The AFm phase in Portland cement
TL;DR: In this article, a scheme of phase balances was proposed to calculate the mineralogical balances of a hydrated cement paste with greater accuracy than hitherto practicable, and experimentally-determined phase relationships were depicted at 25 deg. C.
About: This article is published in Cement and Concrete Research.The article was published on 2007-02-01. It has received 604 citations till now. The article focuses on the topics: AFm phase & Portlandite.
Citations
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TL;DR: In this paper, the influence of the presence of limestone on the hydration of Portland cement was investigated, and it was shown that the stabilisation of monocarbonate in the absence of limestone indirectly stabilised ettringite, leading to a corresponding increase of the total volume of the hydrate phase and a decrease of porosity.
1,089 citations
TL;DR: In this article, the effect of minor additions of limestone powder on the properties of fly ash blended cements was investigated using isothermal calorimetry, thermogravimetry (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) techniques, and pore solution analysis.
849 citations
TL;DR: In this article, the phase assemblage and pore solution of Portland cements hydrated between 0-60°C were modeled as a function of time and temperature, and a good correlation between calculated porosity and measured compressive strength was observed.
785 citations
Additional excerpts
...5· 12H2O) and stratlingite (2CaO·Al2O3·SiO2·8H2O) between 5 and 85 °C have been recently determined [27,28]....
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...AFm phases have essentially fixed compositions, with exception of the limited solid solution between C4AHx and monosulphoaluminate [28,79,80]....
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...sulphate in the monosulphoaluminate may be replaced by OH, while less than 3% of the OH of the C4AHx-endmember can be replaced by sulphate [28]....
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...Solubility products for cement minerals at 25 °C were taken from the compilation of Lothenbach and Winnefeld [6] completed with the data recently determined [27–29], resulting in the set of thermodynamic data for cements as given in Table 4: “cemdata2007”....
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...[27,28]; g Möschner et al....
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TL;DR: In this paper, it is shown by experiment and calculation that much, if not all, of this calcite is reactive and affects the distribution of lime, alumina and sulfate and thereby alters the mineralogy of hydrated cement pastes.
708 citations
TL;DR: In this paper, the mechanisms that govern the transport of ions, moisture, and gas are described, and different chemical degradation phenomena are reviewed, such as sulfate attack from external sources and formation of ettringite and thaumasite.
562 citations
References
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TL;DR: PHREEQC as discussed by the authors is a C program written in the C programming language that is designed to perform a wide variety of low-temperature aqueous geochemical calculations.
Abstract: PHREEQC version 2 is a computer program written in the C programming language that is designed to perform a wide variety of low-temperature aqueous geochemical calculations. PHREEQC is based on an ion-association aqueous model and has capabilities for (1) speciation and saturation-index calculations; (2) batch-reaction and onedimensional (1D) transport calculations involving reversible reactions, which include aqueous, mineral, gas, solidsolution, surface-complexation, and ion-exchange equilibria, and irreversible reactions, which include specified mole transfers of reactants, kinetically controlled reactions, mixing of solutions, and temperature changes; and (3) inverse modeling, which finds sets of mineral and gas mole transfers that account for differences in composition between waters, within specified compositional uncertainty limits. New features in PHREEQC version 2 relative to version 1 include capabilities to simulate dispersion (or diffusion) and stagnant zones in 1D-transport calculations, to model kinetic reactions with user-defined rate expressions, to model the formation or dissolution of ideal, multicomponent or nonideal, binary solid solutions, to model fixed-volume gas phases in addition to fixed-pressure gas phases, to allow the number of surface or exchange sites to vary with the dissolution or precipitation of minerals or kinetic reactants, to include isotope mole balances in inverse modeling calculations, to automatically use multiple sets of convergence parameters, to print user-defined quantities to the primary output file and (or) to a file suitable for importation into a spreadsheet, and to define solution compositions in a format more compatible with spreadsheet programs. This report presents the equations that are the basis for chemical equilibrium, kinetic, transport, and inverse modeling calculations in PHREEQC; describes the input for the program; and presents examples that demonstrate most of the program's capabilities.
7,654 citations
TL;DR: In this paper, it is shown by experiment and calculation that much, if not all, of this calcite is reactive and affects the distribution of lime, alumina and sulfate and thereby alters the mineralogy of hydrated cement pastes.
708 citations
TL;DR: In this paper, a thermodynamic model is developed and applied to calculate the composition of the pore solution and the hydrate assemblage during the hydration of an OPC.
674 citations
"The AFm phase in Portland cement" refers methods in this paper
...[25] using GEMS with the Nagra/PSI database [24]....
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TL;DR: The Nagra/PSI Chemical Thermodynamic Data Base has been updated to support performance assessments of the planned Swiss repositories for radioactive waste as discussed by the authors, and more than 70% of the database contents have been revised.
Abstract: The Nagra/PSI Chemical Thermodynamic Data Base has been updated to support performance assessments of the planned Swiss repositories for radioactive waste. The update from version 05/92 to 01/01 involved major revisions for most of the actinides and fission products. Altogether, more than 70% of the database contents have been revised. Data for U, Np, Pu, Am and Tc recommended by the NEA TDB project were considered in the update. Thermodynamic data for Th, Sn, Eu, Pd, Al, and solubility and metal complexation of sulphides and silicates were extensively reviewed. Data for Zr, Ni and Se were examined less rigorously as these elements are currently being reviewed in phase II of the NEA TDB project. Our experiences from this two year team effort can be summarised as follows. Detailed in-house reviews and critical appraisal of NEA recommendations greatly improved the chemical consistency and quality of the selected data. On the other hand, we could discern major gaps in the data, especially missing carbonate complexes. In some systems, e.g. Th(IV)-H 2 O and U(IV)-H 2 O, experimental data could not be described by a unique set of thermodynamic constants. There, a pragmatic approach based on solubility data was chosen for application to performance assessment. The electronic version of our database and information concerning its full documentation is available on our PSI web site (http://www.psi.ch/les).
614 citations
"The AFm phase in Portland cement" refers background or methods in this paper
...80 [24]...
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...[24] but supplementary data were required, some of which were generated in the course of the present study; these are given in Table 3....
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...[25] using GEMS with the Nagra/PSI database [24]....
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TL;DR: In this article, the CaOAl2O3CaSO4H2O system at 25°C has been investigated by calculations on the equilibrium solubility surfaces of AH3, C3AH6, CH, C 6 A S 3 H x, C 4 A S H x and gypsum.
230 citations