Properties of three newly developed quick cements

Cement and Concrete Research, Vol. 24, No. 5, pp. 801-812, 1994 Copyright © 1994 Elsevier Science Ltd Printed in the USA. All rights reserved 0008-8846/94 $6.00+.00

Pergamon

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0008-8846(94)00023-9

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PROPERTIES OF THREE NEWLY DEVELOPED QUICK CEMENTS D. KnOfel and J.-F. Wang Laboratory for Chemistry of Construction Materials, University of Siegen Paul-Bonatz-Strafe 9-11, 5900 Siegen / Germany

(Communicated by F.H. Wittman) (Received August 3; in final form Sept. 20, 1993)

ABSTRACT In CaO-SiO2-AI203-Fe203-SO3-CaF2 systems, three kinds of quick cements from different clinkers were produced (C3S-CIIAT-CaF2-C2(A,F), CI1AT-CaF2-C2S-C2(A,F) and C4A3"~-C2S-C2(A,F)). Blast furnace slag and lime stone were added as interground additives to these quick cements (20% - 50% weight). During the first 2 hours the compressive strengths of the quick cements reached gD,2h = 7-28 N/mm 2 and after 28 days BD,28d= 45-64 N/mm 2 In this paper the formation of cement clinker as well as the hydration behaviour, the development of strength, the pore structure (for a storage in water, in atmosphere and in an atmosphere of 1 vol.-% CO2; for a temperature of 5°C and 20°C) and the setting process of quick cements, as well as the carbonization of quick cement mortar were investigated and discussed.

Introduction This paper is concerned with the development of different quick cements in the system CaO-SiO2-AI203-Fe203-SO3-CaF2 with the phases CI1A7-CaF2 and C4A3~ (1). After considerable optimizing efforts, three quick cement clinkers composed in rather different systems (C3SCI1A7.CaF2-C2(A,F), CIlA7.CaF2-C2S-C2(A,F) and C4Aa~-C2S-C2(A,F)) have been selected for the main tests and will be described below.

Production of samples The three different quick cement clinkers were produced with chemically pure substances The potential content of clinker phases has been listed in table 1. TABLE 1 ' Potential content of clinker phases according to theoretical caculation (ma-%) Clinker A B C

C3S 70

CllA7.CaF2 25 60 5 801

C4A3s

C25

60

30 30

C2(A,F) 5 10 5

802

D. Kn6fel and J.-F. Wang

Vol. 24. No. 5

The clinkers have been milled together with sulphate bearers, activators and interground additives to a fineness of 5000+200 cm2/g according to Blaine fineness. The corresponding chemical composition of the quick cements are given in table 2. TABLE 2 "Chemical composition of quick cements (ma.-%) No. 1 2

S

A

F

C

M

N

SO3

F-

16.6 14.2

11.9 19.0

1.12 1.25

56.0 48.7

1.85 2.57

1.09 0.86

7.84 7.12

1.29 0.96

TiO2 0.07 1.17

loss. 2.03 4.05

3

12.2

21.1

1.00

44.9

1.67

1.11

12.8

0.49

0.69

4.17

4

19.7

18.0

1.14

46.8

4.01

0.87

7.63

0.76

1.06

5

5.78

21.0

1.40

51.0

0.48

1.06

9.21

1.25

1.32

7.93

Quick cement: 1 = clinker A + sulphate bearer + activator + BFS + LS 2 = clinker B + sulphate bearer + activator + BFS + LS 3 = clinker C + sulphate bearer + activator + BFS + LS 4 = clinker B + sulphate bearer + activator + BFS 5 = clinker B + sulphate bearer + activator + LS ( BFS = blast furnace slag, LS = lime stone )

Results and Discussion Formation of clinker phases 1. Influence of temperature The results of X-ray diffraction investigations and of determinations of free lime are displayed in table 3 and Fig. 1. TABLE 3 "Phases of clinker A, B and C depending on burning temperatur Clinker

A

B

C

IO00°C C28, CllA7"CaF2 C4A3g, C4AF 3C2S'3C-s'CaF2 2C2S'Cg, 3C3S'CaF2 fr- CaO C11A7"CaF2, C2S C4A3g, C4AF 3C2S.3Cg'CaF2 2C2S.Cg, 3C3S.CaF2 fr- CaO CllA7"CaF2, C4A3g C2S, C4AF, C3A 3C2S'3Cg'CaF2 2C2S-Cg, 3C3S'CaF2 fr- CaO

