Monitoring of autogenous crack healing in cementitious materials by the nonlinear modulation of ultrasonic coda waves, 3D microscopy and X-ray microtomography

Abstract

In this work the non-destructive monitoring of the self-healing progress of cracked mortars is presented through the use of three combined methods: nonlinear Coda Wave Interferometry, 3D microscopy and X-ray computed microtomography (CT). The aim of the acoustic method is to compare, at various healing stages, both the ultrasonic velocity variations and decorrelation coefficients between a reference coda signal and a signal perturbed by a high level lower-frequency elastic wave. The decrease in the relativevariation of the extracted nonlinearities demonstrates its ability to accurately monitor global crack filling.3D microscopy also reveals this capability. Measurement results of these two techniques agree for the influence of age at cracking on healing potential. In reducing the voxel size to 12 l m, X-ray CT images confirm the creation of localized bridges between crack faces and provide information on their location

Determination of volume and distribution of pores of concretes according to different exposure classes through 3D microtomography and mercury intrusion porosimetry

“…It consists of a technique that verifies images of the sample's total volume sequentially . Moreover, this technique has been used as a means to identify the formation of cracks on cementitious materials and correlate the results to the lifespan of the structure …”

“…18 Moreover, this technique has been used as a means to identify the formation of cracks on cementitious materials and correlate the results to the lifespan of the structure. 19 Considering the need to understand properties of concrete through diagnostic tests, four concrete compositions were mixed under parameters set by Eurocode 1 (EN 1992-1) and EN 206-1, according to the aggressiveness of the environment that the structure is exposed to. The aim was to assess the relation between tests of MIP and 3D microtomography and the mechanical properties of the material.…”

Validation of Self‐Healing Properties of Construction Materials through Nondestructive and Minimal Invasive Testing

“…When the X‐ray radiography images are combined after scanning the sample over 360° to obtain a tomography, this approach can be used to confirm the creation of localized bridges (healing product) between the cracks faces and can confirm their location within the crack . The results found by the latter researchers corresponded with other nondestructive tests used in that research, which were nonlinear modulation of ultrasonic coda waves and 3D microscopy.…”

“…But in this way, the healing products can easily be investigated, using a portable UV lamp. If the crack depth morphology and/or the volume of healing crystals need to be known, a 3D microscope can be used . By using this 3D representation, conclusions may be drawn on the extent of healing, the morphology of the crystals and their structure.…”

“…In time domain, the velocity of the ultrasonic signals (derived out of the “time of flight”) is an important parameter of the signal . Other useful information for the characterization or monitoring of concrete structures, mainly based on coda waves, can be provided by the amplitude or energy of the full signal waveform in terms of coda wave interferometry . A transformation into the frequency domain can give further insight into material properties.…”