The evolution of masonry mortar in America has undergone many interesting changes over the last two centuries. The ingredients of mortar, methods of producing mortar, and specifications have all changed in some way. Many of these discoveries originated in Europe and eventually reached America many decades later. For example, Smeaton’s discovery of hydraulic lime in 1756 was not fully realized in America until the building of the Erie Canal in 1817, some 61 years later. The English discovery of portland cement by Joseph Aspdin in 1824 took 47 years before it was ever manufactured in the United States in 1871.
The development of masonry cement in the 1920s was the most interesting of mortar developments in the United States. The relationship between the cement and lime industries has been strained ever since, due to the fact that masonry cement was the first formulated mortar product that did not contain hydrated lime as a major ingredient. As a result, two sides of the mortar industry have evolved since the early 1930s. Some promote mortar products with hydrated lime, and some promote mortar products that do not contain hydrated lime.
The methods of producing cement and lime changed at the beginning of the 2oth century, allowing much more material to be fired in a shorter period of time with the use of the rotary kiln. The use of the mortar mixing machine after World War II and the introduction of the mortar silo systems after 1988 were both substantial improvements that directly influenced the methods of mixing mortar at the jobsite.
The American Society for Testing and Materials (ASTM, 1902) has been instrumental in providing the construction industry with voluntary standards on mortar products. The society has ultimately pioneered the way to standardization which has lead to better mortar products and more efficient methods of production. By taking this look into our past, it is hoped that we can gain some insight into our future.