A new cement phase discovered on the road towards zero carbon emissions

In order the fight global warming, industrial sector has been actively developing methods to reduce CO2 emissions during the operations processes. The Ca- based Portland cement (PC) industry is critical to human civilization in the sense that it manufactures cement, which is the second most utilized resource (after water) in terms of volumetric consumption. However, it is also a known fact that cement industry is contributing as much as 8% to the overall CO2 emissions. With the cement production poised to increase dramatically in the next couple of decades due to large demand in developing countries, there is a greater concern to reduce the CO2 emissions associated with cement manufacture.

Reducing the carbon footprint associated with the cement manufacturing industry is the primary research theme of the Fibre and Particle Engineering Research Unit at Oulu University. Doctoral student Harisankar Sreenivasan works on similar research theme under the principal supervision Associate professor Päivö Kinnunen. The doctoral thesis is focused on Mg-containing alternative cementitious materials (technically known as geopolymers/alkali activated materials) with reduced carbon emissions. This research involves external collaboration (Prof. John Provis, University of Sheffield, UK) as well as internal collaboration (Assoc. Prof. Wei CaO, NANOMO, Oulu University). The PhD thesis work is funded by European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie COFUND and is part of the InStreams hub concentrating on the science of industrial side stream utilization.

During the research, researchers obtained evidence for the formation of an amorphous magnesium silicate phase (AMS) with cementitious properties. The formation of this phase was confirmed by advanced characterization techniques including Scanning Electron Microscopy (SEM) and Silicon-targeting Nuclear Magnetic Resonance (NMR) spectroscopy (Figure 1). The existence of the cementitious phase has been speculated in the scientific literature previous, but its existence and properties have not been directly observed previously. The significance of this phase is that its components are magnesium and silicon, which offer advantages over calcium-based cements. In Finland, there are massive volumes of industrial side streams which are non-carbonate based and contains significant proportion of silicon and magnesium. If these side streams can be utilized as raw materials, then it would enable production of a cementitious binder with zero raw-material-related carbon emissions, while simultaneously utilizing industrial waste. The research work was published in Cement and Concrete Research, the most prestigious scientific journal journals focusing on cement research.

“This is an exciting finding”, starts Kinnunen, thinking. “It is an example of a small win that are needed against the climate crisis. The research around carbon-neutral and carbon capturing concrete has increased tremendously in short time, and things that seemed impossible only five years ago, are now at the verge of being common practice. To me it is very real possibility that cement and concrete industry could be climate neutral by 2035”.

Future work has to be done to understand how the magnesium silicate phase impact the desirable cementitious properties in a detailed manner. Properties like compressive strength, chemical durability, shrinkage, fire resistance are important in this respect. Furthermore, the emissions in the alkali activator are also important to tackle if an alkali activator is used.