List of abbreviations - OPUS4

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The hydration of an Ordinary Portland Cement (OPC) and the influence of selected
polymers: A mineralogical study using an external standard method for quantitative X
-
ray diffraction



Die Hydratation eines Portlandzementes und der Einfluss ausgewählter Polymere:
Mineralogische Charakterisierung mittels einer externen Standard Methode zur
röntgenographischen Quantifizierung





Der Naturwissenschaftlichen Fakultät der

Friedrich
-
Alexander
-
Universität Erlangen
-
Nürnberg

zur

Erlangung des Doktorgrades Dr.rer.nat.


vorgelegt von


Daniel Jansen

aus

Bamberg





Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

2
-








Als Dissertation genehmigt von der Naturwissenschaftlichen Fakultät der Friedrich
-
Alexander
-
Universität
Erlangen
-
Nürnberg









Tag der mündlichen Prüfung:

18.11.2011

Vorsitzender der

Promotionskommission:

Prof. Dr.
Rainer
Fink

Erstberichterstatter:


Prof. Dr. Friedlinde Götz
-
Neunhoeffer

Zweitberichterstatter:

Prof. Dr. Jürgen Neubauer





Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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3
-


List of abbreviations

................................
................................
................................
.........................

-

4
-

Abstract

................................
................................
................................
................................
..............

-

6
-

Zusammenfassung

................................
................................
................................
............................

-

7
-

1.

Introduction

................................
................................
................................
...............................

-

8
-

2.

Aim of the Research Work

................................
................................
................................
.....

-

10
-

3.

State of Knowledge

................................
................................
................................
.................

-

14
-

3.1.

Ordinary Portland Cement (OPC) CEMI 52.5 R

................................
................................

-

14
-

3.2.

Polymers

................................
................................
................................
............................

-

16
-

3.3.

Heat
Flow Calorimetry

................................
................................
................................
.......

-

17
-

3.4.

Powder Diffraction and the Rietveld
-
Method

................................
................................
.....

-

19
-

4.

Results (Publications)

................................
................................
................................
............

-

22
-

4.1.

Does Ordinary Portland Cement contain amorphous phase? (Published in PDJ)

............

-

22
-

4.2.

XRD Qua
ntification of cement hydration using an external standard (Published in CCR)

-

43
-

4.3.

The hydration of alite (Published in JA
C)

................................
................................
..........

-

64
-

4.4.

The early hydration of Ordinary Portland Cement (Published in CCR)

............................

-

81
-

4.5.

Influence of PDADMAC on the hydration of CEMI 52.5R( Submitted to CCC)

.................

-

98
-

4.6.

Influence of superplasticizers on the hydration of CEMI 52.5 R (Published in CCR)

.....

-

117
-

5.

Conclusion

................................
................................
................................
............................

-

134
-

Acknowledgement

................................
................................
................................
.........................

-

144
-






Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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4
-


L
IST OF ABB
REVIATIONS


XRD





X
-
ray Diffraction

wt.
-
%





weight percent

OPC





Ordinary Portland Cement

w/c
-
ratio




water/cement
-
ratio


Cement minerals and hydration products of OPCs


Alite




C
3
S



Ca
3
(
SiO
5
)

Belite




C
2
S



Ca
2
(SiO
4
)


Aluminate



C
3
A



Ca
3
Al
2
O
6


Brownmillerite



C
4
AF



Ca
4
Al
2
Fe
2
O
10

Gypsum



CsH
2



CaSO
4
*2H
2
O

Bassanite



CsH
0.5



CaSO
4
*1/2H
2
O

Anhydrite



Cs



CaSO
4

Quartz




S



SiO
2

Calcite




Cc



CaCO
3

Arcanit

e



Ks



K
2
SO
4

Ettringite



C
3
A 3Cs H
32


Ca
6
Al
2
(SO
4
)
3
(OH)
12
∙26H
2
O

Portlandite



CH



Ca(OH)
2


Polymers


PDADMAC

Polydiallyldimethylammonium chloride, cationic homopolymer of
diallyldimethylammonium chloride, (
Cl
-

can be

subs
tituted by e.g.
OH
-
,SO
4
2
-
)

SP

Superplasticizer, in the present work
polycarboxylate eth
er based
superplasticizers (PCE
)


Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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5
-



Professional Journals


PDJ




Powder Diffraction Journal

CCR




Cement and Concrete Research

JAC




Journal of Applied Crystallography

CCC




Cement and Concrete
Composites















Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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6
-


A
BSTRACT


The influence

on the
hydration of a commercial Portland cement

of two different
polymers used in dry
-
mix
-
mortar technology was examined by means of X
-
ray diffraction. To
this end an external standard method was used and evaluated which turned out to be the
most elegant method available when working with cement pastes

containing amorphous
phases. The external standard method was also used in order to examine the amorphous
content of the dry cement powder.

It was found that several structural parameters
,

such as atomic dislocation and
microstrain of the structure models
,

used for quantitative Rietveld analysismight lead to the
determination of false “amorphous” content. No actual amorphous content (phase with
missing crystalline structure) could be proven

in the cement examined.

It turned out that the hydration process can be
precisely examined
using the
externalstandard method evaluated in this research. New insights into the hydration process
of a commercial OPC could be
achieved.
The heat resulting fro
m the hardening of the
cement with water could be assigned to different reactions, namely the silicate reaction, the
dissolution of the aluminates
,

and the precipitation of ettringite.

The cationic polymer (PDADMA
-
X)

which was

used affects the hydration of

the
cement as a function of the anionic counterion. The influence of the polymer is due to the
interaction of the polymer with

the

anions in

the

pore solution indirectly

influencing

the
cationic composition of the

latter
.

The polycarboxylate
-
based superpl
asticizer leads to a retardation of all reactions
during cement hydration
,

without

thereby

showing a higher influence on a
ny

specific reaction.
Both the silicate reaction
and
the aluminate reaction are retarded where the superplasticizer
is
present. Thus i
t is very conceivable that an interaction may here occur between the
superplasticizer and the Ca
2+

ions
from the cement pore solution, though other mechanisms
are also conceivable.



Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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7
-


Z
USAMMENFASSUNG


Die Hydratation eines handelsübliche
n

Portlandzements wurde mittels Röntgen
-
diffraktometrie und Wärmeflusskalorimetrie untersucht. Dabei wurde eine Methode mit einem
externen Standard angewandt und evaluiert, welche in abbindenden Zementen noch nie
zum
Einsatz kam
. Die Methode stellt
e

sich al
s eine sehr elegante Methode für die Untersuchung
von Zementpasten heraus.

Außerdem wurde der amorphe Gehalt eines handelsüblichen Zements untersucht. Es stellte
sich heraus, dass der Zement keinen amorphen (nicht kristallinen) Bestandteil aufweist.
Vielm
ehr ist es möglich mit falschen
Werten für die Auslenkungsparameter der einzelnen
Atome oder den Microstrain

für den Standard bzw. aller Phasen der Probe einen „falschen“
amorphen Anteil zu errechnen.

Weiterhin wurde d
er Einfluss zweier Polymere, welche i
n Trockenmörteln neben dem
untersuchten Zement eingesetzt werden, auf das Abbindeverhalten d
es Zements
untersucht.

Dabei zeigt sich, dass das
kationische
PDADMA
-
X einen deutlichen Einfluss auf die
Hydratation hat und diese in Abhängigkeit des anionischen
Gegenions zu dem kationischen
Polymer entweder beschleunigt oder verzögert.
Dabei

spielt offensichtlich ein

Anionenaustausch zwischen Po
ly
mer und Zementporenlösung eine entscheidende Rolle.

Das Fließmittel (Polycarboxyla
t
-
basierend) verzögert sowohl die S
ilikatreaktion als auch die
Aluminatreaktion

während des Abbindens des Zementes
.
Es
ist

am denkbarsten, dass das
Polymer durch das Entziehen von Ca
2+
-
Ionen aus der Zementporenlösung verzögernd auf
das Abbinden des Zementes wirkt
.








Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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8
-


1.

I
NTRODUCTION


Cementitious building materials have been playing a major role in human life

for

thousands of years
. Binders less reactive than cement,
such as lime or gypsum
,

have
an
even longer history
.

The introduction of cement
on
to the market in the 19
th

century provided the possibility of
new applications and products with better properties and durability.

