Experimental investigation of tensile fatigue behaviour of Textile-Reinforced Concrete (TRC): Effect of fatigue load and strain rate

Abstract

The objective of this study is to provide, by describing the experimental approach, a detailed description of the behaviour of multilayer Textile-Reinforced Concrete (TRC) composites under axial (tensile) olygocyclic fatigue. Different multilayer TRC composite configurations are proposed based on the carbon grid and glass grid associated with the carbon and/or glass fibre rods. A parametric study is conducted to validate the performance of these composite configurations with fatigue loads of 60% and 80% of the rupture load over 100 cycles. The experimental results show an increase in the rigidity and the dissipative capacity of the composite under fatigue loading with an invariance of the degradation mechanisms. An improvement in composite performance is observed with the addition of carbon and/or glass rods. Damage to composite during experiments is characterized by cracks orthogonal to the effort; their density is proportional to the applied fatigue load. The monotonous tensile tests (Post Fatigue) show that global and macroscopic performances have not declined after 100 cycles. The latex resin integration allows an improvement in residual capacities of composites that are subjected to cyclic tensile loading of up to 1000 cycles. The TRC composite performance increases with the rate of loading in the case of reinforcement with large size mesh.

Introduction

Textile-Reinforced Concrete (TRC) composites are a new generation of fibre-cement materials and are distinguished by the continuity of their textile reinforcement, which is a grid of multi-strand fibres (e.g., carbon, glass, and aramid) arranged in two directions, which are typically orthogonal. These composites are also distinguished by the necessity to have a cement matrix with a suitable particle size for textile reinforcement. This condition for the matrix enables both an enhancement of the yarn impregnation and easy filling without deficiency of the textile reinforcement. TRC composites have attracted the interest of a wide scientific community [1], [2], [3], [4], [5], [6], [7]. TRC composite materials are known for a significant improvement of the bearing capacity and ductility [8] with respect to existing mineral-based solutions. In particular, TRC composite use is fully justified in the context of structural applications that require high and ultimate performances with lightness or fine thickness as an externally strengthening material [9]. Thus, in the framework of structural rehabilitation, these composites constitute alternative solutions to fibre-reinforced polymer (FRP) composites. They enable one to consider structural composites while attempting to reconcile the advantages of cement matrix traditional composites.

Several authors were interested in the mechanical behaviour under direct tensile of TRC composites [5], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29]. The behaviour of TRC depends on several parameters such as the nature of the textile reinforcement, its mechanical properties, [13], [14], [16], [26], and the volume rate of reinforcement composite, which depends on the number of reinforcement layer and the surface through which it is applied [14], [27]. Recent studies [24], [25] have been devoted to investigate the strain rate effect on the mechanical properties of vegetable TRC composite based on sisal fibres through dynamic tensile tests. These experiments show an increase in tensile resistance and deformation energy with the strain rate but also a decrease in deformation capacity.

To refine and enhance the service performance of TRC composites, the behaviour of these materials under cyclic loading is investigated with a focus on fatigue tests that are representative of the seismic activity with a cycle number below 103 [30]. Indeed, cyclic loading reduces the rigidity of the structure material [31]. Nevertheless, the fatigue study of TRC composites remains a little discussed topic [23], [24], [25]. From this perspective, this work aims to describe in detail the behaviour of the composite TRC with respect to cyclic loading of the direct tensile type according to an experimental approach. Different strengthening configurations are proposed based on carbon and glass grids associated with carbon and/or glass rods that are arranged in parallel to the textile reinforcement layers. A second strengthening alternative is applied, which is the integration of the latex resin. The thickness of the mortar layers between the grids depends on whether latex resin is used and the manual impregnation process. A parametric study is performed to investigate the effect of the fatigue load, loading cycle number, and strain rate. Finally, monotone post-fatigue tensile tests are performed to evaluate the effectiveness of TRC composites against olygocyclic fatigue.