Concrete units for strain-monitoring in civil structures: Installation of cement-based sensors using different approaches

Abstract

Cementitious materials with self-sensing properties have been recently proposed for strain-monitoring of civil structures. Although different methods have been used to install cement-based sensors in concrete elements, there is a lack of systematic experimental comparisons between self-sensing mechanisms provided by these different methodologies. The present work investigated the bonding performance of different interface agent types (cement-based bonding agent, polyurethane-based interface and epoxy-based structural adhesive) between self-sensing cementitious materials and concrete substrates. It also reported the strain-monitoring performance and the compressive behavior of self-sensing cementitious composites embedded into solid concrete units using three different installation methods: (i) the cement-based sensor was in the hardened state and the concrete structural element was in the fresh state during the installation process (HS/FC method - hardened sensor/fresh concrete); (ii) the fresh cement-based sensor was installed in hardened concrete units (FS/HC method - fresh sensor/hardened concrete); and (iii) both components were in the hardened state during the installation process (HS/HC method - hardened sensor/hardened concrete). Results indicated that the epoxy-based structural adhesive provided the best bonding performance and ensured suitable transference of stresses between cement-based sensors and the monitored concrete element. The HS/FC and the FS/HC approaches were found to be appropriate for future cement-based sensors installations because they provided composites with appropriate values of average gauge factor and mechanical performance.