In the relentless pursuit of sustainable construction practices, a groundbreaking study led by Jian Wang of the Beijing Building Research Institute Corporation Ltd., China State Construction Engineering Corporation, has unveiled a novel method to enhance the performance of recycled concrete aggregates (RCA). The research, published in Buildings, explores the use of microbial-induced calcium carbonate precipitation (MICP) technology to address the long-standing challenges of high water absorption and low mechanical strength in RCA.
The construction industry is under increasing pressure to reduce its environmental footprint. The rapid urbanization and infrastructure development have led to a significant amount of construction and demolition waste (CDW) each year. RCA, derived from processing CDW, offers a sustainable alternative to natural aggregates. However, its high water absorption and low density due to residual old mortar and internal microcracks have limited its use in structural concrete. Traditional methods like mechanical grinding, chemical treatment, and carbonation technology have proven ineffective or environmentally harmful.
Wang’s study introduces a more sustainable and efficient solution. “MICP technology uses bacteria to produce calcium carbonate, which fills the pores and microcracks in RCA, significantly reducing water absorption and increasing strength,” Wang explains. The research systematically investigated the effects of key parameters such as bacterial strains, bacterial concentration, modification duration, and urea addition sequence. The findings reveal that optimized MICP treatment can reduce RCA water absorption by up to 32.5%, with the optimal conditions being a bacterial concentration of 2.4 × 107 cells/mL, a modification duration of 7 days, and a two-hour urea resting period.
The study highlights the importance of selecting the right bacterial strain. Bacillus pasteurii emerged as the top performer due to its high urease activity and uniform calcium carbonate deposition. Mixed bacteria showed synergistic effects but uneven deposition, while Bacillus mucilaginosus had moderate efficiency. “Selecting the right bacterial strain is crucial for effective RCA modification,” Wang emphasizes.
The implications of this research are far-reaching. By enhancing the performance of RCA, MICP technology not only improves the strength and stability of recycled aggregates but also offers a cost-effective and environmentally friendly solution. This breakthrough could revolutionize the construction industry, reducing the need for natural aggregates and minimizing waste.
The energy sector, in particular, stands to benefit from this innovation. The construction of energy infrastructure, such as power plants and renewable energy facilities, requires large quantities of concrete. By adopting MICP-treated RCA, the industry can significantly reduce its carbon footprint and operational costs. Furthermore, the technology’s compatibility with cement-based materials makes it a viable option for a wide range of construction applications.
Looking ahead, the study paves the way for future developments in sustainable construction materials. The research provides a robust theoretical framework for efficient RCA modification and lays a practical foundation for promoting MICP technology in the green construction materials sector. As the industry continues to evolve, the integration of smart algorithms to optimize process parameters and advance pilot production trials will be crucial. This will not only enhance the efficiency of MICP technology but also accelerate its adoption in the construction sector.
The findings of this study, published in Buildings, offer a glimpse into a future where construction waste is transformed into high-performance building materials, contributing to a more sustainable and resilient built environment.