info on exterior insulation/filling material, etc.-1999

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EPS Geofoam 2001,3rd International Conference, Salt Lake City,December 2001 13 Figure 23.Earth pressure below EPS layer at Hjelmungen DURABILITY Although polystyrene is a stable chemical compound it may dissolve when exposed to petrol agents.When placed in a road fill the EPS blocks are therefore protected either by a concrete slab on top of the blocks also serving as a load distributing layer,or a high density polypropylene sheet.Although it is possible that a petrol tanker may overturn and spill petrol on the road surface at the location of an EPS fill,the statistical likelihood that such an event should occur is very small and the precautions mentioned above should be sufficient to protect the EPS.Also it will take some time for the petrol fluid to percolate through the soil on the side slopes,allowing time for corrective measures.Still,if a petrol spill should find its way to the EPS,only the outer blocks are likely to be effected and repair should be easy to perform.During the nearly 30 years that have passed since the first EPS fill was placed and the accelerated use of the EPS method on a worldwide scale in later years,no such spill incident has been reported. FAILURES Of the many EPS projects now completed in many parts of the world,only five known failures have been reported. Two failures are associated with water fluctuations and buoyancy forces.The other three are caused by fires. On the 16s'of October 1987 Northern Europe experienced exceptionally strong storms with high wind velocities and high rainfall intensities.Norway was also exposed to major floods,and in the Oslo area the first EPS fill built in 1972-floated off_as did an adjacent section of motorway constructed-somt years later.What was wrong?Had the dangers of buoyancy forces not been considered?Yes,such calculations had been performed,but the highest possible flood level predicted at the design stage in 1972 was 0,85 in lower than the flood level that occurred in October 1987.So it was rainfall and flood level predictions in 1972 that were misleading. Also the second failure reported from Thailand involved an unexpected high water level causing a completed road fill to be washed away.So it should be duly noted that the dangers of buoyancy forces should be carefully studied when considering the design of an EPS fill.Often soft subsoils are located in lowland areas subjected to flooding.In such cases accurate predictions of the highest possible water level are essential in order to obtain a safe and lasting road structure. Ordinary polystyrene is a combustible material and will burn when set on fire.For this reason some precautions should be taken when constructing EPS fills using normal quality material.Such precautions may include fencing in any stockpiles at the construction site and provide guards round the clock,or place the blocks directly in the fill when they arrive on site,working round the clock if necessary.Alternatively a self-extinguishing quality of EPS may be used at approximately 5%increase in production costs.However,once the EPS is covered by the pavement material on top,and soil on the slopes,there will not be sufficient oxygen available to sustain a fire. Two failures due to fires have occurred in Norway,and both were caused by welding activities on bridge abutments adjacent to EPS fills,during the construction phase.In the first case 1500 m3 of EPS were transformed into black smoke in a matter of some 10 minutes.The concrete bridge abutment was also damaged due to the heat developed with concrete spalding from the reinforcing bars.Since the fire was initiated by sparks from welding activities on the bridge,the contractor responsible for the welding had both to repair the bridge abutment and replace the EPS fill at his own expense.A similar incident occurred in 1995 and again the repair costs had to be covered by the contractor responsible for the welding activities.So the fire potential should not be overlooked and in some counties in Norway the local highway offices are only using self-extinguishing material at a somewhat higher cost in order to exclude fire hazards. Long term performance and durability of EPS as a lightweight filling material