Application of ultrasonic wave propagation to the cure monitoring of epoxy adhesives for restoration of concrete

Ultrasonic technique has been used to monitor the progress of the curing reactions of an epoxy adhesive employed in civil engineering applications. Ultrasonic velocity and attenuation have been collected in isothermal conditions on the neat resin, as well as in a coupled system concrete-resin-concrete. The evolutions of ultrasonic properties have been correlated with the dramatic increase of mechanical properties changing from those of viscous liquid to a glassy polymer. The change of velocity during cure has been used as a measure of the progress of the reaction, in order to have a precise indication of the hardening of the adhesive.