Advances in Chemical Engineering and Science, 2011, 1, 215-223
doi:10.4236/aces.2011.14031 Published Online October 2011 (http://www.SciRP.org/journal/aces)
Study the Critical Role of Admixtures in Cement
Pr oduction: The Optimum State of Cassiterite (SnO2)
Addition as a Natural Mineralizer-Oxide Influencing
the Cement P roperties
Ioannis Baziotis1*, Andreas Chandrinos2
1School of Mini ng and Metallurgical Engineering, Department of Geological Sciences,
National Technical University of Athens, Athens, Greece
2School of Chemical Engineering, Laboratory of Inorganic and Analytical Chemistry,
National Technica l U niversity of Ath e ns, At hens, Greece
Received July 20, 2011; revised A ugust 10, 2011; accepted September 17, 2011
Abstract
In this work we evaluate the role of a natural mineralizer-oxide like cassiterite (SnO2) on the cement proper-
ties. In particular, we study the effect of different quantities of SnO2 with 0.5, 1.0, 1.5 and 2.0 wt% on bur-
nability of industrial raw mix by free lime evaluation. We obtain four datasets, with successive increase of
temperature at 1250˚C, 1350˚C, 1400˚C and 1450˚C. We study the produced cassiterite-added clinker with
X-ray diffraction (XRD), thermal analysis (DTA) and scanning electron microscopy (SEM). Though, we
characterize the new phases formed and whether, adding excess SnO2 is promote forms of C3S, C2S influen-
cing the final quality of cement.
Keywords: Cement Properties, Cassiterite, Burnability, Hydration
1. Introduction
Cement has a wide range of uses like in pottery, con-
struction and manufacturing; all of them need a high-
potential of energy consumption. Because of that, scien-
tists and manufacturers use admixtures to achieve a bal-
ance between energy and quality. Such admixtures play,
indir ect ly, a n i mpor tant ro le i n the gre en ga se s emi ssio ns;
though the lower the energy consumption the lower the
gas emissions like CO2 [1]. Only small amounts of ad-
mixtures (<2 wt%) could contr ol the temperature at whi-
ch produced high-quality clin ker [2].
Recently [3] and [4], study the influence of synthetic
NaF, KF, SnO2 and TiO2 and their mixtures implying
that they decrease the temperature at which starts the
dissociation of the calcium carbonate from the raw mix.
However, the influence of fluorides on burnability of raw
mix is more intense compared with that of oxides. Be-
sides, according to [5] the presence of SnO2 ~1.0 wt% in
the raw mix lowers more intensively the values of free
lime. Thus preferring the C3S (alite) formation with add-
ing both oxides, fluorides and their mi xtur es.
In this work we evaluate the role of a natural minera-
lizer-oxide like cassiterite (Sn O2) [e.g. 6] on the cement
properties. In particular, we study the effect of different
quantities of SnO2 with 0.5, 1.0, 1.5 and 2.0 wt% on
burna bili ty o f i ndustr ia l ra w mi x b y free li me e valua ti on.
We ob tain four datasets with successive increase of tem-
perature at 1250˚C, 1350˚C, 1400˚C and 1450˚C. The
produced cassiterite-added clinker is studied with X-ray
diffraction (XRD), thermal anal ysis (DTA) and scanning
electron microscopy (SEM). Though, we characterize the
new phases formed and whether adds excess SnO2 is
promote forms of C3S, C2S influencing the final quality
of cement .
2. Experimental Work-Analytical Methods
For the current study we use primary material for the
cement production, gained fr om the Ti tan S.A. factory. It
has the follo wing chemical co mposition (i n wt%) Ca CO3:
79.53, SiO2: 14.52, Al2O3: 3.82, Fe2O3: 2.13. The grain

