The effect of carbonation conditions on the carbonation behavior of enzyme-modified cementitious materials

Please check whether enrolling in this project is possible by directly contacting the responsible supervisor(s) indicated below as soon as possible. Note that although we announce many topics, we won't be able to offer all of them simultaneously due to limited lab capacity.

The emission of CO₂ has increased rapidly in the last decades which has pushed the global environment out of safe boundaries. Concrete can act as a carbon sink since CO₂ penetrates and reacts with Ca(OH)₂ in concrete resulting in the carbonation of concrete, which is a natural process. However, this process is slow due to different factors. Carbonic anhydrase (CA) is a group of enzymes that could be a promising candidate to accelerate CO₂ sequestration. CA acts as a catalyzer for CO₂ hydration to H⁺ and HCO₃^- and has been reported to increase the reaction rate by about 10⁷ times compared to the process in the absence of CA. Larger amounts of CO₂ may thus be sequestered via carbonation in a shorter period. We aim to achieve efficient atmospheric CO₂ sequestration in cementitious materials with the help of CA.

Preliminary results show that cement pastes with trace amounts of CA exhibited higher carbonation rate at the early stage compared to CA-free cement pastes. However, the CA effect was eliminated due to unclear reasons after longer time period. While these results are encouraging, more research is needed for further understanding the carbonation behavior of CA modified cementitious materials.

Many factors can influence carbonation, including CO₂ pressure, temperature, relative humidity, carbonation duration, water content in concrete, and concrete porosity. The aim of this project is to investigate the effects of different carbonation conditions on the carbonation behavior of CA-modified cement pastes. The investigated carbonation factors will be relative humidity (dry or wet conditions), carbonation duration, and concrete porosity (via water-to-cement ratio). The promising potential of CA for CO₂ sequestration can be further applied through a better understanding of the carbonation process.

The student is expected to carry out experiments in the lab, which involve working with concrete samples. The student will get an opportunity to work with characterization techniques such as thermogravimetric analysis (TGA), BET surface area analysis, and microstructural investigations.