Overview of the Mechanical Properties of Steel Reinforced Grout Systems for Structural Retrofitting

Steel Reinforced Grout (SRG) is a mortar-based composite recently developed for structural retrofitting, which provides high tensile strength with limited increase in mass and in stiffness, and whose effectiveness relies on the good interaction between steel cords and inorganic matrices. Many companies already supply SRG systems for rehabilitation activities and the scientific community has been working intensively on experimental and numerical investigations to demonstrate their effectiveness for structural applications, which also led to the inclusion of SRG in national and international standards for product qualification and design. However, a clear view of the mechanical properties of these systems is still lacking, due to their variability, which, in turn, strongly depends upon cord layout, textile architecture, and characteristics of the matrix. This paper provides an overview of the mechanical properties of SRG composites on the basis of the tests carried out at Roma Tre University and of the other experimental evidences available in the literature. The results of tensile tests on bare textiles and SRG coupons with different inorganic matrices, and of bond tests on masonry and reinforced concrete substrates are collected and the performances of the different SRG systems are compared. The influence of the mortar matrix on crack spacing, ultimate strain and tension stiffening in tensile tests is analysed. The capacity of the steel cords to ensure a proper shear transfer through interlocking within the matrix and the effect of cord density on failure mechanisms in bond tests are also discussed.