Monitoring Hardening Behavior of Cementitious Materials Using Contactless Ultrasonic Method

Abstract

We propose a novel contactless ultrasonic method for monitoring the hardening behavior of cementitious materials. The goal of this method is to obtain high-quality data to compare the unique hardening process between rapid setting cement (RSC) and ordinary Portland cement (OPC) mortars without physical coupling to the surface of the specimens. To monitor the hardening behavior of cementitious materials, conventional approaches use contact or embedded-type sensors, which limit field application. Our solution is to measure leaky Rayleigh waves at the interface between air and cementitious materials, which allows for the estimation of the physical state of the medium in real time. The modulus development was back-calculated based on the increment of wave velocity using the developed sensor array and transform-based signal processing. We experimentally demonstrated that the proposed method possibly exhibits unique hardening information about flash setting, effects of a retarder, and modulus increments from RSC specimens.

Contactless estimation of soil moisture using leaky Rayleigh waves and a fully convolutional network

“…The signals were averaged over 100 consecutive events to minimize unintended bias and error, and we saved the signals every 5 min. Those who require a detailed understanding of the ultrasonic system, including circuit configurations and equations, can refer to previous studies (Hong & Choi, 2021; Hong et al., 2020; Woo et al., 2022). To account for the slight variation in speed of ultrasonic waves between the air and soil, particularly under saturated clay, an acoustic barrier was placed between the transmitter and receivers, although the speed of the leaky Rayleigh wave was contingent upon the degree of soil moisture (Dashwood et al., 2020; Yang, 2002).…”

A Novel and Non-Invasive Approach to Evaluating Soil Moisture without Soil Disturbances: Contactless Ultrasonic System

“…In particular, the distortional motion is the unique behavior of the solid due to shear resistance. Recent studies show that the degree of Rayleigh wave propagation well correlates with the phase change of cementitious materials [ 33 , 34 ]. This is because the distortional motion becomes dominant depending on the degree of solidification in the medium.…”

“…The receivers (SPU0410LR5H-QB, Knowles Acoustics, Japan) consisted of 8 micro-electromechanical systems (MEMS), where the sensors were located with 5 mm spacing in a row. The 8-channel microphone array was used for a robust and reliable data acquisition [ 34 ]. The aligned sensors measured the air pressure and the designed circuit amplified the obtained signals about 2000 times.…”

“…Due to the uniqueness of the testing scheme, the air-coupled ultrasonic method is employed in the characterization and non-destructive evaluation of industrial materials, such as paper, wood, and advanced composites [ 29 , 32 ]. In particular, recent studies demonstrated that the propagation of leaky Rayleigh waves is sensitive to phase change of cementitious materials [ 33 , 34 ]. Likewise, this technique could be used to assess the spatiotemporal variations of soil moisture without soil disturbances.…”

Research on the 3D Reverse Time Migration Technique for Internal Defects Imaging and Sensor Settings of Pressure Pipelines

“…Its merits include high sensitivity, compact equipment, and a non-invasive nature that poses no risks to both human health and environmental quality [13]. UT can proficiently ascertain flaw dimensions, identify crack locations [14], delamination location, and determine the stacking sequence of composites [15][16][17] through the propagation of surface waves, guided waves, and body waves [18,19]. Subsequently, employing ultrasonic imaging methods allows for the intuitive visualization of defects within pressure pipelines [20][21][22].…”