1200°C C3S, CllA7"CaF2 C2S, C4A3g, C4AF 3C2S'3Cg'CaF2 2C2S-Cg fr- CaO

1350°C C3S, CllA7"CaF2 C2S, C4A3"g, C4AF fr- CaO

CllA7"CaF2, C2S C11A7"CaF2, C2S C4A3~, C4AF, C3S C4A3~, C3S, C4AF 3C2S'3Cg-CaF2 2C2S'C~ fr- CaO C4A3g, C11AT'CaF2 C2S, C4AF, C3S 3C2S'3Cg'CaF2 2C2S'Cg, C-s fr-CaO

C4A3g, C11A7-CaF2 C2S, C3S, C4AF C3A

It is a striking fact that the binding of lime is accelerated by the formation of intermediate phases if corresponding quantities of CaF2 and SO3 are present. As a result of this the formation of alite is already possible for 1100°C and the content of free lime for A, B and C could be

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reduced to about 1 ma.-% already between 1300°C and 1350°C. At the same time, for these temperatures the main clinker phases alite, CI~A7.CaF2, C4A3g and belite can be determined for clinker A, B and C, i.e., in system CaO-SiO2-AhO3-Fe203-SOa-CaF2 the burning temperature for the different quick cement clinkers is distinctly lower than for normal portland cement clinker (roughly around 100°C-200°C). 3O !

2o

0 ~

15

~

to

0~

5 0

I000 "C

1100 *C

1200 *C

1250 *C

1300 *C

1350 °C

Temperatur •

clinker A

[]

clinker B

•

clinker C

Fig. 1 Content of free lime depending on the burning temperature 2. Ratios of CaF2/SO3 and 803/Al203 The relations between the ratios of CaF2/SO3 and SO3/A1203 for the three clinkers are displayed in Fig. 2. The three part systems C3S-CllAT.CaF2-C2(A,F), CIIA7.CaF2-C2S-C2(A,F) and C4A3~-C2S-C2(A,F) differ with regard to their CaF2/SO3 and SO3/A1203-ratios. In other words: Through selection of corresponding CaF2/SO3 and SO3/A1203-ratios, the three part systems with different mixtures of clinker phases and the phase content in the overall system CaOSiO2-A1203-Fe203-SO3-CaF2 can be obtained. For a more detailed description the CaO-content would at least have to be considered. SO3/A1203

Hydration behaviour 1. Hydration of quick cements In order to test the hydration behaviour of quick cements a uniform water /cement-ratio (0.5) has been used. The measured degree of hydration of the clinker phases and the identified hydration products are listed in Fig. 3 and in table 4. In comparison to the clinker phases C3S and C4A3~, CI1AT.CaF2 showed a higher de.gree of hydration at earlier pomts of measurement (47% after 2 hours), i.e. the hydration o f CIIAT.CaF2 is faster than the

0,3

D

0.2

C

D

A

0,1

I )

0

i

1

i

I B i

i

)

2 3 CaF21SO3 Fig. 2 Relation between CaF2/SO3 and SO3/A1203 for the clinkers A, B and C

804

D. Kn6feland J.-E Wang

Vol.24, No. 5

hydration of the other phases After 2 hours the hydrate phases ettringite (AFt), calcium aluminium oxide carbonate hydrate C4A~HII (possibly C4AHL3),aluminium hydroxide containing fluoride (presumably AIF3.3H (possibly AH3)), C-S-H-Gel, calcium hydroxide (CH) as well as Cg.2H (2,3) can be found in cement A and ettringite, monosulphate (AFm), C4AcHI~ (possibly C4AHx3), AIFs.3H (possibly AH3), C-S-H-Gel and CH are found in cement B, but in cement C only AFt, AFm and AIFs.3H (possibly AH3) can be found. At later times of measurement the hydrate phases AFt, AFm, C4ACHII (possibly CaAHI3), A1F3-3H (possibly AH3), CH and also C2ASHs can be identified. 90 ~'~ 80 o

