IBC 2012 and FRP composite materials (combustible) used to strengthen concrete elements

[Ingenuity]

I am trying to go through IBC 2012 and deal with combustible materials use in Type I and II construction. This is an existing concrete structure and some column and beam elements may require strengthening using FRP composites, which are "combustible".

Am I interpreting the following clauses correctly:

703.5.1 Elementary materials.
Materials required to be noncombustible shall be tested in accordance with ASTM E 136.

703.5.2 Composite materials.
Materials having a structural base of noncombustible material as determined in accordance with Section 703.5.1 with a surfacing not more than 0.125 inch (3.18 mm) thick that has a flame spread index not greater than 50 when tested in accordance with ASTM E 84 or UL 723 shall be acceptable as noncombustible materials.

1) Since the existing concrete elements are non combustible are these concrete elements classified as "elementary materials" as defined in 703.5.1, above.

2) Assuming the concrete elements are "elementary materials", the application of combustible FRP materials to such a structural base is permissible in accordance with clause 703.5.2, assuming the FRP meets the flame spread and thickness requirements.

Correct?

 

[stookeyfpe]

I am going to assume the FRP is mixed with cement, water and aggregate as an additive. I will also assume the mass of FRP in comparision to the total wieight of the unit load is negligible.

ASTM E136 is a vertical tube fire test that is used to estabilish combustibility of materials, primarily for insulation and fire stopping. If I was to take to sample of a concrete mix and attempt to test it per ASTM E136 it would most likely pass.

The IBC assumes certain materials are noncombustible, and this includes concrete with various admixitures. My bigger concern as a fire protection engineer is how the concrete will behave under fire exposure.

I apppreciate your diligence but I don't believe the use of an admixture involving a small amount of glass fibers and resin wattants an ASTM E136 test.

 

[Ingenuity]

Thank you stookeyfpe for the reply.

FRP (fiber reinforced polymer) is not an admixture, not is it mixed with cement or aggregate as a direct component of concrete.

Rather, in structural strengthening applications, FRP composites consists of carbon fiber in an epoxy resin that are wet-applied in numerous layers to existing concrete beams, columns, slab, walls etc to suit the structural demands, and air-cured to form a strengthened element.

The thickness of the completed composite is approx 1/8". Hence, why I am trying to determine if such meets the intent of the above stated clauses.

 

[stookeyfpe]

Ingenuity:

Thanks for the clarification. If the thickness of your composite = or > 1/8 inch then IBC Section 703.5.2 is applicable and your material would be subject to an ASTM E 84 fire test.

You should understand the E84 test is a pretty poor test for polymeric materials because they will sag, deform and drip in the test furnance. ASTM E84 does not measure a material's propensity to contribute to fire growth and spread within a compartment when the FRP is affixed to walls or ceilings.

Given the thickness of the applied product and the building surfaces it can be applied to, I am more concerned with this material as an interior finish under IBC Chapter 8. You should review IBC Section 803.1 for the material thickness limit, because the limit is much less than 0.125 inches specified in IBC Setion 705.3.2. For the conditions you described your material should be evaluated under NFPA 286.

Also, a website reference for the product your evaluating would be beneficial.