The Fire Resistance Test of Filigree Wideslab Composite Concrete Decks

The full scale fire resistant test for the Filigree built composite concrete deck was carried out on August, 1975, at the Underwriter’s Testing Laboratories in Chicago, Illinois.

Testing was conducted in accordance with the code prescribed document: “Standard Fire Tests of Building Construction and Materials UL263″ (ASTM E119, NFPA, No. 251)

The tested assembly consisted of an 8″ thick composite Filigree deck with embedded 4″ thick x 24″ wide polystyrene voids placed at 32″ on center.

All voids have been installed on top of the 2 1/4″ thick pre-cast Filigree slab and covered with a 1 3/4″ layer of poured-in-place concrete to a total thickness of 8″.

The Filigree slab used in the test contained seven 3/8″ diameter, pre-tensioned 270K seven wire strands concentrically placed between two layers of 3/8″ diameter reinforcing bars placed at 48”.

Initially, the pre-cast slab was aged for 149 days. Then the top-placed concrete was added and the completed assembly was aged for an additional 106 days. Finally, the assembly was placed into a curing chamber for 65 days at 120° F. The purpose of drying the test assembly was to reduce the residual humidity (moisture) of the concrete per the ASTM requirements. When the moisture content reached an average level of 69% at mid-depth of the assembly, the sample was ready for testing.

Prior to the actual fire resistance testing, the finished assembly was preloaded for a period of 18 days with a superimposed uniformly distributed live load of 118psf. Testing then proceeded using the standard equipment of the Underwriters Laboratories Fire Resistant Testing of Floor and Ceiling Assemblies. The test furnace was equipped with 16 thermocouples symmetrically located 12″ below the exposed surface to measure the temperature at the underside of the assembly, and 16 thermocouples covered with 6″ X 6″ dry asbestos pads were placed on top of the tested slab to measure the top surface temperature. The furnace fire was distributed uniformly using gas-fired torches.

The initial thermal threshold for raising the unexposed top surface temperature of the assembly by 250° F was achieved after 165 minutes of testing. The test was then continued in order to establish the structural threshold for the assembly fire resistance, which would materialize when actual flames began to pass through it. However, after over four hours of continuous testing the assembly remained stable, fully intact, and structurally sound without any indication of flame penetration, so the test was discontinued. During the test, the presence of embedded polystyrene form voids did not exhibit any adverse effects on the assembly.

By the end of the test, the furnace temperature at the underside of the assembly reached 2000° F, making the concrete of the Filigree pre-cast slab glow bright red as that of hot coal, while the temperature of the top surface only reached 500° F and appeared unchanged. The deck assembly itself continued to support the superimposed fire test loads without any visible signs of damage or delamination.

This test confirms that Filigree designed and constructed composite concrete decks have the ability to structurally and thermally withstand a full scale fire for more than four hours.

Based on these findings, the UL Testing Laboratory assigned Filigree-built deck structures overall fire resistance ratings of from two to four hours, listed by the United Testing Laboratories as Designs #J999-K901.