Applicability of Fibre Optic Sensing in Asphalt

Key concerns centered around the fibre optic cables' ability to withstand temperatures of up to 240°C while maintaining the required strain transfer characteristics from the outer protective coating to the inner fibre core. We assessed various cable solutions, testing their strain transfer capabilities in a strain bed at multiple levels before and after exposure to high temperatures. This allowed the identification of a few promising cable solutions whereas many indicated slippage after the thermal exposure (as shown in Figure 1).

To simulate real-world conditions, we embedded the cable solutions at different heights within 80cm x 30cm x 10cm mastic asphalt samples, while also testing modifications, such as additionally protecting the cables by shrinkage tubes. In the subsequent 3-point bending test, we assessed the performance of the embedded cable solutions within mastic asphalt samples. While some cable solutions encountered challenges like slippage and positioning issues, a few of them measured a precise strain distribution. Notably, certain cables even accurately measured the discontinuous zones near the load introductions, as predicted by a numerical model, indicating their strong bond between the cable layers as well as the mastic asphalt.

Modifications like additional protective layers proved impractical, highlighting the importance of selecting a suitable cable. The characteristics of the successful cables are found in the reference, while product names are communicated upon request. Overall, our findings demonstrated that fibre optic technology is commercially viable for investigating mastic asphalt behaviour, even offering new capabilities for observing the load introduction in pavements.

ASTRA: Forschungsprojekt TRU_20_01B_01 auf Antrag der Arbeitsgruppe Trassee und Umwelt

Urias Morf
Dr. Dominik Hauswirth
Andrey Molinari