In this episode, we talk to Professor Karen L. Scrivener, MA, a research group leader at the Swiss Federal Institute of Technology, Lausanne (EPFL), and an expert on cement chemistry and material science of cement-based materials. She talks about alternative ways to reduce the carbon footprint of concrete to tackle concrete’s CO2 problem, as well as her career and research.
Engineering Quotes:
Here Are Some of the Questions We Ask Professor Karen Scrivener:
Tell us more about the Nanocem network?
Why do you think LC3 has so much potential?
In an article called "Alternative materials could shrink concrete's giant carbon footprint," you talk about how heated clay can reduce the carbon footprint of concrete. Could you talk more about that?
What is the difference between using CSA cement and Portland cement, and what effect does it have on our environment?
Could you talk about geopolymers, which are another category of low CO2-emitting cement?
Is there an economic incentive for owners, engineers, contractors, and architects to use materials like LC3?
How can we encourage more people to get involved in the material science of concrete?
For engineers considering a career like yours, what advice would you give them?
Here Are Some of the Key Points Discussed About Reducing the Carbon Footprint of Concrete:
Nanocem is a research network that brings the leading industrial cement and admixtures companies, and the European Academic Institute, to research cementitious materials. It has brought about a radical change in the research. Rather than short-term research projects, they are more strategic about the fundamental science and the mechanisms it entails. It was recently obtained by the Global Cement and Concrete Alliance (GCCA), and in 2020, Nanocem was replaced by the global network INNOVANDI.
LC3 is a new type of cement that is based on a blend of limestone and calcined clay. It has benefits like low CO2 emission, resistance to chloride penetration, and withstands the alkali-silica reaction. Commercial production of LC3 is still in the early phases, but there are possibilities of exponential growth in the next five to 10 years.
The CO2 emissions from making limestone into clinkers contribute 60% of the CO2 emissions when making cement. When the limestone is replaced by calcined clay, a much lower temperature can be used, and there is no decomposition of limestone. The limestone is then added to the clinker. This method has a negligible contribution to CO2 emissions and can reduce them by approximately 40%.
Clay is different in almost all geographical regions. The amount of kaolin in the clay needs to be measured to determine if it will work for LC3 cement. The clay needs around 40% kaolin in it to be a successful candidate for LC3 cement.
CSA cement and Portland cement need a lesser amount of limestone to be made. The production of CSA cement needs minerals that are high in aluminum content compared to silica. These high-aluminum content elements are expensive and not widely found. CSA is not a very robust cement, and the setting time can be variable. CSA production has a 20-30% CO2 emission reduction, which is much lower than LC3 cement.
Geopolymers need slag or high-calcium fly ash to manufacture. The amount of worldwide slag is approximately 8% of the amount of cement we need. Ninety percent of this slag is in use in cement and concrete. Removing the slag from concrete will not contribute to the reduction of CO2 The adding of alkali activators into the materials to make them work is adding to the CO2 emissions. The alkali activators are expensive to produce. People have been trying to solve all these problems for decades. Billions of dollars are spent on researching these kinds of materials with no result in the f...
