ABSTRACT
The Maastunnel, constructed in 1942, is the first immersed tunnel with a rectangular shape. This tunnel is considered as the prototype of the modern immersed tunnels and heritage construction in the Netherlands. Since 2018, a renovation of the Maastunnel has been carried out due to the extensive corrosion of the reinforcement observed at its bottom floor. The old concrete surrounding the rebar was removed. And, after cleaning the reinforcement, a new concrete layer was cast. In order to monitor the quality of the repaired layer and detect the possible deficiency in terms of delamination between the existing and the newly-cast concrete, a monitoring system was installed in this tunnel, which makes use of embedded piezoelectric sensors named smart aggregates. A total of six smart aggregates, two in new concrete and four in old concrete, were used in the monitoring process, and the monitoring has been running for more than 757 days after the installation. In this paper, we demonstrate the usage of the monitoring data in identifying the hardening process of the newly-cast concrete and monitoring the quality of old-new concrete interface. The test results show no visible delamination between the new and the old concrete up to now. Moreover, the smart aggregates show a stable performance during the two-year monitoring, which illustrates their reliability in the long-term monitoring of concrete structures.
