Changes in the condition of the flexible plug expansion joints, such as debonding, crack- ing, blistering, material displacement etc。, were recorded。 Key mechanical laboratory tests as required by [7] were performed。 Visual inspection after seven years showed that the BEJs were in good condition and that only fine cracks with unknown depth along the sides

of the BEJ–tanking were visible。 The surface chipping (8/10 mm) of the surface dressing论文网

was still in place。

On-site investigations of the remaining rutting resistance of the plug joints within and between the wheel paths were conducted using the MMLS3 as indicated in Figure 11。 MMLS3 testing was performed in a tent at 30 °C measured 20 mm below BEJ surface。 This temperature condition was produced with a pair of heating fans。 The experimental setup and the results are shown in Figure 12。

Except for the testing between wheel track at the testing site “MMLS-3”, with partly re-

placement of the BEJ top, all rut depths after 6'000 passings at 30 °C remained clearly be- low 5 mm, i。e。 in the order of 3 mm。 From this result one can conclude that partial renewal of the BEJ surface material can only be considered as a temporary solution and should be evaluated very carefully。

  7。0    Direction Lugano

6。0    T=30°±2°C 5mm

5。0

4。0 MMLS-3

MMLS-1

3。0

2。0 MMLS-4

1。0 MMLS-2 6000

0。0

0 2000 4000 6000 8000 10000  12000

Nr Passings

Figure 12。 MMLS3 Setup before installing tent and heating fan (left) and rutting results on the northbound MMLS3 testing sites

5。2 Experience with BEJ's for large Joint Movements

Polymer-modified BEJ systems with movement aids have been developed recently in Swit- zerland for total annual maximum joint movements of 100 mm and 70 mm [5]。 These sys- tems, here labeled S9 and S7, consist of a row of springs which are embedded in the bitu- minous joint filling material at spaces of approximately 100 mm and anchored to two opposite L-shaped profiles as shown in Figure 13。 The springs are used to enforce a homo- geneous longitudinal strain distribution in the plug joint during joint movements and to re- duce the risk of local strain concentrations which could lead to cracks and failure。 The joint

filling material is supported over the joint gap by specially configured steel plates with slid- ing capabilities。

All test specimens were made by the manufacturer using gap graded 22 mm aggregates and 25 Mass-% binder with ca。 11 Mass-% SBS polymer-modified bitumen。 The air void content was negligible。

JMS tests were performed at -5, -10, -20 °C with a max。 joint opening of w = 65 mm (S9) and at -20 °C with w = 45。5 mm (S7)。

Pavement    BEJ Trench 900mm Movement Aid

Fix Moving Concrete

A D C   E B Pav。 700mm

A

Figure 13。 System S9 (left) and S7 (right); A = spring anchor, B = upper steel plate, C = bottom steel plate, D = sliding bearing, E = deformation layer, PBM = Polymerbitumen sheet

L-profile for anchoring the springs