End of the Induction Period in Ordinary Portland Cement as Examined by High‐Resolution Scanning Electron Microscopy

Abstract

/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://dx.doi.org/10.1111/j. 1551-2916.2008.02304.x Journal of the American Ceramic Society, 91, 4, pp. 1292Society, 91, 4, pp. -1299Society, 91, 4, pp. , 2008 End of the induction period in ordinary Portland cement as examined by high resolution scanning electron microscopy Makar, J. M.; Chan, G. W.http://irc.nrc-cnrc.gc.caEnd of the induction period in ordinary Portland cement as examined by highresolution scanning electron microscopy NRCC-49236Makar, J.M.; Chan, G.W.A version of this document is published in / Une version de ce document se trouve dans: Journal of the American Ceramic Society, v. 91, no. 4, April 2008, pp. 1292-1299 doi: 10.1111/j.1551-2916.2008 The material in this document is covered by the provisions of the Copyright Act, by Canadian laws, policies, regulations and international agreements. Such provisions serve to identify the information source and, in specific instances, to prohibit reproduction of materials without written permission. For more information visit http://laws.justice.gc.ca/en/showtdm/cs/C-42Les renseignements dans ce document sont protégés par la Loi sur le droit d'auteur, par les lois, les politiques et les règlements du Canada et des accords internationaux. Ces dispositions permettent d'identifier la source de l'information et, dans certains cas, d'interdire la copie de documents sans permission écrite. Pour obtenir de plus amples renseignements : http://lois.justice.gc.ca/fr/showtdm/cs/C-42 AbstractThe early stages of ordinary Portland cement (OPC) hydration were studied by cold field emission scanning electron microscopy and isothermal conduction calorimetry. Particular attention was paid to samples from the end of the induction period, where an additional peak in the tricalcium silicate hydration reaction has recently been discovered. Higher resolution images were obtained than is possible with current in-situ imaging techniques, allowing for the observation of features on the 5 nanometer scale. The peak in the hydration at the end of the induction period was associated with both the formation of pores in the surface of the cement grains and the formation of nanoscale C-S-H structures on those surfaces. The effects of grinding of OPC and additions of tricalcium aluminate and tetracalcium aluminoferrite on the peak at the end of the induction p...

Nanotechnology in Civil Infrastructure

“…Although Ca(OH) 2 appeared to be less common on the surfaces of OPC during the early stages of hydration than is C-S-H Chan 2008, Makar et al 2007], it was readily identified when it did form. Investigation of the effect of SWCNT on the formation of Ca(OH) 2 , however, has shown that the same amount of Ca(OH)2 was present in samples with and without SWCNT when the same amount of hydration had occurred [Makar and Chan 2008]. The three observations together suggest the SWCNT may be preferentially nucleating C-S-H, with the Ca(OH) 2 forming elsewhere in the system.…”

“…In summary, sonication of OPC alone reduced the maximum heat flow and retarded its timing compared to the as-delivered OPC control. Secondary C 3 A and C 4 AF reactions [Pratt andGhose 1983, Makar andChan 2008] were suppressed or spread out in time compared to the control. The SWCNT bundles accelerated the hydration reaction compared to both the control as-delivered OPC and OPC sonicated alone.…”

“…Imaging was done under high vacuum conditions in order to obtain the maximum possible resolution. A discussion of the advantages and disadvantages of using this approach to imaging hydrated OPC samples is given elsewhere [Makar and Chan 2008]. Samples were typically imaged at 40-50,000x magnification, but magnifications as high as 180,000x were used as appropriate.…”

“…Details of the OPC composition have been given elsewhere [Makar and Chan 2008]. Single walled carbon nanotubes from two sources were used.…”

Calorimetric study of the early stages of the nanosilica - tricalcium silicate hydration. Effect of temperature

“…A number of theories (protective layer, semipermeable layer, C-S-H nucleation and growth rates, CH nucleation, crystallographic defects) have been put forward to explain the decline in heat flow during the induction stage in alite hydration (11)(12)(13)(14). Juilland et al (14) proposed a mechanism based on geochemical data, noting that during induction period the concentration of Ca 2+ and OH − ions rose, with portlandite reaching supersaturation.…”