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On the reactivity of the cement clinkers components by means of Laser Granulometer
CEMENT and CONCRETE RESEARCH. Vol. 15, pp. 315-319, 1985. Printed in the USA. 0008-8846/85 $3.00+00. Copyright (c) 1985 Pergamon Press, Ltd.
ON THE REACTIVITY OF THE CEMENT CLINKERS COMPONENTS BY MEANS OF LASER GRANULOMETER
A. Negro, L. Montanaro and A. Bachiorrini Dipartimento di Scienza dei Materiali e Ingegneria Chimica Politecnico di Torino - Corso Duca degli Abruzzi 24 -
ITALY
(Communicated by M. Regourd) (Received August 9, 1984)
ABSTRACT The Laser Granulometer is an efficient instrument for detecting the reactivity of cement clinkers components in contact with water. Results are satisfactorily comparable with those obtained by means of different analysis techniques. Further applications are suggested.
INTRODUCTION The Laser Granulometer, at first perfected at CERILH Paris (l-4),showed itself the most suitable instrument to carry out quick,accurate and reproducible particle size analyses (5). It works on the principle of light diffraction by an array of particles. The classic technique consists in suspending a powder in an unreactive liquid, achieving the particle size distribution and its respective histogram. We have used a Malvern 3600 D Particle Sizer with a computer, connected with a multi-element detector (6). It also supplies further parameters,such as the " obscuration ", which represents the fraction of the incident light on the particles, that is scattered or absorbed, and the " sample concentration",which is the volume of sample material per unit volume of the suspending media, ie. the sum of the volumes of all particles, present on average (7). Since these data were available, we thought we could investigate the behaviour of a powder in contact with a reactive liquid, following the time depending variation of " sample concentration ". As first approach, we have considered the case of the cement clinkers components. EXPERIMENTAL This investigation was carried out on the main Portland clinker and alumina clinker constituents: triclinic C 3 S , ~ C 2 S , cubic and orthorhombic C3A , 315
316
Vol. 15, No. 2 A. Negro, et al.
C6A2F , C12A7, CA, CA 2. All the samples were ground at a particle size range between 44 507~m. However, considering the sieving accuracy, we verified that samples had similar particle size distributions.
and the
Measurements were carried out at 22 i 2°C using such water/solid ratio that a starting "sample concentration" value, placed near 0.033, was reached . This was achieved using about 15 mg of solid in 18 ml of distilled water, kept in continous stirring by a magnetic stirrer at constant rate in all the tests. The starting " obscuration " value was into the best use limits of the instrument. On the ground of the fixed particle size range, we have chosen, among the available lenses, a " Fourier transform lens " with focal length of IO0 mm, which allowed data optimization. At the beginning of each test, the computer was program~ned to carry out sixty-one storages, every 4 minutes. Each data storage consisted of five hundred successive sweeps and a single sweep took about 20 msec. The data, stored in the computer memory, were processed by means of a pluri-modal " Model independent programme " (6). Unlike the " Two parameter programmes ", as Rosin Rammler, Normal and Log Normal, in which processing is modelled by an analytical function having two independent variables, by means of " Model independent programme " the computer optimises sixteen independent parameters, generally obtaining a lower error value, due to the greater degrees of freedom (6). In our tests, the " Log Error ", which gives the degree of fit between "measured" and "computed" data, always kept itself in a range of accurate fit values. Nevertheless, it must be always kept in mind that,when the " obscuration " falls below the limit value, the signal plus background scattering is not adequately separable from the background measurement to allow accurate signal estimation. RESULTS AND DISCUSSION In the Figures 1 and 2 the "sample concentration" values, respectively for Portland and alumina clinkers components, as a function of time are shown. Each curve represents the average obtained from three determinations. The recording was stopped after 4 hours since, especially for silicates, the presence of gel sticking to cell walls falsified measurements. Our curves are comparable to those obtained by Boikova et al. (8) for cubic and orthorhombic C3A , by Midgley et al. (9) for ferrites, by Kondo and Ueda (i0) for C3S,by Galtier (ii) for CA, CI2A 7 and CA2, even if those authors worked with water/solid ratios very different from ours and with different analysis techniques ( X-Ray diffraction, Conductimetry ). Even if, of course, a quantitative relation between our results and others is not possible, our method leads to the same conclusions. In fact, it allows to distinguish different reactivity of the clinker components and to scale it, showing that reactivity of aluminates and silicates increases with increasing of C/A and C/S ratios. Furthermore, it allows to discriminate reactivity of different crystal forms of C3A. A detailed examination of each curve makes possible to get further informations about the behaviour of the solid in contact with water. It can be observed that in some phases ( C~A, C12A7, C6A2F ) the dissolution regularly goes on in function of time; on ~he contrary, in others ( C A 2 , ~ C 2 S , C3S ) an opposite phenomenon, probably due to an agglomeration and/or gel formation , sets itself against dissolution more or less efficiently and durably. As for CA, the agglomeration and/or gel formation seem to oppose dissolution only in the early minutes.
