Cementitious Materials

Herbert Pöllmann, Herbert Pöllmann

• Publisher: De Gruyter
• Year: 2017
• ISBN:
  9783110473919
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Mineralogy

Aside from water the materials which are used by mankind in highest quantities arecementitious materials and concrete. This book shows how the quality of the technical product depends on mineral phases and their reactions during the hydration and strengthening process. Additives and admixtures infl uence the course of hydration and the properties. Options of reducing the CO2-production in cementitious materials are presented and numerous examples of unhydrous and hydrous phases and their formation conditions are discussed.

This editorial work consists of four parts including cement composition and hydration, Special cement and binder mineral phases, Cementitious and binder materials, and Measurement and properties. Every part contains different contributions and covers a broad range within the area.

Contents
Part I: Cement composition and hydration
Diffraction and crystallography applied to anhydrous cements
Diffraction and crystallography applied to hydrating cements
Synthesis of highly reactive pure cement phases
Thermodynamic modelling of cement hydration: Portland cements – blended cements – calcium sulfoaluminate cements

Part II: Special cement and binder mineral phases
Role of hydrotalcite-type layered double hydroxides in delayed pozzolanic reactions and their bearing on mortar dating
Setting control of CAC by substituted acetic acids and crystal structures of their calcium salts
Crystallography and crystal chemistry of AFm phases related to cement chemistry

Part III: Cementitious and binder materials
Chemistry, design and application of hybrid alkali activated binders
Binding materials based on calcium sulphates
Magnesia building material (Sorel cement) – from basics to application
New CO2-reduced cementitious systems
Composition and properties of ternary binders

Part IV: Measurement and properties
Characterization of microstructural properties of Portland cements by analytical scanning electron microscopy
Correlating XRD data with technological properties
No cement production without refractories

Part I:Cement composition and hydration

Ángeles G. De la Torre*, Isabel Santacruz, Laura León-Reina, Ana Cuesta, and Miguel A.G. Aranda

1Diffraction and crystallography applied to anhydrous cements

*Corresponding author: Ángeles G. De la Torre, Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, Málaga, Spain, [email protected]

Isabel Santacruz, Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, Málaga, Spain

Laura León-Reina, Servicios Centrales de Investigación, Universidad de Málaga, Málaga, Spain

Ana Cuesta, Miguel A.G. Aranda, Alba Synchrotron Light Source, Barcelona, Spain

Abstract: In this chapter, X-Ray powder diffraction (XRPD) combined with the Rietveld method is discussed to quantify both full crystalline and amorphous/crystalline non-quantified phases in anhydrous cements. For the latter, different approaches, such as internal and external standard methods, are addressed. In particular, the use of powder diffraction is shown in the characterization of Portland clinkers, Portland cements with supplementary cementitious materials, anhydrous cements for alkaline-activation, and ye’elimite-containing cements. In addition, the structural details of phases that are usually present in Portland clinkers are shown. Finally, the use of diffraction in the characterization of anhydrous cementitious materials under non-ambient conditions, viz. high temperature and high pressure, is also reviewed.

Keywords: clinker, Rietveld quantitative phase analysis, internal and external standard methods

1.1Introduction

X-Ray powder diffraction (XRPD) combined with the Rietveld method is a powerful tool for characterizing materials and obtaining a quantitative phase analysis of them in general [1, 2] and of cementitious related systems in particular [3–6]. This chapter gives some insight into the Rietveld quantitative phase analysis (RQPA) of cement-related materials. The Rietveld method is known to be a standardless one, but the structural descriptions for each phase present in a mixture must be known and included in the Rietveld control file. Tab. 1.1 [7–27], which summarizes the findings of a previous publication [5], shows an updated compilation of the crystal structures of phases that are commonly present in anhydrous cements and could be used to perform RQPA. Here, we have made a selection of the “best” crystal structures since sometimes there is more than one structural description available in the literature for a given phase. The criteria for the selection of the “best” ones have been: (i) type of data, i.e. single crystal diffraction was preferred over powder diffraction; and among powder diffraction, synchrotron or neutron were preferred over laboratory; and (ii) anisotropic atomic displacement parameters (ADPs) were preferred over isotropic ADPs. Moreover, if two or more suitable structural descriptions exist for a given phase, two (or more) RQPA of them should be carried out. The structure chosen should be that which gives the best fit based on a lower RF factor, hopefully linked to a higher quantification value.

The powder Diffraction Database (www.icdd.com) is the appropriated tool that should be used to identify minor phases by searching the extra-peaks of the experimental pattern. Once the phase is identified, the crystal structure can be searched for in three structural data bases: (i) AMCSD ‘American Mineralogist Crystal Structure Database’ (http://rruff.geo.arizona.edu/AMS/amcsd.php); (ii) COD ‘Crystallography Open Database’ (www.crystallography.net); and (iii) ICSD ‘Inorganic Crystal Structure Database’ (www.fiz-karlsruhe.de/icsd.html). Special care should be taken when using the COD database as ADPs are not included in the downloaded files. Finally, site occupation factor(s) for a given crystal structure sometimes must be adapted to describe a given stoichiometry, mainly for solid solutions, but this should be done with caution and by experts. An example of this is the solid solution C4AF, where the Al/ Fe ratio may be different from 1.0, which affects the diffraction signals.

1.2Rietveld quantitative phase analysis (RQPA) – full crystalline phase content, internal and external standard methods

The Rietveld method was developed in the late sixties [28] for the extensive characterization of polycrystalline compounds and uses the entire data of the measured powder pattern instead of only the reflection (peak) intensities; this method makes it possible to properly deal with strongly overlapping reflections. The Rietveld method carries out least-squares refinements to optimize a theoretical line profile until it fits (in the best possible way) the measured sample powder diffraction profile (whole-profile). For a successful RQPA, several steps must be fulfilled: (i) the sample has to be properly prepared; (ii) the diffractometer should be well aligned and maintained, and the optimal set-up should be used; (iii) every crystalline phase in the sample should be identified. When strong peak overlapping is present in the diffraction patterns, we compute the RQPA with the phases which are clearly present in the pattern and, from the net intensity in the difference curve, the remaining low-content phases are determined; and finally, (iv) when the main (...

Table of contents

• Cover
• Title Page
• Copyright
• Preface
• Contents
• Part I: Cement composition and hydration
• Part II: Special cement and binder mineral phases
• Part III: Cementitious and binder materials
• Part IV: Measurement and properties
• Index