Methodology for monitoring Cement Based Materials at Early Age combining NDT techniques

Abstract The chemical process that takes place in Cement Based Materials (CBM) produces microstructural changes and the development of mechanical properties at Early Age (EA). CBM composition, curing conditions (temperature, relative humidity and wind speed) and structural member size can modify the chemical reaction and microstructural development, producing undesirable effects, as EA shrinkage and cracking. Thus, a robust testing methodology is required to monitor CBM at EA. To take advantage of Non-Destructive Tests (NDT) for EA monitoring but considering the uncertainty related to indirect measurements, a testing methodology that combines simultaneous measuring of temperature, capillary pressure, evaporation rate, free shrinkage, and p- and s- waves Ultrasonic Pulse Velocities (UPV) was developed. The multi-parameter technique allows to follow both the chemical, microstructural and mechanical properties development processes that take place in CBM at EA. An integrated analysis allowed defining new EA shrinkage, stress demand estimation and cracking risk models combining EA NDT parameters. The experimental setup presented in this study can be used for pastes and concretes and was verified in laboratory conditions, inside a climate chamber and in on-site real scale applications.