The Contribution of Elastic Wave NDT to the Characterization of Modern Cementitious Media

Lefever, Gerlinde; Snoeck, Didier; Belie, Nele De; Vlierberghe, Sandra Van; Hemelrijck, Danny Van; Aggelis, Dimitrios G.

doi:10.3390/s20102959

Cited by 33 publications

(35 citation statements)

References 45 publications

(68 reference statements)

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“…The relatively large fraction of unhydrated cement in the reference sample, i.e., 18 ± 2%, demonstrates the low water-to-cement ratio, causing incomplete hydration of cement particles, beneficial for self-healing [ 24 , 51 ]. Similar to the outcome of TGA, where a higher amount of bound water was seen, the addition of SAPs led to an increase in the amount of hydration products formed and a subsequent decrease in unhydrated cement.…”

Section: Resultsmentioning

confidence: 99%

The Influence of Superabsorbent Polymers and Nanosilica on the Hydration Process and Microstructure of Cementitious Mixtures

et al. 2020

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Superabsorbent polymers (SAPs) are known to mitigate the development of autogenous shrinkage in cementitious mixtures with a low water-to-cement ratio. Moreover, the addition of SAPs promotes the self-healing ability of cracks. A drawback of using SAPs lies in the formation of macropores when the polymers release their absorbed water, leading to a reduction of the mechanical properties. Therefore, a supplementary material was introduced together with SAPs, being nanosilica, in order to obtain an identical compressive strength with respect to the reference material without additives. The exact cause of the similar compressive behaviour lies in the modification of the hydration process and subsequent microstructural development by both SAPs and nanosilica. Within the present study, the effect of SAPs and nanosilica on the hydration progress and the hardened properties is assessed. By means of isothermal calorimetry, the hydration kinetics were monitored. Subsequently, the quantity of hydration products formed was determined by thermogravimetric analysis and scanning electron microscopy, revealing an increased amount of hydrates for both SAP and nanosilica blends. An assessment of the pore size distribution was made using mercury intrusion porosimetry and demonstrated the increased porosity for SAP mixtures. A correlation between microstructure and the compressive strength displayed its influence on the mechanical behaviour.

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Section: Resultsmentioning

confidence: 99%

The Influence of Superabsorbent Polymers and Nanosilica on the Hydration Process and Microstructure of Cementitious Mixtures

et al. 2020

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“…These processes include water mobility through the pores, as well as shrinkage of the swollen SAPs particles towards their original size after releasing their water and leaving empty cavities (of approximately 250 μm) in the matrix. These processes emit elastic waves and they have been recently monitored by AE [ 19 ]. In addition, SAPs delay the hydration, due to the absorption of alkali ions, which dilutes the initial ion concentration and decelerates the hydration reaction.…”

Section: Methodsologymentioning

confidence: 99%

Chasing the Bubble: Ultrasonic Dispersion and Attenuation from Cement with Superabsorbent Polymers to Shampoo

et al. 2020

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This study aims to experimentally investigate the ultrasonic behavior of fresh cement focusing on the contribution of the entrapped air bubbles. Frequency dispersion and attenuation carry delicate information that is not possible to gather by traditional ultrasonic pulse velocity. This is measured by simple indicators that quantify the frequency dependence of propagation velocity of longitudinal waves through fresh cementitious media. It seems that dispersion shows much stronger sensitivity to the microstructural processes, since the presence of superabsorbent polymers in mortar induces a large difference in dispersion parameters when compared to reference cement mortar, while only marginal difference in threshold-based pulse velocity. To reach this aim, references are taken from, and comparisons are made to other liquids in order first in order to validate the reliability of the methodology and to better understand the contribution of the cavities in the obtained dispersion and attenuation curves. Ultrasonic dispersion assessment of cementitious media has the potential to bring a lot of information on the microstructure of materials, as well as the ongoing processes.

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“… Acoustic emission set-up for fresh monitoring: ( a ) top view showing two opposing sensors attached to the longitudinal walls by means of magnetic holders and ( b ) side view showing the bottom sensor (reprinted from [ 20 ]). …”

Section: Figurementioning

confidence: 99%

“…Two piezoelectric sensors, attached to an instrumented steel ring for autogenous shrinkage measurements, captured an elevated amount of hits closely after setting, revealing the onset of internal curing. A deeper investigation of the received wave parameters showed that the internal curing mechanism exhibited a peak intensity period, likely during which most of the water is released to the surrounding matrix [ 20 ]. AE therefore provides a non-destructive, easily applicable technique to monitor the internal curing process.…”

Section: Introductionmentioning

confidence: 99%

Elastic Wave Monitoring of Cementitious Mixtures Including Internal Curing Mechanisms

Lefever

Snoeck

Belie

et al. 2021

Sensors

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The mitigation of autogenous shrinkage in cementitious materials by internal curing has been widely studied. By the inclusion of water reservoirs, in form of saturated lightweight aggregates or superabsorbent polymers, additional water is provided to the hydrating matrix. The onset of water release is of high importance and determines the efficiency of the internal curing mechanism. However, the monitoring of it poses problems as it is a process that takes place in the microstructure. Using acoustic emission (AE) sensors, the internal curing process is monitored, revealing its initiation and intensity, as well as the duration. In addition, AE is able to capture the water evaporation from saturated specimens. By ultrasonic testing, differences in the hydration kinetics are observed imposed by the different methods of internal curing. The results presented in this paper show the sensitivity of combined AE and ultrasound experiments to various fundamental mechanisms taking place inside cementitious materials and demonstrate the ability of acoustic emission to evaluate internal curing in a non-destructive and easily implementable way.

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The Contribution of Elastic Wave NDT to the Characterization of Modern Cementitious Media

Cited by 33 publications

References 45 publications

The Influence of Superabsorbent Polymers and Nanosilica on the Hydration Process and Microstructure of Cementitious Mixtures

The Influence of Superabsorbent Polymers and Nanosilica on the Hydration Process and Microstructure of Cementitious Mixtures

Chasing the Bubble: Ultrasonic Dispersion and Attenuation from Cement with Superabsorbent Polymers to Shampoo

Elastic Wave Monitoring of Cementitious Mixtures Including Internal Curing Mechanisms

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