Masonry Magazine October 2004 Page. 18
STONE MATERIALS
By Paul E. Stutzman and Jaime Raz
Inorganic Building Materials Group
National Institute of Standards and Technology
BUILDING STONES OF AMERICA:
Ον
In 1880, the Census Office and the National Museum in Washington, D.C., conducted a study of building stones of the United States and collected a set of reference specimens from working quarries. The census that year reported descriptions of producing quarries, commercial building stones, and their use in construction across the country. This collection of stones, now augmented with the Centennial Collection of U.S. building stones from the 1876 Centennial Exhibition in Philadelphia, as well as building stones from other countries, has moved around over the years, but still serves its purpose as a stone test wall to study the effects of weathering.
Originally on display in the Smithsonian Institution, in 1942 the ASTM Committee C-18 on Building Stone decided that a study of actual weathering on such a great variety of stone would yield valuable information. The committee developed a plan for using the stones to build a test wall at the National Bureau of Standards (NBS) as a cooperative study with NBS. Subsequently, the test wall was constructed in 1948 at the NBS site in Washington, D.C., then eventually moved intact in 1977 to its present site at NBS, now the National Institute of Standards and Technology (NIST) in Gaithersburg, Md.
Today, the wall provides a rare opportunity to study the effects of weathering on different types of stones, with the climatic conditions being the same for all stones. It offers a comparative study of the durability of many common building stones that have been used in commercial and government buildings, as well as in monuments. Also, the wall has served to preserve a valuable collection of building stone and should be useful as a reference for builders in identifying the kinds of stone that may be locally available.
The wall contains 2,352 individual samples of stone: 2,032 domestic stones from 47 states and 320 stones from 16 foreign countries. It is constructed in a mirror-image pattern, with the stone in the left wall set in lime mortar and the stone in the right wall set in Portland cement mortar. Over 30 distinct types of stones are represented, many of which are common varieties used in building, such as marble, limestone, sandstone and granite.
Stone Studies
In 1942, a committee decided that a study of actual weathering on such a great variety of stone would yield valuable information.
In 1998, the Inorganic Building Materials Research Group of the Building and Fire Research Laboratory (BFRL) in NIST started a project to evaluate and document the changes due to 50 years of weathering. The project is sponsored by the National Center for.
16 Masonry
October 2004