Researchers at the University of Sharjah have demonstrated that concrete can be reinforced using polymer plates instead of steel bars, with the new material showing superior strength, ductility, and energy dissipation.

The details of their findings, published in the journal Construction and Building Materials, could pave the way for more sustainable and environmentally friendly construction materials.

According to the study, polymer plates significantly outperformed steel bars, achieving nearly double the peak load capacity and absorbing five times more energy than configurations reinforced with steel bars.

“Results showed that optimized wavy geometries significantly enhanced bond strength, improved post-cracking behavior, and increased energy dissipation compared to traditional straight reinforcement,” they write. “The best-performing specimens reached nearly 80 % of the flexural strength of steel-reinforced samples.”

Rather than simply substituting steel bars with plastic versions, the research explored how the shape and geometry of the reinforcement influence structural performance. The researchers evaluated two primary reinforcement configurations.

“We tested bars versus plates, comparing standard rod-like shapes to flat, plate-like structures,” said Dr. Muhammad Talha Junaid, associate professor of materials and structures at the University of Sharjah. “We also tested traditional straight lines against innovative wavy, serrated, and triangular patterns designed to grip the concrete better and achieve better stress transfer.”

Strong alternative to steel

Concrete, the most widely used construction material on the planet, depends heavily on steel reinforcement to provide tensile strength. Globally, it is estimated that half of all steel production, approximately 900 million tons annually, is used in construction, with a substantial portion allocated specifically to reinforcing concrete.

While effective, steel comes with drawbacks: it is heavy, costly, and susceptible to corrosion, which can compromise the longevity of structures, explained Dr. Junaid. “In our study, we investigated a cutting-edge solution: reinforcing concrete with 3D-printed polylactic acid (PLA), a biodegradable thermoplastic.”

One of the key findings, according to Dr. Junaid, is that “plates outperform bars. Beams reinforced with PLA plates achieved up to twice the peak load capacity and absorbed up to five times more energy (toughness) than those using simple PLA bars. The increased surface area of the plates allowed for a much stronger bond with the concrete.”

The researchers also discovered that non-traditional shapes, especially triangular and wavy forms, greatly enhanced the beam's ability to handle post-cracking stress. Dr. Junaid said, “These serrated shapes acted like teeth, locking into the concrete to prevent slipping.”
However, the most effective configuration was the triangular wavy PLA plate, which achieved “nearly 80% of the bending strength of a traditional steel-reinforced beam and matched its ductility (flexibility),” added Dr. Junaid.

Thermoplastic plates outperform traditional steel bars

One of the key takeaways from the study is that it provides a pathway for the mass production of innovative reinforcing shapes, demonstrating that the performance of reinforced concrete depends not only on material itself but also on the geometry of reinforcement.

“We found that the ‘wavy’ or serrated shapes (resembling teeth) grip the concrete much better than straight bars, preventing the reinforcement from slipping when the beam is loaded or stressed,” said Dr. Junaid. “This increased the bond to help distribute the stress, thereby enhancing the strength performance of the elements.”

The researchers also discovered that using flat plates with longitudinal reinforcing elements, rather than traditional rod-like bars alone, significantly improved performance. “The plates provided more surface area for the concrete to bond to, resulting in beams that could handle twice the load and absorb five times more energy than those with bars only,” Dr. Junaid added.

The authors emphasize that their reinforcement method “presents a viable, non-corrodible alternative to conventional steel reinforcement. While its strength is slightly lower, it has demonstrated comparable performance in certain configurations. It offers a sustainable, lightweight solution, particularly suitable for applications requiring corrosion resistance or material compatibility.”

They further note that “PLA plate configurations consistently outperformed PLA bars, with their effectiveness governed by parameters such as increased bond strength, continuity of the reinforcement path, cross-sectional area, and increased bonded surface area with the surrounding concrete.”

In their study, the researchers outline several practical implications, noting that the thermoplastic plates offer substantial advantages over traditional teel bars, particularly in their superior resistance to corrosion, light weight, customization on demand, and overall sustainability.