Vol. 15, No. 2
317 CLINKER,
REACTIVITY,
LASER GRANULOMETER
•..=...•-"° ,~ i....~ ,-'.•'.o•'• •
%
0.03.
Q03
k
=o o~002 U
0.02\
e
U) 0.01,
\
}, f\"\
E u)
",.,.
0.01
"\",,
~ ~
"~
\\
..~"
L"~=.~.~....~ ............. ::,h,:."J ............ 1
2 Time
3 (hours)
O
4
¸
0
1
2 Time
3 (hours)
4
FIG. i FIG. 2 Dissolution curves for the main Portland clinker components: • Cubic C3A o Orthorhombic C3A C6A2 F • C3S • > C2S
Dissolution curves for the main alumina clinker components: e C12A7 • CA • CA 2
However, w h e r e a s ~ C 2 S and CA dissolution definitively prevails at long time, owing to destruction of agglomeration and/or passing of gel into liquid phase, the following, continous increase of CA " sample concentration" could justify the hypothesis of the prevalence of th~se processes over dissolution. SEM observation strengthened gel formation on CA 2 grains ( Figure 3 ). Furthermore, we can explain the singularity of the C3S curve through a more complex process. The starting dissolution is followed by a period of competition between dissolution and gel coating phenomenon, as previously observed by Regourd (12) by means of TEM. After, dissolution again prevails till the saturation of the solution is reached. Then, another " sample concentration " increase takes place, due to formation of a partly crystallized hydrated phase, which wraps the silicate grains ( Figure 4 ). The sensitivity of the suggested method also allows to show clearly the influence of stockage period on solid reactivity• Two examples are reported in Figure 5. On acquired experiences,
it seems possible to use
this method
in
the
318
Vol. 15, No. 2 A. Negro, et al.
v
2~m
;
(a)
(b)
!
4,7U'rn
FIG. 3 Development of CA 2 grains and gel coating in function of contact time water: (a) after 2 hours; (b) after 4 hours 30 minutes
(a)
2 7;J'm I
~
(b) FIG.
with
;~L~m
2
4
Development of surface of C^S grains in function of contact time with water: • (a) after 2 hours 30 mlnutes; (b) after 4 hours field of hydraulic binders, not only to study phenomena of dissolution and hydration, but also the influence exerted on them by admixtures, in the early stages; some of our tests carried out with grinding aids and strength improvers support us in this opinion.
Vol. 15, No. 2
319 CLINKER, REACTIVITY, LASER GRANULOMETER
0.05
P
FIG. 5
? o
~*~
~ 0.03,
ot
o
(J =g
.-&
E g,
Influence of stockage period on reactivity of C3A a n d ~ C2S • C3A just prepared o C3A after 2 years stockage in drier • ~ C 2 S just prepared > C 2 S after 2 years stockage in drier
0.01
"e
O'
0
Time
(hours)
ACKNOWLEDGEMENT We wish to thank Dr. Regourd of CERILH Paris, Prof.Brisi and Lucco Bor lera of our Department for supplying us with the samples of C 3 S , ~ C 2 S , orthorhombic C3A , CA2. This work was supported by National Research Council of Italy. REFERENCES i 2 3 4 5 6
. . . . . .
7 . 8 . 9 . IO. Ii. 12.
M.R.Peltier, Revue de l'Industrie Min~rale 4, 319 (1971) M.R.Peltier, Ciments et chaux 602, 23 (197~) J.P.Meric, Rev. Mat. Const. 687, 80 (1974) C.Barthelemy and J.C.Hugon, Rev. Mat. Const. 701, 227 (1976) G.Pintor, Ii Cemento (1),15 (1977) Malvern Instruments Ltd., 2600/3600 Particle Sizer Handbook, Version2.0 (1982) Malvern Instruments Ltd., private communication (1984) A.I.Boikova, A.I.Domansky, V.A.Paramonova, G.P.Stavitskaja and V.M. Nikushchenko, Cem. Concr. Res. 7, 483 (1977) H.G.Midgley, D.Rosaman and K.E.Fletcher, Proc° IV Int. Sym. Chem. Cem. ~, 69 , Washington D.C. (1960) R.Kondo and S.Ueda, Proc. V Int. Sym. Chem. Cement II- 4, 203 Tokyo (1968) P.Galtier, Th@se de Docteur-lng@nieur "Hydratation et r~activit~ des liants calciques: sulfate de calcium, aluminate monocalcique", E.N.S.M. St Etienne (1981) M.Regourd, Rev. Mat. Const. 745, 359 (1983)
ON THE REACTIVITY OF THE CEMENT CLINKERS COMPONENTS BY MEANS OF LASER GRANULOMETER
A. Negro, L. Montanaro and A. Bachiorrini Dipartimento di Scienza dei Materiali e Ingegneria Chimica Politecnico di Torino - Corso Duca degli Abruzzi 24 -
ITALY
(Communicated by M. Regourd) (Received August 9, 1984)
ABSTRACT The Laser Granulometer is an efficient instrument for detecting the reactivity of cement clinkers components in contact with water. Results are satisfactorily comparable with those obtained by means of different analysis techniques. Further applications are suggested.
