In a groundbreaking study published in the journal *Developments in the Built Environment* (translated from Chinese as “Advances in Construction and Urban Planning”), researchers have discovered a novel way to transform an industrial by-product into a valuable resource for the construction industry. The study, led by Xun Sha from the Faculty of Civil Engineering and Mechanics at Kunming University of Science and Technology, explores the potential of lime mud (LM), a highly alkaline waste from the paper industry, to enhance the strength and CO2 sequestration capabilities of cement-based materials.
Traditionally, lime mud has been disposed of in landfills, posing environmental risks and wasting a potential resource. Previous attempts to incorporate LM into cementitious materials have either required energy-intensive calcination or resulted in reduced strength and poor durability. However, Sha and his team have found a more sustainable solution. “By directly incorporating uncalcined lime mud into cement-based materials and subjecting them to carbonation curing, we can significantly enhance their performance while reducing CO2 emissions,” Sha explains.
The researchers found that lime mud provides nucleation sites and high alkalinity, accelerating CO2 uptake and enhancing early strength. At just 14 days, a mixture containing 20% lime mud (LM20) under carbonation curing reached a compressive strength of 52 MPa, a 54% increase compared to its normally cured counterpart. When combined with slag, the LM20A10 mixture achieved an impressive balance of strength and CO2 sequestration, with a carbonation degree exceeding 11% by weight.
The study’s multi-scale analyses confirmed the formation of N,C-A-S-H gels and CaCO3–SiO2 composites, which densified the matrix and linked microstructure with macroscopic performance. Furthermore, carbonation-cured specimens retained over 60% of their compressive strength at 600°C, whereas normally cured specimens showed severe degradation, indicating improved thermal resistance.
This research presents a sustainable strategy for lime mud valorization, integrating solid waste recycling, CO2 sequestration, and performance enhancement. The findings could have significant commercial impacts for the energy sector, particularly in reducing carbon emissions and improving the durability of construction materials. As the world seeks to transition to a low-carbon economy, innovations like this one will be crucial in shaping the future of the construction industry.
Sha’s work not only contributes to the development of low-carbon and durable construction materials but also highlights the importance of interdisciplinary research in addressing global challenges. As the lead author notes, “This study demonstrates the potential of waste materials to be transformed into valuable resources, paving the way for a more sustainable and circular economy.”