Onsite Use of Recycled Asphalt Pavement Materials and Geocells to ...

Figure 3.8 Strain gauge affixed on geocell Figure 3.9 Pavement strain gauge
3.6.3 Displacement Transducers and Tell-Tales
The displacement transducers used in this research were strain gauge-type sensors
manufactured by Tokyo Sokki Kenkyujo, Co., Ltd., Japan. They had two displacement ranges: 0
to 100 mm (Model: CDP-100) and 0 to 50 mm (Model: CDP-50). Two displacement transducers
of 100 mm limit were affixed on the loading plate. One displacement transducer of 100 mm limit
was affixed at a distance 25 cm from the center of the plate. Moreover, two displacement
transducers of 50 mm limit each were affixed at distances of 50 and 75 cm away from the center
of the loading plate. All of the displacement transducers were suspended from the reference
beam fastened on the top of the box. The displacement transducers were rested on the loading
plate or the metal plates on the HMA surface.
Moreover, displacement transducers were also used to measure the vertical displacements
at the interface of HMA surface and RAP base and the interface of RAP base and subgrade
through pre-installed tell-tales. Each tell-tale included a hollow metal tube measuring 6.3 mm in
diameter and 0.40 mm in wall thickness, inside of which was a steel rod 3.15 mm in diameter.
The steel rod was connected to two steel plates measuring 15 mm in diameter on both ends. The
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