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(PDF) The AFm phase in Portland cement | Barbara ...

The AFm phase in Portland cement

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A New Investigation of the Cl−–CO32− Substitution in AFm ...

Chloride to carbonate substitution in AFm phase of general formulae [Ca 2 Al(OH) 6]·[Cl 1−x ·(CO 3) x /2 ·(2+x /2)H 2 O] (or 3CaO·Al 2 O 3 ·(CaCl 2) 1−x ·(CaCO 3) x ·(10+x )H 2 O written in cement notation) has been characterized by studying 12 powdered samples synthesized at 25° and at 85°C. The existence of a solid solution has been highlighted. It forms one stable .

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Hydration of C3A with Calcium Sulfate Alone and in the ...

Tricalcium aluminate (C3A) is one of the main constituents of Portland cement. Even though it represents less than 10% of the total composition, its strong reaction with water can lead to a rapid setting, called flash set. Gypsum is added to regulate this reaction and preserves the workability of the cement paste at early ages. The understanding of the C3A-gypsum reaction is therefore crucial ...

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The Density of Cement Phases M. Balonis* and F.P. Glasser

[2] Taylor H.F.W., Cement Chemistry 2nd edition 1997, Thomas Telford Publishing, London, UK [3] I. G. Richardson, The calcium silicate hydrates, Cement and Concrete Research 38 (2008) 137-158 2. Synthesis and characterization of AFm and AFt phase s The synthesis of the relevant cement hydrates required several solid precursors. These were

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Relevance of Chemistry in Concrete

If cement contains higher C 3 A a substantial amount of Ca-monosulphate (Afm) phase will form during hydration. This substance is reactive and if additional SO 4 from an outside source such as soil or groundwater penetrates the concrete, the monosulphate will readily react with it and convert back to Aft phase or ettringite.

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Chloride-BindingCapacityofPortlandCementPaste ...

AFm phase in concrete, the compounds where chloride ions are •xed between positively charged layers of the AFm phase increase [19, 22, 23].šis can e€ectivelydelay the penetration ofchlorideionsintoconcrete,asitreducestheamountoffree chloride. It is well known that anhydrous C 3A (3CaO·Al 2O 3), C 4AF (4CaO·Al 2O 3·Fe 2O 3), and AFm ...

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The role of calcium carbonate in cement hydration — The ...

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. Calcite affects the mineralogical variant of the AFm phase (s).

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Hydration States of AFm Cement Phases | Request PDF

The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively ...

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Hydration of C3A with Calcium Sulfate Alone and in the ...

Tricalcium aluminate (C3A) is one of the main constituents of Portland cement. Even though it represents less than 10% of the total composition, its strong reaction with water can lead to a rapid setting, called flash set. Gypsum is added to regulate this reaction and preserves the workability of the cement paste at early ages. The understanding of the C3A-gypsum reaction is therefore crucial ...

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Thermodynamic and crystallographic model for anion uptake ...

May 21, 2018· Amongst all cement phases, hydrated calcium aluminate (AFm) plays a major role in the retention of anionic species. Molybdenum (Mo), whose 93 Mo isotope is considered a .

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Retention of selenium by calcium aluminate hydrate (AFm ...

Here we report for the first time wet chemistry and spectroscopic data on the interaction of the most relevant selenium anion species under the expected strongly reducing conditions, i.e. HSe −, with two AFm phases commonly found in cement, monocarbonate (AFm-MC) and hemicarbonate (AFm-HC).

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Crystal Structures and Phase Transition of Cementitious Bi ...

Latina Nedyalkova, Barbara Lothenbach, Guillaume Renaudin, Urs Mäder, Jan Tits, Effect of redox conditions on the structure and solubility of sulfur- and selenium-AFm phases, Cement and Concrete Research, 10.1016/j.cemconres.2019.105803, 123, (105803), (2019).

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Uptake of iodide by calcium aluminate phases (AFm phases)

54 as X depending on the cement composition and the service environment (e.g. repository near-55 field), -the most common ones being CO 3 2-, OH, SO 4 2--and Cl (Evans and Slade 2006, Matschei 56 et al. 2007a). An AFm phase may also contain more .

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Early Hydration of Portland cement compounds

The most common phase in cement clinkers is β-belite. The reaction rate of β-belite is very slow compared with the one of alite. Therefore is it not very important for the early strengthening phase in cement. On the other hand, it is important for the strength of the final hardened cement.

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Stability of strätlingite in the CASH system | SpringerLink

Abstract. Strätlingite, a siliceous AFm-type phase associated with blended cement hydration, is often assigned a fixed composition, 2CaO·Al 2 O 3 ·SiO 2 ·8H 2 O, but our knowledge of its stability and compatibility with other phases is limited. The phase relations and thermal stability of strätlingite in the CASH system are reported.

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A New Investigation of the Cl−–CO32− Substitution in AFm ...

