Stay informed! Subscribe to the
Traditional Masonry
Newsletter
Synopsis
The Brooklyn Bridge in 1894.
The Return of American Natural Cement
Learn about the history of American natural cement, the differences between natural cement and portland cement, and why there is an increasing interest in this natural building material. by Susan Brimo-Cox
If you don’t know what natural cement is, you’re not alone. Even experts in traditional and historic masonry have been scratching their heads when the topic of “natural cement” is raised. Part of the problem is that natural cement use in the United States had a strong burst of use in the 19th century, but was quickly overtaken by portland cement from 1900 on. Now, as restoration and conservation activities increase on buildings constructed in the 1800s, the industry is relearning about American natural cement.
American natural cement rock was formed a very long time ago. Kurtis Burmeister, assistant professor of geology at University of the Pacific in Stockton, Calif., has studied American natural cement geology in the Rosendale region of New York. “I always get a kick trying to explain that the binder is ground-up remains of sedimentary rock deposited 420 million years ago in a world very different from today,” he says.
The rocks used to make natural cement include dolostone or limestone. Limestone is essentially calcite. Calcite plus magnesium makes dolomite. Dolomite forms dolostone when combined with fossils and some clay content. This ideally balanced, naturally occurring rock makes natural cement that needs no additives.
Because of the natural history of the land mass that became the United States, there are many areas where you find these kinds of rocks, Burmeister explains. Sedimentary rock, like dolostone and limestone, is deposited in shallow seaways. A good portion of the American continent was a shallow sea at one time. Natural cement rock has been found in New York, Pennsylvania, Maryland, Virginia, Georgia, Kentucky, Indiana, Illinois, North Dakota, Wisconsin and other states. In mountainous areas, such as along the Appalachians, originally flat layers of rock were uplifted and folded. Then, centuries of weathering exposed the underlying rock.
