Novel sensor detects corrosion in concrete

Said to be more resilient and longer lasting than traditional corrosion sensors, the new devices are designed to constantly monitor conditions within structures such as bridges and vital coastal defences, enabling a warning message to be sent via text message or email when conditions for corrosion threshold have been crossed. Tong Sun, professor of sensor engineering at City University London and principal investigator, explained: "Key to this successful prototype is our monitoring the variation of the sensor signals of a sample as an indicator of corrosion levels. This means we can use optical sensors made of polymer, which is much more resistant to the high alkaline environments of these structures than sensors currently on the market." A trio of novel, robust probes is at the heart of the team's sensors: one that monitors temperature, one for humidity and one that senses chloride and pH levels. Changes in these factors indicate the onset of the potentially destructive corrosion. Within the probes are also advanced optical sensors specifically designed and built by the City team. "Our design means several probes can be installed semi-permanently in a structure and then connected to a computer data logger, which will constantly collect readings," said Sun. "This can be left until the readings indicate conditions have changed enough to warrant a full investigation. Remedial work will be simpler, cheaper and more effective at this stage, rather than waiting until there is visible damage, such as parts of the concrete coming away." While traditional optical corrosion sensors usually have a limited lifetime of a few weeks, the new sensors are expected to last for several years, even in areas with high PH levels. The research was carried in out in collaboration with Queen's University Belfast, with funding provided by the EPSRC.