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Testing shows rock wool maintains stability as steel elements heat and buckle.
A new peer-reviewed study provides fire-test data that may help inform future design and compliance pathways for modular steel buildings, including systems widely used across Australia’s resources, temporary accommodation and rapid-delivery sectors. Published in Scientific Reports, the research examines how different fire protection systems influence the structural performance of thin-walled steel columns used in container-style modular units. (image credit: Achim Hering)
What the study tested and why it matters for Australia
Australia’s modular sector encompasses a wide range of construction approaches and building types, with different structural systems used across residential, commercial and temporary accommodation projects. Within this landscape, container-style steel modules remain an established option for worker accommodation, remote facilities and rapid-delivery buildings. These modules rely on thin-walled steel columns rather than the framing systems used in other modular approaches, making the fire behaviour of these elements an important consideration for manufacturers supplying this category of product.
The study investigated the fire resistance of L-shaped thin-walled columns with a 3.5 mm wall thickness, a profile commonly used in container-style steel modular buildings. Four column configurations were tested:
All specimens were tested in a vertical furnace following the ISO-834 standard fire curve, with axial loads applied to represent conditions in modular buildings.
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Rock wool achieves the highest fire resistance
The results show clear differences between protection systems. The unprotected column failed after 12.3 minutes, demonstrating how rapidly steel loses strength under elevated temperatures. Coatings increased resistance to 18.7 minutes, while coatings combined with 16 mm calcium silicate boards reached 34.9 minutes. The boards experienced cracking and partial exfoliation as the column deformed under heating.
The strongest performance came from the column encased in 75 mm rock wool sandwich panels, which achieved a fire resistance limit of 102.1 minutes—more than four times that of the unprotected sample. The rock wool panels remained stable throughout testing, deforming with the column without cracking. The study attributes this to rock wool’s insulation properties when not directly exposed to flames and the protective steel facing of the sandwich panel preventing ablation.
Practical implications for Australian modular construction
The results may have practical relevance for container-style modular buildings, particularly where thin-walled steel elements carry stacked loads between modules. The strong performance of the rock wool panels suggests that flexible insulation systems may offer more reliable protection than rigid boards in situations where columns can deform under heat.
For manufacturers, the study may also offer a clearer understanding of how different protection methods behave as temperatures rise, including how coatings, boards and rock wool interact with column buckling. For engineers and certifiers, the findings provide tested data that may help when assessing fire-rating strategies for lightweight steel components, especially in projects where rapid installation or repeatable module formats are required.
The study also outlines a calculation method for estimating insulation thickness for different fire-resistance targets. While developed under laboratory conditions, it provides a structured way to compare design options for container-style steel modules and may support more informed decision-making when selecting protection systems.
Find the rock wool panel study HERE
