Calcium aluminoferrite - Wikipedia

In the case of Portland cement, subsequent slow reaction with dissolved sulfate forms an AFm phase, which has negligible strength-giving properties. In the case of calcium aluminate cements (CAC),: 726 the situation is less clear-cut, but there is little contribution to early strength. Calcium aluminoferrite is also present in calcium ...

Study on the hydration product of ettringite in cement ...

Jul 19, 2019· The third peak, in deceleration period at about 16 h, is associated with the secondary hydration of aluminates or ferrite phase and the conversion of AFt to AFm [15, 23, 24]. Hydration heat release rate curves of cement pastes with different dosages of EDIPA are given in Fig. 3 .

Multiscale investigations on hydration mechanisms in ...

Dec 10, 2018· During the later stage (about 40–60 hours), the small peak was associated with the transformation of AFt phase to AFm phase, and it was also enhanced by seawater. This enhancement perhaps can be caused by the formation of Friedel's salt due to chloride in seawater. ... The C-S-H matrix phase for cement paste with seawater mixing contained ...

Advances in Cement Research - ICE Virtual Library

Dec 04, 2015· Stratlingite, Ca4Al2(OH)12[AlSi(OH)8]2·2H2O, is an AFm phase which appears as a hydration product of aluminium-rich cements. These binders may be calcium aluminate cements, calcium sulfoaluminate cements and also belite calcium sulfo-aluminate (BCSA) cements. The structure of stratlingite is known from single-crystal studies of tiny minerals but their bulk formation, crystal …

The AFM phase in Portland cement | Request PDF

However, in cement science, hydrocalumite is an AFm phase (Matschei et al. 2007; Tian and Guo 2014). This compound could be formed as the major stable hydration phase of concrete and cement …

(PDF) AFm-phase in cementitious materials

Apr 17, 2011· AFm-phase in cementitious materials ... The paper describes the whole family of potentially occurring AFm-phases in cement and their role during hydration of cements but also their role as new ...

Delayed Ettringite Formation in Fly Ash Concrete under ...

During the hydration of cement, tricalcium aluminate (C3A) reacts with gypsum and forms ettringite (AFt). Once all gypsum is consumed, ettringite can further react with remaining C3A and form monosulfate (AFm) at 1–2 days. Normally, at early ages, ettringite all transfers to AFm phase. After several months or years, ettringite can form again if a new source of sulfate becomes available in ...

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

Solubility data are reported and thermodynamic data are derived. The 25 °C stability of AFm phases is much affected by the nature of the anion: carbonate stabilises AFm and displaces OH and SO4 at species activities commonly encountered in cement systems. However in the presence of portlandite, and as carbonate displaces sulfate in AFm, the ...

Dissolution kinetics of hydrated calcium aluminates (AFm ...

The determination of reliable weathering/dissolution rates for cement phases is of fundamental importance for the modelling of the temporal evolution of both radioactive waste repositories and CO 2 geological storage sites (e.g. waste matrix, plug in boreholes). Here, the dissolution kinetics of AFm-Cl (hydrated calcium aluminates containing interlayer Cl) has been studied using flow-through ...

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

Sep 15, 2009· 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.

The AFm phase in Portland cement — The University of ...

Feb 01, 2007· The AFm phase of Portland cements refers to a family of hydrated calcium aluminates based on the hydrocalumite-like structure of 4CaO center dot Al2O3 center dot 13-19 H2O. However OH- may be replaced by SO42- and CO32-. Except for limited replacement (50 mol%, maximum) of sulfate by hydroxide, these compositions do not form solid solutions and ...

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).

Effects of sulfates on the hydration of Portland cement â ...

Portland cement influences the hydration, rheology, setting, phase assemblage, porosity distribution, ... [26], this layer is an OH-AFm type phase, which also forms when C 3A is hydrated in the absence of calcium sulfate, in which the delay in the reaction is not observed. As noted earlier, this hydrate

The AFm phase in Portland cement - ScienceDirect

Feb 01, 2007· The AFm phase of Portland cements refers to a family of hydrated calcium aluminates based on the hydrocalumite-like structure of 4CaO·Al 2 O 3 ·13–19 H 2 O. However OH − may be replaced by SO 4 2− and CO 3 2−.Except for limited replacement (50 mol%, maximum) of sulfate by hydroxide, these compositions do not form solid solutions and, from the mineralogical standpoint, …

Ettringite - Wikipedia

In the cement system, the presence of ettringite depends on the ratio of calcium sulfate to tri-calcium aluminate (C 3 A); when this ratio is low, ettringite forms during early hydration and then converts to the calcium aluminate monosulfate (AFm phase or (Al 2 O 3-Fe 2 O 3-mono)). When the ratio is intermediate, only a portion of the ...

