Abstract
The use of high-performance polymeric microfibres in enhancing the ductility of cementitious composites is widespread. A vivid example is the application of strain-hardening cement-based composites (SHCCs) in the construction industry. However, there are a few challenges which need to be addressed with respect to material design. For instance, the ductility of SHCC diminishes under alternating tension–compression loading, where the fibres lose their crack-bridging capacity due to specific damage mechanisms. The damage development and its influence on crack-bridging capacity have been studied in previous works by the authors. The paper at hand focuses on the influence of crack width on the crack-bridging capacity of polymeric microfibres in conjunction with the number of cycles in an alternating tension–compression regime with different cyclic compressive force levels. It shows that bridging capacity can be markedly influenced by crack width: an increase in crack width leads to more severe damage to the fibres and thus to lower crack-bridging capacity. Then, after analysing the specimens by means of electron microscopy, a hypothesis is presented to address the effect of crack width on damage development. Finally, a simple approach is proposed for estimating the influence of different parameters on fibre degradation.
Highlights
The use of cementitious materials is repeatedly compromised due to their low tensile strength and brittleness
This paper presents the results of an extensive investigation into the influence of crack width along with the loading parameters in cyclic tension–compression regimes on the bridging capacity of polyvinyl alcohol (PVA)
The influence of small and large crack widths along with different loading parameters such as cyclic bridging stress level in the fibre, cyclic compressive stress level acting on the fracture section of the matrix, and number of cycles have been studied with respect to the development of damage on the PVA microfibres in alternating tension–compression regime
Summary
The use of cementitious materials is repeatedly compromised due to their low tensile strength and brittleness. They showed that the maximum crack width could be over 100 μm at a strain of 0.7%, while the average value pointed to be around 40 μm This finding can be relevant for the evaluation of the crack-bridging capacity of the fibres in alternating tension–compression loading since only critically wide crack openings in a section are expected to affect the ductility of SHCC unfavourably. The influence of small and large crack widths along with different loading parameters such as cyclic bridging stress level in the fibre, cyclic compressive stress level acting on the fracture section of the matrix, and number of cycles have been studied with respect to the development of damage on the PVA microfibres in alternating tension–compression regime. The damage quantification approach proposed by the authors in a previous study [14] has been adapted under consideration of crack width and relevant loading parameters
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