In the study at hand the Joule heating effect of electrically conductive cementitious nanocomposites filled with different loadings of multi-walled carbon nanotubes (MWCNTs) is investigated. Nanofiller dispersions were initially prepared via ultrasonication in deionized water (d-H 2 O) utilising a commercial superplasticizer as surfactant. Electrically percolated nanocomposites were fabricated via shear mixing and subsequent casting into moulds. Storing the prepared samples under different humid conditions enabled explanation of the role of water content as well as cement age on Joule heating performance. All prepared specimens were investigated at ages of 3 d, 7 d and 28 d by applying two different DC bias voltages. Infrared-thermography (IR-T) images were recorded after 1 min, 5 min and 10 min in order to visualize the differences in the Joule heating effect as a function of time, keeping contact with the DC bias voltage. The observed results showed a significant dependency of the Joule heating effect on water content as well as on filler concentration. Moreover, increasing cement age provided more effective electrical heating. This work elucidates the complexity of the electrical heating phenomena occurring in cementitious/MWCNT nanocomposites via the well-known Joule heating effect because it contributes to the understanding of the underlying mechanism. The main parameters used and the corresponding results are envisaged to be applicable for large-scale, heatable concrete structures in future respecting buildings temperature, aerial control, de-icing, thermal management, and better energy efficiency, etc.

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Strain-hardening cement-based composites are a promising class of materials for a wide variety of applications due to their considerable tensile strength and pronounced ductility caused by the development of multiple fine cracks. Nevertheless, the safe use of such composites requires sound knowledge of their mechanical behaviour under different types of loading, particularly under fatigue loading, while considering distinct influences like initial crack width and fibre orientation. To deepen this knowledge, single-fibre pull-out tests on PVA-fibres from a cementitious matrix were carried out to gain information about the micro-mechanical and degradation processes of the fibre. It could be shown that the fibres tend to rupture instead of being pulled out under quasi-static loading. When changing the loading regime to alternating loading, this failure mechanism shifts to pull-out. By varying the experimental parameters such as initial crack width, inclination angle or compressive-force level a clear influence on the fibre’s crack bridging capacity could be observed associated with effects on the degradation processes. Based on the data obtained, a micro-mechanical numerical model was developed to support the assumptions and observations from single-fibre pull-out tests and to enable predictions of the performance of the material on the microscale under cyclic loading.

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