A new characterization technique,a repeated load CBR test,was used to evaluate the resilient properties recycled mix-granulate unbound base material. This is a mixture of crushed concrete and crushed masonry,so recycl...A new characterization technique,a repeated load CBR test,was used to evaluate the resilient properties recycled mix-granulate unbound base material. This is a mixture of crushed concrete and crushed masonry,so recycled demolition waste,this is used on a wide scale in the Netherlands as road base material. The repeated load CBR test,done with standard CBR testing facility,was conducted to estimate the resilient modulus. For comparison and assessment purposes the tests were carried out with the same material conditions (composition,grading,moisture and compaction degree) as have been applied in earlier triaxial testing in the Road and Railway Engineering Laboratory,Delft University of Technology. The results indicate that the repeated load CBR test yields a good estimate of the stress dependent equivalent modulus for the sample material as bulk,which can be used in mechanistic pavement analysis in the absence of triaxial test results.展开更多
In 2008 structural failures occurred on the asphalt pavement,with a hydraulic blast furnace slag base,of the motorway A32 (constructed in 1986～1988) in the Netherlands. Within a few weeks serious depressions occurred...In 2008 structural failures occurred on the asphalt pavement,with a hydraulic blast furnace slag base,of the motorway A32 (constructed in 1986～1988) in the Netherlands. Within a few weeks serious depressions occurred,in which the asphalt pavement was full of cracks and the base had a very low stiffness. In 2008 and 2009 the pavement including the base was rehabilitated over a length of 10 km.The Dutch Ministry of Public Works has initiated an extensive research into the risks of occurrence of this type of unexpected structural damages on the main road network in the Netherlands. Among many other things this research includes material research into the base material of the A32 to find the cause of the structural failure.In total 130 cores,divided over 26 cross-sections,were drilled from the A32. The cross-sections were divided over 3 areas,with a high and low base stiffness respectively and also at heaves that had grown into the pavement since 1998. In areas with high base stiffness the cores mainly contained bound base material,in areas with low base stiffness mainly granular material and at the heaves it was a mix thereof. Standard (static) and dynamic crushing tests were done on the granular material. Dynamic and monotonic indirect tensile tests and compression tests were performed on the bound material. In all cases no systematic difference was found between the mechanical properties of the blast furnace slag base material from the heavily loaded right traffic lane and the material from the other locations.It is concluded that the pavement failure on the A32 is introduced by the occurrence of full depth asphalt fatigue cracks in the pavement that was originally designed for 12 years (but was never strengthened) in areas where the base stiffness always has been low or became low through crushing (that also has resulted in the heaves). Penetrated rainwater then has weakened the base and pumping has occurred,resulting into loss of bearing capacity and decrease of volume.展开更多
文摘A new characterization technique,a repeated load CBR test,was used to evaluate the resilient properties recycled mix-granulate unbound base material. This is a mixture of crushed concrete and crushed masonry,so recycled demolition waste,this is used on a wide scale in the Netherlands as road base material. The repeated load CBR test,done with standard CBR testing facility,was conducted to estimate the resilient modulus. For comparison and assessment purposes the tests were carried out with the same material conditions (composition,grading,moisture and compaction degree) as have been applied in earlier triaxial testing in the Road and Railway Engineering Laboratory,Delft University of Technology. The results indicate that the repeated load CBR test yields a good estimate of the stress dependent equivalent modulus for the sample material as bulk,which can be used in mechanistic pavement analysis in the absence of triaxial test results.
文摘In 2008 structural failures occurred on the asphalt pavement,with a hydraulic blast furnace slag base,of the motorway A32 (constructed in 1986～1988) in the Netherlands. Within a few weeks serious depressions occurred,in which the asphalt pavement was full of cracks and the base had a very low stiffness. In 2008 and 2009 the pavement including the base was rehabilitated over a length of 10 km.The Dutch Ministry of Public Works has initiated an extensive research into the risks of occurrence of this type of unexpected structural damages on the main road network in the Netherlands. Among many other things this research includes material research into the base material of the A32 to find the cause of the structural failure.In total 130 cores,divided over 26 cross-sections,were drilled from the A32. The cross-sections were divided over 3 areas,with a high and low base stiffness respectively and also at heaves that had grown into the pavement since 1998. In areas with high base stiffness the cores mainly contained bound base material,in areas with low base stiffness mainly granular material and at the heaves it was a mix thereof. Standard (static) and dynamic crushing tests were done on the granular material. Dynamic and monotonic indirect tensile tests and compression tests were performed on the bound material. In all cases no systematic difference was found between the mechanical properties of the blast furnace slag base material from the heavily loaded right traffic lane and the material from the other locations.It is concluded that the pavement failure on the A32 is introduced by the occurrence of full depth asphalt fatigue cracks in the pavement that was originally designed for 12 years (but was never strengthened) in areas where the base stiffness always has been low or became low through crushing (that also has resulted in the heaves). Penetrated rainwater then has weakened the base and pumping has occurred,resulting into loss of bearing capacity and decrease of volume.
