In Defense of Natural Cement

There are a number of opportunities for academic research related to the historic concrete fortifications at Fort Totten at Willets Point in Queens, NY. Built by U.S. Army Corps of Engineers (USACE), whose headquarters was at Willets Point, these structures incorporate three significant fortification periods, including the Third System (1863-1867), the Post-Civil War era (1867-1884) and the Endicott period (1891-1905). These late 19th century structures represent a transformative period in the technological development of concrete which evolved from a simple mortar containing rocks to bulk out the mix, to an interdependent mixture of binder, sand and aggregate. In addition, the first fortifications at Fort Totten were built during the heyday of the natural cement industry and the last fortifications coincided with its demise, as portland cement came to dominate the market. The rivalry between American natural and portland cement manufacturers was fierce, and the biases engendered on both sides persisted long after the natural cement industry collapsed in the early 20th century. This has translated into the conventional view that there was an inherent problem in the natural cement concrete used to build these fortifications. However, for reasons of economy, the Corps of Engineers were prevented from using portland cement, until advances in domestic manufacturing permitted a reduction in costs. Through historical and archival research, as well as the petrographic analysis of concrete samples, a more detailed assessment of the concrete used at Fort Totten was conducted. Using polarized light microscopy an analysis was conducted on the binder, the aggregates, the gradation, the water/cement ratio, and any deterioration in order to evaluate changes in the concrete mix design over time. These observations were then related to a conditions survey of the concrete structures at Fort Totten, to assess the performance of the concrete used to build these historic structures. Laboratory work for this thesis was conducted at Columbia University GSAPP’s Historic Preservation Conservation Laboratory and at Highbridge Materials Consulting, Inc.