Today Ordinary Portland Cement (OPC) is an important product
in
our daily life and it is
an irreplaceable part of numerous

other

products. It is th
e basis of many products of the
building
industry
such as concrete and dry
-
mix
-
mortars. The worldwide production of Ordinary
Portland Cement amounts to almost 3 billion tons a year. The global production of dry
-
mix
-
mortars has already
exceeded
the amount of

100 mio tons a year [1].

The f
irst investigations
into
the hydration of cements date back to the early 20
th

century
.However,
there are still many unsolved problems concerning the hydration of
cements
,

especially in modified cementitious systems like dry
-
m
ix
-
mortars. One of the main
issues of research is to clarify the kinetics behind the hydration of Portland cement
,

which
can be seen from heat flow curves and the influence of all kinds of additives on the hydration
behavior.

It is a well known fact that
two reactions are assumed for the hydration of an OPC with
water. The phase alite (chemically
impure

C
3
S) reacts with water
,

forming portlandite and C
-
S
-
H
-
phase (equation 1). The sulfate carriers of the cement (anhydrite, gypsum, bassanite)
react with C
3
A
and water
,

forming ettringite (equation 2).


Equ.1


C
3
S + 3.9 H → C
1.7
SH
2.6
+ 1.3 CH



(silicate reaction)

Equ.2


C
3
A + 3 Cs + 32 H → C
3
A*3Cs*H
32
[ettringite]

(aluminate reaction)


Dry
-
mix
-
mortar systems are very important products and today’s standard when
it
comes to
efficient and resource
-
saving construction sites [1, 2].
S
o
-
called
ready
-
to
-
use
mortars are
applied more and more often
and
are tending
to replace job
-
site
-
mixed morta
rs
at construction sites.
Since they need to fulfill

very different requirements for different
products
,

dry mortars are complex mixtures of many components such as inorganic binders
(Ordinary Portland Cemen
ts, Calcium Aluminate Cements, S
ulfates), organic

binders
(redispersible polymer powders, polymer dispersions), additives and aggregates. The
systematic
addition of additives and functional polymers
gives rise to
products with a varying
field of application possibilities.
The
modification of concrete and

mortars with polymers
, in
particular, has

turned out to be very advantageous
.

Research
into
dry
-
mix
-
mortar systems is a very broad field. The

best means of
improving

mechanic
al

properties
,

such as strength and adhesion
,remain live
scientific issues
[e.g. 3, 4, 5] and
form the aims set by
many research programs. The study of

the

microstructuredevelopment of mortar systems [e.g. 6, 7, 8] is also a very important issue.

Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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9
-


In addition, there also exists a
need to understand and investiga
te the influence of
numerous organic additives and aggregates on the hydration behavior of the inorganic
binders in mortar systems (references in chapter 4.5 and 4.6).

From a mineralogical point of view
,

OPC (a very important inorganic binder in many
pro
ducts) is a mixture of several crystalline phases. During hydration (the hardening of the
cement after adding water) several crystalline phases are dissolved and hydration products
crystallize from

the
pore solution. The fact that OPC is a crystalline prod
uct
means
that
mineralogical studies using X
-
ray diffractometry
can be
helpful
in examining
the raw material
cement, the hardened cement stone
, and also

the hydration process. The quantification of
the phase development during cement hydration is a very po
werful tool
for demonstrating
reactions during hydration. A problem
, however, for

the quantification of the hydration
process is the fact that

neither

the water added to the cement
nor

the C
-
S
-
H
-
phase which is
formed during hydration can
, at present,

be q
uantified by means of X
-
rays. This problem can
be overcome by using standard methods which also allow the quantification of the
amorphous phases (water, C
-
S
-
H
-
phase) in the cement paste.




[1] F. Leopolder, The global drymix mortar industry, ZKG Internati
onal, 4 (
2010
)

32
-
45

[2] C. Winter, J. Plank,
The European Drymix Mortar Industry, ZKG Internati
onal, 60 (2007)

62
-
69

[3] J. M. Geist, S. V. Amagna, B.B. Mellor, Improved Portland Cement Mortars with Polyvinyl
Acetate Emulsions, Industrial and E
ngineering
Chemistry, 45 (1953)

759
-
767

[4] J. Schulze, Influence of water
-
cement ratio and cement content on the properties of
polymer
-
modified mortars, Cement a
nd Concrete Research, 29 (1999)

909
-
915

[5] J.
-
H. Kim, R. E. Robertson, A. E. Naaman, Structure and prope
rties of poly(vinyl alcohol)
-
modified mortar and concrete, Cement and Concrete Research, 29 (
1999)

407
-
415

[6] J. Rottstegge, M. Arnold, L. Herschke, G. Glasser, M. Wilhelm, H.W. Spiess, W.D.
Hergeth, Solid state NMR and LVSEM studies on the hardening of l
atex modified tile
mortars, Cement a
nd Concrete Research, 35 (2005)

2233
-
2243

[7] S. Seifert, J. Neubauer, F. Goetz
-
Neunhoeffer, H. Motzet, Application of two
-
dimensional
XRD for the characterization of the microstructure of self
-
leveling compounds
, Powder

Diffraction, 24 (2009)

107
-
111

[8] A. Jenni, L. Holzer, R. Zurbriggen, M. Herwegh, Influence of polymers on microstructure
and adhesive strength of cementitious tile adhesive mortars, Cement a
nd Concrete
Research, 35 (2005)

35
-
50



Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

10
-


2.

A
IM OF THE
R
ESEARCH
W
ORK


The aim of the present work was to clarify, from a mineralogical point of view, the
processes occurring in the course of the hydration of a commercial Portland cement, using
X
-
ray diffractometry combined with heat flow calorimetry. On this basis, the
re can be
examined the influence of two selected polymeric additives which are used in dry
-
mix
-
mortars on the hydration behavior of the cement. Within the scope of the present research
work the focus was on the first 22 hours of the hydration process.

For
the above
-
mentioned reasons, an OPC which is very often used in German dry
-
mix
-
mortar technology was chosen for the research performed.

The hydration of OPCs can be examined very well by means of X
-
ray diffraction analysis.
Studies of this sort are nowada
ys helping us to understand many processes which occur
during the application of cement based products.

When working with X
-
rays the scientist has always to keep in mind that only crystalline
phases with a known structure and sufficient peak intensities c
an be quantified. Although
possibilities exist for quantifying phases with partially
-
known or unknown crystal structures
[1], the mixing water introduced into the cement in order to start the hardening process
cannot be quantified by means of X
-
rays. Moreo
ver, hydration products may also display
(especially during early hydration) an unsatisfying degree of crystallinity (e.g. C
-
S
-
H
-
phase).
These factors might lead to wrong quantitative values for the crystalline phases in a cement
paste (see chapter 4.2.).

The application of X
-
ray diffraction to hydrating cementitious systems was already
suggested by scientists several years ago. Neubauer et al. [2] suggested a conversion of the
data obtained from Rietveld analysis in order to get true quantitative results
for the cement
paste. This method was carried on by Hesse [3]. Mitchell et al. [4] and Scrivener et al. [5],
however, suggested using an internal standard method for the quantitative analysis of
cement pastes.

Generally speaking, one
of the most important

aims

of the scientists who work with X
-
ray
diffraction and hydrating cementitious systems is to find the most suitable standard method in
order to quantify the crystalline phases in a cement paste. A standard method suitable for
obtaining absolute quantit
ies for each crystalline phase in a mixture of crystalline (clinker
phases, hydrate phases) and amorphous phases (e.g. water, C
-
S
-
H
-
phase) is therefore most
appreciated.







Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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11
-


The first step of the present work is therefore the application of the chosen m
ethod in
order to examine the dry cement powder. The question of whether or not the dry cement
powder already has amorphous phases which cannot be quantified with X
-
rays is also a
scientific issue. These investigations lead to the first question to be answ
ered within the
scope of the present research work.


i.

Does Ordinary Portland Ceme
nt contain amorphous content? (C
hapter 4.1.)


After the above
-
mentioned external standard method turned out to be very promising for
the dry cement, its evaluation and implemen
tation for the in
-
situ investigation
of cement
hydration

is the next task of the present work.


ii.

Is the standard method applied to the dry cement powder suitable for characterizing
the

cement during hydration? (C
hapter 4.2.)


