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Cement was produced in the Lehigh Valley during this period using the English intermittent vertical kiln. A student thesis at Lehigh University provides a detailed account of manufacturing at the American Improved Cements Co. First, the raw materials, a combination of limestone and clay, are quarried. Then the materials are formed into bricks, weighing about four pounds. These bricks are then dried for about twenty-four hours. The bricks and coke are loaded into the large vertical kilns and then burnt for about 72 hours. The kiln is then let to cool down for 10 hours and the bricks removed. The bricks have been cooked to a very hard material referred to as clinker. This clinker is then ground into Portland cement. Note two features of this production process. First, the cement produced is not of a uniform quality as heating is not uniform throughout the kiln. This required sorting of the cooled clinker by hand into cements of different grades to be sold. Second, a considerable amount of labor is required to handle and prepare the raw materials for the kiln, and then unload and sort the clinker.
In 1890, the United States Geological Survey estimated that the Lehigh Valley produced 60% of Portland cement produced in the United States. However, their statistics do put this success into context. Just 3.5% of the 9.7 million barrels of cement consumed in the United States was American manufactured Portland cement. 20% was imported Portland cement, mainly from England and Germany, and the remaining 76.5% was American natural cement.
Why had the American Portland cement industry not grown faster? The first problem was that while American manufacturers used the same labor-intensive technology as the Europeans, they would have higher costs as wages were higher in the United States. Second, American Portland cement sold at a lower price than imported Portland cement because it was perceived (and in the main was) lower quality. German and English Portland cements had excellent reputations. The cheaper Rosendale cement also had an established reputation, as well as being cheaper to make. Portland cement was protected by tariffs but shipping costs were low as imported cement came across to the United States as barrels of ballast for the holds of the sailing ships that would return to Europe with American exports. These conditions made it difficult for American cement manufacturers to operate profitability.
But from 1890, production in the Lehigh Valley rose from 201,000 barrels to, by 1913, reach 27.1 million barrels out of 92.1 million barrels nationally. Simultaneously the real price of Portland cement fell from $8.43 a barrel in 1890 to $4.86 in 1902 to $3.34 in 1913 while the quality improved considerably. Natural cement and imports made up less than 1 per cent of consumption in 1913.