70

~ 6o ~.~ 50 40 Q 30 2o

o

Oh

2h

6h

Id

7d

Time •

a ~ b

©

c 1

a : Alit, b : C1]A7.CaF2, c" C4A3s Fig. 3 Degree of hydration depending on the hydration time TABLE 4 " The hydration phases of cement stones identified by X-ray diffraction analysis and Differential thermal analysis Cement 2h ld 28d AFt AFt, AFm AFt, AFro C4A(:Hll C4A~Hll C4AEH11 A1F3"3H A1F3"3H AIF3"3H CH~ Cs'2H CH CH AFt, AFm AFt, AFm AFt, AFm C4AEH11 C4A~.Hn C4A~.Hn A1F3"3H AIF3"3H A1F3"3H CH CH, C2ASH8 CH, C2ASH8 AFt, AFm AFt, AFm AFt, AFm AIF3"3H C4A~H11 C4A'~Hn A1F3"3H AIF3'3H CH, C2ASHS CH, C2ASH8 : C4AdHll ( possibly C4AH13) : AIF3"3H ( possibly AH3) (2) Influence of SO3/AhO3-ratios As an example, Fig. 4 shows the development of compressive strength of quick cements BOO* for different SOa/AhO3-ratios after 2 hours and 1 day (4). Important values for an increasing strength between 2 hours and 1 day can only be observed for low SO3/AhOa-ratios = 0.26, whereas only slightly increasing strength (at 0.38) resp. an increasing loss of strength can be stated for further increasing SOa/AhO3-ratios. The reason for this is the fact that for higher *BOO: Clinker B with different sulphate bearer content

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SO3/Al~O3-ratios, an expansion in the pore is caused by the formation of quickly growing ettringite crystals, which increases with rising SO3/A1203-ratios. As a result of this ettringite expansion, the strength of quick cements for a high SO3/AhO3-ratio is rapidly reduced. Setting 1. Setting times of quick cements TABLE5 : The setting times of quick cements (in mir .) Cement 1 2 3 4 Beginning-end

11-16

6-8

6-11

11-16

5 6-8

The setting times of quick cements are very short (see Table 5). Therefore, it is necessary to slow down the setting times. The tests of the slowing down were described below (see 5.2.). 2. Influence of setting 30- / retarders in the presence and in absence of Portland E 25-~" Cement (setting time and ~z strength) ,= 20<. Fig. 5 shows the ~o influence of a setting ~ / retarder (SKW Trostberg) ~ 13~ in the presence and in .~ I 0 . / absence of Portland Cement (PZ 35F, DIN 1164) with 5./ regard to the setting time of quick cement (5). 0 ~ s/A=0,26 s/A=0,38 s/A=0,51 s/A=0,76 Fig. 5 shows that the addition of retarders Fig. 4 Influence of different SO3/AhO3-ratios on the (A0-1.5) alone does not compressive strength after 2h and ld for cements made of clinker B cause any relevant slowing down of setting. However, through simultaneous adding of setting retarder and Portland Cement, the beginning and the end of setting could be slowed down distinctly by about 15 min. each. This means that the slowing down depends on the amount of added retarder as well as on the phase mixture of the quick cement, resp. the basicity of its pore solution. Small quantities of added amounts did not cause a sufficient slowing down. Figs. 6a and 6b show the development of strength in the presence of Portland Cement with and without setting retarder alter 2 hours and 1 day. With the help of using a setting retarder, the compressive strength of quick cements 1 and 2 with Portland Cement is not only increased alter 2 hours, but also after 1 day, and through using of Portland Cement, the compressive strength of quick cements made of clinker B can be improved. (for example, zero samples: cement 2, BD,2h=I5.4 N/ram~, 13D,~a=28.6 N/ram:). This can be explained by the "more favourable" crystallization of ettringites (5).

806

D. Kn6fel and J.-E Wang

Vol. 24, No. 5

35

30

E

25-

20

"~

10-

0 A0-0

A0-1.5

AI-0

AI-I.5

I D Beginning [] End A0-O A0-1.5 A1-0 A1-1.5

: : : :

Quick cement 1 Quick cement 1 with setting retarder Quick cement 1 with Portland Cement Quick cement 1 with setting retarder and Portland Cement

Fig. 5 Influence of the setting retarder in the presence and in absence of portland cement on the setting time of quick cements

E

25

Z 20-

[] A1-o

t2~ .~ 15-

II A1-1,s >

~o

5

2h

Id

Fig. 6a A1-0 : Quick cement i with portland cement; A1-1,5 • Quick cement 1 with portland cement and setting retarder Strength 1. Influence of interground additives Fig. 7 shows that higher amounts of added blast furnace slag and lime stone powder

Vol. 25, No. 5

Q U I C K CEMENTS, SLAG, LIMESTONE, FLUORIDE, SULFOALUMINATE

807

45-

"E 4o35Z t.e-

30 25-

[] BI-O

"~

20-

• BI-I, 5

m, '~

15-

t_

~:~ lO-

E 0

50

2h

id

Fig. 6b B1-0 • Quick cement 2 with portland cement; B1-1,5 • Quick cement 2 with portland cement and setting retarder 8O

a)~ 70 > 60 40

o =2o I0

0 Oh

2h

6h

1d

7d

28d

90d

Time

I

1"3

l ~

2

A

3 --×

4 --Yg

I 5 J

Fig. 7 Compressive strengths of cement mortars with different interground additives (see table 2) (20%-50%) do not have a distinctly negative influence on the development of strength in the three systems. It is obvious that blast furnace slag as an interground additive does improve the later development of strength. It is necessary to add interground additives, as particularly the cements made of pure clinker B and C show strong expansion. 2. Influence of temperature The development of compressive strength of quick cements made of clinker A and B for a temperature of 20°C and 5°C are given as an example in Figs. 8 and 9 (6).

