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The New York State Pavilion terrazzo is based on the unbonded sand cushion method; however the makers took liberties with regard to the thickness of the terrazzo layer and underbed and utilized individual tiles rather than a direct pour on site. This latter innovation was no doubt necessitated by the time constraints during construction. Each tile is 2” thick and consists of a 5/8” terrazzo topping, bonded to a 5/8” cementitious underbed, which sits on plywood, which has been bolted to a steel frame that supports and edges the terrazzo tile. The three layers--the topping, underbed and plywood-- are contained within the metal frame and the height from the bottom of the frame to the terrazzo surface is 2”. The plywood was likely ½” to 5/8” thick. The “L” shaped metal frame conceals the underbed and plywood base on all four sides, and holds the plywood on the bottom. The “L” shaped metal frame measures 1” x 1” x ⅛” in thickness, and supports the bottom and sides of the tile. The tiles rest on a sandy concrete slab that was poured during the Tent’s construction. Underneath the “L” shaped metal frame, on the bottom of all the tiles, are protruding metal locks measuring 1” x ½” x ⅛”, and corresponding grooves in neighboring tiles that are designed to link the tiles together in a tongue and groove detail. A thin elastomeric gasket separated each tile frame and allowed for thermal movement.

 
An image taken during the installation of the map reveals the way in which the floor was set in place. Individual 4 foot by 4 foot tiles were placed on top of a section of sandy concrete which allowed for fine tuning, ensuring a level floor.
 

  Materials
Terrazzo is a composite material consisting of chips of marble, quartz, glass or other aggregate in a cement or epoxy binder that can be pigmented for additional color. Traditional terrazzo dates back to antiquity, having evolved from the ancient Roman technique of opus signinum. Terrazzo is poured in place or precast, and cured, ground and polished to a mirror finish to produce a durable and artistic surface. It was introduced in the United States in the late eighteenth century, but became quite popular by the early twentieth century with the advent of Portland cement and the many skilled Italian marble workers who immigrated to America at that time. Today, terrazzo remains a highly versatile and durable floor finish, which is still the material of choice for many public buildings, especially where artistic effect is desirable.
An image taken shortly after the fair opened shows how bright the original terrazzo was. All the elements of the design were intended to appear bright and colorful like a real road map.

Deterioration of any material or construction system may be attributed to its composition, manufacture, installation, environment, and maintenance. The terrazzo floor map of the New York State Pavilion has undergone significant changes since its inception and its deterioration is likely a combination of all the factors listed above. The current conditions identified on the terrazzo pavement include loss, disaggregation, deformation, incipient spalling, and parallel and network cracking ranging from minor to severe.

 

The deterioration of the pavement is also a result of its environment within the Pavilion and the changes that have occurred over the past 40 years. The Tent of Tomorrow was always an open-air structure with a tented roof and an open oculus at the center, which would have protected most of the map from direct contact with rain and snow. The dismantling of the roof in the mid 1970s left the floor completely exposed to the elements. Poor drainage, extreme temperature changes, major vegetation, lack of maintenance, and vandalism have all contributed to the deterioration of the pavement.

 
A thin section of the red terrazzo: glass aggregate with pigmented paste, cross polarized transmitted light, 5x magnification.
 

While the open-air environment of the Pavilion, material composition, and unique manufacture and installation of the terrazzo have influenced its deterioration, an assessment of the entire pavement based on location and severity of conditions was an important part of understanding the patterns of decay and quantifying the number of tiles in various states of condition. Two condition assessments were completed in 2007, an overall assessment of every tile of the map and a detailed assessment of the tiles that make up the Long Island portion of the pavement for the pilot conservation project.

 

Both surveys provide important information about the relative condition of the pavement and inform decisions regarding its preservation. Based on the two assessments and the pilot conservation program, which included the full treatment of four tiles, an estimate is now possible on the type and level of intervention needed to conserve the entire pavement.