Natural cement was indeed a magic powder during most of the 19th century when it was used extensively for a myriad of public works and buildings but it had an especially significant synergistic relationship with the construction of canals. The network of canals provided a relatively inexpensive means of shipping cement to market; on the other hand hydraulic cements were essential for the construction of locks, dams, and other canal structures. The synergistic relationship is explored in terms of the Erie, Lehigh, Delaware and Hudson, Chesapeake and Ohio canals and the navigation on the Ohio River. The secret of the "magic powder" rested upon its ability to "set" under water and equally important, the hydrated material was waterproof. Thus, in contrast with lime mortar, hydraulic cement could be used for foundation work and especially for hydraulic structures such as bridge piers and abutments and a wide range of canal structures. Although there were significant pioneering efforts in America by Hyatt, 1816-1901, and in France by Joseph Monier, 1823-1906, Lambot, patent 1855, and Francois Coigent, patent 1861, to overcome the inherent weakness of concrete in tension by the addition of metal reinforcement, the era of reinforced concrete was to wait until the introduction of Portland cement at the end of the 19th and early part of the 20th centuries. (Straub 1964, 208) As a result, natural cement found its greatest application in hydraulic mortar in brickwork and stone masonry. Thus, the discussion will rest on the use of hydraulic cements as a bonding agent in mortar and not in reinforced concrete structural components. The material aspects of hydraulic cements, including Portland cement, are linked to the history of 19' century transportation and industry.
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