The data obtained from the XRD in
-
situ investigation of the cement paste during
hydration are suitable in order to calculate heat flow diagrams. But in order to do this the
enthalpies of reaction for all reactions which take place during the hydration proc
ess have to
be taken into account.

By comparing the calculated heat flow diagrams with measured heat flow diagrams, we
can arrive at detailed statements concerning the kinetics behind cement hydration. Hesse et
al. [6] proved that this is possible for syn
thetic cementitious systems. The intention of the
present work is to take the idea of Hesse et al. [6] further and to apply it to a commercial and
more complex system. Hesse et al. assumed that the reactions described in equations 1 and
2 (chapter 1) run s
ynchronously. They made use of the alite dissolution curve and the
ettringite precipitation curve in order to calculate the heat released during both reactions and
compared it with heat flow curves from heat flow experiments. The aim of the present work is

to figure out whether or not both reactions have not rather to be separated into dissolution
and precipitation reactions, specifically, into the dissolution of the clinker phases and sulfate
carriers and the precipitation of the hydrate phases.

The first
step will be the examination of the early hydration of the pure phase alite with
water in order to answer the following question.


iii.

Is it possible to calculate the heat releasedduring the hydration of alite with water
from the alite dissolution curve quant
ified by me
ans of X
-
ray diffraction? (C
hapter
4.3.)




Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

12
-


If it is possible to calculate the heat released during hydration of pure alite with water
using the dissolution curve of alite, then this curve, determined from the paste of the whole
cement, can be

used in order to show the contribution of the silicate reaction (equation 1 in
chapter 1) to the total amount of heat released during the hydration of the cement.

This question immediately and automatically gives rise to the next:


iv.

Is it necessary to spl
it the aluminate reaction into dissolution and precipitation
reactions in order to calculate heat flow cu
rves from the X
-
ray data? (C
hapter 4.4.)


The four questions posed all have the aim of clarifying the process of hydration of the
OPC used in the study
. On the basis of the new knowledge acquired from the answers to the
first questions we can set about examining the influence of selected polymers on the
hydration of the Portland Cement used.


v.

Does the PDADMA
-
X with different counterions have an influenc
e on the hydra
tion
behavior of the OPC? (C
hapter 4.5.)


vi.

Does the polycarboxylate
-
based superplasticizer have an influence on the
hydration
behavior of the OPC? (
Chapter 4.6.)


The focus of the research performed is not only on the documentation of the influences of
said polymers on the hydration behavior, but also on the generation of theories that might
explain and account for these influences.











Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

13
-


[1] N.V.Y. Scarlett,
I.C. Madsen, Quantification of phases with partially known or no known
crystal structures
, Powder Diffraction, 21 (2006)

278
-
284

[2] J. Neubauer, F. Götz
-
Neunhoeffer, D. Schmitt, M. Degenkolb, U. Holland,
In
-
situ
Untersuchung der frühen PZ
-
Hydratation, Tag
ungsbericht 16. Internationale Baust
offtagung,
Weimar (2006)
1
-
0375


1
-
0382

[3] C. Hesse, Der Reaktionsverlauf der frühen Hydratation von Portlandzement in Relation
zur Temperatur, Dissertation Universität Erlangen
-
Nürnberg (2009)

[4] L.D. Mitchell, J.C. M
argeson, P.S. Whitfield, Quantitative Rietveld analysis of hydrated
cementitious systems
, Powder Diffraction, 21 (2006)

111
-
113


[5] K.L. Scrivener, T. Füllmann, E. Gallucci, G. Walenta, E. Bermejo, Quantitative study of
Portland cement hydration by X
-
ray
diffraction/Rietveld analysis and independent methods,
Cement a
nd Concrete Research, 34 (2004)

1541
-
1547


[6] C. Hesse, F. Goetz
-
Neunhoeffer, J. Neubauer, A new approach in quantitative in
-
situ
XRD of cement pastes, Correlation of heat flow curves with ear
ly hydration reactions,
Cement a
nd Concrete Research, 41 (2001)

123
-
128




Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

14
-


3.

S
TATE OF
K
NOWLEDGE


3.1.

O
RDINARY
P
ORTLAND
C
EMENT
(OPC)

CEMI

52.5

R


The term CEMI 52.5 R is defined according to DIN EN 197
-
1[1]. A CEM I is a Portland
Cement with a clinker content of
at least 95 wt.%. In addition, sulfate carriers and
aggregates (e.g. calcite) are added to the cement in order to optimize hardening and reduce
production costs.

The term 52.5 refers to the standard compressive strength of the cement, which has to
reach

at least 52.5 N/mm
2
after 28 days wet curing.
In compliance with DIN
-
EN 196

1, the
compressive strength is tested on mortar prisms of 4
×
4
×
16 cm (defined composition of
cement and sand
-
mixture; defined w/c
-
ratio).
The letter R indicates a high early st
rength after
2 days.

Ordinary Portland Cement (OPC) consists of several phases which are shown in
Table 1 [2]. Alite is the main phase of Ordinary Portland Cement and mainly determines the
early hydration (first 24 hours) of
the latter
, though the reactio
n of the C
3
A with the sulfate
carriers is also an important process during the early hydration. The reaction of belite does
not take place during the first 24 hours of hydration [3].


T
ABLE
1

M
AIN PHASES IN AN
O
RDINARY
P
ORTLAND
C
EMENT

C
LINKER

Mineral

Form
ula

Cement nomenclature

Amount [wt.%]

Alite

Ca
3
SiO
5

C
3
S

40
-
80

Belite

Ca
2
SiO
4

C
2
S

0
-
30

Tricalciumaluminate

Ca
3
Al
2
O
6

C
3
A

3
-
15

Brownmillerite

Ca
4
Al
2
Fe
2
O
10

C
4
AF

4
-
15



Sulfate carriers (calcium sulfate) are added to the cement clinker and interground in
order to control the setting of the cement. The particular calcium sulfate employed is usually
gypsum (CaSO
4
*2H
2
O) or natural anhydrite (CaSO
4
) or a mixture of both. The hemihydrate
(bassanite, CaSO
4
*0.5H
2
O) in the cement is a product of the dehydration
of gypsum during
milling at temperatures above 80 °C. Bassanite is a metastable mineral phase and is not
found in large amounts in nature. There are two forms of bassanite. The α
-
form results from
heat treatment of gypsum under vapor pressure [4]. Hence, i
n Ordinary Portland Cements
only the β
-
form can be found. The formation of calcium sulfate phases from gypsum is a
function of temperature and time [5]. The reaction of the sulfate carriers during cement
hydration is mainly based on the different solubilit
ies and the availability of the sulfate
carriers, which are a function of pH value and temperature [6
, 7
].






Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

15
-



T
ABLE
2

T
YPICAL SULFATE CARRI
ERS IN AN
O
RDINARY
P
ORTLAND
C
EMENT

Mineral

Formula

Cement nomenclature

Abbreviation

Gypsum

CaSO
4
*2H
2
O

CsH
2

Gy

Bassanite (β)

CaSO
4
*0.5H
2
O

CsH
0.5

HH

Anhydrite

CaSO
4

CsH

AII



















[1]
14. DIN EN 197
-

Part 1 (6/
2000
): Cement

Composition, specification and conformity
criteria for common cements
-

Part 2 (6/2000): Cement
-

Conformity evaluation.


[2] S.
Sprung, Cement, Ullmann`s Encyclopedia of Industrial Chemistry, (2009)

[3] I. Jelenic, A. Bezjak, M. Bujan, Hydration of B
2
O
3
-
stabilized α`
-
C
2
S and β
-
modifications of
dicalcium silicate, Cement
and Concrete Research, 8 (1978)

173
-
180

[4] F. Wirsching,
Calcium Sulfate, Ullmann`s Encyclopedia of Industrial Chemistry, (2009)

[5] S. Seufert, C. Hesse, F. Goetz
-
Neunhoeffer, J. Neubauer, Quantitative determination of
anhydrite III from dehydrated gypsum by XRD, Cement a
nd Concrete Research, 39 (2009)

936
-
941

[6] L. Amathieu, Solubility of calcium sulfate hemihydrates as a function of pH and the
calcination temperature and process, Ciments, Betons, Plat
res, Chaux, 789 (1991)

101
-
106

[7] D. Freyer, W. Voigt, Crystallization and phase stability of CaSO
4

and CaSO
4
-
based salts,
Mon
atshefte für Chemie, 134 (2003)

693
-
719



Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

16
-


3.2.

