In the quest for sustainable construction materials, researchers are turning to industrial waste streams, seeking to transform them into valuable resources. A recent study published in Discover Materials, the English translation of the journal name, has shed new light on the potential of oil shale ash, a byproduct of the energy industry, to create robust cementitious materials. The research, led by Fawwaz I. Khalili from the Chemistry Department at the University of Jordan, explores how blending oil shale ash with kaolin and metakaolin can enhance the formation of cementitious gels, with significant implications for the construction and energy sectors.
Oil shale ash, rich in silicon, calcium, and aluminum, has long been an underutilized resource. Previous attempts at alkali activation, a process that uses alkaline solutions to dissolve and react silicate and aluminate phases, have met with limited success. However, Khalili’s team has found a way to overcome these challenges by blending the ash with aluminum-rich kaolin and metakaolin, and further investigating the effects of various foaming agents.
The study identified two key sets of FTIR absorption bands, indicating the formation of sodium aluminosilicate (NASH) and calcium silicate hydrate (CSH) gels. “The synergistic effect of dissolving anhydrite, silicates from oil shale ash, and aluminosilicate from kaolin/metakaolin is crucial for the formation of these gels,” Khalili explained. This synergy was confirmed through X-ray diffraction (XRD) analysis, which showed the successful formation of both NASH and CSH.
However, the addition of foaming agents—aluminum, zinc, and hydrogen peroxide—had a significant impact on gel formation. While the formation of CSH was almost completely interrupted, the formation of NASH was reduced in the order of aluminum, zinc, and hydrogen peroxide. This order reflects the reactivity of each foaming agent with sodium hydroxide, a key component in the alkali activation process.
The researchers also found that introducing 50% of the ash into the alkali-activated kaolin/metakaolin mixture increased compressive strength to 18.3 MPa, compared to 12.5 MPa for alkali-activated metakaolin alone. This finding is particularly promising for the energy sector, as it provides a potential use for oil shale ash, a waste product of the energy industry.
The study’s findings could pave the way for future developments in the field of sustainable construction materials. By transforming industrial waste into valuable resources, the construction and energy sectors can work together to create a more sustainable future. As Khalili noted, “This research is just the beginning. There’s still much to explore in terms of optimizing the process and scaling it up for industrial application.”
The research was published in Discover Materials, a journal that focuses on the discovery and development of new materials. The study’s findings are a testament to the potential of interdisciplinary research, combining chemistry, materials science, and engineering to address real-world challenges. As the construction and energy sectors continue to evolve, the need for sustainable materials will only grow. This study provides a promising step forward in that direction.