Hydration of water- and alkali-activated white Portland cement pastes and blends with low-calcium pulverized fuel ash

abstract

Pastes of white Portland cement (wPc) and wPc-pulverized fuel ash (pfa) blends were studied up to 13 years. The reaction of wPc with water was initially retarded in the presence of pfa particles but accelerated at intermediate ages. Reaction with KOH solution was rapid with or without pfa. A universal compositional relationship exists for the C-A-S-H in blends of Pc with aluminosilicate-rich SCMs. The average length of aluminosilicate anions increased with age and increasing Al/Ca and Si/Ca; greater lengthening in the blends was due to additional Al3+ at bridging sites. The morphology of outer product C-A-S-H was always foil-like with KOH solution, regardless of chemical composition, but with water it had fibrillar morphology at high Ca/(Si + Al) ratios and foil-like morphology started to appear at Ca/(Si + Al) approximate to which from the literature appears to coincide with changes in the pore solution. Foil-like morphology cannot be associated with entirely T-based structure. (C) 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

keywords

C-S-H; BLAST-FURNACE SLAG; MAS NMR-SPECTROSCOPY; TRICALCIUM SILICATE PASTES; PORE SOLUTION CHEMISTRY; RESOLUTION SI-29 NMR; BEARING SOLID-PHASES; FLY-ASH; HYDROGEN SILICATES; CRYSTAL-STRUCTURE

subject category

Construction & Building Technology; Materials Science

authors

Richardson, IG; Girao, AV; Taylor, R; Jia, S

our authors

acknowledgements

Thanks are due to the Nuclear Decommissioning Authority for financial support; to the Engineering and Physical Sciences Research Council for funding under Grant Nos. GR/S45874/01 and GR/R07073/01 and for a studentship (RT); to Dr. M. Zhang-Williams, Dr. C.A. Love, Dr. H.M. Dyson and Mr. J. Boomer for some of the experimental work; to a number of industrial collaborators for additional financial and technical support (Castle Cement, Lafarge, and W.R. Grace); and to Dr. D.C. Apperley at Durham University's EPSRC-funded NMR service for collection of the 27AL NMR spectra.

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