Very early age concrete hydration characterization monitoring using piezoceramic based smart aggregates

Abstract

Very early age (0–20 h) concrete hydration is a complicated chemical reaction. During the very early age period, the concrete condition dramatically changes from liquid state to solid state. This paper presents the authors’ recent research on monitoring very early age concrete hydration characterization by using piezoceramic based smart aggregates. The smart aggregate (SA) transducer is designed as a sandwich structure using two marble blocks and a pre-soldered lead zirconate titanate (PZT) patch. Based on the electromechanical property of piezo materials, the PZT patches function as both actuators and sensors. In addition, the marble blocks provide reliable protection to the fragile PZT patch and develop the SA into a robust embedded actuator or sensor in the structure. The active-sensing approach, which involved a pair of smart aggregates with one as an actuator and the other one as a sensor, was applied in this paper’s experimental investigation of concrete hydration characterization monitoring. In order to completely understand the hydration condition of the inhomogeneous, over-cluttering, high-scattering characteristics of concrete (specifically of very early concrete), a swept sine wave and several constant frequency sine waves were chosen and produced by a function generator to excite the embedded actuating smart aggregate. The PZT vibration induced ultrasonic wave propagated through the concrete and was sent to the other smart aggregate sensor. The electrical signal transferred from the smart aggregate sensor was recorded during the test. As the concrete hydration reaction was occurring, the characteristic of the electrical signal continuously changed. This paper describes the successful investigation of the three states (the fluid state, the transition state, and the hardened state) of very early age concrete hydration based on classification of the received electrical signal. Specifically, the amplitude and frequency response of the electrical signal were of main interest. Both the swept sine wave and the constant frequency sine wave excitation methods presented the same conclusion on the three concrete states during the hydration, which enhances the reliability of the active-sensing approach for very early age concrete hydration monitoring.

Cyclic Crack Monitoring of a Reinforced Concrete Column under Simulated Pseudo-Dynamic Loading Using Piezoceramic-Based Smart Aggregates

“…Since the crack in this period is much larger than the previous step from 1100 to 2100, the propagating stress wave attenuates more than the previous period. The cycles (6)(7)(8)(9)(10)(11) shown in the damage index are more clear than the previous cycles (1)(2)(3)(4)(5). In addition, the highest values of the damage index reached to one, which implies the concrete column was subject to severe damage in the maximum displacement of each cycle.…”

“…In this project, piezoceramic-based devices, called smart aggregates (SA), were utilized as transducers for structural health monitoring of RC columns under a pseudo-dynamic loading procedure. In addition to the structural health monitoring function, the smart aggregate can be used to perform early-age concrete strength monitoring [8,9], impact detection [10], seismic detection [11], and soil freeze-thaw monitoring [12], demonstrating that SAs are multi-functional devices. In previous studies, SAs have been successfully implemented for structural health monitoring of various concrete structures under different loading cases including: a concrete bridge bent-cap under static loading [13], a concrete frame under static loading [14,15], a shear wall under reversed cyclic loading [16], columns under seismic loading [17], stress wave base communication in concrete structures [18,19] and columns under reversed cyclic loading [20,21].…”

Detecting Debonding between Steel Beam and Reinforcing CFRP Plate Using Active Sensing with Removable PZT-Based Transducers

“…With both sensing and actuation functions, PZTs are often used in active sensing methods for structural health monitoring (SHM) and damage detection. For example, the active sensing method was used in characterizing concrete hydration [38], monitoring circular reinforced concrete columns under seismic excitations [39], and detecting damages in circular RC columns [40]. With the PZT transducer, the electro-mechanical impedance (EMI)-based technique was applied to health-monitoring plate-like structures [41], pin connection loosening [42], and grout compactness of concrete-filled steel tubes [43].…”

“…However, few studies on debonding detection between a CFRP plate and steel beam using active sensing have been reported. In addition, the PZT-enabled active sensing methods often require the permanent installation of the transducers on or in the host structures [4,34,38,42,47,48], which brings inconvenience to large-scale implementation. These factors motivate the authors to develop a new approach to detecting debonding between steel structures and the reinforcing CFRP plates.…”

Experimental Damage Identification of a Model Reticulated Shell

“…By using SHM technologies, the real-time damage detection of various structures, including concrete structures [2][3][4][5][6], pipeline structures [7][8][9][10][11][12], and steel structures [13][14][15][16][17][18][19], can be investigated in order to provide early warning and hopefully to avoid accidents. In the aerospace industry, several application areas have garnered significant interests.…”