P
OLYMERS


Polymers (also called macromolecules) are large molecules composed of repeating units.
Polymers are characterized by very high molecular weights. The repeating units are
connected by covalent chemical bonds. Polymers play an essential role in our daily lif
e
inasmuch as they cover a large class of materials (natural as well as synthetic) with a wide
variety of properties and therefore lots of fields of applications.

Mortars and
c
oncrete made with Ordinary Portland Cements (OPCs) have been the most

widely

us
ed construction materials for
several centuries now
.
In recent
decades many
attempts have been made to use polymers in order to improve the properties of these
products [1]. Numerous polymer additives
,

such as redispersible polymer powders,
superplasticizers, thickeners, cellulose ethers and many others
,

are nowadays responsible

for the fact

that modern products
display such
excellent performance characteristics
as
self
-
leveling properties, water

r
etent
ion, good tensile adhesive strength, good flexural strength,
workability and more.
M
odern dry
-
mix mortar technology
, in particular,

is based on the
interplay between inorganic binders and organic binders and additives [2].

The present investigations focus

on the influence of two specific polymers
,

namely
:

a
new
-
generation polycarboxylate
-
based superplasticizer
,

and polydiallyl
-
dimethylammonium
chloride (Poly
-
DADMAC; PDADMAC) which are both used in dry
-
mix
-
mortar technology [3].

Superplasticizers improve w
orkability and fluidity of concrete and mortars [4]. A
distinction is made between polycondensates, polycarboxylates, small molecules and
biopolymers (e.g. casein). The superplasticizer used in this study belongs to the group of
polycarboxylates. These pol
ymers are synthesized by radical polymerization using suitable
monomers such as methacrylic acid.

Polydiallyldimethylammonium chloride (PDADMAC)
,

a homo
-
polymer of Diallyl
-
dimethylammonium chloride
,

is a cationic polymer with a high charge density and wit
h a
molecular weight of hundreds of thousands grams per mole. PDADMAC is synthesized by
radical polymerization and is soluble in water. The counterion to the positive charge of the
nitrogen is usually chloride. PDADMAC is mainly employed in

the

papermaking

process
,
since

it can be used in order to control disturbing substances

which occur in this process
. In
addition to this
,

PDADMAC can be used as an organic coagulant in waste water treatment.
The use of PDADMAC in dry
-
mix
-
mortar technology is also importa
nt [
3
].


[1] Y. Ohama, Handbook of polymer
-
modified concrete and mortars, Noyes Publications,
Park Ridge, New Jersey, U.S.A. (1995)

[2] H. Lutz, R. Bayer, Dry Mortars, Ullmann`s Encyclopedia of Industrial Chemistry, (2009)

[3] EP 1984 428, Wacker Chemie AG
; Schorm, A., Weitzel, H.P., Killat, S., Lutz, H.

[4] J. Plank, applications of Biopolymers in Construction Engineering, in: Biopolymers, Vol.
10 General Aspects and Special Applications (Publisher: A. Steinbüch
el), Wiley
-
VCH,
Weinheim (2003)

29
-
95



Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

17
-


3.3.

H
EAT
F
LOW
C
ALORIMETRY


One method which is implemented in orde
r to study cement hydration is
heat flow
calorimetry [1, 2]. Heat flow calorimetry is a technique used in order to study processes
through the thermal power which they produce or consume. The sample
is placed in an
ampoule that is inserted into a channel from the calorimeter. The ampoule is in contact with a
heat flow sensor on a thermostated heat sink. The heat produced in the sample is balanced
by a heat flow of the heat in excess in the sample thro
ugh the sensor into the heat sink. This
heat flow produces a voltage which can be expressed as a specific heat on the premise that
the calorimeter was calibrated with a known heat, resulting in a calibration coefficient K
calib

(WV
-
1
). The calibration coeff
icient converts the voltage U (V) as measured into a thermal
power P
thermal
(Equ.1).


Equ.1


P
thermal

= K
calib
х (U


U
0
)

where U
0
(V)is the base line signal of the calorimeter.



The output of a calorimeter can be plotted against time in order to arrive

at the heat
flow (HF) and can also be integrated with respect to time in order to arrive at the total heat of
reaction H
R
(Equ.2).


Equ.2



The correction factor 3.6 is to be used only when mW is plotted against hours (J = W
х
s). A detailed evaluation of the method as regards its use in the examination of cement
hydration can be found elsewhere [3].

The calorimeter used in this work was a commercial TAM Air calorimeter produced by
TA Instruments. It is an eight
-
channel twin
-
typ
e calorimeter. Each channel has a twin
channel in which an inert sample is placed, with the difference between the heat output of the
sample and that of the reference sensor being recorded.




Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

18
-


Cement and water were weighed in separately, the former in spe
cial plastic vessels
and the latter in syringes according to the chosen water/cement ratio. The cement and water
were equilibrated before the measurements in a tempered room. Mixing of the cement with
the water was carried out externally for one minute emp
loying a special tool which allows
reproducible stirring. The samples were then put into the calorimeter. The first half
-
hour of
the heat
-
flow experiments have to be evaluated with care because of the disturbance of the
signal when opening the calorimeter.


The time constant [4] of the TAM Air calorimeter turned out to be 234 s. Since the
experiments in this study are focused on the main reaction of cement, it was not necessary
to take into account the time constant for the evaluation of the heat flow diagr
ams.













[1] L. Wadsö, Applications of an eight
-
channel isothermal conduction calorimeter for cement
hydration studies,

Cement International, 5 (2005)

94
-
101

[2] J. Neubauer, F. Goetz
-
Neunhoeffer, Efficiency of highly sensitive heat flow
calorimetry in
examination of OPC hydration, Proceedings of the 24
th

International Conference on Cement
Microscopy, San Diego, California

(2002)

58
-
68

[3] L. Wadsö, Operational issues in isothermal calorimetry, Cement a
nd Concrete Research,
40 (2010)

1129
-
1137

[4] W.F. Hemminger, H.K. Cammenga, Methoden der thermischen Analyse, Springer
-
Verlag,
Berlin (
1989
)



Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

19
-


3.4.

P
OWDER
D
IFFRACTION AND THE
R
IETVELD
-
M
ETHOD


X
-
ray powder diffraction is a powerful tool for examining samples with crystalline phase
content. This ha
s meant that it has been regularly used for the examination of cements for
years. Because of the ongoing development of new X
-
ray equipment the opportunities are
continuously improving.

The interaction between X
-
rays and crystalline materials was first de
scribed in 1912 by
Max von Laue, who found out that X
-
rays have wave
-
like properties and that crystals have a
3
-
dimensional periodic structure [1].

W.L. Bragg formulated the basic equation which explains the diffraction of X
-
rays on
crystals with periodic

structures, which has consequently come to be known as Bragg’s
Equation [2]. Intensities can only be observed if Bragg’s Equation is fulfilled.

Today`s state
-
of
-
the
-
art quantitative use of X
-
ray patterns dates back to the
considerations of Hugo Rietveld
[3], who formulated the fundamental relations concerning
peak intensities obtained from X
-
ray experiments. The so called Rietveld method is
nowadays implemented in specific software. In the case of the present work the Rietveld
software Topas V4.2 from Bru
ker AXS was employed.

Modern Rietveld software uses the fundamental parameters approach [4]. When using
this approach, an XRD diagram is calculated from structure models and refined as long as
there is close agreement to the observed XRD diagram from the e
xperiment.

The final observed profile Y(2θ) depends on several parameters [5] (Equ.1).


Equ.1 Y(2θ) = (W х G
Eq
х G
Ax
) х S х P х U + Bkg

where


W


=

Source emission profile



G
Eq
and G
Ax

=

Equatorial and axial instrumental contributions



S


=

Sample
contributions



P


=

Real structures effects



U


=

User convolutions



Bkg


=

Background




In recent years the XRD analysis procedure has been adjusted for the examination of
hydration processes [6]. For this purpose, a special sample holder with a
cooling/heating
-
unit
has been developed [7]. Preparation of the cement paste, and the covering of the paste with
a Kapton film, allows the examination of the phase content in the cement paste over time.


Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

20
-


Figure 1 shows the equipment for the XRD in
-
situ ana
lysis of the cement hydration.
On the left side, the X
-
ray tube produces X
-
rays which are used for the irradiation of the
sample. The diffracted X
-
rays can be detected by the detector on the right side.



F
IGURE
1

XRD

EQUIPMENT AND TYPICA
L PATTERNS OBTAI
NED FROM
XRD

IN
-
SITU
EXPERIMENTS


The respective instrumental settings for the experiments performed are shown in the
respective chapters.








Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

21
-


[1] M. Laue, Röntgenstrahlinter
ferenzen, Physik. Z., 14 (1913)

1075
-
1079

[2] W.H. Bragg, W.L. Bragg, The ref
lection of X
-
rays by crystals, Proc.
Roy. Soc. London (A),
88 (1913)

428
-
438

[3] H.M. Rietveld, A profile refinement method for nuclear and magnetic structures,
Journal of
Applied Crystallography
, 2 (1988)

65
-
71

[4] R.W. Cheary, A. Coelho, A fundamental
parameters approach to X
-
ray Line
-
Profile
Fitting,
Journal of Applied Crystallography
, 25 (1992)

109
-
121

[5]
R.W. Cheary, A.A. Coelho, Axial Divergence in a Conventional X
-
Ray Powder
Diffractometer. II. Realiyation and Evaluation in A Fundamental
-
Parameter

Profile Fitting
Procedure, Journal of Applied Crystallography
, 31 (1998)

862
-
869

[6] J. Neubauer, F. Goetz
-
Neunhoeffer, U. Holland, D. Schmitt, In
-
situ XRD investigation of
OPC hydration, Proceedings of the 26
th

International Conference on Cement Microsco
py,
San Antonio, Texas, (2004), on CD
-
ROM

[7] C. Hesse, M. Degenkolb, P. Gaeberlein, F. Goetz
-
Neunhoeffer, J. Neubauer, V. Schwarz,
Investigation into the influence of temperature and w/c
-
ratio on the early hydration of white
cement,

Cement International,
6 (2008)

68
-
78








Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

22
-


4.

R
ESULTS
(P
UBLICATIONS
)



4.1.

D
OES
O
RDINARY
P
ORTLAND
C
EMENT CONTAIN AMORPH
OUS PHASE
?

(P
UBLISHED IN
PDJ
)


Does Ordinary Portland Cement (OPC) contain amorphous phase?
A

quantitative study
using an external standard method


D.
Jansen,
Ch.
Stabler,
F.
Goetz
-
Neunhoeffer,
S.
Dittrich, and
J.
Neubauer


Published

in
:
Powder Diffraction
Journal
(2011), 26,
31
-
38


A suitable external standard method which was first described by
O´Connor

(1988)
was used to determine the quantitative phase composition of a commonly used Ordinary
Portland Cement (OPC). The method was also applied in order to determine amorphous
contents in OPC. Also investigated were the impact of atomic displacemen
t parameters and
the microstrain on the calculated amorphous content. The investigations yielded evidence
that said parameters do indeed exert an influence on the calculated amorphous content. On
the basis of the data produced we can conclude that the meth
od used is entirely to be
recommended for the examination of OPC. No significant amorphous content could be
proven in the OPC used.



Key words:
Ordinary Portland Cement, amorphous content, external standard, G factor




Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

23
-


INTRODUCTION

The worldwide consumption of Ordinary Portland Cement (OPC), the most commonly
used foundation for building materials on this planet, amounts to around
3 b
illion tons a year.
OPCs are complex powders of worldwide importance, and knowledge of their mineralo
gical
composition
s

is of great economic importance inasmuch as it enables us to predict hydration
behavior. Major phases are alite, belite, aluminate and ferrite. Lime, periclase as well as
alkali sulfates may also exist as minor phases in cement clinkers
(Taylor, 1997).
Furthermore, sulfate carriers are added to the clinker to avoid an unintended rapid setting of
the cement. As a result, OPCs are mixtures of ten and more phases. This means that the
quantitative analysis of OPCs is quite a challenging task.

The cement industry uses a number of techniques to characterize their clinkers and final
cement products, such as the Bogue method, microscopic point counting and quantitative X
-
ray diffraction. Quantitative phase analysis of OPCs and clinkers based on si
ngle
-
peak
intensities has only a limited applicability to OPCs because of overlapping reflections and the
tendency to preferred orientations displayed by several phases. These limitations of single
-
peak intensity methods can be overcome by utilizing the Ri
etveld method of refinement
(Rietveld, 1969).

Rietveld analysis always gives the total of the determined crystalline phases normalized
to 100 wt.% (Hill and Howard, 1987) (
E
q
.

1). If amorphous or unknown phases are present,
the amounts of the crystalline
phases estimated by the analysis will differ from the actual
amounts present.













(1)



where


c
j

= weight fraction of phase j
,

S
j

= Rietveld scale factor of phase j
,

Z

=
n
umber of
formula units per unit cell
,

M

=
m
ass of the formula unit
,

V

=
u
nit
-
cell volume
.



Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

24
-


Nevertheless, the presence of a glassy or amorphous component in cements and
clinkers has been debated by several authors (Maki, 1979; Han
et al.

1980). X
-
ray
experiments h
ave been performed in order to determine amorphous contents in cements and
clinkers. Mainly two strategies, namely internal standard methods as well as external
standard methods, have been reported.

De La Torre
et al.

(2001) examined several standard mater
ials using the internal
standard method and concluded that corundum is the best standard, displaying as it does
contain almost no amorphous content. De La Torre
et al.

(2001) assumed, in addition, that
atomic displacement parameters exerted an impact on th
e quantitative results. Furthermore,
it was shown that the phase alite has an amorphous content of 21.7 wt.%. The impact of the
atomic displacement parameters on the scale factors was also described by Madsen
et al.

(2001) who assumed that errors made when

using incorrect values for the atomic
displacement parameters are propagated to the quantitative analysis. Le Saoût
et al.

(2007)
examined cementitious materials by use of external and internal methods. They employed
the external standard method in order
to avoid problems of homogenization. As regards the
internal standard method, they expressed doubts as to whether levels of amorphous phases
below 10 wt.% can be proven. Le Saoût
et al.

(2007) also noted that it is imperative to take
into consideration the

influence of refinement parameters on the quantification of amorphous
contents. More research concerning the amorphous level of cements and clinkers was
carried out by Whitfield
et al.

(2003). They employed the internal standard method and
calculated an a
morphous content in the cement used of 18

to
25 wt.%. They concluded that
the most serious source of error is the standard used and its amorphous content.
Mathematical consequences of the experimental approach for internal standard methods
have been worked

out by Westphal
et al.

(2009). They showed that the calculation of the
amorphous content via Rietveld analysis using an internal standard follows a non
-
linear
function, which in turn leads to a significant degree of error, especially when determining
minor amounts of amorphous
content. Thus, Westphal
et al.

(2009) concluded that to prove
amorphous contents below 20 ma.% using an internal standard is quite a challenging task,
because of the considerable degree of error which is also a function of the amount of
standard added. For

low amounts of amorphous content in the sample (like OPCs) Westphal
et al.

(2009) recommended an amount of internal standard measuring at least 50 ma.%.
Even with that amount of internal standard there exists an uncertainty of the amorphous
portion of alm
ost 4 wt.%, as compared to the assumed uncertainty of 1 wt.% of the Rietveld
quantification.

It is certainly the case that determination of amorphous contents from analyses using
internal standards is a very challenging operation indeed. First of all, a p
roper mixing of the
standard with the sample has to be guaranteed. Furthermore, the experiments are
complicated enormously by issues such as micro
-
absorption, especially if significant
differences exist between the respective mass attenuation coefficients
of sample on one
hand and standard on the other (Hermann and Ermrich, 1989).

Suherman
et al.

(2002) employed internal and external standard methods in order to
examine the amorphous content of different cement clinkers and described an amorphous
content in clinkers amounting to between 6.1 and 15.9 wt.%, depending on clinker type and
on the metho
d (internal or external standard) used. They refer to O`Connor
et al.