808

D. Kn6fel and J.-E Wang

70 60 50 40 30 20 10 0: Oh

;>

"2

2h

6h

Vol. 24, No, 5

1d

7d

28d

56d

90d

Time []

1 : 20°C

~-

1 : 5"C

Fig. 8 Development of compressive strength of cement 1 made of clinker A for 20°C and 5°C

70

60 •~ o

50 40

o

~°20 10 0

O~

~'~

30

Oh

2h

i

i

i

i

i

i

6h

ld

7d

28d

56d

90d

Time r-1

2 : 20"c

x

2 : 5"c

Fig. 9 Development of compressive strength of cement 2 made of clinker B for 20°C and 5°C

The strengths do not only increase for 20°C, but also for 5°C. The development of strength for 20°C and 5°C is quite different, at a low temperature, cement A in particular shows a reduced development of strength for a period of up to a few days. The cement made of clinker B, however, does show nearly the same strength for all testing times for 20°C and 5°C (the cement made of clinker C shows a development of strength similar to the cement made of clinker B). This means that these quick cements do not only have a good development of strength at a normal temperature, but also show a satisfactory development of strength at a low temperature.

Vol. 24, No. 5

QUICK CEMENTS. SLAG, LIMESTONE, FLUORIDE, SULFOALUMINATE

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3. Influence o f carbonation The development o f compressive strength o f the quick cements made o f clinker A and B (the cement made o f clinker C shows a development o f strength similar to the cement made o f clinker B) during different conditions o f storage (in water, in atmosphere and in a CO2-cabinet) are displayed in Figs. 10 and 11. TABLE 6 : The phases o f cement mortars in CO2-enriched atmosphere (1 vol.-% CO2) identified by X-ray diffration a n a l y s i s Cement

1

phase ettringite monosulfate CaA/:Hn

I* ÷ ÷

÷ +

++

+ +

C4A'I/2CO2H12

++

+

CaSO4.1/2H20

CaSO4.2H20 Ca(OH)2 AI(OH)3 calcite vaterite aragonite

3

II

++++ ++

III

II

III

÷ ÷ +

+

+

+ + ++

+ +++ + ++++ ++++

++ ++

I

+

+ ++

+

++

+ + + ++

+ + + ++++

++

+ ++ +

* : I : Storage in water for two months II : Storage in CO2-enriched atmosphere with 1 vol.-% CO2 for one month (27 days o f pre-storage in water) III Storage in CO2-enriched atmosphere with 1 vol.-% CO2 for six months (27 days o f pre-storage in water) 100

60

~- ~

40

o

20

~

01 2h

,

,

ld

7d

28d

56d

210d

396d

Time •

In water

O

In air

*

In CO2

Fig. 10 D e v e l o p m e n t of compressive strength of c e m e n t 1 during different conditions of storage (27 days of pre-storage in water)

810

D. Kn6fel and J.-F. Wang

80 70 60 50 40 30 20~ I0 0 2h

Vol. 24, No. 5

,.J"

i

ld

7d

28d

56d

210d

396d

Time -"

In water

U

In air

--#

In C02

Fig. 11 Development of compressive strength of cement 2 during different conditions of storage (27 days of pre-storage in water) In a CO2-enriched atmosphere (1 vol.-% CO2) the compressive strength of cements made of clinkers B decreases for a period of 28 days until up to 1 year. In contrast to this, cements made of clinker A show a distinctly more favourable behaviour. After one year of storage in a CO2-enriched atmosphere (which corresponds to about 30 years of exposure to weather), the strength is still distinctly higher than after 28 days. The reason for this is the considerable formation of C-S-H and CH during this cement hydration. However, with an increasing carbonation, not only CH, but also other hydrate phases do react together with CO2, which here can also cause slight decreases in strength in the long run. The carbonation products which were identified by X-ray diffraction analysis are listed in table 6 (7). Porosity The porosity of mortars was measured by mercury intrusion. The distribution of pore size of mortars from cement made of clinker B (Figs. 12 and 13) show greater differences for different conditions of storage (8). The cement mortar made of clinker C shows a similar behaviour, the one made of clinker A could not be measured owing to test conditions. All samples had been prestored in water for 27 days. After a storage in water for 28 days, the biggest amount of pores can be found in the size range of 1.9 - 30 nm, up to 180 days the pore volume between 1.9-10 nm increases, in particular for smaller pore 1.9-3.0 n m , but the pore volume which is bigger than 10 nm decreases very distinctly. In comparison to the development of porosity during storage in water this cement mortar shows an unfavourable tendency in CO2-enriched atmosphere. With increasing carbonisation the volume of capillary pores increases (particularly the pore radii area between 30 - 250 nm) and the volume of gel pores decreases (between 1.9- 30nm). CO2 does react with the hydration products; as a result of these changes bigger pores (capillary pores) for an increase and smaller pores (gel pores) for a decrease turn up,

