How can you prevent fire-induced spalling in structural elements?

1 What causes fire-induced spalling?

Fire-induced spalling occurs when the moisture inside the concrete or masonry expands due to heating, creating internal pressure and cracking the material. The spalling can be more severe if the material has a low permeability, a high strength, a low tensile strength, or a high reinforcement ratio. The spalling can also be influenced by the fire exposure, the shape and size of the element, and the boundary conditions.

2 How to design for fire-induced spalling?

One of the main ways to design for fire-induced spalling is to use materials that have a high fire resistance and a low susceptibility to spalling. These include concrete with a low water-cement ratio, a low cement content, a high aggregate content, and a low alkali content. You can also use additives or admixtures that improve the permeability, the thermal conductivity, or the spalling resistance of the concrete. For example, you can use polypropylene fibers, steel fibers, or expansive agents.

3 How to construct for fire-induced spalling?

Another way to prevent fire-induced spalling is to follow good construction practices that ensure the quality and durability of the structural elements. You should avoid using excessive compaction, vibration, or curing that can increase the density and strength of the concrete. You should also avoid creating voids, cracks, or defects that can trap moisture and reduce the fire resistance. You should also provide adequate cover and protection for the reinforcement, such as using fireproof coatings, insulation, or membranes.

4 How to test for fire-induced spalling?

To verify the performance of the structural elements under fire conditions, you can conduct fire tests that simulate the realistic scenarios and loads. You can use standard fire tests, such as ISO 834 or ASTM E119, or performance-based fire tests, such as natural fire tests or parametric fire tests. You can measure the temperature, the deformation, the cracking, and the spalling of the elements during and after the fire exposure. You can also compare the results with the design assumptions and criteria.

5 How to repair fire-induced spalling?

If fire-induced spalling has occurred in your structural elements, you should assess the extent and severity of the damage and determine the appropriate repair methods. You should remove the loose and spalled material, clean and treat the exposed reinforcement, and restore the original shape and strength of the element. You can use repair materials that match the properties and compatibility of the original material, such as concrete, mortar, grout, or epoxy. You should also consider the aesthetic and functional aspects of the repair.

6 How to prevent fire-induced spalling in the future?

To prevent fire-induced spalling in the future, you should adopt a holistic approach that considers the fire risk, the design objectives, the material selection, the construction quality, the fire testing, and the maintenance and repair of the structural elements. You should also follow the relevant codes, standards, and guidelines that provide recommendations and requirements for fire-resistant design and construction. You should also consult with experts and professionals who have experience and knowledge in structural fire engineering.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?