As a manufacturer of innovative construction products for the static-construction sector, Schöck has built an enviable reputation, mainly through its core competencies in the noise insulation and thermal insulation fields. In the last few years however, reinforcement technology has become another mainstay of this specialist construction industry supplier from Baden-Baden in southern Germany.

For concrete reinforcement requirements, steel has been used almost exclusively, but there are special considerations when faced with issues such as corrosion resistance, electrical insulation and chemical attack – areas in which steel is found wanting. The Schöck ComBAR system really comes into its own in these situations. It is a glass fibre reinforced polymer (GFRP) reinforcing bar which offers all the benefits of steel in terms of design, tensile strength and bonding properties, but it is also much lighter and easier to handle.

The key to ComBAR’s special properties as a reinforcing bar is the pultrusion manufacturing process. Basically, this is a method by which the raw materials – plastic resin and continuous glass fibre – are ‘pulled’ together under heat, rather than ‘pushed’ as in the case of extrusion, to form a composite rod which is ideally suited to applications where high strength, thermal stability, weather and corrosion resistance are required. With its ribbed surface and a bond behaviour and stability comparable to BST 500, ComBAR is particularly suitable for applications involving tunnel construction, where the reinforcement must withstand enormous forces. Partly this results from the constant pressure of the earth – which makes special demands on the tensile strength of the material – and from tunnelling heads with diameters of more than 13 m which are driven through the head walls of the launching shafts and also through the shaft reinforcement.

New Amsterdam subway uses 75 tons of ComBAR

The new North-South route of the Amsterdam subway, currently under construction, is certainly a project that has helped change people’s thinking in terms of reinforcement for international tunnel projects. More than 75 tons of Schöck ComBAR glass fibre reinforcement is embedded in six diaphragm walls and a reinforcement cage is braided with straight bars, stirrups and double headed bolts, which will then be concreted to provide the required stability of the diaphragm wall. The low material weight simplifies the processing during the reinforcement layout. Tunnel construction though is only one of the possible Schöck ComBAR application areas. Since this exceptional material has thermal separation effects and is also non-magnetic and electrically insulated, this glass fibre reinforcement can also be used in housebuilding, road works, harbour building, medical facilities, power supply facilities or as foundations in corrosive ground. 

Schöck began developing the glass fibre reinforced polymer reinforcing bar as early as 1995 and after a four year transition period, during which the company acted as the sole distributor for an American product under license in Europe, started proprietary development in 2000. The final outcome was an improved reinforcing bar that met the standards of the Munich Institute for Building Materials and Construction; the Darmstadt Institute for Materials and Mechanics in the Building Trade; the Erlangen Chair for Plastics Technology – and last and certainly by no means least, the German Federal Environment Foundation which has made an essential contribution to the development of the product during the last three years.

Product- and technical Papers and further information to Schöck ComBAR® you find  H E R E