Discrete element modeling and electron microscopy investigation of fatigue-induced microstructural changes in ultra-high-performance concrete

In view of the growing demand for sustainable and lightweight concrete structures, the use of ultra-high-performance concrete (UHPC) is becoming increasingly important. However, fatigue loads occur more frequently in nature than static loads. Despite the impressive mechanical properties of UHPC, a reduced tolerance for cyclic loading is known. For this reason, our paper deals with experimental and numerical investigations regarding the main causes for crack initiation on the meso, micro, and nanoscale. After mechanical fatigue tests, we use both scanning (SEM) and transmission electron microscopy (TEM) to characterize microstructural changes. A new rheological model was developed to apply those changes to the mesoscopic scale. The origins of fatigue damaging can be traced back to a transformation of nanoscale ettringite, resulting in a densification of the surrounding binder matrix. Additionally, a higher content of unhydrated cement clinker in the matrix benefits fatigue resistance. On the mesoscale, stress peaks around aggregate grains expand into the surrounding binder with increasing load cycles and lead to higher degradation.

Subjects

ultra-high-performance concrete

fatigue

electron microscopy

ettringite transformation

bonded particle model

discrete element method

rheological model

crack propagation

DDC Class

530: Physik

540: Chemie

600: Technik

620: Ingenieurwissenschaften

690: Hausbau, Bauhandwerk

Publication version

publishedVersion

Lizenz

https://creativecommons.org/licenses/by/4.0/

Name

materials-14-06337.pdf

Size

7.05 MB

Format

Adobe PDF

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Discrete element modeling and electron microscopy investigation of fatigue-induced microstructural changes in ultra-high-performance concrete