Continuous monitoring of cement paste E-modulus since casting : a method based on modal identification

Abstract

Recently the authors proposed an ambient vibration-based test to characterize the concrete E-modulus evolution during hydration. Here a variant is presented, with several adaptations to allow the technique to be easily handled under lab conditions, and specifically devised to cement pastes. The methodology uses an acrylic tube with an internal diameter of 16mm as a formwork for the paste. Along hydration the paste endures a composite behavior with the tube. By clamping one extremity of the composite element a cantilever with a 0.45 m span is obtained, and the accelerations at the free extremity are monitored using an ambient vibration technique for modal identification, which allow to determine the first resonant frequency of vibration. As the paste hardens this frequency increases, and so does the paste Emodulus, making it possible to trace evolution curves for the paste E-modulus since casting. The experimental setup is described, and experiments with pastes are commented, illustrating the capabilities of this novel method.