Experimental evaluation and numerical modelling of bond-slip behaviour in textile-reinforced concrete

Textile reinforced concrete (TRC) is a lightweight and efficient composite material composed of continuous fabrics embedded in fine-grained concrete. Existing studies mainly focused on the use of TRC as a repair material, as well as for aesthetic purposes. The usage of TRC as a structural member is still in its infancy, due to the complex modelling issues, particularly on the bond-slip relation. The pull-out capacity, bond length, and interface modelling must be established in order for this material to be utilized structurally. These challenges are addressed by characterizing the bond-slip behaviour through experimental work, developing numerical bond-slip models, and incorporating the bond-slip model through the tensile test of TRC specimens. First, the suitable materials were selected based on their mechanical performance. Pull-out tests were conducted on a single fibre embedded in a cement-based mortar with different bond lengths (20 mm to 60 mm). Later, two bond-slip models (Model-I and Model-II) were introduced in the numerical modelling to simulate the pull-out response of fibre. In Model-I, bond-slip parameters were calibrated from pullout tests with simplified assumptions, while Model-II incorporated an analytical approach with progressive damage and friction degradation stages. Subsequently, uniaxial tension tests (stress- strain behaviour, and failure modes) were performed on TRC plates with multiple layers to explain its global structural behaviour. Finally, numerical models were developed, considering bond-slip responses (20 mm and 60 mm bond lengths) obtained from pull-out curves to simulate the tensile response of the TRC plates with multiple layers of reinforcements. The results conclude that the specimens with shorter bond lengths (20 mm, 30 mm, and 40 mm) failed due to fibre pullout while longer bond lengths (50 mm and 60 mm) failed due to fibre rupture, with maximum pullout capacity. The numerical models utilizing Model-II bond-slip relation performed better, showing a 3.6% pullout load difference compared to tests, while Model-I showed slightly higher deviations of 6.36%. It also over-predicted the relative displacement, causing an earlier friction phase initiation affecting overall stiffness. The uniaxial tensile tests revealed that the increasing textile layers enhance the load-carrying capacity. The numerical analysis (Model-II) revealed that the samples with a 20 mm bond-slip relation matched test results, with a stress difference of 5.9%. Samples with a 60 mm bond-slip relation exhibited higher stresses (18%) and increased fibre displacement. It is found that Model-II performed better compared to other studies reported in the literature. In addition, shear tractions and relative displacements of the textile were evaluated, explaining the load transfer mechanism in different stages. The novelty of the work lies in identifying a precise bond-slip relationship to accurately predict the interfacial responses in TRC. The developed numerical method predicts the bond-slip behaviour and optimizes bond lengths for accurate pullout response. The outcome of the developed numerical models can advance TRC design and its application in the industry. This research benefits the construction industry by optimising multi-layered textile-reinforced concrete elements and facilitates the design of lightweight shell structures.

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