INTRODUCTION The Laser Granulometer, at first perfected at CERILH Paris (l-4),showed itself the most suitable instrument to carry out quick,accurate and reproducible particle size analyses (5). It works on the principle of light diffraction by an array of particles. The classic technique consists in suspending a powder in an unreactive liquid, achieving the particle size distribution and its respective histogram. We have used a Malvern 3600 D Particle Sizer with a computer, connected with a multi-element detector (6). It also supplies further parameters,such as the " obscuration ", which represents the fraction of the incident light on the particles, that is scattered or absorbed, and the " sample concentration",which is the volume of sample material per unit volume of the suspending media, ie. the sum of the volumes of all particles, present on average (7). Since these data were available, we thought we could investigate the behaviour of a powder in contact with a reactive liquid, following the time depending variation of " sample concentration ". As first approach, we have considered the case of the cement clinkers components. EXPERIMENTAL This investigation was carried out on the main Portland clinker and alumina clinker constituents: triclinic C 3 S , ~ C 2 S , cubic and orthorhombic C3A , 315
316
Vol. 15, No. 2 A. Negro, et al.
C6A2F , C12A7, CA, CA 2. All the samples were ground at a particle size range between 44 507~m. However, considering the sieving accuracy, we verified that samples had similar particle size distributions.
and the
Measurements were carried out at 22 i 2°C using such water/solid ratio that a starting "sample concentration" value, placed near 0.033, was reached . This was achieved using about 15 mg of solid in 18 ml of distilled water, kept in continous stirring by a magnetic stirrer at constant rate in all the tests. The starting " obscuration " value was into the best use limits of the instrument. On the ground of the fixed particle size range, we have chosen, among the available lenses, a " Fourier transform lens " with focal length of IO0 mm, which allowed data optimization. At the beginning of each test, the computer was program~ned to carry out sixty-one storages, every 4 minutes. Each data storage consisted of five hundred successive sweeps and a single sweep took about 20 msec. The data, stored in the computer memory, were processed by means of a pluri-modal " Model independent programme " (6). Unlike the " Two parameter programmes ", as Rosin Rammler, Normal and Log Normal, in which processing is modelled by an analytical function having two independent variables, by means of " Model independent programme " the computer optimises sixteen independent parameters, generally obtaining a lower error value, due to the greater degrees of freedom (6). In our tests, the " Log Error ", which gives the degree of fit between "measured" and "computed" data, always kept itself in a range of accurate fit values. Nevertheless, it must be always kept in mind that,when the " obscuration " falls below the limit value, the signal plus background scattering is not adequately separable from the background measurement to allow accurate signal estimation. RESULTS AND DISCUSSION In the Figures 1 and 2 the "sample concentration" values, respectively for Portland and alumina clinkers components, as a function of time are shown. Each curve represents the average obtained from three determinations. The recording was stopped after 4 hours since, especially for silicates, the presence of gel sticking to cell walls falsified measurements. Our curves are comparable to those obtained by Boikova et al. (8) for cubic and orthorhombic C3A , by Midgley et al. (9) for ferrites, by Kondo and Ueda (i0) for C3S,by Galtier (ii) for CA, CI2A 7 and CA2, even if those authors worked with water/solid ratios very different from ours and with different analysis techniques ( X-Ray diffraction, Conductimetry ). Even if, of course, a quantitative relation between our results and others is not possible, our method leads to the same conclusions. In fact, it allows to distinguish different reactivity of the clinker components and to scale it, showing that reactivity of aluminates and silicates increases with increasing of C/A and C/S ratios. Furthermore, it allows to discriminate reactivity of different crystal forms of C3A. A detailed examination of each curve makes possible to get further informations about the behaviour of the solid in contact with water. It can be observed that in some phases ( C~A, C12A7, C6A2F ) the dissolution regularly goes on in function of time; on ~he contrary, in others ( C A 2 , ~ C 2 S , C3S ) an opposite phenomenon, probably due to an agglomeration and/or gel formation , sets itself against dissolution more or less efficiently and durably. As for CA, the agglomeration and/or gel formation seem to oppose dissolution only in the early minutes.
