A Materials Science-Based Approach to Characterizing Fire Resistive Materials

While ASTM E119-07a is commonly employed to establish a fire rating for a fire resistive material (FRM)/steel assembly, the test method provides little quantitative information on either the thermophysical or adhesion properties of the FRM, beyond indicating that they are sufficient to achieve the measured rating. As part of the Building and Fire Research Laboratory (BFRL) Structural Performance Under Multi-hazards program, a materials science-based approach is being applied to develop new methodologies and test methods for characterizing these complex dynamic materials. These quantitative characterizations can then be used as inputs to thermal/mechanical performance models and also for obtaining a better understanding of how these materials perform their intended role and how they could be improved. Thermophysical properties that must be characterized as a function of temperature include density, heat capacity, thermal conductivity, and heats of reactions and phase changes. For example, for high temperature thermal conductivity, a new measurement technique based on the use of a slug calorimeter has been developed and standardized in the ASTM E37 Thermal Measurements committee. In addition to adequate thermophysical properties, adhesion properties are critical to ensure that the FRM continues to protect its substrate during a fire exposure. Research on developing new test methods for both laboratory and field evaluations of adhesion will be presented. Like thermal properties, adhesion has also been observed to be strongly influenced by exposure to elevated temperatures. Finally, capabilities developed at NIST to obtain quantitative descriptions of the three-dimensional microstructures of FRMs and relate them to thermal properties such as thermal conductivity will be demonstrated. Much of this research has been completed as part of the ongoing NIST/industry consortium on “Performance Assessment and Optimization of Fire Resistive Materials.”