Scientists develop stronger, crack-resistant concrete using recycled carpet fibers

Carpet waste, a byproduct of modern life, has become a significant environmental challenge worldwide. Accounting for over 70% of floor coverings, carpets are a common sight in homes, offices, and commercial spaces.

Despite their widespread use, their disposal poses severe issues. Most carpets, made of synthetic fibers, outlast their usability by hundreds of years. This longevity results in millions of tons of waste that either fill landfills or are incinerated, releasing toxic gases.

Europe generates 1.6 million tons of carpet waste annually, with 60% directed to landfills and the rest incinerated. The United States faces an even larger problem, producing 3.4 million tons in 2018, accounting for 3.5% of all landfill waste.

Australia, too, grapples with this challenge, as discarded carpets represent 2% of its landfill materials. In the UK, 400,000 tons of carpet waste are produced annually, with half going to landfills. The global reliance on landfill or incineration exacerbates pollution and wastes resources, creating an urgent need for sustainable solutions.

In parallel, the construction industry confronts its own challenges. Concrete, a ubiquitous material, suffers from weaknesses in tension, leading to early-age cracking that compromises structural integrity and durability.

Repair costs are staggering: $8 billion annually in Australia and $76 billion in the United States. Moreover, demolition waste adds to the environmental burden, as Australia alone generated 27 million tons of construction waste during 2018–2019.

Researchers have turned to fibers as a remedy for concrete’s shortcomings. Artificial and natural fibers have demonstrated the potential to reduce cracking and improve durability.

Natural fibers like flax and luffa require surface treatments to enhance their performance, but their cost can be prohibitive. Recycled materials offer a sustainable alternative, aligning with the principles of a circular economy.

A research team at RMIT University in Melbourne, Australia, led by Dr. Chamila Gunasekara, has unveiled a groundbreaking method to address both carpet waste and concrete deficiencies. Their innovative approach incorporates discarded carpet fibers into concrete mixtures, resulting in a material that resists cracking and improves durability.

"Cracking in early-age concrete slabs is a long-standing challenge in construction projects," Gunasekara explained. "Scrap carpet fibers can increase concrete's strength by 40% in tension and substantially reduce shrinkage."

In laboratory tests, concrete reinforced with carpet fibers met Australian Standards for engineering performance and environmental safety. The addition of 1% carpet fibers improved compressive strength by up to 17.5% and flexural toughness significantly. A fiber content of 1–2% reduced shrinkage by 15–30%, demonstrating its effectiveness in mitigating cracking.

These advancements are promising for various construction applications, from airport runways and pavements to tunnels and sound barriers. However, rigorous testing remains essential before this material is used in critical structural projects.

The research extends beyond the lab. The RMIT team is conducting field trials with support from industry partners like Textile Recyclers Australia and Godfrey Hirst Australia, as well as local councils in Victoria. These trials will assess the performance of fiber-reinforced concrete in real-world conditions.

Professor Sujeeva Setunge of RMIT leads the ARC Industrial Transformation Research Hub, which funds these efforts. Collaborative work with international experts, such as Professor Andrzej Cwirzen from Sweden, enhances the research with advanced computational modeling.

Textile waste, including discarded clothing, is another pressing issue. Australians discard 23 kilograms of textiles per person annually, making the country the second-largest consumer of textiles worldwide. Textile recycling presents vast opportunities, as up to 70% of waste could be converted into usable fibers.

Dr. Shadi Houshyar, a textile scientist at RMIT, highlighted the challenges posed by specialized materials like firefighting clothing. "These materials, while essential for safety, are incredibly difficult to recycle," she said. Collaborative recycling strategies could integrate such textiles into innovative applications like concrete reinforcement.

The potential for carpet fiber-reinforced concrete goes beyond environmental benefits. Its reduced shrinkage and enhanced durability can significantly lower repair costs, making it an economically viable solution for infrastructure. This innovation demonstrates the power of combining waste management with advanced engineering to solve global challenges.

As field trials continue, researchers and industry leaders are optimistic about scaling up the use of waste textiles in construction. The project embodies a circular economy approach, turning waste into valuable resources while addressing pressing environmental and industrial issues.

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

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