Sprayed Fire-Resistive Material (SFRM), more commonly referred to as spray-applied fireproofing, is a passive fire protection material intended for direct application to structural building members. The intent of this material is to increase the fire resistance characteristics of those members, primarily through insulation. The fire resistance of structural building elements provides an important contribution to the fire protection system design implemented in building construction. Commissioning and field testing of SFRM is not only important in new construction, but now with the recent enactment of renovation requirements in many jurisdictions, such as Local Law 26 of 2004 in New York City,1 retroactive special inspection of SFRM in existing structures is becoming a requirement whenever SFRM is exposed as part of a building renovation.


SFRM materials come predominantly in cementitious-, gypsum-or mineral-fiber-based forms. The fire-resistive qualities of SFRM materials differ with the specific characteristics of each material, as well as the manner in which they are prepared and applied. Further, the ability of SFRM to protect a given structural assembly varies with the characteristics of the members being protected. Because of this, laboratory testing is used to evaluate fire resistance ratings for complete assemblies of structural members, including the characteristics of their applied thermal protection.

 

The relative fire resistance of an assembly is measured by its performance when subjected to standard fire endurance tests such as ASTM E119. This includes the type of SFRM applied to the structural members, along with its minimum required thickness, density and bond strength. However, the method with which to field verify that the installation is consistent with the intention of the manufacturer and with the tests conducted in the laboratory is outlined in other ATSM standards. These standards, specifically ASTM E 6052 and ASTM E 736,3 form the basis for the testing and commissioning process for SFRM.

 

The controlled environment and care associated with preparing a structural test assembly for the laboratory fire endurance test can vary greatly with the amount of time and attention available during the application of SFRM to a structural assembly in the field. For this reason, field verification of SFRM installation is critical to the building commissioning process. In the laboratory, only the most skilled laborers are used for preparation of the structural test assemblies to ensure that the tests perform as expected. However, on the construction site, the skill level and training of the installers cannot be controlled. Furthermore, in the laboratory the environmental conditions for the preparation of a test assembly, such as temperature and the presence of obstructions, are controlled, whereas environmental conditions at a job site are subject to change in ways that could inhibit proper SFRM preparation and application.

 

 

Thickness

One of the more obvious critical elements for a properly installed SFRM is its applied thickness. Proper SFRM thickness is critical to ensure that sufficient insulation is available to mitigate the passage of heat from a fire to the structure being protected. The level of thermal protection provided by the installed-SFRM must be at least equivalent-to that provided for the test assembly-during the standard test. ASTM E 605 specifies procedures and methods with which to evaluate SFRM thickness, while taking into consideration the realities of field installations.

 

ASTM E 605 recognizes that an objective and consistent method is required with which to evaluate the general compliance of SFRM application in the field with the design assembly tested in the laboratory. The test also recognizes that the nature of the SFRM application process does not permit a predictable homogeneous thickness to be achieved. Therefore, the standard permits for limited inadequacies in specific minimum thicknesses, provided the impact on the thermal protection by the SFRM to its structural member is negligible.

 

The thickness of SFRM as installed on a structural member should be measured with a calibrated thickness gauge, consisting of a needle or pin for penetrating the SFRM and a sliding disk oriented perpendicular to the needle. See Figure 1.

 

ASTM E 605 requires that the gauge be graduated to take measurements in a minimum of 1 mm (1/16-inch) intervals. The disk should have a friction device to hold it in place after inserting the pin into the SFRM. This device will allow for the pin to remain in place as the thickness gauge is removed from the SFRM, thereby allowing for increased accuracy in measurements. In instances when the density of SFRM is too thick for a standard-depth gauge to be used, small diameter holes (slightly larger than that of the depth gauge pin) should be drilled into the SFRM. Thickness measurements can then be taken by inserting the depth gauge into these holes, which should then be filled in with SFRM after gathering measurements.

