Structural health monitoring of lightweight concrete beams strengthened with ultra-lightweight ECC-FRP mesh composite

The structural health monitoring (SHM) and structural strengthening of degraded reinforced lightweight concrete (LWC) structures are important. In this paper, ultra-lightweight engineered cementitious composite (ULWECC) with calcined petroleum coke was used as an SHM and strengthening material. Its mechanical properties and self-sensing behaviours (under monotonic and cyclic loading) were evaluated. ULW-ECC showed a desirable compressive strength of 76.4 MPa and a tensile strain capacity of 8.4 %. Furthermore, it also possessed sensitive and stable piezoresistivity under various stress conditions. The SHM and flexural strengthening performance of reinforced LWC beams were investigated, concluding that ULW-ECC performed satisfactory self-sensing behaviour and effective enhancements in flexural strength as well as ductility. The load condition can be sensitively reflected in the variation of fractional change in impedance. Compared to the reinforcement of carbon fibrereinforced polymer (CFRP) meshes, ULW-ECC reinforced with glass FRP (GFRP) as well as basalt FRP (BFRP) meshes exhibited better interactions, which equipped more sufficient material utilisation and more reliable selfsensing performance. By comprehensively considering the SHM and strengthening performances, BFRP mesh is recommended for collaborating with ULW-ECC.