✍ Scribed by D.W. Kessler
No coin nor oath required. For personal study only.
THIS paper is the first report of the Bureau of Standards in connection with an extensive cooperative program for 'investigating the building stones of the United States. The. other government departments participating in the work on different phases of this investigation are the U. S. Geological Survey, Bureau of Mines and Office of Public Roads.
This paper comprises the results of strength tests, water absorption, porosity, specific gravity, freezing, thermal expansion, electrical conductivity and chemical tests on fifty-two different types of marbles produced in this country.
The purpose of the work is to determine the relative value of the different types for building purposes, and other special uses.
Compressive strength tests were made on specimens in the original condition and on specimens after being soaked in water for two weeks. The strength of the dry specimens gave values ranging from 7850 to 50,205 pounds per square inch. As a rule the soaked specimens gave lower compressive strengths than the dry, and in a few cases the loss due to soaking was over 25 per cent.
Transverse and tensile strength tests are included and show the strength of the specimens when broken perpendicular and parallel to the bedding planes.
The freezing tests made for this report consisted in determining the loss in weight and strength due to thirty freezings and thawings.
While these losses were considerable in most cases, some samples showed practically no loss and occasionally a gain in strength was indicated.
Hence it was decided that thirty freezings are not enough to give a trustworthy indication of the durability of such materials.
An apparatus has been installed which automatically shifts the specimens back and forth between a cold chamber and warm chamber at certain intervals.
With the use of this apparatus, it is possible to make a great number of freezings which will correspond to several years of exposure to the weather.
It is proposed to make extensive weathering tests with this apparatus to determine more definitely the relative effect of ~~____ ~__ --.~__
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