(1988) who
recommended an external standard method using a G
-
factor for examinations of powdered
mixtures as an alternative to conventional discrete peak methods as described by Klug and

Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

25
-


Alexander (1974) and Chung (1974). O´Connor pointed out that it is imperative to be aware
of the degree of crystallinity of the standard used, which ideally should be 100

wt.%. The
calculation of a G
-
factor as a calibration factor for the whole experiment

set
-
up has not
subsequently been used for powder diffraction experiments on hydrating cementitious
systems.



EXPERIMENTAL

In the experiments we performed we made use of an Ordinary Portland Cement CEMI
52.5R (OPC). As only small amounts of sample are nec
essary for the XRD experiments
performed, representative components for analysis were obtained by using the “cone and
quarter” method. All samples were ground to a grain size of about 10
μ
m using a McCrone
micronizing mill (liquid: waterfree ethanol). Stan
dard zircon was recrystallized from Alfa
Aesar zircon. To this end the zircon was heated at 1300 °C for 4 h. Afterwards the zircon was
cooled in five hours to 150 °C. A second thermal treatment was carried out at 1400 °C for 6 h
and the zircon was cooled a
gain. The treated
zircon was found to be a suitable standard with
a crystallinity as good as the corundum standard recommended by De La Torre (2001).

X
-
ray powder diffraction patterns were recorded on a D8 automated diffractometer
equipped with a Lynx Eye

position
-
sensitive detector. Cement and standard were measured
as frontloaded pressed
-
powder samples, seven times respectively, using the same
conditions and settings as shown in Table I.


T
ABLE
I.

D
ATA ACQUISITION COND
ITIONS FOR THE
X
-
RAY EXPERIMENTS PER
FORMED
.

Instrument

Bruker D8

Radiation

Cu


Geometry

Bragg
-
Brentano

Divergence Slit

0.3°

Generator

40 mA, 40 kV

Range

7

to
70°

Step width

0.02°

Integration time / step

1 s

Detector

Lynx Eye (PS
-
Detector)



To ensure a proper detection of all phases in the OPC used, minor
-
phase enrichment
experiments were performed. The dissolution of the interstitial phases using KOH sucrose
solution permits an accurate analysis of the silicate phases such as alite and belit
e
(Gutteridge, 1979). The dissolution of the silicate phases using a salicylic acid
-
methanol
solution permits an accurate analysis of the interstitial phases (Struble, 1985).

Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

26
-


Phase composition of the OPC used was determined using the peak finding program
EVA 14 from Bruker AXS. Topas V 4.2 from Bruker AXS was used as a least
-
squares
Rietveld refinement program (fundamental parameters approach). The scale factors for each
phase were calculated using Topas. Table II shows the models used for the Rietveld
ref
inement of each of the phases detected in the OPC, as well as the respective ICSD codes.



T
ABLE
II.

S
TRUCTURE MODELS USED

FOR THE
R
IETVELD REFINEMENT O
F THE
OPC.

Phase

ICSD


Code (reference)

Occurrence

MAC [cm
2
/g]

Zircon

158108 (Kolesov
et al.
, 2001)

Standard

82.9

Zircon

71943 (Mursic
et al.
, 1992)

Standard

82.9

Zircon

15759 (Robinson
et al.
, 1971)

Standard

82.9

Alite

94742 (De La Torre
et al.
, 2002)

Cement

101.4

Belite

963 (Jost
et al.
, 1977)

Cement

93.8

α
`
-
C
2
S

(Mueller, 2001)

Cement

93.8

C
3
A
kub

1841 (Mondal
et al.
, 1975)

Cement

86.9

C
3
A
ortho

100220 (Takeuchi
et al.
, 1980)

Cement

86.9

C
4
AF

51265 (Jupe
et al.
, 2001)

Cement

134.8

Gypsum

27221 (Pedersen, 1982)

Cement

63.3

Bassanite

(Weiss
et al.
, 2009)

Cement

73.4

Anhydrite

16382 (Kirfel
et al.
, 1980)

Cement

77.4

Calcite

80869 (Maslen
et al.
, 1995)

Cement

74.1

Quartz

174 (Le Page
et al.
, 1976)

Cement

36.0

Arcanite

79777 (Ojima
et al.
, 1995)

Cement

86.5

Silicon

51688 (Toebbens
et al.
, 2001)

Standard

63.7



To avoid complications that might possibly have ensued from mixing an internal standard
with the cement used, we decided to make use of an external standard method. The well
-
known zircon standard used in the study was employed for the derivation of factor
G using
E
q
.

2 (O´Connor, 1988).







Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

27
-













(2)




where


S
zir

= Rietveld scale factor of zircon
,



ρ
zir

=
d
ensity of zircon
,



V
zir

=
u
nit
-
cell volume of zircon
,



C
zir

=
w
eight fraction of zircon (100 wt.%)
,



µ
*
zir

=
m
ass attenuation coefficient
(MAC) of zircon
.


The calculated Factor G represents a calibration factor for the whole experimental setup
and comprises the diffractometer used, radiation, and all data acquisition conditions, such as
temperature and integration time. This factor G was th
en used to determine the mass
concentration of each phase j in the sample (
E
q
.

3). This meant that the sample had to be
measured under the same conditions as the standard.













(3)



In multi
-
phase systems the absorption of X
-
rays strongly depends on the linear
attenuation coefficients and the mean particle size of the single phases. If the linear
attenuation coefficients differ strongly from each other, effects of microabsorption can
occur if
a critical particle size defined by Brindley (1945) is exceeded leading to an underestimation
of phases with a high linear attenuation coefficient (De La Torre
and
Aranda, 2003). The
linear attenuation coefficients of the phases of an OPC (except
the ferrite phase) do not differ
strongly from each other. The ferrite
-
phase yielding the highest attenuation coefficient only
appears as interstitial phase in the multi
-
phase cement grains of technically produced OPCs.
Therefore only small particle sizes
(around 1
μ
m) of this phase can be expected leading to
negligible microabsorpti
on

effects (Le Saout et al., 2010).


Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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28
-


In order to evaluate the accuracy of the method presented we applied the method to
powder mixtures of known composition. For this purpose we
produced mixtures of the zircon
standard material and a NIST glass (NIST 622) of defined ratios. The mass attenuation
coefficient of the NIST glass is 44.8

cm
2
/g. The mass attenuation coefficients of the mixtures
are shown in Table III. In order to guaran
tee a proper mixing both components were ground
and sieved to a particle size below 5
μ
m and were then homogenized over 2 weeks. The
amount of zircon in the mixtures was calculated using the G
-
factor derived from the pure
zircon standard and the calculated

scale factors for zircon from Rietveld refinement of the
mixtures.



T
ABLE
III

E
XAMINED ZIRCON
/NIST

622

MIXTURES
.

Mixture

Zircon [ma.%]

NIST 622 [ma.%]

MAC [cm
2
/g]

1

25

75

54.35

2

50

50

63.89

3

75

25

73.44




For all cement phases the values
ρ

and
V

were computed within the refinement, both
of them being checked against data from the literature (Table II). Scale factors for the phases
detected in the OPC were acquired from the Rietveld refinement. The mass attenuation
coefficient of the OPC (
µ
*
OPC
) w
as measured and calculated from elemental analysis carried
out by X
-
ray fluorescence spectrometry. The mass attenuation coefficient of the OPC used
was found to be 97.9 cm
2
/g. The chemical composition of the OPC and the mass attenuation
coefficients of the

oxides used (Prince, 2004) are given in Table IV.












Dissertation Daniel Jansen, University Erlangen
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Nürnberg, 2011

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29
-



T
ABLE
IV.

C
HEMICAL COMPOSITION
AND MASS ATTENUAT
ION COEFFICIENT OF T
HE
OPC

Oxide

Wt.%

MAC [cm
2
/g]

CaO

66.7

124.04 × 0.667 = 82.73

SiO
2

22.9

36.03 × 0.229 = 8.25

Al
2
O
3

3.8

31.69 × 0.038 = 1.2

Fe
2
O
3

1.3

214.9 × 0.013 = 2.79

MgO

0.8

28.6 × 0.008 = 0.229

Na
2
O

0.1

24.97 × 0.001 = 0.025

K
2
O

0.7

122.3× 0.007 = 0.856

SO
3

3.4

44.46 × 0.034 = 1.51

TiO
2

0.2

124.6 × 0.002 = 0.249

P
2
O
5

0.1

39.66 × 0.001 = 0.04

OPC


97.9



We furthermore made use of different models for the zircon standard used. The
authors Mursic
et al.

