Monitoring early age property of cement and concrete using piezoceramic bender elements

Abstract

Ultrasonic waves are commonly used for non-destructive evaluation of concrete structures. For fresh concrete, ultrasonic waves have also been used to monitor concrete setting and strength development at early ages. However, the conventional ultrasonic test setup typically needs access to the two opposite sides of concrete structures, which is not always possible for in situ field testing. In this paper, embedded piezoceramic bender elements are proposed to measure ultrasonic shear (S) waves in fresh cement paste, mortar and concrete. The shear wave velocities are obtained from B-scan images of a collection of recorded signals over time. Experimental results indicate that the shear wave velocity is closely related to the setting time, and this relationship is independent of air void content and w/c of cement pastes. The low cost bender elements can also be of use to monitor the setting of fresh concrete and the long term evaluation of hardened concrete.

Comparison Between Different Experimental Techniques for Stiffness Monitoring of Cement Pastes

“…Both the generated and received signals are recorded in order to measure the time delay between the signals and thus obtain the wave travel time through the material. These methods can be applied using compressional (P) or shear (S) waves (Van Den Abeele et al 2009), generated by means of: an ultrasonic wave transmitter (Reinhardt and Grosse 2004), a smartaggregate (embedded piezoelectric element) (Dumoulin et al 2012), a bender or bender-extender element (Zhu et al 2011b), or an external impact (Lin et al 2010).…”

“…The application of BE for studying the evolution of the stiffness characteristics of cement pastes is still taking its first steps, with very few published works so far (Zhu and Kee 2010;Zhu et al 2011b). However, the success already achieved in the application of BE to cementstabilized soils at the University of Minho Silva et al 2013) has justified the interest on this testing methodology.…”

“…Hence, the capacity of characterizing the evolution of mechanical properties, such as E-modulus, since casting assumes crucial importance, especially taking into account the increasing demands that society poses on construction, with tight schedules and technically challenging projects. In order to fulfil these needs, several destructive and non-destructive methods have been proposed over the years for characterization of mechanical properties of cementitious materials since early ages (Azenha et al 2010;Boulay et al 2010;Reinhardt and Grosse 2004;Staquet et al 2012;Zhu et al 2011b;Jau and Yang 2010;Naik 2003). This paper is focused on non-destructive approaches for characterization of the cement paste hardening, particularly on setting and stiffness monitoring.…”

“…This paper is focused on non-destructive approaches for characterization of the cement paste hardening, particularly on setting and stiffness monitoring. To evaluate these properties, several non-destructive methods can be found in the literature, namely: mechanical methods (Chamrová 2010;Maia et al 2012b;Boulay et al 2010;Staquet et al 2012;Boulay et al 2013b); wave propagation methods (Voigt 2005;Reinhardt and Grosse 2004;Song et al 2008;Zhu and Kee 2010;Zhu et al 2011a;Zhu et al 2011b;Voigt et al 2005;Kim et al 2009); resonance methods (Kim et al 2009, Malhotra andSivasundaram 2003;Wang et al 2010;Shin et al 2008;Azenha et al 2012); and methods based on dielectric properties (Beek 2000Princigallo et al 2003). The Cyclic Compression (CC) method is the oldest and the most accepted method for characterizing the elastic modulus of concrete.…”

“…Alternatively, Zhu and Kee (2010) have applied a methodology commonly used in soil characterisation to cement paste: bender-extender elements (BE) (Thomann and Hryciw 1990). Even though the BE methodology does not eliminate problems associated with local effects, this method is not influenced by the air bubbles since the measurements are performed with shear waves instead of compressional waves (Zhu et al 2011b).…”