I. BAZIOTIS ET AL.
216
size was nearly 90 μm.
Industrial cassiterites SnO2, granted by a large multi-
national ceramics industry in Chalkis, used in similar
particle size to the raw meal. We produce five sample s o f
raw meal weighting 220 gr, by adding cassiterites with
increasing ratio of 0.0, 0.5, 1.0, 1.5 and 2.0 wt%. After-
wards, homogenization in a ball mill occurs and format
of the samples in pellets. We burn pellets in a
high-temperature oven at four different temperatures
1200˚C, 1350˚C, 1400˚C and 1450 ˚C.
Clinker studied using the following methods: 1) Dif-
ferential thermal analysis (DTA) with raw meal samples
weighting 60 mg. In particular, we used the Thermo-
gravimetric Analyzer TGA/SDTA 851e METTLER
TOLEDO’s at the Laboratory of Inorganic and Analyti-
cal Chemistry, Schoo l of Che mical En gineeri ng, Nation-
al Technical University of Athens. The air gas was ni-
trogen with 50 cm3/min flow. The study begins at 25˚C
with a constant rate 20˚C /min until the maximum tem-
perature of 1500˚C. 2) We apply the method of X-ray
diffraction (XRD) for determination of free-lime in
clinker. Irradiating the powdered samples took place in
the range between 3 and 75 degrees. We use amplified
electronic scales of four decimals, which weighed 0,5 gr
of ground clinker. We used 50 ml ethylene glycol and
HCl 0.1 N and 1 N accordingly. 3) Secondary electron
microscopy (SEM) analyses of two clinker samples
heated at 1400˚C, one cassiterite-free and the other’s
content was 2 wt%. The analyses performed using a
JEOL JSM 5600 SEM equipped with a LINK ISIS 3000
energy dispersive system at the Department of Geology,
Universit y of Athens. Analytical conditions were 20 KV
acceleration voltage, 0.5 nA probe current with acquisi-
tion time 50 sec. Covering the granules of the two sam-
ples with gold to avoid concentrating electrons.
Afterwards thermal treatment at 1450˚C applied to
transform clinker to cement; therefore we used plaster in
powder form and in a rate of 5% w/w. Then followed a
synalesis in a grinder for 10 min. From the resulted ce-
ment, we prepare pastes to study the hydration rate.
Pastes with different mode of cassiterite took place in
disk-shaped format and placed in water for 1, 2, 7 and 28
days. At the end of the two days, we remove samples
with cassiterite content 0.0, 0.5, 1.0, 1.5 and 2.0 wt%
from the water and soaked them in acetone solution to
stop the hydration. The samples placed in an oven at
1200˚C for one da y and then pulve riz ed i n a grind er. The
total weight loss from pastes is attributed to chemical
bounded water liberated during dehydration at 100˚C -
300˚C and dehydroxylation of portlandite at 450˚C -
550˚C. The results are presented in detail in table 1. Lat-
er, the samples analyzed with XRD to discover whether
they had formed all the necessary steps. Also we study
the calcination loss in the samples. We repeat the proce-
dure at the end of seven and twe nty ei ght d ays.
3. Results and Discussion
For the study of clinker we use industrial raw mix with
cassiterite as admixture in different quantities 0.5, 1.0,
1.5 and 2.0 wt%. We study the burnability of raw mix
with TG and DTA thermal methods. The samples heated
up to 900˚C hold two endothermal peaks at ~200 and
~850˚C which are because of dissociation of cla y miner-
als and calcite respectively. The thermal range between
900˚C - 1200˚C doesn’t add important knowledge into
the thermal behavior of the studied samples. However,
we prove the first app ear of belite (C2S) by developing
an exothermic peak above 1200˚C. The early formation
of belite (at <1200˚C) is concurrent with the maximum
cassiterite content (2 wt%; Figure 1(a)). A significant
point at SnO2 = 1 wt% is the presence of a broad endo-
thermal peak, covered the belite one, assigned to melt
formation (F igures 1(a) and (b)).
Evaluating X-ray diffraction diagrams before hydra-
tion (Figures 2-4) show the absence of calcite peak be-
cause of its completed dissociation at te mperat ures up to
1350˚C. Since 1350˚C formation of belite phases with
minor amounts of C3A, C4AF, CaO and Ca(OH)2 com-
ponents. SiO2 is absent. At 1400˚C we obey all phases
whereas alite (C3S) comes for first time; however de-
creasing of CaO content occurs. At higher temperatures
(>1400˚C) CaO is continuously decreasing; at SnO2 = 1
wt% CaO content drop down to its minimum value. Also
we note the phase Ca2SnO4 only in the sample heated at
1400 and 1450˚C with cassiterite content at 2 wt%.
Evaluating X-ray diffraction diagrams after hydration
(Figures 5 and 6) sho w that a t 1 and 2 days a mixture o f
hydrated and non-hydrated phases occur. The ma i n hy-
drated phase is Ca(OH)2. The samples of 7 and 28 days
from hydration, showed a clear decrease of non-hydrated
phases; the samples contain 1 wt% cassiterite point out
the highest h ydration rate (Figure s 7 and 8).
Determining fCaO and burnability rate suggest that
cassiterite in the raw mix influences positively the heat
treatment and lowers more intensively the values of free
lime. We gain the best results at SnO2 = 1 wt% (Figure
9).
Calculating the water content bounded on pastes
shows the cassiterite-free sample takes over the highest
hydration rate at 1.2 and 7 days (Table 1). However at
28 days the highest hydration rate occupied in the sample
with 1 wt% cassiter ite (Table 1).
SEM investigation suggests the C2S and C3S phases
have similar shape with or without adding cassiterite in
the primary material. However the presence of cassiterite

I. BAZIOTIS ET AL.
217
(a)
(b)
Figure 1. Comparison of DTA thermal analysis results of samples with SnO2 = 1 and 2 wt% respectively. (a) At ~850˚C an
endother mal pea k occurs du e to calcite dissoci ation. At 1200˚C devel oping a n exother mic pea k sugg ests the first presence of
belite (C2S). Th e early for mation of belite (at <1200˚C) is concurrent with the max imum of cassiterite content (SnO2 = 2 wt%).
(b) Early melt formation at SnO2 = 1 wt% probably hide form ing belite.