(1992), Kolesov
et al.

(2001) and Robinson
et al.

(1971) all suggest the
same symmetry (I41/amdZ). They differ strongly, however, in their suggestions regarding the
refined atomic displacement parameters. When using Rietveld programs, the user has
always to ensure that correct values are being employed a
s regards atomic displacement
parameters. Most of the displacement parameters given in the literature are anisotropic
displacement factors (e.g.
U
aniso
/
B
aniso
). When using the GUI (Graphical User Interface) some
Rietveld programs will not convert those ani
sotropic values into equivalent isotropic values.
Therefore, in such cases the user needs to calculate the equivalent isotropic displacement
factor himself. The calculation of the equivalent isotropic displacement factor is an
eigenvalue calculation so tha
t the equivalent isotropic parameter can be easily calculated
from the anisotropic values given (Fischer
et al.

1988). Secondly, in the crystallographic
literature, there tend to occur inconsistent terms and symbols for said parameters (Trueblood
et al.

19
96).
U


2
] is the mean square displacement of an atom from its equilibrium position
Dissertation Daniel Jansen, University Erlangen
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Nürnberg, 2011

-

30
-


x. The Debye
-
Waller factor
B

can be derived from
U

by multiplying the value for
U

with 8π
2
.
Very often, atomic displacement parameters are given as
ß
s. These parameters ha
ve then to
be converted into equivalent
B
s for the Rietveld programs, employed while taking into
account the reciprocal lattice vectors
a
*,
b
* and
c
*. If these parameters are not converted and
inserted into the Rietveld software, then the software will som
etimes automatically employ
the default value 1, which is in many cases far away from
the correct values for ions in
i
norganic solid
-
state structures. In order to estimate the error that might possibly ensue from
different and/or wrong atomic displacement
parameters, we made use of all three zircon
structures and added the value 1 at all sides of the zircon structure used by Robinson
et al.

(1971), knowing that the values are incorrect.

During Rietveld refinement the operator has the opportunity to refine

the strain of all
phases in the mixture. Real crystals contain imperfections which tend to produce local
distortions of the lattice. This fact has an impact on peak profiles (Dinnebier and Billinge,
2008). The refinement of the strain leads to a better a
greement between observed and
calculated data. Although the refinement of the strain is important, it is not always to be
recommended. Especially in a mixture of many phases such as cements, any refinement of
the strain might lead to wrong strain values. T
he fact that many phases in OPCs, such as
bassanite, arcanite and C
4
AF, display small crystallite sizes and are difficult to differentiate
from the background also complicates the refinement of the strain. Hence, it is recommended
that the strain be refine
d using the residues of the minor
-
phase enrichment experiments,
keeping these latter fixed while refining the OPC. In order to estimate the error that might be
caused by different and/or wrong values for the microstrain, our calculation of the amount of
am
orphous phase present in the cement that we were using was a calculation of same
specifically as a function of the microstrain (Lorentz function) of the major phase alite.

Because of the problems with standard materials just discussed, we also made use of
a
silicon standard. We ground, to only a very slight degree, a single piece of a silicon single
crystal produced for wafer production. These single crystals are known to have a high
chemical purity, which in turn is important if one is to proceed on the as
sumption of a
precisely correct mass attenuation coefficient of the standard. Silicon is a highly symmetric
material (cubic,

Fd
-
3
m
) which is very well
-
known and used very often as a peak position
standard. Because of the brittleness of the material one min
ute’s grinding in a micronizing
mill entirely sufficed in order to achieve our purpose. For this reason, we assume that no
amorphous content was produced during the grinding process.



Dissertation Daniel Jansen, University Erlangen
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Nürnberg, 2011

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31
-


RESULTS AND DISCUSSION


Figure 1 shows the Rietveld refinement of a recorded powder pattern of the zircon
-
standard. A good fit was obtained as a result of Rietveld analysis.



F
IGURE
1.

R
IETVELD REFINEMENT O
F A POWDER PATTERN O
F THE ZIRCON
-
STANDARD
.


The calculated G
-
factor, as well as further structural details of the standard used, is
shown in Table V. The calculated standard deviations (SD) for the determined values for
the G
-
factors were all approximately 1% of the mean values. For the calculation
of the
phase composition of the mixtures and the cement we made use of the mean values for
the G
-
factors. Indeed, different values for the G
-
factors mean also an impact on the
determined content of all crystalline phases and therefore different amorphous c
ontents.
Hence, it is to be recommended that the G
-
factor has to be calculated several times from
samples of independent preparation.










Dissertation Daniel Jansen, University Erlangen
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Nürnberg, 2011

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32
-


T
ABLE
V:

C
OMPUTED
G
-
FACTOR AND STRUCTURA
L DETAILS REGARDING
THE ZIRCON
-
STANDARD EMPLOYED
.

Scale Factor from Riet
veld

0.002980685

Cell volume

2.60E
-
22 [cm
3
]

Density

4.67 [g/cm
3
]

Mass attenuation coefficient

82.98 [cm
2
/g]

G Factor

7.80824E
-
44 [cm
5
/wt.%]


Figure 2 shows the determined amounts of zircon in the mixtures of zircon and the
NIST 622. The horizontal lines show the actual amounts present in the mixtures, the stars
the calculated amount using the
G
-
factor derived from the pure zircon standard as
well as
the calculated standard deviations. It can be seen that there is close agreement between the
actual amount of zircon in the mixtures and the amount calculated using the external G
-
factor
standard method. Hence, we can conclude that the method is su
itable for highly accurate
examinations of phase compositions in mixtures with amorphous contents.


F
IGURE
2.

C
OMPARISON BETWEEN TH
E ACTUAL AMOUNT OF Z
IRCON IN THE MIXTURE
S
PRODUCED AND THE AMO
UNT DETERMINED BY TH
E
G
-
FACTOR METHOD
.

Dissertation Daniel Jansen, University Erlangen
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Nürnberg, 2011

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33
-


All phases detectable i
n the residues of the minor
-
phase enrichment experiments of
the cement used are shown in Table VI.



T
ABLE
VI.

P
HASES DETECTED IN TH
E RESIDUES OF THE MI
NORPHASE ENRICHMENT
EXPERIMENTS
(ICDD
-
PDF
-
C
ODE
).

Phases in the residue using KOH
sucrose solution

Phas
es in the residue using
salicylic
acid
-
methanol solution

Alite (42
-
0551)

C
3
A
kub
(38
-
1429)

Belite (33
-
0302)

C
3
A
ortho
(32
-
0150)

α
`
-
C
2
S (Mueller, 2001)

C
4
AF
(30
-
0226)

Calcite
(05
-
0586)

Gypsum
(33
-
0311)

Quartz
(46
-
1045)

Bassanite
(41
-
0224)


Anhydrite
(37
-
1496)


Calcite
(05
-
0586)


Quartz
(46
-
1045)


Arcanite
(83
-
0684)



The calculated phase composition for the OPC used, including the amorphous
content which was established (actual: amorphous + not determined + misfitted) are shown
in Table VII
(Standard: Zircon #158108). It was found that the OPC does not contain
significant quantities of amorphous material. All in all, we were only able to observe an
amorphous content of around 3.3 wt.%. In view of the large error of 3.9 wt.%, resulting from
th
e additive effect of the errors of each single phase, we were not in the end able to prove
the existence of any amorphous phase. The Rietveld refinement of the OPC is shown in
Figure 3.










Dissertation Daniel Jansen, University Erlangen
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Nürnberg, 2011

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34
-



T
ABLE
VII.

D
ETERMINATION OF CONC
ENTRATIONS OF ALL PH
ASES IN

THE
OPC

USED
.

Phase

wt.%

SD [wt.%]

Alite

56.8

1.2

Belite

13.1

0.6

Alpha`C
2
S

9.2

0.5

C
3
Acub

4.4

0.3

C
3
Aortho

3.9

0.3

C
4
AF

1.8

0.2

Gypsum

1.0

0.1

Bassanite

1.2

0.1

Anhydrite

2.0

0.2

Calcite

2.0

0.2

Quartz

0.4

0.1

Arcanite

0.9

0.1

XX (total of
crystalline phases)

96.7 +/
-

3.9


Amorphous + not determined + misfitted

3.3 +/
-

3.9







F
IGURE
3.

