Large-scale Experimental Study On The Fire Behaviors Of Organic Exterior Wall Insulation Materials And System

The exterior thermal insulation system of building exterior wall is a kind of building energy conservation thermal insulation system outside the building base wall.At present,EPS board,XPS board,modified polyurethane,phenolic and other organic materials together with thin plaster protection layer are widely used in Xinjiang region.However,most organic thermal insulation materials have the characteristics of flammability,high combustion heat,and high concenration of poisonous gas during combustion.After being ignited,they will form a vertical fire spread along the exterior wall,which will become a threat to the lives and property.In this paper,the fire propagation behaviors of building exterior wall insulation materials and systems are experimentally studied through the large-scale exterior wall window fire test device.The main research content includes:(1)The fire spread characteristics of the building exterior wall under two kinds of ignition modes of wood crib fire and gasoline fire in the window are studied.The influence of ignition mode on the vertical fire spread of EPS bare board is in focus.The research results show that gasoline fire(terrorist activity)has a short heating time for the exterior wall,but it will form a flashover phenomenon in the early stage of the fire,which is adverse to the fire rescue work.Therefore,it is necessary to strengthen supervision and management work to prevent such fires from happening.The wood crib fire(standard fire)develops slowly and the heating time of the outer wall is long,so the EPS outer thermal insulation material shrinks and melts more fully.In addition,under two ignition modes,the risk of lateral fire spread of the outer wall is far less than the vertical fire spread,and no combustion occurs in the auxiliary wall.(2)The fire spread characteristics of the building exterior wall under the condition of 1.1 m/s ambient wind and 6.0 m/s forward mechanical air are studied using wood crib fire in the window.The influence of forward wind on the vertical fire spread of building exterior insulation materials is in focus.The research results show that the forward wind shortens the burning time of the EPS exterior insulation material by accelerating the burning speed.Besides,the forward wind promotes the convective heat transfer between the fire plume and the EPS insulation material,resulting in more intense shrinkage and melting.It further promotes the vertical fire spread of the EPS insulation material of the main wall and increases its fire risk,which puts higher requirements on the use of building exterior wall insulation materials in windy areas.Based on the experimental results,the fire spread characteristics of EPS insulation material for building exterior wall under different wind speeds and directions are futher studied using FDS.It is found that the fire spread degree of insulation materials of exterior wall first increases and then decreases with the increase of wind speed.The later decrease is mainly related to the cooling effect of cold air on the fire plume.The change rate of vertical fire spread with lateral wind is lower than that with forward wind.(3)The fire spread characteristics of the building exterior wall EPS with thin plaster protection layer and without thin plaster protection layer are studied using wood crib fire in the window.The influence of the protective layer on the vertical fire spread is in focus.The research results show that the thin plaster protection layer can significantly delay the initial melting and burning time of the EPS insulation material above the window.But when the thin plaster protection layer is thinner,under the action of wood crib fire and high temperature fire plume,the interior of the thin plaster protective layer is heated and then gradually forms a cavity structure,which causes the EPS to burn intensely on the main wall and even the auxiliary wall.The area of fire and the burning intensity are greater than those without the thin plastering layer,which will increase the fire risk to some extent.It puts forward higher requirements on the thickness of the protective layer of the building exterior wall insulation material and the selection of the protective layer material.(4)The fire spread characteristics of EPS,PIR and PF organic insulation materials with thin plaster protective layer are studied using wood crib fire in the window.The fire performance of thermosetting organic thermal insulation materials is analyzed.The research results show that PIR and PF do not shrink and melt like EPS under fire conditions,but carbonization appears on the surface and form carbonized cracks under flame heating.In the PIR carbonization crack,a strip-shaped combustion flame appears.But the PF does not show a burning flame at the carbonization crack,and the main wall flame height is only half of the height of the main wall,and no combustion occurs in the auxiliary wall.Overall,the PF insulation system is superior to the PIR insulation system in overall fire resistance,and the EPS insulation system has a worse fire performance.Therefore,the use of thermosetting insulation materials on the first floor of the building exterior walls and even above has an important role in suppressing the fire spread of the building exterior walls under various reasons and environmental conditions.