In the heart of La Rochelle, France, and Danang, Vietnam, researchers are tackling one of the construction industry’s most pressing challenges: how to make recycled aggregate concrete (RAC) as durable as its traditional counterpart. Led by Tien-Dung Nguyen, a researcher at LaSIE – UMR CNRS 7356, La Rochelle University, and the Faculty of Road and Bridge Engineering at The University of Danang, a team has delved deep into the mechanisms that govern the longevity of RAC, with promising implications for the energy sector and beyond.
The global construction industry is a voracious consumer of natural resources, and the push for sustainability has led to a surge in interest in recycled materials. But while reusing construction waste is environmentally friendly, the durability of RAC has been a sticking point. Nguyen and his team have been working to change that, and their latest findings, published in the journal Cleaner Materials, offer a roadmap for enhancing RAC’s performance and reducing the ecological footprint of construction and demolition waste.
At the core of the issue lies the adhered mortar (AM) in coarse recycled aggregates (CRA). This mortar, a remnant of the original concrete, is more porous and absorbs more water than natural aggregates. This increased porosity leads to weaker interfacial transition zones (ITZs), reducing the concrete’s impermeability and its resistance to carbonation and chloride ingress. “The adhered mortar is a double-edged sword,” Nguyen explains. “It’s what makes recycling concrete aggregates possible, but it also introduces complexities that affect durability.”
The team’s review of existing literature reveals a tangled web of factors influencing RAC’s durability, from the replacement ratio of recycled to natural aggregates, to particle size, chemical admixtures, mixing techniques, and curing conditions. Moreover, the mechanisms governing chloride ingress, carbonation, and permeability are complex, non-linear, and multivariable, rendering conventional modeling techniques inadequate.
So, what’s the solution? According to Nguyen and his team, the answer lies in artificial intelligence (AI) and a comprehensive understanding of the factors at play. “AI methods, supported by extensive databases, can provide precise durability predictions,” Nguyen says. “This is crucial for the energy sector, where the durability of concrete structures can significantly impact the lifespan and efficiency of energy infrastructure.”
But AI is just one piece of the puzzle. The team also highlights several treatment strategies to enhance RAC’s durability, with CRA carbonation standing out as a potential game-changer. This process, which involves treating CRA with carbon dioxide, not only strengthens the microstructure but also offers environmental benefits by reducing the carbon footprint of construction and demolition waste.
The implications of this research are far-reaching. For the energy sector, improved RAC durability could lead to more sustainable and cost-effective construction of power plants, wind turbines, and other infrastructure. For the construction industry at large, it could pave the way for more widespread adoption of recycled materials, reducing the demand for natural resources and lowering the environmental impact of construction and demolition waste.
As Nguyen and his team continue their work, the future of RAC looks increasingly promising. With AI-driven durability predictions and innovative treatment strategies, the day when recycled aggregate concrete is as durable and reliable as traditional concrete may not be far off. And when that day comes, the energy sector and the planet will be all the better for it. The research was published in Cleaner Materials, which translates to Cleaner Building Materials in English.