A new way of testing concrete strength has been trialled in London by contractors Laing O’Rourke and Costain.
The pair have used the Strength Monitoring Using Thermal Imaging (SMUTI) technique at the Bond Street station upgrade (BSSU) on behalf of London Underground.
The new technique was created by Dr Benoit Jones from Cambridge University and uses a thermal imaging camera to track the temperature of concrete as it is sprayed to form the tunnel lining. Knowing this temperature history enables the engineers to calculate the amount of hydration that has taken place in the concrete, and hence its strength.
According to Costain’s Aled Davies, a senior tunnel engineer, it is a significant step forward for health and safety. He said: “SMUTI allows us to directly monitor the compressive strength development of sprayed concrete whilst remaining at a safe distance. This is a substantial improvement over the current method, which relies upon a small test panel being representative of the entire sprayed concrete advance to prevent personnel being at risk from sprayed concrete lining falls.”
In March, following extensive laboratory testing, production trials began on-site at BSSU. First, the concrete in 12 sprayed concrete panels was tested simultaneously using the established in-situ tests and SMUTI. This provided sufficient data to carry out trials in an actual production environment and in March, BSSU implemented the SMUTI system alongside existing test methods for the first time.