Mechanical Characterization of a Basalt Fabric for TRM Composites: Role of the Test Variables

Textile reinforced mortar (TRM) materials are currently receiving great attention for the strengthening of reinforced concrete and masonry structural elements. Mortars with different strength classes have been coupled with different kind of synthetic fabrics, such as carbon, glass, steel, PBO. Recently natural fibres and, in particular, basalt fibres are receiving increasing interest since they proved to be a promising alternative to the most common synthetic fabrics, thanks to the reduced production costs and the consequent benefits in terms of environmental impact. This paper presents an experimental investigation comprising forty-one monotonic tensile tests on textile strips made with a primed basalt fibre bidirectional grid. The tests were performed considering the influence of different setup variables, such as the clamping system, the size of the specimens, the measurement device and the testing elongation rate. Part of the tests was carried out by using a video-extensometer for the measurement of the strains, taking advantage from the digital image correlation (DIC) technique. The goal of the work was to find the most suitable configuration for the mechanical characterization of basalt grids, in order to fully exploit the tensile strength. The results showed to be influenced by the different test setup parameters considered. In particular, the outcomes were affected by the slippage of the grid at the gripping zone and by the testing rate.