Experimental Fire Study of Expanded Polystyrene Insulation in Concrete and Lightweight Concrete Wall Constructions

University essay from Luleå tekniska universitet/Institutionen för samhällsbyggnad och naturresurser

Abstract: In today’s building industry creating and finding a cheaper and more efficient way of construction with the same standards is the primary goal. The necessity in testing the constructions in different scenarios is of highest interest, primarily in saving future lives but also in the residual value for the insurance point of view. The purpose of this thesis was mapping of unprotected Expanded Polystyrene, i.e. EPS, insulation columns reaction to fire in wall constructions. The wall construction was made of compositions of concrete, lightweight concrete and a medium density fiberboard i.e. MDF. This design was to test the EPS insulation in different extremities exploring the possibility of the fire spread ceasing by itself. The constructions were exposed to fire a short period of time from above the construction. The vertical fire exposure occurred during a brief period of time of a few minutes, which was closely determined with the pre-experiments of bare EPS to 1-minute-long. This direction of fire exposure was to represent a developed fire from an attic fire downwards in the column of EPS compositions. The hypothesis in the experiments was that the fire development would cease due to the heat devouring into the concrete and lightweight concrete. Thermocouples measured the ignition fire exposure time of 1 minute, to 600 – 1000 ℃, and the depth of the EPS ascension determined with a slight temperature rise indicating the depth of the vertically slowly burning EPS. Until a point where the temperatures began a rapid increase which was an indication of the EPS reaching its bottom and end. When the EPS had reached its bottom a burning puddle of EPS similar to a pool fire ignited the surrounding materials of plywood and MDF above turning into a vigorous incineration upwards. After the final temperature peak the experiment was extinguished. Actions that can be acknowledged from the experiment is the cooling effect of the concrete, lightweight concrete and in some part the air gap with the chimney effect. Temperatures in the EPS fire development downwards is in the range of 100 – 150 ℃ not inflicting high radiation to the surrounding combustible materials. This rather low temperature can easily be observed in the absent charring of the MDF and plywood sides displayed in Figure 40 and Figure 58. According to performed experiments above the reaction of EPS after an initial external fire exposure is slowly melting and burning. The combustion rate in this downwards burning/ melting is like a candle slightly pre – heating the surrounding plywood and MDF. But the incineration of the plywood and MDF of all experiments did not begin until the EPS had progressed all the way to the bottom. At this point the bottom plywood is ignited by the “pool fire” leading to the vigorous incineration upwards in the pre – heated plywood and MDF sides. The reason why the plywood and MDF did not begin until the EPS was consumed is probably due to the lack of oxygen. The aim of this thesis was to investigate which of the setups would cease burning by themselves. Results of the experiments revealed that neither of them did. These experiments did not show any differences in having an air gap or not, the differences occurred after the EPS reached its bottom. When reaching its bottom, the air gap construction turned more efficiently into a vigorous incineration due to the differences in the oxygen supply due to a chimney effect. For a closer viewing of the performed experiments see the video links in the Appendix.

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