What ASTM C580 Flexural Testing Reveals About Flooring Performance in Seismic Retrofit Projects
- Finish + Form
- Jul 2
- 7 min read
On Spec #2 — published by Finish + Form
Author’s Note: This article interprets independent laboratory testing conducted under ASTM C580-18 and ISO 196 standards to examine how flooring materials respond to stress. It is intended to inform specification discussions, not replace engineering judgment. As California's SB 1953 seismic retrofit program reshapes healthcare construction ahead of the 2030 compliance deadline, understanding material behavior under movement has become an increasingly relevant consideration for specifiers.
Many have a habit of mistaking the largest number as the best answer. We see a higher strength rating and instinctively assume we’ve found the superior material. More strength must mean better durability, afterall. More load capacity. More resilience. More confidence in the spec. It’s a logical conclusion but it may be an incomplete one. For a safer specification, it’s important to ask oneself: is “stronger” truly always better?
Strength tells you when a material breaks. It doesn’t tell you how a material behaves on the way there. In environments where the structure itself is expected to move, that distinction is the one that matters. Does the material absorb stress? Does it deform? Does it redistribute the load? Or does it resist movement until it can no longer do so?
Those questions rarely appear on a product brochure yet they often determine how a flooring system performs once it becomes part of a building.
Why Architects Working on Seismic Retrofit Projects Should Care
California's SB 1953 mandate requires hospitals to meet updated seismic performance standards, formerly administered by the Office of Statewide Health Planning and Development (OSHPD) and now overseen by the Department of Health Care Access and Information (HCAI), by January 1, 2030. Flooring systems are not a compliance category under SB 1953. That determination belongs to structural and designated nonstructural building systems.
But the construction conditions these projects create, including structural modifications, phased work, substrate disturbance, and occupied renovations, mean that design teams are making flooring specification decisions in an environment where substrate movement is a documented reality and not a theoretical concern. Mechanical testing cannot predict how a floor will perform in a seismic event. What it can do is describe how a material responds to force under controlled conditions, providing architects with another piece of evidence when evaluating specification options.
To better understand those properties, Intertek Building and Construction, an accredited third-party testing laboratory, conducted ASTM C580-18 testing on Durabella Matte Finish and standard epoxy terrazzo with Matte Finish at its facility in York, Pennsylvania (Report No. N3216.01-106-31 R0, issued July 18, 2022). Ten specimens of each material were tested under identical conditions. Results were reported as tested values.
In this test, ASTM C580-18 measures two values: 1) flexural strength, the load a material carries before fracturing under bending stress, and 2) modulus of elasticity, the ratio of stress to strain that describes how much a material deforms under load before reaching that fracture point. The results are as follow:
Durabella Matte Finish | Epoxy with Matte Finish | |
Flexural Strength (avg) | 458 psi | 1,330 psi |
Modulus of Elasticity (avg) | 9,803 psi | 175, |
No. of Specimens Tested | 10 | 10 |
Separately, Duracryl International's laboratory tested the Durabella Biopolymer system under ISO 196 methodology (December 2018), reporting compressive strength of 7.368 psi and flexural strength of 3.453 psi at 28 days of cure, with more than 95% of end strength reached within 7 days at room temperature.
Looking Beyond the Numbers in the Results
At first glance, the comparison appears straightforward. The epoxy carries a higher peak flexural load than Durabella, meaning it can withstand a greater bending load before fracturing under ASTM C580-18 testing. For many specifiers, that is where the evaluation ends.
But as previously mentioned, ASTM C580-18 measures more than strength. Because it measures the modulus of elasticity, it allows us to have a clearer understanding of the materials’ performance. Epoxy’s modulus of elasticity is approximately 18 times higher than Durabella's, indicating a system that’s fundamentally more rigid.
A high modulus means a material resists deformation until it reaches its fracture threshold. A lower modulus means the material has a greater capacity for elastic deformation: it deflects, distributes stress, and deforms before fracturing.
Neither characteristic is universally preferable. Their value depends entirely on the conditions in which the material is expected to perform. In a stable, static environment, rigidity is not a problem. In a construction environment where substrate movement is anticipated, whether from active structural retrofit, differential settlement, or seismic loading, a material's capacity to accommodate that movement without fracturing becomes a relevant specification variable.
It doesn’t predict how either flooring system will perform during an earthquake nor does it attempt to replicate the complexities of an active structural retrofit. Laboratory testing isolates material properties. Real buildings introduce variables such as substrate condition, installation methodology, structural design, and the magnitude of expected movement. Those questions remain the responsibility of the design team and the project engineer. But what the testing does provide is evidence that can inform those decisions.
