Basalt Fiber Wraps Give Aging Concrete Columns a Seismic Second Life

When a major earthquake strikes a city, the buildings that collapse are often not new ones but older reinforced concrete structures designed decades ago under codes far less demanding than those in force today. Their columns, the vertical members that carry entire buildings, can fail in a brittle, explosive manner when the concrete cover spalls and the internal steel reinforcement buckles. A research team in South Korea now reports that a wrapping system built from volcanic basalt fiber can dramatically change how these vulnerable columns behave under the repeated shaking of a quake, boosting strength, ductility, and energy dissipation in specimens tested at full structural scale.

The study, published in the Bulletin of Earthquake Engineering by Ju-Seong Jung of Chungwoon University and colleagues at Hanyang University’s Innovative Durable Building and Infrastructure Research Center, proposes a hybrid system the authors call BFC-FRP: a combination of prefabricated basalt fiber sheets and fiber-reinforced polymer panels applied to the surface of reinforced concrete columns. Basalt fiber, drawn by melting volcanic rock at high temperature, has attracted growing attention in structural engineering because it offers a favorable balance of mechanical performance, chemical stability, and cost compared with the glass and carbon fibers that have traditionally dominated the retrofit market.

To test the concept, the team fabricated seven large-scale columns, each with a square cross section of 350 by 350 millimeters and a clear height of 1.5 meters, dimensions representative of real building columns rather than miniature laboratory proxies. Three of the specimens were detailed to fail in shear, the most dangerous failure mode because it is sudden and brittle, while four were designed to be flexure-controlled, meaning their response is governed by bending and tends to be more ductile. Every column was then pushed sideways under reversed cyclic lateral loading, the laboratory equivalent of the back-and-forth motion an earthquake imposes, while a constant axial load corresponding to a ratio of 0.10 pressed down from above.

The strengthening scheme varied along two experimental axes. The first was coverage: some columns received strengthening only in the end regions, where damage typically concentrates, while others were wrapped over their full surface. The second was the arrangement of the prefabricated basalt fiber sheets and the FRP panels, allowing the researchers to compare how different configurations of the composite layers influenced confinement of the concrete and restraint of the longitudinal reinforcement. This systematic variation is what gives the study its practical value, because retrofit budgets rarely allow blanket coverage, and engineers need to know whether partial wrapping is enough.

The results for the shear-critical columns were striking. Full-surface BFC-FRP strengthening increased the ultimate strength by approximately 1.5 times compared with the unstrengthened control specimen, but the more important gain was in deformation: the displacement reached at ultimate strength grew by a factor of 2.0 to 2.6. In seismic terms, that transformation matters more than raw strength. A column that can keep carrying load while being pushed far sideways gives occupants time to evacuate and prevents the soft-story collapse mechanism that has killed thousands of people in recent earthquakes worldwide, from Turkey and Syria to Morocco and Japan.

For the flexure-controlled columns, which started from a more forgiving baseline, the retrofit delivered different but equally consequential improvements. The ultimate displacement increased by roughly 1.4 times, and the ductility ratio, a normalized measure of how much inelastic deformation a member can sustain before losing capacity, nearly doubled. Most notably, the energy dissipation capacity, which quantifies how much seismic energy the column can absorb and dissipate through hysteretic behavior in each loading cycle, rose by approximately 2.4 to 2.5 times. Since earthquake-resistant design fundamentally relies on structures dissipating energy rather than simply resisting force, this multiplication of dissipative capacity is arguably the study’s headline finding.

Alongside the physical tests, the researchers built nonlinear quasi-static cyclic finite element models of the columns using the disturbed stress field model, a mechanics-based formulation for reinforced concrete developed at the University of Toronto and implemented in analysis software widely used for shear-dominated members. The modeling work serves a purpose beyond reproducing the experiments: if a numerical framework can reliably predict how a wrapped column will deform and dissipate energy, engineers can extend the findings to configurations that were never tested, and design codes can eventually incorporate the strengthening system with confidence.

The models performed well. They reproduced both the load-displacement envelopes and the energy-dissipation responses of the tested columns with average deviations of approximately 10 percent, a level of accuracy that is respectable for nonlinear analysis of reinforced concrete, a material whose cracking, crushing, and bond-slip behavior is notoriously difficult to capture. The authors note that these results demonstrate the proposed BFC-FRP system can improve the deformation and energy-dissipation capacities of both shear- and flexure-controlled columns within the tested conditions, a carefully scoped conclusion that reflects the bounded nature of laboratory evidence.

The work sits within a broader and urgent engineering challenge: seismic strengthening of existing buildings. International guidelines, including documents from the American Concrete Institute and the Japan Building Disaster Prevention Association, already recognize externally bonded FRP systems as a legitimate retrofit strategy, but the field continues to search for materials that lower cost and improve sustainability. Basalt fiber fits that agenda well because its raw material is abundant volcanic rock, requiring no energy-intensive precursor chemistry of the kind needed for carbon fiber. Recent studies have explored basalt composites for repairing earthquake-damaged and corroded beam-column joints, for strengthening precast bridge piers, and even for confining columns built with recycled brick aggregates, suggesting a rapidly maturing research ecosystem.

For practitioners, the Korean team’s findings offer a concrete, quantified case for considering basalt-based wrapping when assessing older building stock, particularly in regions where shear-critical columns from pre-modern-code construction remain common. The demonstration that full-surface wrapping can more than double the deformability of brittle shear-critical columns, while partial schemes remain available where budgets constrain coverage, gives retrofit designers a tested menu of options. As with any laboratory campaign, the caveats are real: the tests covered a single axial load ratio, one column size, and specific composite arrangements, and fire performance of FRP-strengthened members remains a recognized consideration in practice. But the combination of large-scale testing, systematic parameter variation, and validated numerical modeling makes a persuasive case that volcanic rock, spun into fiber and bonded onto concrete, can help the world’s aging buildings stand up to the next big shake.

Subject of Research: Seismic retrofit of reinforced concrete columns using basalt fiber-reinforced polymer composites

Article Title: Experimental and numerical investigation on the seismic performance of reinforced concrete columns retrofitted with basalt FRP composites

Article References: Jung, J.-S., Lee, B.-G., Kim, K., & Lee, K.-S. (2026). Experimental and numerical investigation on the seismic performance of reinforced concrete columns retrofitted with basalt FRP composites. Bulletin of Earthquake Engineering. https://doi.org/10.1007/s10518-026-02653-z

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02653-z

Keywords: basalt fiber, FRP, seismic retrofit, reinforced concrete columns, cyclic loading, ductility, energy dissipation, finite element analysis, disturbed stress field model, shear-controlled columns, flexure-controlled columns, earthquake engineering