A study of length changes of compacts of Portland cement on exposure to H₂O

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Journal titleHighway Research Record
Pages106118; # of pages: 13
SubjectPortland cement; Hydration; Volume; Physical phenomena; Concrete
AbstractA new method is described for studying the interaction with H₂O of portland cement and its constituents by following the length change with time of a compact of unhydrated material; the formation and properties of the compacts are also outlined. The advantages of this method are discussed, the chief being that the particles of unhydrated cement are in direct contact with one another; this enables the length change to reflect immediately the formation of hydrated products at the particle boundaries and the study of hydration reaction and other effects within the first seconds of wetting. Sample size of the order of 1 by 0.25 by 0.06 in. allows close temperature control and the possibility of a study of vapor phase hydration is cited as a further advantage. Results of length changes are presented for vapor phase exposure at 20, 50 and 85 percent RH. Results are presented also for liquid phase hydration, including observations made only one minute after the start of hydration and including the effect of pre-exposure for periods from 5 min to 5 days at the three humidities on subsequent liquid phase hydration. The experiments showed that expansion begins immediately on exposure to water ( liquid or vapour) and continues with time and that pre- exposure of the specimens even at low humidities has an effect on subsequent hydration rates. The meaning of " setting" and "hardening" with regard to compacts is discussed.
Publication date
PublisherNational Research Council Canada
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedNo
NRC number8514
NPARC number20375097
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Record identifier234c2cc6-e96d-4c5e-a4c8-7dc730c1b25c
Record created2012-07-23
Record modified2016-06-16
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