Structural Protection of your building

How to protect the load-bearing structure

When a fire breaks out, it is crucial that we give the occupants of a building enough time to evacuate to a safe place and allow the fire fighters to combat the fire. This is why we need to prevent the building from collapsing, even partially, during a fire.

If we can avoid the (partial) collapse of the building, we will be able to limit the damage to the building as well as to the assets contained in it. In most cases, the contents of a building are of special, irreplaceable value. Just think of the objects with historic or emotional value you find in a museum or library. Or the life-saving equipment that is used in a hospital. The damage goes far beyond financial loss.

Promat offers a full range of board, spray and paint products providing flexible solutions to meet a variety of installation and fire protection needs for all common construction materials. All the Promat products and systems have been tested at accredited laboratories around the world according to a variety of standards, such as the EN 13381 and EN 1365 series, BS 476: Part 21, UL 263 and ASTM E119.

Structural concrete protection

When concrete heats up during fire, at some point in time the steel reinforcement will heat up as well. The heating of the steel reinforcement is delayed by the concrete cover since the thermal transfer through the concrete is relatively slow. Moreover, at temperatures in a range of roughly 200-800 ºC the concrete itself loses its load-bearing capacity because of internal micro-cracking and chemical transformation (dehydration) of the cement phase. Typically, design standards simplify this gradual strength loss by assuming a limiting temperature of 500 ºC for concrete.

For concrete structures in low-humidity environments and exposed to the standard (cellulosic) fire curve, most design codes accept that spalling will not occur. In case of more severe fire curves or exposure to humid environments, spalling of concrete could lead to the loss of cover within a short time, and this could result in an additional, more stringent temperature requirement for the concrete surface itself, rather than for the steel reinforcement bar that is placed inside the concrete.

Whenever the concrete cover thickness is insufficient to keep the steel reinforcement temperatures low enough to avoid collapse, or when spalling of concrete could occur or when the concrete itself is deteriorated, fire protection is needed. Promat offers boards, sprays and paints that have been tested and assessed for columns, beams, walls and slabs. In case of a concrete structure that doesn’t spall, the required thickness of the product depends on the amount of concrete cover that is lacking on the steel reinforcement.

Testing by independent institutes is always followed by an assessment which specifies the performance of the fire protection product in terms of ‘equivalent thickness’ and of adhesion and cohesion of the protective material. The equivalent thickness depends on the fire exposure of the element (single-sided such as walls or slabs, or multi-sided such as beams or columns) and on the fire resistance requirement.

Structural timber protection

When timber heats up during a fire, the material starts to burn at the surface, forming a layer of char. During the fire, the charred depth will gradually increase. The charred material has no strength left, and also the pyrolysis zone (between the char and the still unburned wood) has a very limited mechanical resistance. Therefore, the remaining cross-section of the timber element gradually reduces, and at some point, the load can no longer be carried and the element will collapse.

The fire resistance can be improved by applying fire protection. This beneficial effect comes in two ways:

• The fire protection will delay the heating up of the timber, therefore postponing the start of the charring process.

• Once the charring starts, the fire protection will slow down the speed of the charring ( ‘charring rate’ ).

Promat offers board and paint products that have been tested and assessed by independent institutes. The assessment report states the time that the fire protection system delays the start of the charring, as well as the slowed-down rate of charring that occurs during more prolonged fire exposure. With these data, the engineer can calculate the effectively remaining cross-section of the timber element after a certain fire exposure and check that it is still able to carry the loads.