Mechanical characterization of multi-ply steel reinforced grout composites for the strengthening of concrete structures

The use of externally bonded Steel-Reinforced Grout (SRG) composites, comprising Ultra High Tensile Strength Steel (UHTSS) textiles embedded in an inorganic mortar matrix, has been shown to provide an effective and costefficient solution for the repair and strengthening of existing structures. Although several studies have been carried out in the last decade to investigate the SRG-to-concrete bond behaviour, most of the existing literature examines the use of systems with a single layer of steel textile and only limited information is available on multi-ply SRG composites, which are often required for applications to large structural elements. This paper presents the preliminary results of an experimental study on SRG systems comprising multiple layers of galvanized UHTSS textiles within a geopolymer mortar. The investigation comprises three stages: 1) direct tensile tests on SRG coupons to characterize the tensile properties of the composite system; 2) lap-splice tests (for overlap length ranging from 100 mm to 300 mm) to develop an improved understanding of the textile-to-textile load transfer capacity; 3) single-lap bond tests to examine the effect on bond behaviour of number of steel textile plies (one, two or three) and steel cord density (4 and 8 cord/in) on concrete substrates. Digital Image Correlation (DIC) was used to obtain full-field displacement measurements and map crack development.