Non destructive online evaluation of concrete hardening using acoustic emission and harmonic wave spectroscopy

The early stages in the hydration process of concrete are crucial in the development of its mechanical properties and its durability. We have monitored the first three days of the hydration process using an integrated system that combines Acoustic Emission (AE) analysis with Nonlinear Elastic Wave Spectroscopy (NEWS) techniques. With the AE technique, we realize a passive interrogation of sound generation in the concrete that is capable of online monitoring the internal microstructural activity. The nonlinear wave propagation technique is an active interrogation that probes the nonlinear elastic properties of the microstructure through the analyses of the second harmonic generation from a continuous wave transmission through the concrete sample. In addition, common parameters such as temperature and P and S wave speeds are also measured during the curing process at regular time intervals. The evolution in the AE events, and the linear and nonlinear behavior of concrete is analyzed as a function of the degree of hydration and interpreted for various initial compositions, in terms of the phase changes due to chemical reactions and mechanical setting.Paper Th.4.6.4; CD-romstatus: publishe