Carbon Dioxide Sequestration Capacity of Stabilized Malmi Clay, Master´s Thesis Bruk Belay Dejenie

For decades, various deep mixing methods have been implemented for improving the engineering properties of poor ground condition. The huge amount of material and energy involved in deep mixing opens opportunity for significant reduction in environmental impact. The search for ways to developing environmentally friendly deep mixing practice is getting popular by day.

This thesis aimed at examining on CO2 sequestration capacity of Malmi clay stabilized with different binder types in laboratory conditions. Variety of binders produced from recycled material and low CO2 emission were used in the study.

Carbonation of stabilized samples were performed in autoclave and carbonation chamber where the effect of carbonation environments on CO2 absorption assessed. Thermogravimeter analysis (TGA) were used to measure the amount of CO2 absorbed by carbonated-stabilized samples. The strength development was studied using unconfined compression test while microstructures analysis was investigated using Scanning Electron Microscope (SEM).

Carbonation of stabilized soil samples has shown to be a soil stabilization technique which can generate zero carbon dioxide emission. For the four binder types studied, the sequestration capacity of carbonated-stabilized soil was found to range between 2.8% to 4.1% of dry mass or 25 to 37 kg per cubic meter of mixture. The binder type that has the biggest potential to be carbon negative was Nordkalk Terra GTC3. While the use of plant fly ash (UPM Jämsänkoski) with Cement type II as an activator has shown to bring an emission value closer to zero. Despite its relatively high sequestration capacity of Cement type III the relatively bigger emission at production of binder holds the effort to reach zero emission value. Carbonation has shown to reduce 70% of the emission factor during production of cement type III. Carbonation was found to have effect on compressive strength (UCS) of stabilized clay. For samples under normal CO2 environment the strength was lower (by 17% to 80%) than the reference samples strength. Whereas, for samples under elevated temperature and pressure environment the compressive strength found to vary by binder type.