Electrolysis in concrete. (3nd ed.) (1919) (14764427712)

Identifier: electrolysisin1919182rosa (find matches)
Title: Electrolysis in concrete. (3nd ed.)
Year: 1919 (1910s)
Authors: Rosa, E.B. McCollum, Burton Peters, O.S.
Subjects:
Publisher: National Bureau of Standards
Contributing Library: NIST Research Library
Digitizing Sponsor: NIST Research Library



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y, the appearance of the concrete and its mechanical prop-erties both indicate very strongly that there has been no suchaction. This is fully substantiated by special experiments de-scribed in a later section, which appear to show quite conclusivelythat in the body of the concrete remote from either electrode thecurrent has no apparent effect on the concrete. As shown in Table i, most of the specimens cracked in aboutthe same time, the first eight specimens containing Old Dominioncement having shown cracks at the end of 23 hours. Nos. 10 and11, containing Alpha cement, required 72 hours, while No. 9, madewith Medusa White Portland cement, required 96 hours to developa fracture. In the latter case, however, it will be noted that thevoltage at starting was only 24.5 volts, this gradually rising to 54volts at the time of cracking. This low voltage at the start wascaused by the placing of a rheostat in series with the specimen inorder to prevent an unduly rapid rise of temperature. As the
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Electrolysis in Concrete 15 specimen warmed up the resistance of the rheostat was cut out bysteps until full voltage was on. The variation of the electrical resistance of the specimen withtime is of particular interest. In Table 1 the resistances of thetest specimens at three stages are given, viz, at starting, at thetime of cracking, and at the conclusion of the test. It will benoted that the first eight specimens containing Old Dominioncement show a fair degree of uniformity in initial resistance, theaverage of the eight being 69 ohms. At the end of 23 hours, whencracks first appeared, this had increased somewhat, the averagethen being 133 ohms. At the end of the test this average hadrisen to 2194 ohms, or nearly 32 times its initial value. Thisenormous rise in resistance with time is of the greatest importance,particularly from the practical standpoint, and is referred to againin another part of this paper. On breaking open the specimens the embedded iron was foundto have been very