Abstract
Material-scale tests involving milligrams of samples are used to optimize fire-retardant coating formulations, but actual applications of these coatings require them to be assessed with structural-scale fire tests. This significant difference in the scale of testing (milligrams to kilograms of sample) raises many questions on the relations between the inherent flammability and thermal characteristics of the coating materials and their “performance” at the structural scale. Moreover, the expected “performance” requirements and the definition of “performance” varies at different scales. In this regard, the pathway is not established when designing and formulating fire-retardant coatings for structural steel sections or members. This manuscript explores the fundamental relationships across different scales of testing with the help of a fire-protective system based on acrylic resin with a typical combination of intumescent additives, viz. ammonium polyphosphate, pentaerythritol, and expandable graphite. One of the main outcomes of this work dictates that higher heat release rate values and larger amounts of material participating in the pyrolysis process per unit time will result in a rapid rise in steel substrate temperature. This information is very useful in the design and development of generic fire-retardant coatings.
Highlights
It is a regulatory requirement in most countries to protect structural steel members against fire.The common way of achieving this is by using coatings and testing the protected steel members to meet certain fire resistance criteria with the imposed mechanical and thermal loads according to standard fire tests such as BS476 Part 21, ASTM E119 or EN 13381-8
The different thermal, flammability, and fire tests across scales that were chosen to be a part of this work include thermogravimetric analysis (TGA), pyrolysis combustion flow calorimetry (PCFC), cone calorimeter, 1D heat transfer in a laboratory furnace, and structural-scale fire tests where the I-section is exposed to heat from all sides
The emphasis will be on identifying the key performance pointers in the material- and bulk-scale tests that could provide an indication of how the coating might perform in the structural-scale fire tests
Summary
It is a regulatory requirement in most countries to protect structural steel members against fire. The common way of achieving this is by using coatings (such as intumescent and cementitious) and testing the protected steel members to meet certain fire resistance criteria (e.g., deflection limits and/or critical temperature) with the imposed mechanical and thermal loads according to standard fire tests such as BS476 Part 21, ASTM E119 or EN 13381-8 Such large-scale fire tests are usually time-consuming, expensive, and require a lot of resources. This is the reason why Schartel et al [1] proposed that “PCFC is constructed to be blind to flame inhibition.” This is true to certain extent in a forced-combustion bulk-scale test such as a cone calorimeter, which provides heat release rate data along with other important information such as ignition time, smoke production rate, and total heat released [2,3].
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