Innovative solutions for structural reinforcement

Dr. Günther Kast GmbH & Co

Founded sixty years ago, the company Dr. Günther Kast GmbH & Co. Technische Gewebe, Spezial-Faserzeugnisse KG has its Head Office in the town of Sonthofen in Allgäu (Bavaria).

In 2020, Kast intensified their American business by founding the company Kast Technical Textiles LLP. The Kast Group manufactures and markets fibre articles of various kinds (glass, carbon, basalt,  aramid, etc.) for different business sectors such as automotive, composites, construction, etc. In recent years, the use of composite materials in the building sector has been increasing.

Their application succeeds in ensuring the conservation of the building heritage with a non-invasive and at the same time environmentally sustainable approach. They are also attracting greater interest thanks to the profound synergy between research and industry. With this in mind, Kast is concluding, in cooperation with commercial partners, several projects aimed at developing structural reinforcement systems according to the latest Ministerial Guidelines for FRP, FRCM and CRM systems. These systems are currently undergoing certification (CVT) in Italy according to the Guidelines for Qualification and Acceptance on Site. In addition, KAST is also investing in European certification (ETA) on GFRP for CRM systems.

GFRP (GLASS-FIBRE REINFORCED PLASTIC)

GFRP consist of glass fibre yarns and thermosetting resin. Due to their high tensile strength and low deformability, these composites are generally used as reinforcement for both concrete and masonry structures. On the latter, CRM systems are increasingly being used, whereby the GFRP mesh is applied using the reinforced plaster technique. This type of application normally also involves the use of preformed corner meshes and connectors.

CRM systems are used with the aim of absorbing shear and tension stresses, which the structural element itself would not be able to withstand. Kast has developed innovative meshes and fabrics for structural reinforcement systems through a strong collaboration with the Karlsruhe University of Technology (KIT) in Germany. Thanks to the scientific support of Prof. Dr. Ing. L. Stempniewski, his collaborators and the Central Innovation Programme for Small and Medium-sized Companies (ZIM) in Germany, several research projects have been carried out and concluded, in which many experimental campaigns were carried out at the Material Testing Institute (MPA) of the Karlsruhe Institute of Technology.

A further project concerning an FRP system with carbon laminates is nearing completion. The company products developed within the framework of the KIT collaboration are the EQ-GRID mesh for the reinforcement of masonry structures with FRCM technology, the EQ-TOP fabric for out-of-plane prevention using FRP systems and the CP-GRID mesh for mitigating diffuse cracking damage due to differential subsidence phenomena in the subsoil.
 

EQ-GRID (EARTHQUAKE-GRID)

EQ-GRID is a special high-performance multi-axial hybrid mesh made of alkali-resistant glass fibre and special synthetic fibres. It has been developed for integration into inorganic matrices based on natural hydraulic lime, generally characterised by a low modulus of elasticity and high ductility. It is suitable for use on new, existing and historic masonry buildings.

The reinforcement is able to avoid the formation of cracks that can lead to the collapse or overturning of the structural element, mitigating the risk of serious personal injury. As demonstrated by in-plane cyclic tests and diagonal compression tests carried out on masonry panels, the multi-axial mesh is able to increase the shear strength by favouring the redistribution of stresses. Thanks to its particular design, it improves the deformation capacity of the reinforced structural element and guarantees greater energy dissipation. In addition, it does not alter the normal breathability of the substrate and is extremely easy to apply.
 

EQ-TOP (EARTHQUAKE-TOP)

EQ-TOP is a glass fibre fabric made of closely spaced threads arranged in vertical and horizontal directions to form a compact and very strong surface. The opening of the mesh allows the fabric to be applied by bonding, as the arrangement of the threads allows good impregnation and solid adhesion to the substrate. As demonstrated by dynamic tests carried out on a vibrating table, EQ-TOP is suitable for repairing and reinforcing infills and secondary elements, in order to improve stress distribution and increase the ductility of the reinforced elements against mechanical stresses. The reinforcement, to be applied externally and/or internally, has a considerable impact on the reduction of seismic vulnerability and is also validly used as reinforcement for anti–shuttering interventions on concrete slabs.
 

CP-GRID (CRACK PREVENTION-GRID)

CP-GRID is a carbon fibre or alkali-resistant glass fibre mesh. The special coating, characterised by considerable mechanical adherence, makes it particularly suitable for reinforcing elements of buildings subject to differential subsidence phenomena, which cause stress concentrations in the elements themselves. In-plane flexural tests were conducted on masonry walls using an inorganic matrix based on natural hydraulic lime. The mesh applied with this type of matrix gave very satisfactory results, being able to absorb very high loads. Significantly, more than 1 million m² of masonry in historical building has been successfully strengthened with reinforcing grids made by Kast; many actual projects are close to their completion.