Features | Technical Information Corrugated & Flat Permanent Formwork Glassfibre Reinforced Concrete (GRC) has been extensively used as permanent formwork for the past twenty years, corrugated or flat to suit all supporting beam design. The extent of its success and its practical application can be illustrated by the fact that more than 45 000 square metres were used on various bridge and tunnel contracts during the construction of the M25 alone and that many hundreds of thousands of square metres have been used world-wide.

Recent Projects

Road and Rail Bridge Permanent Formwork for M6 Guards Mill Project (M6 at Gretna)

Features

GRC formwork has excellent performance characteristics and its inherent material properties provide the specifier and contractor with a permanent surface skin to the bridge deck concrete which:

• has a thin cross section, yet provides durability and steel protection equal to much thicker concrete cover
• has a high resistance to fire and will not emit toxic fumes
• eliminates spalling of exposed faces
• provides flexibility for pouring sequences and concreting schedules, which can reduce construction time
• enables the final appearance of the deck structure to be assessed on-site before concrete is poured

Practical and Economical

GRC permanent soffit formwork, produced specifically to suit all forms of structures, provides both a practical and economical way of supporting freshly poured in-situ concrete in composite bridge decks. Dependant upon the depth of the concrete deck formwork, spans up to 1200mm do not require temporary support. However, in the case of steel beam designs requiring greater spans, a specialised system for supporting the GRC formwork can be used. In either event, GRC panels - whether flat or corrugated - are designed to meet the stringent conditions laid down in DOT 36/90.

Flexible Formwork manufactured from GRC is capable of supporting various slab thicknesses over a variety of spans between main bridge beams. In addition, it's characteristics allow it to behave as a composite part of the in-situ concrete under normal in-service dynamic loading. Available in thin panels, in either flat sheet or corrugated form, GRC formwork remains in contact with and becomes bonded to the in-situ concrete over the full surface area of the panel. Available in a standard range of panel sizes or produced specifically to suit individual projects, GRC formwork is delivered to site ready to use.

Recommended

The use of GRC single skin bridge deck formwork is recommended in the Department of Transport's Highways and Transport Advice Note BA36/90.

Tested

Tensile tests carried out on specimens taken from actual contracts show that the bond between GRC permanent formwork and the concrete it supports, is generally stronger than either parent material.

This virtue was recognised by the Norwegian Roads & Bridges Department over twenty years ago when it approved the inclusion of GRC formwork within the specified cover thickness to reinforcement.

More recent tests, carried out in the UK in the late 1980's, confirmed the superior protection provided ed by GRC to the steel reinforcement when compared with concrete. These tests also showed a greater resistance than concrete to chloride penetration.