Continuous monitoring of early-age properties of sprayed mortars by in situ ultrasound measurements

The development of early age properties of sprayed concrete is a key factor that governs its mix design and safe application. The conventional methods to evaluate the evolution of mechanical strength in sprayed concrete present a large interval between each set of measurements and results present a high scatter. In this context, the objective of this study is to characterize the early age properties of sprayed mortars through a novel continuous monitoring system based on in situ ultrasound measurements. Sprayed mortars were also analyzed by isothermal calorimetry, needle penetration and stud driving method. Results indicate that the system developed here can monitor the evolution of early age properties of sprayed mortars continuously without the common drawbacks observed in penetration tests. This research may lead to the development of a more reliable procedure to characterize the early age mechanical properties of sprayed materials in the worksite under safer conditions.