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Pressure Mapping of Road Surfaces

Objective – To use XSensor as a tool to help measure early life deformation of bitumen road surface coatings and changes in the shape of aggregates. To provide more detailed information than traditional, single geometry, volumetric methods such as the sand patch test.

To develop a test method that shows how tyre / road surface interaction develops over time utilizing both static and dynamic measurements of contact pressure.

Test Method

A Wessex dry wheel tracker was modified to allow 305 x 305x 50mm asphalt samples to move under a loaded tyre in a controlled manner.  The test allows changes in contact patch phenomena to be easily assessed as test slabs can be subjected to simulated trafficking using the Road Test Machine located at the University of Ulster’s Faculty of Art, Design and the Built Environment (http://www.adbe.ulster.ac.uk)

A Grip Tester tyre is fitted to the test rig, allowing correlation between measurement of in-situ grip and laboratory measured phenomena within the contact area. Contact area and pressure distribution is measured using an XSensor IX500:128.128.10 flexible tyre sensor with XSensor’s Pro V6 software. The sensor is laid active side down on the test slab with the tyre applying pressure the back of the sensor.  The sensor’s flexibility makes it ideal for assessment of rough surfaces.  The ability to measure stresses this way is considered essential as stresses due to a tyre rolling over a highway’s surface are highly concentrated and exploits any surface weakness such as micro texture and aggregate characteristics.

The IX500:128.128.10 sensor mat is capable of capturing up to sixteen individual frames per second and merging them into a single composite trace showing the passage of the tyre across a test slab. The contact patch data also includes contact area and pressure variation. The test sample can be assessed in a static condition with tyre variables such as load and pressure measured. Large numbers of individual contact images can be recorded as assessed statistically.

Testing of different samples was made after 100,000 wheel passes, which is equivalent to approximately four days accelerated trafficking.  Rating of materials is now evident in relation to material type and nominal aggregate size. It was found that application of chips decreases the contact area. The contact area recorded for chipped HRA offering the smallest contact area with 6mm SMA offering the highest contact area of our samples.

Our thanks goes to Dr D Woodward at University of Ulster for the use of his presentation notes. Presented to the 3rd International Surface Friction Conference, Gold Coast Australia 2010. 

Application page last updated: 2015-06-01 14:08:21

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