Chloride to carbonate substitution in AFm phase of general formulae [Ca 2 Al(OH) 6]·[Cl 1−x ·(CO 3) x /2 ·(2+x /2)H 2 O] (or 3CaO·Al 2 O 3 ·(CaCl 2) 1−x ·(CaCO 3) x ·(10+x )H 2 O written in cement notation) has been characterized by studying 12 powdered samples synthesized at 25° and at 85°C. The existence of a solid solution has been highlighted. It forms one stable rhombohedral ...

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Electrostatic Force Microscopy (EFM) - AFM System

Electrostatic Force Microscopy (EFM) with Park AFM maps electric properties on a sample surface by measuring the electrostatic force between the surface and a biased AFM cantilever. EFM applies a voltage between the tip and the sample while the cantilever hovers above the surface, not touching it.

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Hydration states of AFm cement phases - CORE

The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying ...

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Chloride binding in OPC hydration products

AFm phase, as well as the quantity of AFt phase. Besides cement composition, the next important factor that influences chloride binding is the concentration of free chlorides in the pore solution. The relationship between the concentration of bound chlorides and the concentration of free chloride ions, usually

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Materials Genome for Graphene-Cement Nanocomposites ...

Sep 03, 2013· AFM images (5 × 5 μm) of hydrated portland cement type I/II mixed with functionalized graphene nanoplatelets, 0.45 w / c ratio: (a) height image; (b) phase image Force deflection curves are also obtained for the different graphene cementitious nanocomposite specimens to study the adhesion stiffness variation and interpret the AFM images.

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The density of cement phases (Journal Article) | OSTI.GOV

Hydrogarnet, C{sub 3}AH{sub 6}, is destabilised at low carbonate contents and/or low temperatures < 8 deg. C and is unlikely to form in calcite-saturated Portland cement compositions cured at < 40 deg. C. The AFm phase actually consists of several structurally-related compositions which form incomplete solid solutions.

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Cement and Concrete Research

ions — the calcium silicate hydrate (C-S-H) phase [7–9] and the AFm phase [5,7,8,23,24]. Beside these, the chloride binding capacities of portlandite and ettringite are debated in literature [8,16,25,27]. Friedel's salt, a compound formed through the interaction of other AFm phases and intruding chlorides, is considered to be also able to

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Chloride binding in OPC hydration products

AFm phase, as well as the quantity of AFt phase. Besides cement composition, the next important factor that influences chloride binding is the concentration of free chlorides in the pore solution. The relationship between the concentration of bound chlorides and the concentration of free chloride ions, usually

Get Price

A New Investigation of the Cl−–CO32− Substitution in AFm ...

Chloride to carbonate substitution in AFm phase of general formulae [Ca 2 Al(OH) 6]·[Cl 1−x ·(CO 3) x /2 ·(2+x /2)H 2 O] (or 3CaO·Al 2 O 3 ·(CaCl 2) 1−x ·(CaCO 3) x ·(10+x )H 2 O written in cement notation) has been characterized by studying 12 powdered samples synthesized at 25° and at 85°C. The existence of a solid solution has been highlighted. It forms one stable rhombohedral ...

Get Price

Stability of strätlingite in the CASH system | SpringerLink

Abstract. Strätlingite, a siliceous AFm-type phase associated with blended cement hydration, is often assigned a fixed composition, 2CaO·Al 2 O 3 ·SiO 2 ·8H 2 O, but our knowledge of its stability and compatibility with other phases is limited. The phase relations and thermal stability of strätlingite in the CASH system are reported.

Get Price

Hydration states of AFm cement phases - Lund University

Y1 - 2015 N2 - The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer.

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Transition of Friedel phase to chromate-AFm phase ...

Oct 04, 2008· easily substituted for Cl in the Friedel phase forming chromate-AFm. The chemical formula of chromate-AFm was characterised as 3CaO·Al 2 O 3 ·CaCrO 4 ·12H 2 O. Chromate-AFm gave two steps of dehydration, two steps of dehydroxylation and one step of redox reaction of Cr(VI) in the whole heating process from 40 to 1000°C. The Fourier transform infrared .

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Materials | Free Full-Text | Phase Changes of ...

The AFm phase in Portland cement. Cem. Concr. Res. 2007, 37, 118–130. [Google Scholar] Perkins, R.B.; Palmer, C.D. Solubility of ettringite (Ca 6 [Al(OH) 6] 2 (SO 4) 3 ·26H 2 O) at 5–75 °C. Geochim. Cosmochim. Acta 1999, 63, 1969–1980. [Google Scholar] X'Pert ...

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Retention of selenium by calcium aluminate hydrate (AFm ...

Here we report for the first time wet chemistry and spectroscopic data on the interaction of the most relevant selenium anion species under the expected strongly reducing conditions, i.e. HSe −, with two AFm phases commonly found in cement, monocarbonate (AFm-MC) and hemicarbonate (AFm-HC).

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What is effect of silica and alumina content on cement ...

Dec 06, 2017· Silica and Alumina are two out of three main ingredients in cement and the general percentage is given below. The major ingredient of cement is Lime. Silica 17-25 % * Helps in maintaining the consistency and workability of concrete * Sufficient qu...

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