A research team led by Dr. Muhammad Talha Junaid at the University of Sharjah tested cement mortar beams reinforced with FDM-printed PLA profiles. The study found that surface geometry was the dominant variable, with the best-performing configuration reaching nearly 80% of steel’s bending strength and matching its ductility.
Concrete on its own handles compression well but fails under tension. For more than a century, steel rebar has filled that gap, valued for its ability to resist tensile forces, bond reliably with the surrounding matrix, and maintain stiffness under load. The downside is persistent: steel is heavy, and in environments where moisture and chloride ions can reach it through the concrete cover, it corrodes, expanding as it does, cracking the structure from within. Coastal and marine construction, as well as infrastructure salted against ice, all face this problem as a routine maintenance challenge.
Fiber-reinforced polymer bars, glass and carbon variants, are the existing non-metallic answer, but their cost limits how widely they are deployed. The Sharjah research team, publishing in Construction and Building Materials, took a different starting point. Instead of sourcing a higher-performance polymer, they asked whether the shape of the reinforcement profile could carry structural weight that the material alone could not.
Shape as the Structural Variable
To test that premise, the team fabricated thirty small-scale cement mortar beams, embedding FDM-printed PLA profiles as reinforcement and loading each to failure in a three-point bending setup. The variables were cross-section, round bars versus flat plates, and surface treatment: smooth, wavy, serrated, and triangular profiles were all evaluated. Across every configuration, adding surface texture improved load-carrying capacity, with gains ranging from 40% to 120% depending on the specific geometry.
The cross-section comparison produced the sharpest contrast. Flat plates, despite being made from the same PLA filament under identical print conditions as the round bars, carried approximately double the peak load and dissipated around five times more energy before reaching failure. The explanation lies in contact area and mechanical interlock: textured flat surfaces grip the concrete matrix rather than sliding through it. Smooth round bars, by contrast, have little to anchor against and tend to pull out when load is applied.
The study was bounded in scope. Creep under sustained load, behavior at elevated temperatures, and fatigue performance under repeated cycling were not assessed, and those gaps will need to be closed before this approach moves toward use in real structures.
A Corrosion Problem That Will Not Go Away
The practical case for polymer reinforcement rests on the failure mode that steel cannot escape in aggressive environments. When chloride ions penetrate concrete, corrosion begins at the rebar surface. The byproducts expand, generating internal pressure that fractures the surrounding concrete from within and compromises the structural system over time. Repair and replacement in these environments is expensive and disruptive.
PLA does not corrode. Its cost is low relative to fiber-composite alternatives, and the FDM printing process allows profile geometry to be changed between jobs without new tooling. Rather than stocking a range of standardized bar sizes, a fabricator could print whatever cross-section and surface pattern the application calls for.
The Sharjah study’s contribution is to demonstrate that this flexibility, directed at surface geometry, can produce better structural performance, not parity with steel across all conditions, but a competitive option where corrosion resistance is the primary requirement.
3D Printed Polymer Reinforcement Builds a Research Foundation
The Sharjah findings add a geometry-focused data point to a line of research that has been testing whether 3D printed polymers can take on structural roles in concrete construction, each study approaching the problem from a different direction.
Dr. Junaid’s work isolates surface morphology as the key variable within the same material category, demonstrating that the design of the profile matters more than the strength of the compound. Researchers at UC Berkeley previously explored a different geometric strategy, incorporating 3D printed polymer octet lattices into concrete as reinforcement, finding that even as total polymer content increased and compressive strength declined modestly, the toughness of the structure remained largely constant while concrete usage fell by up to 33.7%. That study approached the problem through lattice density rather than surface texture, but the underlying logic was similar: geometry as a structural tool.
A broader scoping review of additive manufacturing in construction noted that polymers including PLA and reinforced composites offer corrosion resistance and low weight, while flagging fire resistance and load capacity as constraints that continue to limit their structural application.
Taken together, these efforts sketch a research trajectory in which 3D printed polymer reinforcement is not competing with steel on equal terms, but carving out a specific role, corrosion resistance, design flexibility, on-demand fabrication, where its tradeoffs are acceptable.
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Featured image shows University of Sharjah. Photo via University of Sharjah.