I. BAZIOTIS ET AL.
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Figure 2. X-ray diffractog rams for 2 θ 3 - 75 (CuKa radiation) showing the clinker at 1350˚C with SnO2. (a) 0.5 w t%, (b) 1.0
wt%, (c) 1.5 wt% and (d) 2.0 wt%.
Figure 3. X-ray diffractog rams for 2 θ 3 - 75 (CuKa radiation) showing the clinker at 1400˚C with SnO2. (a) 0.5 w t%, (b) 1.0
wt%, (c) 1.5 wt% and (d) 2.0 wt%.

I. BAZIOTIS ET AL.
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Figure 4. X-ray diffractog rams for 2 θ 3 - 75 (CuKa radiation) showing the clinker at 1450˚C wi th SnO2. (a) 0.5 wt%, (b) 1.0
wt%, (c) 1.5 wt% and (d) 2.0 wt%.
Figure 5. X-ray diffr actogr ams for 2 θ 3 - 75 (CuK a radiat ion) show ing t he hydr ate d paste s at 1 day w ith SnO 2. (a) 0.5 w t%,
(b) 1.0 wt%, (c) 1.5 wt% and (d) 2.0 wt%.

I. BAZIOTIS ET AL.
220
Figure 6. X-ray diffr actog ra ms for 2 θ 3 - 75 ( CuKa radi atio n) s how ing the hy dr ated p ast es at 2 day s w ith S nO2. (a) 0. 5 w t%,
(b) 1.0 wt%, (c) 1.5 wt% and (d) 2.0 wt%.
Figure 7. X-ray diffr actog ra ms for 2 θ 3 - 75 (C uKa radi ati on) show i ng t he hydr ate d pas tes at 7 days wi th SnO2. (a) 0.5 w t%,
(b) 1.0 wt%, (c) 1.5 wt% and (d) 2.0 wt%.

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221
Figure 8. X-ray di ffrac tograms for 2θ 3 - 75 (C uKa radiation) showing the hydrat ed p a stes at 28 da ys with SnO2. (a) 0.5 wt%,
(b) 1.0 wt%, (c) 1.5 wt% and (d) 2.0 wt%.
Figure 9. fCaO-SnO2 diag ra m show i ng the ide al fC aO co ndi tio ns at va rio us te mper atur es. We re mark t hat at S nO2 = 1 wt%
the fC aO become minimum, influencing the bur nabilit y behavior.

I. BAZIOTIS ET AL.
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Table 1. Experimental data showing the calculated water
bounded on pastes with different cassiterite content at 1, 2,
7 and 28 days.
SnO
2
content
(in wt%) 1 day 2 days 7 days 28 days
0.0
9.23
10.53
13.58
16.31
0.5 8.24 10.26 12.50 16.26
1.0 8.87 10.25 13.04 17.04
1.5
8.23
9.89
12.70
15.92
2.0 8.10 9.50 12.21 16.00
increases the melt production compared with the cassite-
rite-free one. Microanalysis shows incorporating Sn in
the phase of C3S and not in C2S. Finally, needle-like
crystals occur in the form of Ca2SnO4 (Figure 10). In
Figure 11 we present the EDX spectrum of needle-like
crystals marking the Ca2SnO4 formation in contact with
C3S.
Our experimental results are follow those carried out
by [7]. Further investigation suggests that cassiterite in-
crease over 1 wt% could not improve the burnability
behavior because of Ca2SnO4 formation instead of alite
and belite.
(a)
(b)
Figure 10. (a) For mation of needle -like crystals of Ca2SnO4
in conta ct with C3S. (b) Zoomed part of (a).
Figure 11. ED X spectru m of Ca2S nO4 of nee dl e-l i ke crystal s
in contact with C3S (s ee Figure 10).
4. Conclusions
Our results show that during cement production adding
cassiterite in the raw mix influences positively the heat
treatment and lowers more intensively the values of free
lime. Though we get the best results with SnO2 = 1 wt%.
Therefore, the presence of cassiterite, results in the
following: 1) promotes creating white, needle-like, crys-
tals of Ca2SnO4 and 2) easier formation of C3S (alite)
instead of C2S (belite). Therefore Sn has the ability to
incorporate into the crystal lattice of alite and cannot
dissipate during cooling. Finally, cements that contain
cassiterite as an admixture show a small delay in their
early hydration at 1, 2 and 7 days, which stops after 28
days.
5. Acknowledgemen t s
Vgenopoulos A., Tsivilis S. and Tsimas S. are greatly
acknowledged for helpful remarks and their persistent
assistance to Chandirnos A. during his MSc Thesis.
Careful and constructive review by an anonymous re-
viewer has helped to improve the manuscript. We want
to express our sincere thanks to the editor of ACES for
his editorial handling.
6. Referen ces
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223
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