Concrete - Moving Direction

stationary 30 moving

Figure 6。 Joint movement simulator JMS and test setup

The local expansion of the BEJ during loading is measured by determining the change in position of optical line markings that are drawn at spacing of 50 mm both on the surface and on the side of the bituminous joint filling material。

The force is continuously recorded while the BEJ is expanded from an original joint gap width of approximately W0 = 30 mm to a maximum joint opening of W0 +ΔW and then, at

the same rate, pushed back to the original value W0。 This triangular movement cycle is re- peated at least 20 times。 The idea behind this approach is to determine fatigue behavior of the asphaltic plug joint system for 20 years; however, without being able to take into ac- count long-term effects of traffic and weather in practice。

Nevertheless, the test can be considered as quite severe, since it assumes that one full possible annual tension cycle takes place at the lowest declared design temperature of the

BEJ with a fast gap opening rate of 10 mm/h。 The test is performed at constant tempera- ture, typically at –20 °C, up to a joint opening movement of approximately 65% of the

maximum admissible annual total movement for each system on a bridge。

Test results are evaluated as shown in Figure 7 by determining the load and cycle to failure and the strain distribution from evaluating the permanent deformation between the optical line markings in the horizontal direction。 In addition, the vertical and lateral contraction is determined, which in case of large joint movement BEJs, can be considerable and has to be taken into account in terms of driving safety and risk of lateral water infiltration。

0

1 2 3 4 5 6 7 8 10

-5 Position

Steel plate Crack

Figure 7。 LMS results at -20 °C (left); lateral contraction from joint opening (right)

4 Long-term field performance of BEJs for small joint movements

4。1 Selection of test sites and installation of BEJs

As a scientific basis for the Swiss guidelines [7], the impact of material properties, installa- tion procedures, on site conditions and the field performance of plug expansion joints over a five-year period was extensively monitored and studied in a long term performance evaluation research program [2]。

With the assistance of various public works departments of six regional Swiss govern- ments (cantons), 18 BEJs for monitoring were installed in 1996 and 1997 on seven motor- way and regional road bridges in typical climatic regions (Fig。 8)。 The bridges were designed for joint movements between 5&pide;48 mm and located at height above sea level ranging from 225&pide;1710 m (Tab。 1)。 The selected BEJ systems were the four most commonly used products in Switzerland at that time。 All bridge deck pavement surface layers consisted of mastic asphalt MA or asphalt concrete AC, except for the bridge (VD) where the top layer consisted of porous asphalt PA。

All operations performed during installation were precisely observed and recorded。 In order to assess the impact of the produced materials on the BEJ behaviour and for deter- mining the changes in material properties under service conditions, the properties of the installed materials were examined in the original (as-delivered) state, after installation and during service, using chemical/physical analytical methods。 Changes in the condition of the plug joint systems, e。g。 debonding, cracking, blistering, material displacement, were periodi-