Bridges presentation
(Figure 8). Here, the central pier was built on a wrought-iron caisson 37ft (11m) in diameter, sunk to
bedrock in 70ft (21m) of water and 16ft (5m) of mud.
Another improvement in foundations in the early 19th century involved hydraulic cement. A better
scientific understanding of the material by the Frenchman Vicat and the Englishman Aspdin and
discovery of the material in a natural state in 1796 on the Isle of Sheppey in the Thames estuary, by
Lafarge at Le Teil (France), and by Canvass White on the Erie Canal in New York in 1818, led to its
use in sinking foundations by the new method of direct flow into coffer dams underwater, as at the
suspension bridge at Tournon (France) in 1824. Hydraulic cement had the amazing ability to set
under water, and was consequently used in aqueducts, piers and abutments, culverts, and locks.
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