Costain and Laing O’Rourke have for the first time tested in a working environment a new technique to calculate the strength of sprayed concrete.
Working at the Bond Street station upgrade project for London Underground, the joint venture used the Strength Monitoring Using Thermal Imaging (SMUTI) technique, developed and patented by Cambridge University’s Benoit Jones.
According to Costain, the technique uses a thermal imaging camera to track the temperature of concrete as it is sprayed to form the tunnel lining. The data of temperature history enables engineers to calculate the amount of hydration that has taken place in the concrete, and hence its strength.
Costain senior tunnel engineer Aled Davies 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.”
He added: “The trials have gone very well and the workforce was very appreciative of the time and efforts being taken to improve their safety. The data is now being analysed but we hope to have the results by September, when we will present them to tunnelling sector clients and design partners. We hope to see SMUTI become the primary method of early strength monitoring on all tunnelling projects.”
Costain section engineer Francisco Gallego is pictured using a thermal imaging camera to monitor a section of sprayed concrete lining within the Concourse 1 tunnel at Bond Street station upgrade.