Mould for concrete elements for first circular viaduct
The Netherlands is going circular – including the construction industry. Increasingly more frequently the industry is turning to circular construction, with the Directorate-General for Public Works and Water Management (Rijkswaterstaat), as major client, in the lead. This is how the first circular viaduct in the Netherlands was built in cooperation with Van Hattum en Blankevoort and Consolis Spanbeton. Hendriks precon supplied the moulds for the production of the concrete elements.
Ease of use was the principal economic model used in recent decades. Acquire, use and throw away, was the ‘motto’. This economic model is no longer appropriate. The work must be performed without generating waste. Rijkswaterstaat aims to be ready for this by 2030. Numerous activities are already being developed for this purpose. One of these activities is the development of a circular viaduct; an engineering structure whose components are reusable after a period of time. Kees Quartel at Consolis Spanbeton: ‘That entails special requirements that must be met; for example, the lifespan of the concrete elements used to build the viaduct. Although viaducts are built to last 100 years, in actual practice they are often modified or demolished after just 30 to 40 years. By contrast, the circular concrete elements are built to last 200 years – sufficiently long to be used a total of five times during their lifespan.’
The circular viaduct’s concrete elements can be reused in their entirety and undamaged at another location. This avoids waste and the unnecessary use of new raw materials. The concrete elements are produced by prefab builder Consolis Spanbeton, which is conveniently using two moulds for this purpose. The moulds were specifically developed for this application by Hendriks precon.
The concrete elements all are of the same dimensions, namely 2.5 x 1.5 x 1 metres (l x w x h). ‘In the Consolis Spanbeton’s plant, the concrete elements are connected together by prestressing them in a longitudinal direction to make them continuous. The elements are fitted with voids for this purpose through which the cables are pulled,’ Mr Quartel explains. ‘This way, the elements are transformed into girders for spans of 15 to 25 metres. The dimensioning of the elements makes it possible to span various distances.’ At the construction site, the girders constructed with the concrete elements are in turn assembled into a road deck through means of transverse prestressing. The cables are installed in the round recesses in a transverse direction. The longitudinal and transverse prestressing cables are encased in a material that protects them from corrosion.
Hendriks precon developed two moulds for the efficient production of the concrete elements. ‘As a Spanbeton partner, Hendriks precon was involved in the project at an early stage,’ Kees Quartel explains.
‘A Programme of Requirements and precise specifications were developed in advance for the moulds. Hendriks precon then translated these into a formwork mould. The formwork’s side panels can be rotated hydraulically and the end-panels can be opened hydraulically and then moved out. The design is such that the blocks interlock with each other at the ends and sides. The mould is fitted with tapered recess formers for this purpose. The recesses ensure that the concrete elements precisely fit together for the purpose of absorbing the vertical forces. Consolis Spanbeton specified strict criteria for the dimensional stability of the elements. After all, it must be possible to use them the same way and with the identical dimensioning for a subsequent project.’ To guarantee the dimensional stability, the formworks were measured 3-dimensionally by Hendriks precon after production.
In addition to concrete blocks with recesses, the same formwork mould can also be used to produce the end-elements for the viaducts. These massive blocks constitute the connection to the land abutment. A total of 40 concrete elements are incorporated into the circular viaduct, of which 30 with voids and 10 that are solid.