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