In the quest for sustainable construction materials, a team of researchers led by Chunxiang Qian from Southeast University in Nanjing, China, has made a significant breakthrough. Their study, published in the journal *Engineering* (known in Chinese as *Gongcheng Kexue*), explores a novel method for fixing CO2 emissions from cement kiln flue gas using microbial-enhanced steel slag. This innovative approach not only addresses environmental concerns but also promises to revolutionize the construction materials sector.
Steel slag, a byproduct of steel production, has long been an underutilized resource. However, Qian and his team have discovered a way to transform it into a valuable supplementary cementitious material through a process called accelerated carbonation. By combining microbial technology with a rotary kiln process, they have significantly increased the CO2-fixation rate, achieving a 10% CO2-fixation ratio within just one hour. This process is consistent throughout the year, regardless of seasonal variations.
“The key to this process lies in the CO2-fixation ratio and the particle fineness,” explains Qian. “When the CO2-fixation ratio exceeds 8% and the specific surface area is at least 300 m2/kg, the soundness issue of steel slag can be effectively addressed, facilitating its safe utilization.”
The implications of this research are profound for the energy and construction sectors. By using steel slag as a supplementary cementitious material, the demand for cement clinker—the primary component of traditional cement—can be reduced. This not only lowers carbon emissions but also provides a sustainable solution for the safe and efficient utilization of steel slag.
Moreover, the residual microbes in the carbonated steel slag powder act as nucleating sites, increasing the hydration rate of the silicate phases in Portland cement. This results in the formation of more hydration products, enhancing the strength of the hardened cement paste. “Microbial regulation results in the biogenic calcium carbonate having smaller crystal sizes, which facilitates the formation of monocarboaluminate to increase the strength of hardened cement paste,” Qian notes.
The commercial potential of this technology is immense. With a CO2-fixation ratio of 10% and a specific surface area of 600 m2/kg, replacing 30% of cement clinker with microbial mineralized steel slag powder yields an activity index of 87.7%. This means that the resulting material is nearly as strong and durable as traditional cement, but with a significantly lower carbon footprint.
As the world grapples with the challenges of climate change and resource depletion, innovations like this one offer a glimmer of hope. By harnessing the power of microbial technology, researchers are paving the way for a more sustainable future in the construction materials sector. This study not only provides a practical solution for reducing carbon emissions but also expands the application scope of microbial technology, opening up new avenues for research and development.
In the words of Qian, “This study provides a sustainable solution for reducing carbon emissions and safely and efficiently utilizing steel slag in the construction materials sector.” As the industry continues to evolve, the insights gained from this research will undoubtedly shape future developments, driving the transition towards greener and more sustainable construction practices.