Optical fibre grout flow monitor for post-tensioned reinforced tendon ducts

We report on preliminary experimental trials aimed at assessing the suitability of a distributed water monitor as a means of determining the presence of grout in reinforced tendon ducts of civil engineering structures. This sensing capability is realized through a combination of Optical Time Domain Reflectometry (OTDR) and chemically sensitive water swellable polymers (hydrogels). This form of sensor cable can detect water as a function of linear position along its length with a spatial resolution of a few centimeters1,2. The experiments carried out here indicate that this approach has considerable potential as a means of providing quality assurance during the grouting procedure.