 

 

Because SFRM cannot be installed predictably at a homogeneous thickness, evaluating SFRM thickness based on individual point thickness measurements would not provide sufficient data with which to determine the general level of thermal insulation provided by the material. Similarly, evaluating the general compliance of installed thicknesses of SFRM in a localized region of a building cannot provide a global representation as to how the SFRM was installed throughout other areas of the building. Out of recognition that the consistency in the application of SFRM may change over the course of the day due to a change in the personnel, the time of day or the quality of the mixed product, the testing procedure outlined in ASTM E 605 requires that comprehensive local tests that encompass all surfaces of the structural members being protected throughout the building be included in the representative sample of thickness tests.


ASTM E 605 requires that thickness tests be conducted randomly at a rate of one bay per floor or one bay for every 930 square meters (10,000 square feet), whichever is greater, for each structural member being tested. Local jurisdictions may adopt alternate requirements in terms of the number of random samples to be taken and how many point thickness tests are required when calculating a sample's average thickness. However, the basic principles outlined in the ASTM E 605 requirements evaluating SFRM thicknesses remain intact.

 

 

A series of point thickness measurements are to be collected in each of these randomly selected locations. The specifics related to the series of test measurements differ depending on the structural member being tested. For example, a standard H-column requires a minimum of 24 individual point thickness measurements to make up a single ASTM E 605 thickness measurement. Similarly, a standard I-beam supporting a floor/ceiling assembly will require a minimum of 18 individual point tests to make up a single requirement thickness measurement.

 

Once the random beam is selected, a 0.305 m (12-inch) length is selected in which the test measurements will be taken. Along one end of the sample length, a total of nine point test measurements are taken as follows, moving around from one side of the beam to the other;2 (1) at the underside of the top flange, (2) in the middle of the web, (3) on top of the bottom flange, (4) at the flange tip, (5) at the underside of the bottom flange, (6) at the other flange tip, (7) at the top of the other bottom flange, (8) in the middle of the other side of the web and (9) at the underside of the other top flange. See Figure 2.

 

 

Once these measurements are taken, an identical series of measurements must be taken at 0.305 m (12 inches) from that point. These 18 thickness measurements represent the field thickness testing for this one bay or 930 square meters (10,000 square feet) area.

 

Each of these individual point measurements should be carefully recorded, since not only are the individual point measurements important, but the average of these point measurements also are considered when evaluating the pass/fail criteria for each thickness test.

 

With regard to pass/fail criteria, the thickness of SFRM protecting a given member is considered deficient if any individual measurement is more than 6 mm less, or more than 25 percent less, than the required fire resistance design thickness of the listed assembly, or if the calculated average thickness of the SFRM is less than that required for the design. In the event that a structural member is found to be deficient in terms of thickness, the member that is found to be deficient is to be corrected and retested, along with another member of that specific type (e.g., another column if a column failed, etc.), which is to be selected at random, preferably in the same bay or 930 square meters (10,000 square feet), and tested.

 

 

Certain design assemblies, columns, beams and trusses may be allowed to have a reduced thickness on flange tips. In these instances, flange measurements and thickness are to be averaged separately. The same may also be true for SFRM applied to the underside of fluted floor decks.

 

Density

The frequency outlined by ASTM E 605 for density testing is the same as that required for thickness testing; specifically, one test per structural member type, per floor or 930 square meters (10,000 square feet), whichever is greater, with the specific locations selected at random.

 

For density testing, a .03 m2 (48-square-inch) specimen, with no dimension less than 76 mm ( three inches), is measured in place for thicknessusing the method described previously. The average thickness of the sample is taken as the thickness of the specimen. After carefully cutting and removing the specimen from the substrate, the specimen should be allowed to cure at no greater than 60 percent humidity for a period of time until successive weight readings differ by less than one percent. Once the dried weight of the specimen is stabilized, the density of the specimen can be calculated by dividing the mass by the volume.

