Dr. Behzad Nematollahi developed a form of “cement-free bendable concrete” at Swinburne University in Australia. Rather than cracking and breaking under stress, this concrete can “bend”, making it ideal for construction in earthquake-prone areas. In addition, his developments could reduce the carbon emissions associated with producing concrete as much as 76%.
HayatLife contacted Dr. Nematollahi to learn more about his work.
How does this synthetic, bendable concrete behave differently under the kinds of pressure posed by earthquakes? What makes it superior?
Concrete has good compressive strength – the ability to bear loads that push it together. However, it does not have enough capacity to carry tensile load—the ability to deform or stretch without fracturing. That is why steel reinforcements are often added to concrete to increase its tensile strength. Nevertheless, the reinforced concrete cannot bend, and cracks under stress, causing deterioration and damages that necessitate frequent expensive maintenance.
Instead of this, novel cement-free bendable concrete contains some short polymeric fibers, which can slip rather than break under heavy loads, allowing the material to have multiple fine cracks before it fails. So, this concrete can experience excessive bending and does not rupture into pieces. In fact, it is 400 times more ductile than conventional concrete, but has similar compressive strength.
Do you think this development will replace older forms of concrete entirely (over time, of course)? How does your work differ from previous forms of concrete?
The basic constituents of conventional concrete are Portland cement, water, sand, and gravel. Cement-free concrete has the same ingredients, except Portland cement. Portland cement production needs a considerable amount of energy and emits a significant amount of carbon dioxide—about 4.8 GJ of energy and one tonne of carbon dioxide per tonne of manufactured Portland cement. Compared to conventional concrete made of Portland cement, cement-free concrete has significantly lower environmental footprints as it is made of geopolymer that is a sustainable alternative to Portland cement. Carbon emissions from Portland cement manufacture are second only to those of fossil fuels. Geopolymer utilizes industrial waste materials such as fly ash and slag and does not contain any Portland cement, thereby reducing the carbon emissions by as much as 80%.
However, concrete, regardless whether it is made of Portland cement or geopolymer, is brittle in nature. Therefore, cement-free concrete is also brittle, similar to Portland cement-based concrete.
To solve the brittleness of concrete, a new class of concrete, commonly known as ‘bendable concrete’, has been developed in the 1990s. Bendable concrete, similar to conventional concrete, uses the same ingredients except gravel. This material can undergo a lot of bending without fracturing into pieces, which is why it is known as bendable concrete.
One of the main shortcomings of bendable concrete (developed in the 1990s) is that a very high amount of Portland cement is used for its production—typically 2-3 times higher than that of conventional concrete. This very high cement content results in the high autogenous shrinkage, heat of hydration, and cost of the material. In addition, the increase in the carbon emissions associated with the production of Portland cement production can compromise the sustainability performance of bendable concrete.
That is why I decided to develop the “cement-free bendable concrete”. The performance of my “cement-free bendable concrete” is comparable (if not superior) than conventional bendable concrete. But at the same time, it has significantly lower environmental footprints —requires about 36 per cent less energy and emits up to 76 per cent less carbon dioxide as compared to conventional bendable concrete made of cement.
Cement-free concrete is a good alternative to conventional concrete. Considering the significant increase in the awareness of societies of the devastating effects of global warming, we can have no choice except using low carbon concretes such as cement-free concretes. However, bendable concrete, regardless of whether it is made of Portland cement or geopolymer, is a special type of concrete suitable for specific applications such as for construction in earthquake zones where the brittle nature of conventional concrete often leads to disastrous building collapses. So it is not made for everyday use and for normal applications, simply because of its high cost compared to conventional concrete. It should be noted that cost of “cement-free bendable concrete” is expected to be lower than that of conventional bendable concrete made of cement, because no Portland cement needed for its production. In addition, waste materials are used for its production.
You’ve mentioned both earthquake resistance and an environmentally friendlier production process as pluses of your research. Was reducing environmental harm always a part of your interest and research, or merely a happy by-product of the production process?
One of my main areas of research has always been and will be sustainable construction materials and low carbon concretes including cement-free (geopolymer) concrete. That is because sustainability and sustainable development is very important. At the same time, my other area of research is on high performance and ultra-high performance concretes, which are suitable for specific applications such as bendable concrete that is suitable for structures that are subjected to earthquakes, hurricanes, projectile impacts, and blasts.
Per your LinkedIn, you studied in Iran and Malaysia before starting with Swinburne. How did you get to where you are now?
I completed my undergraduate degree in Civil Engineering in Iran. After working in Iran as a Civil/Structural Engineer for 4 years, I moved to Malaysia and completed a Masters by Research in Structural Engineering. Subsequently, I moved to Australia in 2012 to do my PhD in Civil/Structural Engineering at Swinburne. After my PhD, I have continued working at Swinburne. My parents and siblings are still living in Iran.
How did you get into this field? Was there any specific memory or experience that sparked an interest in engineering?
Engineering was my passion from the beginning. My cousin was a Civil Engineer when I was studying at high school. That is how I got to become familiar with Civil Engineering and decided to study in this field for my undergraduate. After my undergraduate study, I became passionate about my field of study which gave me the driver to continue my study in postgraduate levels.
What’s the best part of your job and research? What do you enjoy most about the work you do?
I really love my job as a researcher. I love conducting trials and experiments in the laboratory to come up with better, more sustainable solutions for the challenges that our today’s construction industry is facing.
How do you most like to spend your free time?
During my free time, I like traveling, hiking, swimming and internet surfing.