For design teams working on SB 1953 retrofit projects, that evidence may prompt a broader specification conversation. How closely does the flooring system's elastic range align with the anticipated deflection of the structural assembly it will be installed over? Has the substrate been thoroughly evaluated, not only for its current condition but for how it is expected to behave over time? Is a bonded installation appropriate or would a floating system better accommodate the movement the project is likely to experience?
It also leads to conversations that allow architects to also assess the rapid cure rate of the Durabella Biopolymer system, reaching more than 95% of end strength within 7 days, as relevant to construction sequencing in occupied healthcare renovation environments where minimizing room downtime is an operational priority.
Taken together, these considerations are not purely theoretical but point to a broader principle. Flooring systems are not specified in isolation. Their performance depends not only on the properties of the finish material, but also on the substrate beneath it, the method by which it is installed, and the conditions it will be expected to endure. The most resilient specification is rarely the one built around the highest strength value. It’s the one that best matches the behavior of the material to the behavior of the building.
Laboratory testing helps explain why a material behaves the way it does. What it cannot show is the moment those properties become part of a real specification decision, where existing cracks, construction sequencing, installation methods, and structural movement all compete for consideration. That is where mechanical data stops being academic and begins informing practice.
A Real-World Example: The Ontario Fire Station
During construction of the Ontario Fire Station, the second-floor concrete substrate exhibited significant cracking that extended across corridor spans and through multiple door openings. The conditions emerged during the installation phase, forcing the project team to respond to the material conditions of the building as it existed.
Rather than proceeding with a conventional bonded installation, Duracryl first evaluated the substrate conditions. They followed by recommending a floating system using a crack isolation membrane, allowing the flooring assembly to better accommodate substrate movement without transferring stress to the finished surface.
The project illustrates a principle that applies well beyond seismic contexts: substrate evaluation and installation methodology are as important to a flooring specification as the mechanical properties of the finish material itself. Substrate condition, anticipated movement, and installation methodology remain integral parts of the flooring system and should be evaluated together rather than independently. The right material installed the wrong way for the conditions does not perform as specified.
This is especially relevant for projects involving significant substrate cracking or anticipated structural movement. These conditions, common to many SB 1953 retrofit projects, may warrant the same kind of substrate-first evaluation that shaped the Ontario specification.
That same principle applies to Durabella's seamless, jointless poured-in-place installation. While Durabella is marketed as a seamless, jointless poured-in-place terrazzo system, that installation capability is achieved through more than one factor. Independent flexural testing helps explain one aspect of the material's mechanical behavior, while system design, substrate preparation, and installation methodology all contribute to successful large-area installations, (But these topics warrant their own in-depth discussion for another time. So stay tuned).
Honest Limits
As already mentioned, the ASTM C580-18 test measures material properties under controlled laboratory conditions. It doesn’t simulate seismic loading, substrate deflection under live loads, or the construction conditions specific to any individual project. The modulus of elasticity figures reported by Intertek describe how each material responds to bending stress in isolation and not how an installed flooring system performs in a building undergoing structural modification.
Design teams should treat these figures as one input among several, alongside substrate assessment, installation methodology, structural engineering review, and project-specific conditions.
Great specifications are built on evidence, engineering judgment, and an understanding of how materials perform, not assumptions or marketing claims. Every On Spec article is grounded in published standards, independent testing, or documented project experience.
If you want to read the full Intertek test reports, you may reach out to our team today. They are available upon request.
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Sources:
Intertek Building and Construction. Test Report No. N3216.01-106-31 R0: ASTM C580-18 Flexural Strength and Modulus of Elasticity, Durabella Matt Finish and Epoxy with Matt Finish. York, Pennsylvania. Issued July 18, 2022.
Duracryl International BV. Test Report: Durabella Biopolymer Flexural and Compressive Strength. ISO 196 methodology. Authored by P. Groeneweg, Paint Technologist. December 20, 2018.
California Department of Health Care Access and Information (HCAI), formerly the Office of Statewide Health Planning and Development (OSHPD). SB 1953 Seismic Compliance Program. Senate Bill 1953, Alfred E. Alquist Hospital Facilities Seismic Safety Act.
ASTM International. ASTM C580-18: Standard Test Method for Flexural Strength and Modulus of Elasticity of Chemical-Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes.
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