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Natural Cement Needs New ASTM Standards

Natural Cement Needs New ASTM Standards
Posted in: Commentaries
Feb 9, 2012 - 10:30:27 AM

Restoration of our historical structures made of cement, such as canals, army bases, monuments, museums, and capitols is bringing back the notion and use of natural cement over the mostly used Portland cement of this generation. There are thousands of natural cement structures which were built back in the 19th century and are still loved and used today. The need for restoration of these structures has led to a need to produce natural cement once again, because restoration using the original materials are preferred to achieve strength and continuity throughout the structure. In historical structure restoration, avoidance of stress to the original building and its materials is obviously very important. Natural cement is lower in elasticity than present day Portland cement; this allows for its successful use in large concrete and masonry structures without the need of expansion joints. Natural cement deforms as the cement expands and contracts with changes in temperature and moisture levels, relieving stress. Continuity in this material is the goal to achieving the restoration of our historic structures. But there is a problem, the C10 natural cement standard by the ASTM no longer exists.

History and restoration with natural cement

Back in the 1980s, historic restoration of old structures reached a critical crunch time due to time and the environment. The adaptive use of these structures, rather than their destruction and replacement with something more modern was introduced because of the publics growing interest in preserving these historical structures. The government introduced investment tax credits for historic buildings restored in accordance with the Secretary of the Interior’s guidelines. Because the guidelines favor use of original materials to the greatest extent feasible, resurgence in the commercial production of traditional masonry materials such as natural cement was reintroduced. Today’s construction professionals have never seen or heard of natural cement, even though it was once the most widely used hydraulic binder for concrete, masonry mortar, stucco and grout. At one time, natural cement was used for 95% of the greatest engineering structures in North America. So it would be prudent to reinstate natural cement production in order to save these grand structures.

To fulfill the growing need for authentic 19th century masonry materials, natural cement was reintroduced in 2004, yet according to the ASTM standards, the C10 standard (natural cement standard) still needs to be reinstated. Lack of a current ASTM standard specification for natural cement is an obstacle to the full realization of historically accurate and appropriate restoration work. Natural cement was used as a structural material, and will be required to fulfill structural performance requirements in the course of some of its applications in historic repair and rebuilding. To protect the structures and the public, it is essential that materials marketed today as natural cement meet the same requirements that governed performance historically. Thus, to exclude natural cement from any eventual ASTM standard for historic mortars would be to forsake the history of America.

For Example, the Century Cement Company in Rosendale, N.Y., was the center of the American natural cement industry from 1817 to 1970. It was the source of more than half of all natural cement produced in America. Once Portland cement was instated, the industry diverted its attention, and discontinued natural cement in 1979. As previously mentioned, there was still a need for natural cement in the 80s but there was no longer a standard to follow. Then in 2004 the restoration industry pushed to find a compatible repair and maintenance material for historic structures. Today in America, another natural cement company in Rosendale, N.Y. named Edison Coatings, they are applying to reinstate natural cement standard C10 to provide their restoration company’s ability to access a material which meets or exceeds the performance requirements of the original materials used in our historical structures.

More power to them, for the restoration industry as well as the future of our historic structures. It is imperative to the restoration industry to reinstate the C10 standard in order to ensure today’s natural cement meets or exceeds the performance of the original materials.

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