In the quest for sustainable construction practices, researchers have turned to an unlikely ally: lignin, a byproduct of paper mill waste. A recent study led by Mohammad Hosein Dehnad from the University of Qom in Iran, published in the journal ‘Results in Materials’ (which translates to ‘نتائج في المواد’ in English), explores the potential of calcium lignosulfonate (CLS) as a stabilizing agent in Full Depth Reclamation (FDR) of asphalt pavement. This innovative approach could significantly reduce the environmental impact of road construction and maintenance, with substantial implications for the energy sector.
Traditional stabilizing agents used in FDR, such as bitumen and cement, come with considerable environmental costs. They contribute to greenhouse gas emissions and high energy consumption. Dehnad’s research offers a greener alternative by leveraging CLS, a derivative of lignin, which is typically discarded as waste. “By using CLS, we not only reduce the need for conventional stabilizing agents but also repurpose an industrial byproduct, turning waste into a valuable resource,” Dehnad explains.
The study evaluated the performance of CLS in FDR, both as a standalone stabilizer and in combination with Portland cement. Two mix designs were tested: one with 85% reclaimed asphalt pavement (RAP) and 15% base soil, and another with 60% RAP and 40% base soil. Various combinations of cement and lignin were considered, with percentages ranging from 0% to 100% for each component.
The results were promising. CLS, when used in conjunction with Portland cement, enhanced the stabilization process and increased the Unconfined Compressive Strength (UCS) compared to using either material alone. “The synergistic effect of combining CLS with cement leads to improved mechanical properties, making the treated base more durable and stable,” Dehnad notes.
The study also found that a higher RAP content led to an increase in the optimal cement percentage while reducing the optimal percentage of CLS. For 28-day cured samples, specific combinations of cement and lignin yielded UCS values that were 10.6% and 5.8% higher, respectively, compared to samples stabilized only with the optimal percentage of cement without lignin.
The commercial impacts of this research are substantial. For the energy sector, which often requires extensive road infrastructure for transportation and logistics, adopting CLS as a stabilizing agent could lead to significant cost savings and reduced environmental footprint. “This approach not only aligns with sustainability goals but also offers a cost-effective solution for maintaining and repairing road infrastructure,” Dehnad adds.
As the construction industry continues to seek eco-friendly and efficient practices, the use of CLS in FDR presents a compelling case. This research could shape future developments in soil stabilization, paving the way for more sustainable and resilient road construction methods. By turning an industrial byproduct into a valuable resource, Dehnad’s work highlights the potential for innovation in the pursuit of greener construction practices.