Rubber Compression Seal Expansion Joint Installation Temperature Requirements

Rubber compression seal expansion joints must be installed at the correct gap width for the installation temperature to ensure that the seal operates within its design range throughout the temperature cycle. Incorrect gap setting is one of the most common causes of premature seal failure. The design gap at any temperature is calculated from the design movement range and the temperature range. For a seal with a design movement range of 40 mm and a temperature range of 50 degrees C, the gap changes by 40/50 = 0.8 mm per degree C. If the mean temperature is 15 degrees C and the installation temperature is 25 degrees C, the gap should be set 8 mm smaller than the mean gap. Gap setting jigs are used to maintain the correct gap during installation. The jig consists of two steel plates connected by threaded rods that can be adjusted to the required gap width. The jig is placed in the joint gap, the gap is adjusted to the correct width, and the seal is installed. The jig is removed after the seal is in place. Temperature measurement during installation is critical for correct gap setting. The temperature of the bridge deck, not the air temperature, should be measured, as the deck temperature may differ from the air temperature due to solar radiation and thermal mass. An infrared thermometer is the most convenient tool for measuring deck surface temperature. Cold weather installation requires special procedures. The seal must be warmed to at least 10 degrees C before installation to ensure adequate flexibility. Warming can be achieved by storing the seal in a heated enclosure or by using a heat gun. The seal must not be overheated, as this can damage the rubber. Hot weather installation requires that the seal is installed with a smaller gap than the mean gap to allow for thermal expansion. If the installation temperature exceeds the design maximum temperature, the seal may be compressed beyond its design limit, causing extrusion from the joint gap. In extreme cases, installation should be postponed until the temperature decreases.