In the quest for sustainable construction materials, researchers are turning to an unlikely source: wood biomass ash (WBA), a by-product of biofuel energy plants. Yiying Du, a researcher at the Laboratory of Concrete Technology within the Institute of Building Materials at Vilnius Gediminas Technical University in Lithuania, has been exploring ways to recycle WBA into alkali-activated materials (AAM), potentially offering a circular solution to both waste management and construction needs.
The challenge with WBA lies in its unstable characteristics, which can hinder the development of mechanical properties in AAM. To address this, Du and her team experimented with various pozzolanic additives, including coal fly ash (CFA), metakaolin (MK), and natural zeolite (NZ). These additives were incorporated at replacement ratios ranging from 10% to 40%, with the goal of enhancing the material’s strength and durability.
The team used a combination of calcium hydroxide, sodium hydroxide, and sodium silicate as ternary activators. The samples were initially cured at 60°C for 24 hours, followed by 27 days at room temperature. The results were promising. “The optimum replacement ratios were found to be 30% for CFA, 20% for MK, and 20% for NZ,” Du explained. The highest compressive strengths achieved were 22.71 MPa for CFA, 20.53 MPa for MK, and 24.33 MPa for NZ. The corresponding flexural strengths were 4.49 MPa, 4.32 MPa, and 4.21 MPa, respectively.
Natural zeolite emerged as the most effective additive, attributed to its highest Si/Al ratio in a calcium-rich environment. Coal fly ash showed moderate effectiveness, while metakaolin was the least efficient when combined with WBA in AAM. The study also revealed that reducing the Ca/Si ratios in the AAM, facilitated by the pozzolanic additives, favored the formation of a binder system composed of various hydrates, thereby enhancing strength when the Ca/Si ratio was below 0.35.
The implications for the energy and construction sectors are significant. As biofuel energy plants continue to generate WBA as a by-product, this research offers a viable pathway for recycling this waste into valuable construction materials. “This not only addresses environmental concerns related to waste disposal but also opens up new avenues for sustainable construction,” Du noted.
The findings, published in the journal ‘Buildings’ (translated as ‘Pastatai’), could pave the way for future developments in the field of sustainable construction materials. By optimizing the use of WBA and pozzolanic additives, the construction industry can move towards more eco-friendly practices, reducing reliance on traditional raw materials and minimizing waste.
As the world grapples with the challenges of climate change and resource depletion, innovative solutions like this one are crucial. The research conducted by Yiying Du and her team at Vilnius Gediminas Technical University highlights the potential of recycling industrial by-products into high-performance construction materials, contributing to a more sustainable future.