Vol. 24, N o . 5

3

QUICK CEMENTS, SLAG, LIMESTONE, FLUORIDE, SULFOALUMINATE

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

T ............... : ............ i ...........................

i...............

~

811

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

t

2,5 2

"~ O t_ O

1,5 1

0,5

o

: 1.93.0

i

3.05.0

5.010

1020

i 20-30

30-40

Pore •

28d-C02

[]

40-50

radius

50-75

75100

100250

250500

5001000

nm *

28d-air

28d-water

Fig. 12 Distribution of pore sizes of cement mortar B after 28 days (27 days of pre-storage in water)

2

-~

],5

O t_ O

o.:T

,

.............. ~................................ ...............

1.93.0

3.05.0

5.010

1020

20-30

30-40

Pore •

180d-C02

40-50

radius

D---- 1 8 0 d - a i r

50-75

75100

, 100250

250500

5001000

nm --*

180d-water

Fig. 13 Distribution of pore sizes of cement mortar B after 180 days (27 days ofpre-storage in water)

812

D. Kn6fel and J.-E Wang

Vol. 24, No. 5

Conclusions

1. In the CaO-SiO2-AhO3-Fe:O3-SO3-CaF2-system at least three quick cements with different clinker phases C3S, C~A7.CaF2, C4A3s, C:S, C2(A,F) can be produced through the selection of suitable CaF2/SO3 and SO3/AhO3-ratios. -

2.

Owing to the formation and the decomposition of "intermediate phases" (for example

3C3S.CaF2, 2C2S.C~,,3C2S.3C'g.CaF2)during the burning of clinker, a burning temperature for the quick cement clinker between 1250°C - 1350°C becomes possible.

3. Such quick cements with rather short setting times do not only have a high compressive strength at early age (13D,2h = 7 - 28 N/mm2), but also a high compressive strength at later test age (for example 13D.2Sd= 45 - 64 N/mm2). 4. Low temperatures do only retard the hydration of quick cements from the system C3SCIxAT-CaF2-C2(A,F), however, they do not have a distinctly negative effect on the hydration of quick cements from the systems C llA7.Ca_F2-C2S-C2(A,F) and C4A3g-C:S-C2(A,F). 5. Through simultaneous adding of setting retarders and Portland Cement, the beginning and the end of setting times of the quick cements can be slowed down and can possibly be set precisely. 6. The cement from the system C3S-CllA7.CaF2-C2(A,F)which is rich in alite has a better resistance to carbonation than the cements from the systems C~1AT.CaF2-C2S-C2(A,F) and C4A3gC2S-C2(A,F). 7. Owing to the use of high amounts of the interground additives blast furnace slag and lime stone powder (20% - 50%) for the quick cements, it would be possible to reduce production costs.

References

1. Kn6fel, D. and Wang, J.-F., 11. Inter. Baustoff- und Silikattagung, Weimar/Germany, 1, 360 (1991) 2. Uchikawa, H. and Tsukiyama, K., Cem. Concr. Res., 3,263 (1973) 3. Uchikawa, H. and Uchida, S., Cem. Concr. Res., 3, 607 (1973) 4. Kn6fel, D. and Wang, J.-F., Advanced Cement Based Materials, in print 5. Kn6fel, D. and Wang, J.-F., 3th. Beijing Inter. Symposium on Cement and Concrete, Beijing/China (1993) 6. Kn6fel, D. and Wang, J.-F., Zement-Kalk-Gips, in print 7. Wang, J.-F., Dissertation, FB Geowissenschaften, Philipps-Universit~it Marburg, (1993/94) 8. Kn6fel, D. and Wang, J.-F., 9th Inter. Congr. Chem. Cem., New Delhi/India, vol. IV, 370, (1992)