Vol. 15, No. 2
317 CLINKER,
REACTIVITY,
LASER GRANULOMETER
•..=...•-"° ,~ i....~ ,-'.•'.o•'• •
%
0.03.
Q03
k
=o o~002 U
0.02\
e
U) 0.01,
\
}, f\"\
E u)
",.,.
0.01
"\",,
~ ~
"~
\\
..~"
L"~=.~.~....~ ............. ::,h,:."J ............ 1
2 Time
3 (hours)
O
4
¸
0
1
2 Time
3 (hours)
4
FIG. i FIG. 2 Dissolution curves for the main Portland clinker components: • Cubic C3A o Orthorhombic C3A C6A2 F • C3S • > C2S
Dissolution curves for the main alumina clinker components: e C12A7 • CA • CA 2
However, w h e r e a s ~ C 2 S and CA dissolution definitively prevails at long time, owing to destruction of agglomeration and/or passing of gel into liquid phase, the following, continous increase of CA " sample concentration" could justify the hypothesis of the prevalence of th~se processes over dissolution. SEM observation strengthened gel formation on CA 2 grains ( Figure 3 ). Furthermore, we can explain the singularity of the C3S curve through a more complex process. The starting dissolution is followed by a period of competition between dissolution and gel coating phenomenon, as previously observed by Regourd (12) by means of TEM. After, dissolution again prevails till the saturation of the solution is reached. Then, another " sample concentration " increase takes place, due to formation of a partly crystallized hydrated phase, which wraps the silicate grains ( Figure 4 ). The sensitivity of the suggested method also allows to show clearly the influence of stockage period on solid reactivity• Two examples are reported in Figure 5. On acquired experiences,
it seems possible to use
this method
in
the
318
Vol. 15, No. 2 A. Negro, et al.
v
2~m
;
(a)
(b)
!
4,7U'rn
FIG. 3 Development of CA 2 grains and gel coating in function of contact time water: (a) after 2 hours; (b) after 4 hours 30 minutes
(a)
2 7;J'm I
~
(b) FIG.
with
;~L~m
2
4
Development of surface of C^S grains in function of contact time with water: • (a) after 2 hours 30 mlnutes; (b) after 4 hours field of hydraulic binders, not only to study phenomena of dissolution and hydration, but also the influence exerted on them by admixtures, in the early stages; some of our tests carried out with grinding aids and strength improvers support us in this opinion.
Vol. 15, No. 2
319 CLINKER, REACTIVITY, LASER GRANULOMETER
0.05
P
FIG. 5
? o
~*~
~ 0.03,
ot
o
(J =g
.-&
E g,
Influence of stockage period on reactivity of C3A a n d ~ C2S • C3A just prepared o C3A after 2 years stockage in drier • ~ C 2 S just prepared > C 2 S after 2 years stockage in drier
0.01
"e
O'
0
Time
(hours)
ACKNOWLEDGEMENT We wish to thank Dr. Regourd of CERILH Paris, Prof.Brisi and Lucco Bor lera of our Department for supplying us with the samples of C 3 S , ~ C 2 S , orthorhombic C3A , CA2. This work was supported by National Research Council of Italy. REFERENCES i 2 3 4 5 6
. . . . . .
7 . 8 . 9 . IO. Ii. 12.
M.R.Peltier, Revue de l'Industrie Min~rale 4, 319 (1971) M.R.Peltier, Ciments et chaux 602, 23 (197~) J.P.Meric, Rev. Mat. Const. 687, 80 (1974) C.Barthelemy and J.C.Hugon, Rev. Mat. Const. 701, 227 (1976) G.Pintor, Ii Cemento (1),15 (1977) Malvern Instruments Ltd., 2600/3600 Particle Sizer Handbook, Version2.0 (1982) Malvern Instruments Ltd., private communication (1984) A.I.Boikova, A.I.Domansky, V.A.Paramonova, G.P.Stavitskaja and V.M. Nikushchenko, Cem. Concr. Res. 7, 483 (1977) H.G.Midgley, D.Rosaman and K.E.Fletcher, Proc° IV Int. Sym. Chem. Cem. ~, 69 , Washington D.C. (1960) R.Kondo and S.Ueda, Proc. V Int. Sym. Chem. Cement II- 4, 203 Tokyo (1968) P.Galtier, Th@se de Docteur-lng@nieur "Hydratation et r~activit~ des liants calciques: sulfate de calcium, aluminate monocalcique", E.N.S.M. St Etienne (1981) M.Regourd, Rev. Mat. Const. 745, 359 (1983)