R
IETVELD REFINEMENT O
F A POWDER PATTERN O
F THE
OPC

USED
.


Except for some problems in the fit of the major phase alite, there is close agreement
between the observed and the calculated data. Due to the fact that the fit for alite is not
perfect


depending on superstructure and/or MI/MIII modifications


we assum
e that the
misfit of the major phase alite is the cause of the amorphous content which was established,
and which is, in this specific case, no glassy component but rather non
-
fitted parts of the
Dissertation Daniel Jansen, University Erlangen
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Nürnberg, 2011

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35
-


crystalline phases. If we use the silicon as standard for th
e derivation of the factor G
-
factor,
we even arrive at an amount of 98.8 wt.% of crystalline phases, assuming the same error of
3.9 wt.% (Figure 4).


F
IGURE
4.

A
MORPHOUS CONTENT OF
THE
OPC

USED AS A FUNCTION O
F STRUCTURES
AND ATOMIC DISPLACEM
ENT PARAMETE
RS
.


Since the silicon powder used was acquired from a single crystal, there is no reason
to assume that it has a lower degree of crystallinity than commercial zircon powder. The
Rietveld refinement of the silicon powder is shown in Figure 5.



F
IGURE
5.

R
IETVELD REFINEMENT O
F A POWDER PATTERN O
F THE SILICON STANDA
RD
.


Dissertation Daniel Jansen, University Erlangen
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Nürnberg, 2011

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36
-


Furthermore, we calculated the G
-
factor using the zircon structures and the atomic
displacement parameters reported by Mursic
et al.

(1992) and Robinson
et al.

(1971). These
G
-
factors were then used to calculate over again the entire phase composition of the cement.
Figure 4 shows the amorphous content of the cement as a function of the structures of the
zircon employed. The higher the atomic displacement param
eters in the structure of the
standard are, the higher the calculated amount of the amorphous content of the investigated
OPC. This fact might possibly be explained as follows.

The atomic displacement factors modify the atomic form factor f and consequentl
y
also the structure factor F. Where the atomic displacement factors
U

increase, the structure
factor decreases correspondingly (
Eq.

4; Dinnebier and Billinge, 2008).


F

~
f

~ e
-
U






(4)


The structure factor F, in its turn, is proportional to the relati
ve intensity I resulting
from the proposed structure (Eq. 5; Young, 1995).


I
~ [
F
]
2







(5)


The scale factors s obtained via Rietveld refinement convert the relative intensities
resulting from the structures into the absolute intensities obtained from

the experiment (
Eq.

6; Hubbard
et al.
, 1976).


I
absolute

= s ×
I
relative





(6)


Where there obtains a low relative intensity due to large atomic displacement
parameters, the Rietveld scale factor will tend to be high. This will in turn tend to give rise

to
a G
-
factor which is oversized, and which will therefore result in an undersizedness of every
single phase in the mixture (
Eqs.

2
and

3). In this case, it is not to be recommended that one
refer to an “amorphous content” in respect of the difference be
tween the total of crystalline
phases and 100 wt.%, since it might be understood as a glassy (not crystalline) component.

Figure 6 shows the amorphous content of the OPC which we investigated as a
function of the microstrain
for

the major phase alite, as
well as the Rwp of the refinement.





Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

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37
-




F
IGURE
6
.

A
MORPHOUS CONTENT OF
THE
OPC

USED AS A FUNCTION O
F THE
MICROSTRAIN
FOR

ALITE
.






F
IGURE
7
.

R
IETVELD REFINEMENT O
F A POWDER PATTERN O
F THE
OPC

USED USING
DIFFERENT MICROSTRAI
NS FOR ALITE
.





Dissertation Daniel Jansen, University Erlangen
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Nürnberg, 2011

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38
-



It can be clearly seen that the microstrain has had an impact on the amount of alite,
and therefore also on the amount of the amorphous phase established. Although the Rwp
increases with increasing microstrain
for

the phase alite, no distinct worsening of
the
difference plot is visible until we reach a microstrain of about 0.225 (Figure 7).

The difference in the amount of amorphous content obtaining at a microstrain of 0.16
and that obtaining at a microstrain of 0.225 for the phase alite is already 2 wt.%.

We assume
that a very high value for the microstrain might give rise to this intensity, which is actually part
of the background and thereby involved in the intensity (scale factor) of any phase.

Furthermore, any other sort of error made in computing the

scale factors of the
phases in the OPC (e.g. misfits of structures, imprecise lattice parameters, unrealistic
crystallite sizes, insufficient characterization of the background below the peaks, etc.), or a
failure to take into consideration any phase, wil
l likewise tend to create “amorphous content”.
Therefore, we strongly recommend that care be taken to differentiate between amorphous
(glassy, not crystalline) content and the amount of non
-
determined phases arising through
Rietveld refinement, and “amorph
ous content” arising as a result of refinement misfits.

The results of the experiments which we performed lead to the conclusion that no
amorphous content could be proven to exist in the OPC used. In light of the descriptions of
possible experimental errors which we have given in this study, it is possible that

certain
findings regarding the discovery of amorphous content that have been published in recent
years may in fact only
have been the result of e.g. inadequate atomic displacement
parameters or other refined parameters. Especially atomic displacement para
meters should
only be used if they correspond to meaningful values which are between 0.005 and 0.02 Å
2

(
U
) for heavy atoms in inorganic solids and considerably higher in organic compounds (0.02
to 0.06 Å
2
).

Indeed, an amorphous (glassy) content might b
e observed in other

cements produced in
any one of several other ways, such as white cements and calcium aluminate cements. The
difference between the total of the detected crystalline phases and 100 wt.% in our studies
can be explained by misfits which oc
curred while performing Rietveld refinements of the
complex OPC and which were therefore passed on to the computed scale factors. Finally,
the study indicates that the method used is a very promising method for quantitative study of
the phases in cements.








Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

39
-


CONCLUDING REMARKS

The hydration of OPCs is a complex scientific issue and the kinetics of the hydration
process is a topic which is still under discussion. Several scientists have published articles
quantifying the crystalline phases of cement pas
tes during the process of hydration (Hesse
et
al.
, 2009; Scrivener
et al
., 2004). During hydration of OPCs, a C
-
S
-
H phase is formed which
is hardly to be detected by X
-
ray diffraction because of its low degree of crystallinity. In order
to arrive at the tr
ue phase content of each phase in the cement paste, the results obtained
via Rietveld analyses have to be converted


namely, by taking into account also the C
-
S
-
H
phase, the free water, and the bounded water (Hesse
et al .
, 2009). The implementation of
th
e method presented in this paper offers a lot of advantages. Firstly, the concentration
obtaining in each phase can be detected directly from the scale factor. Secondly, errors in
Rietveld quantification do not, here, necessarily have an impact on the othe
r phases present
in the OPC paste. Lastly, the difference between the total of crystalline phases and 100 wt.%
can be attributed directly to the amorphous components in the OPC paste, e.g. not to
crystalline bounded water and to C
-
S
-
H phase. This makes it
possible to calculate the
amorphous content of the cement paste during hydration. The G
-
factor method which we
have presented is very promising for the quantitative study of cement hydration.







ACKNOWLEDGEMENTS

The authors would like to thank Rainer Ho
ck and Helmuth Zimmermann of the
Department of Crystallography and Structural Physics for useful discussion.

Dissertation Daniel Jansen, University Erlangen
-
Nürnberg, 2011

-

40
-


References

Brindley, G.W. (1945).

“The Effect of Grain or Particle Size on X
-
ray Reflections from Mixed
Powders and Alloys, considered in relation to the Quantitative Determination of Crystalline
Substances by X
-
ray Methods.” Phil. Mag. (7) 36, 347
-
369.

Chung, F.H. (1974). “Quantitative I
nterpretation of X
-
ray Diffraction Patterns of Mixtures. II.
Adiabatic Principle of X
-
ray Diffraction Analysis of Mixtures.” J. Appl. Cryst. 7, 526
-
531.

De La Torre, A.G., Bruque, S. and Aranda, M.A.G. (2001). “Rietveld quantitative amorphous
content analy
sis,” J. Appl. Cryst. 34, 196
-
202.

De La Torre, A.G., Bruque, S., Campo, J. and Aranda, M.A.G. (2002). “The superstructure of