NICOM 4: 4th International Symposium on Nanotechnology in Construction Graphene-based resistive humidity sensor for in-situ monitoring of drying shrinkage and intrinsic permeability in concrete

Nanosensors dedicated to the structural health monitoring of concrete structures have been only marginally studied. They would however be particularly well-suited to monitor durability-related processes, as these phenomena involve transport of gas and liquids through micro and nano-porosity. In this paper we discuss the relevance and feasibility of embedding relative humidity nanosensors within concrete. It appears that the localized, continuous knowledge of relative humidity within a concrete structure could provide a useful insight into drying shrinkage; it could also contribute to improved intrinsic permeability measurements, leading to improved assessment of structural durability. For the task, we propose a low-cost, downscalable resistive device made of a 10 nm graphene sheet grown directly on glass and atop which are ink-jet printed silver electrodes. The device resistance increases significantly with relative humidity (RH), especially above 40% RH. Relative amplitude of variations are only of about 3% for the two tested devices, but absolute variations (80  and 480 ) appear measurable by a low-cost and robust signal conditioning electronics. Thus, the idea of using our graphene-based resistive device for embedded humidity monitoring in concrete appears quite promising.