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Railway Structures
Concrete

The Egyptians used forms of concrete when constructing the pyramids. The Romans used concrete made from pozzolana, an unusual type of sand found near Naples that reacts with water and lime to produce a solid mass. However, it was not until the development of an improved Portland cement in 1824 that concrete was used at all extensively. (Portland cement has nothing to do with the Isle of Portland, but it was suggested that it produced concrete comparable in appearance with Portland stone). Isambard Kingdom Brunel made use of Portland cement in construction of the Thames Tunnel at Wapping.

Concrete, like cast iron, is strong in compression, but weak in tension. It was, therefore, little used during the Victorian heyday of railway construction, save in foundations and for filling hollow structures, such as cast iron columns and bridge spandrels. French engineers developed reinforced concrete, which contained steel reinforcing bars, during the mid-nineteenth century but it was not until the 1880s that the material was widely used in Britain. The oldest surviving concrete bridge in Britain was built in 1870. It carries a road over the River Waveney at Homersfield, near Bungay, Suffolk. The earliest British railway bridge to be built of concrete is believed to be a viaduct on the Callander & Oban Railway, constructed in 1880.

Mass Concrete Mass Concrete, photographed on 2nd May 2009.

photograph by Gregory Beecroft

 
Reinforced Concrete, photographed on 28th July 2007.

photograph by Gregory Beecroft

Reinforced Concrete

Mass concrete (above left, in a retaining wall) contains coarse aggregate. A finishing screed of much finer concrete has failed. Reinforced concrete (above right, in a bridge parapet) contains steel wires and finer aggregate. In this case water has penetrated sufficiently far into the concrete to cause the steel to rust. Steel expands when it rusts, resulting in the concrete surface spalling off.

Hockley Viaduct
Hockley Viaduct, photographed on 18th April 2009.

photograph by Gregory Beecroft

One of the oldest concrete railway structures in Southern England is Hockley viaduct, at Winchester on the Didcot, Newbury and Southampton Railway. The piers are of concrete, though brick-clad. The viaduct was completed in 1891 and is noteworthy as the largest railway bridge in Hampshire, having 33 arches and being 614 metres long. It is now in the ownership of Winchester City Council.

Another early concrete viaduct was Cannington Viaduct, on the Lyme Regis branch.

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