AFm Phases | Solubility | Cement

Cement and Concrete Research 37 (2007) 118 – 130. The AFm phase in Portland cement T. Matschei a,⁎, B. Lothenbach b, F.P. Glasser a a Department of Chemistry, University of Aberdeen, Meston Building, Meston Walk, Old Aberdeen, AB24 3UE Scotland, UK b EMPA, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Concrete and Construction Chemistry, …

_ - baike.baidu.com

The effect of autoclave temperature on the expansion and hydrothermal products of high-MgO blended cements CEMENT AND CONCRETE RESEARCH Volume: 28 Issue: 1 Pages: 1-6 Published: JAN 1998 Qian, G; Li, A; Xu, G, et al. Hydrothermal products of the C3MS2-C(12)A(7)-MgO system CEMENT AND CONCRETE RESEARCH Volume: 27 Issue: 12 Pages: 1791 ...

Performance of Limestone Calcined Clay Cement (LC3) with ...

Sep 20, 2018· The production of Portland cement (PC) is the major source of CO 2 emissions associated with concrete materials. Due to the very large volumes of cementitious materials used (around 50% or all manufactured materials), it is estimated to be responsible for 6–8% of global anthropogenic greenhouse gas emissions [1, 2].This originates mainly from decomposition of …

Study on the hydration and microstructure of Portland ...

Jan 15, 2015· The AFm phase in Portland cement Journal Article Matschei, T ; Lothenbach, B ; Glasser, F - Cement and Concrete Research The AFm phase of Portland cements refers to a family of hydrated calcium aluminates based on the hydrocalumite …

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. It is known that these phases present different hydration states ...

Crystal Structures and Phase Transition of Cementitious Bi ...

Monosulfate (3CaO·(Alx Fe1x )2O3·CaSO4·12H2O) is an AFm phase that can be formed during the hydration of cement. Fe‐containing monosulfate and (Al,Fe) mixed monosulfate were synthesized and ...

Lecture 10: Basics of Atomic Force Microscope (AFM)

Mode AFM, the cantilever is excited into resonance oscillation with a piezoelectric driver. • Phase imaging is used to map variations in surface properties such as elasticity, adhesion and friction, which all may cause the phase lag. • Phase detection images can be produced while an instrument is operating in

Thermodynamic and crystallographic model for anion uptake ...

May 21, 2018· This type of stacking defect has been described repeatedly for AFm during SO 4 2− /I − exchange 8, for C-S-H (the main cement phase) 43,56, and more generally for …

Phase evolution of slag-rich cementitious grouts for ...

Aug 15, 2018· Other AFm phases, such as hemicarboaluminate and monocarboaluminate, are detected (10·75° and 11·5° 2θ) as a result of reaction of the small amount of calcite in the cement (as identified by XRD, Figure 4) during hydration, and potentially some superficial carbonation contamination of …

Premature Stiffening of Cement Paste Associated with AFm ...

other AFm phase. The stiffening of cement paste will be monitored using both oscillatory shear rheology and modified ASTM C403 penetration resistance test. The validity of penetration resistance test for monitoring stiffening of cement paste has been thoroughly …

Molecular simulation of the structure and elastic ...

Abstract Ettringite (AFt) and monosulfoaluminate (AFm(MS)) are the two of the main hydration products of tricalcium aluminate. Ettringite formation is favored in the presence of gypsum, and monosulfoaluminate is the usual AFm phase in a system with low calcium carbonate content. In this article, a new empirical force field, AFFF, is proposed to describe the interactions among species in ...

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

The transition of the Friedel phase to the chromate-AFm phase in chromate solution and the thermal stability of the products was investigated using thermal analysis combined with mass spectrometry,...

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 ...

Cement hydration - Understanding Cement

The general definitions of these phases are somewhat technical, but for example, ettringite is an AFt phase because it contains three (t-tri) molecules of anhydrite when written as C 3 A.3CaSO 4.32H 2 O and monosulfate is an AFm phase because it contains one (m-mono) molecule of anhydrite when written as C 3 A.CaSO 4.12H 2 O.

Hydration states of AFm cement phases

Hydration states of AFm cement phases. 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 …