the work was the carbon intensity of the concrete industry, and as concrete is one of the most widely used materials in the world, and in vast quantities, there is a pressure to deal with the problem. 

‘It is the second-most consumed material by human beings after water. Its quality has a massive effect on the resilience of our infrastructure such as buildings, bridges and tunnels,’ said Nematollahi. 

Also, the team tested the geopolymer against SHCC M45 concrete and concluded that ‘production of this novel concrete requires about 36% less energy and emits up to 76% less carbon dioxide as compared to conventional bendable concrete made of cement’. 

The paper, Micromechanics-based investigation of a sustainable ambient temperature cured one-part strain hardening geopolymer composite, published in Construction and building materials, can be read here:

Image: Dr Behzad Nematollahi holding a slab of the bendable concrete. Credit: Swinburne University of Technology.