AIC's 41st Annual Meeting

The U.S. Civil War had shown that fortified masonry structures were effectively obsolete with the advent of rifled cannon fire. Therefore, during the 1870s, the U.S. Military sought improved materials and defensive systems. Concrete was one of these materials, and, combined with reinforced steel rods and earthen embankments; it formed the backbone of the Endicott-Taft Period of Coastal Defensive Works in the United States (1885-1914).
At Fort Totten in Queens, New York, a series of concrete defensive works began in 1870, to replace a masonry fortification begun in 1859, but abandoned in 1867. These included a vehicular munitions tunnel, numerous torpedo and munitions magazines, and finally a series of Endicott batteries. Natural cement was used initially in the 1870s, primarily because it was less expensive than Portland cement. However, reported problems of deterioration signaled the change to Portland cement, and then reinforced Portland cement concrete in the 1890s. Interestingly, the testing of concrete on site was facilitated by the construction of a cement works and the preparation of aggregate on site.
The objectives of this project will be to identify the different types of cast concrete used in the fortifications of Fort Totten, as well as to identify the cement binders, aggregate, and mix proportions. The qualitative differences in the types of concrete used in the fortifications will also be examined, in order to see if the complaints about the natural cement concrete were justified, and whether this was due to the cement itself or the mixture. Furthermore, the project will attempt to determine how much deterioration of the concrete and corrosion of the rebar have occurred since they were built, given their coastal location, and whether there any traces of Alkali Silica Reaction is present. Core samples (3 ½ inch diameter) will be taken from selected structures, and a variety of testing methods will be employed for this project, include X-Ray diffraction, compressive strength tests, and thin section petrography.
The project will also examine the on-site methods of concrete manufacture, focusing on the cement works and the aggregate crushing. These will be documented primarily using the records of the US Army Corps of Engineers at the National Archives. Finally, the project will try to determine whether the lessons learned about the use and manufacture of concrete at Fort Totten were implemented at other coastal fortifications.
This project will form the basis of a Masters Research Thesis at Columbia University, under Professor Norman R. Weiss, and is facilitated by the Director of Preservation at the New York City Parks Department. In addition, laboratory and sampling equipment will be supplied by John Walsh of Highbridge Materials Consulting.