 

A density failure is recorded whenever the calculated density falls below the minimum individual density value of the fire resistance rated design assembly. In the event that a density test falls between the minimum average and minimum individual values for the design assembly, an additional density specimen should be tested in that same test area. If the average density of the two tested specimens is greater than the minimum average density values for the assembly, then the density test has passed. If the average is not achieved, then those structural elements in that test area must be corrected such that the appropriate density criteria are achieved.

 

Adhesion Testing

The ability of SFRM to adhere to the structural member that it protects is another critical performance criterion that must be verified in the field following the application of SFRM. If the SFRM is improperly applied, the substrate is improperly prepared or the conditions in which the material is applied are inconsistent with manufacturers' recommendations, then ineffective adhesion to the structural members could result. In extreme cases, deficient adhesion could result in SFRM delamination, as indicated in Figure 3.

 

The adhesive strength of SFRM is measured using the methods specified in ASTM E 736,3 the Standard Test Method for Cohesion/Adhesion of Sprayed Fire-Resistive Materials Applied to Structural Members. The specific adhesion strength pass/fail criteria will vary from product to product and manufacturer to manufacturer; however, recommended adhesion bond strength criteria are on the order of magnitude of those indicated in the Table 1.

 

The standard SFRM adhesion test is performed at a frequency identical to that for SFRM thickness measurements. The test procedure itself consists of affixing a 51 mm to 83 mm (2 in. to 3-1/2-in.) diameter metal or plastic cap, with a hook attached to the center, directly to in-place SFRM material using a singleor dual-component adhesive. Once the adhesive is allowed to cure, a standard graduated spring scale (see Figure 4) is attached to the cap's hook, and force is slowly applied at a minimum uniform rate of approximately 5 kg (11 pounds) per minute.

 

Force should be applied until failure occurs, a predetermined value is reached or until the capacity of the scale is maximized. The cohesive/ adhesive force can then be calculated by multiplying the maximum recorded force (or force at the time of failure) by the area of the cap.

 

This calculated force can then be compared to the minimum adhesion strength requirements listed by the manufacturer to evaluate whether or not the test results achieve the minimum-requirements. Cohesive failure is reported if separation occurs within the material, and adhesive failure is reported if separation occurs at the interface of the substrate and the SFRM.

 

The proper steps should be taken to assure that areas where adhesion tests have failed are rectified and retested such that the material installed conforms to the minimum standards of the assembly installed.

 

Recent Developments

In September 2005, NIST issued its Final Report on the Collapse of the World Trade Center Towers.4 Some of the recommendations of this report are now making their way into the code and standard test development processes,5,6 including recommendations-applicable to SFRM. Although the specific language to be adopted by the various code and standards bodies remains in the developmental stage, the changes that are adopted can be expected to require more rigorous and better documented testing requirements for both newly applied and in-service SFRM.

 

Michael Rzeznik is with Schirmer Engineering.

 

References

  1. Local Law 26, New York City Department of Buildings, The Department of Citywide Administrative Services, The City of New York, New York, New York, 2004.
  2. ASTM E 605, Standard Test Methods for Thickness and Density of Sprayed Fire-Resistive Material (SFRM) Applied to Structural Members, ASTM, West Conshohocken, PA, 2000.
  3. ASTM E 736, Standard Test Method for Cohesion/Adhesion of Sprayed Fire-Resistive Material Applied to Structural Members, ASTM, West Conshohocken, PA, 2000.
  4. Final Report on the Collapse of the World Trade Center Towers, National Institute of Standards and Technology, September 2005.
  5. Status of WTC Recommendations, National Institute of Standards and Technology, March 21, 2006, http://wtc.nist.gov/recommendations/recommendations.htm.
  6. Draft Review of Findings on the NIST World Trade Center Report, ICC AD HOC Committee on Terrorism-Resistant Buildings, January 20, 2006.