Causes of Variation in Chemical Analyses and Physical Tests of Portland Cement

Causes of Variation in Chemical Analyses and Physical Tests of Portland Cement PDF

Author: Benjamin Leonard Bean

Publisher:

Published: 1969

Total Pages: 60

ISBN-13:

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Variations in testing that could lead to the rejection of a material fully conforming to specification requirements, or the acceptance of a material with undesirable chemical or physical properties, are apparent in the results reported by laboratories participating in comparative tests of portland cements.Many of the causes for variation in chemical analyses and physical test results are listed in this discussion, and remedies for some of the more frequently encountered deficiences in apparatus and methods are suggested.Particular consideration is given to problems which do not seem to have been covered in sufficient detail in previous discussions of cement testing procedures.Literature references are given for additional information.(Author).

Development of High-temperature Strain Gages

Development of High-temperature Strain Gages PDF

Author: J. W. Pitts

Publisher:

Published: 1961

Total Pages: 318

ISBN-13:

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A summary is presented of a research program aimed at the improvement of high-temperature strain gages of the electrical resistance type. Potential ceramic and metal components were evaluated and a gage was devised that was based on these evaluations. This gage (NBS 5B) was flexible and easy to install; however, it lacked resistance stability at higher temperatures. In an attempt to minimize this deficiency, ceramic cements were developed that showed greater electrical resistivity than had been previously observed in the range 800 to 1800 degrees Fahrenheit; also, a technique was devised for increasing the resistance to ground by applying a fired-on ceramic coating to the grid of a specifically developed unbacked gage. A study was made of the cause of the erratic response of cemented gages that had not been preheated prior to use. There were strong indications that the erratic response was caused mostly by the rapid decrease in resistance that accompanied structural changes in the cement.

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