Portland cement production using mineral wastes

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Portland cement production using mineral wastes

Citation for published version (APA):

Bhatty, J. I., Marijnissen, J. C. M., & Reid, K. J. (1985). Portland cement production using mineral wastes.

Cement and Concrete Research, 15(3), 501-510.

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Gepubliceerd: 01/01/1985

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PORTLAND CEMENT PRODUCTION USING MINERAL W A S T E S

Javed I. Bhatty, Jan M a r i j n i s s e n and K e n n e t h J.Reid Mineral Resources R e s e a r c h Center, 56 East River Road U n i v e r s i t y of Minnesota, Minneapolis, MN 55455, USA

(Communicated by J.P. Skalny) (Received Dec. 14, 1984)

ABSTRACT

A T y p e I P o r t l a n d c e m e n t has b e e n p r o d u c e d u s i n g a n o r t h i t e f r o m c o p p e r - n i c k e l t a i l i n g s a n d r a w t a c o n i t e t a i l i n g s . T h e c e m e n t exhibited better strength properties than ordinary Type I P o r t l a n d c e m e n t a n d g a v e a s t r o n g e r c o n c r e t e w h e n t e s t e d u n d e r i d e n t i c a l c u r i n g c o n d i t i o n s . F a c t o r s l e a d i n g to the a t t a i n m e n t of t h e s e h i g h e r s t r e n g t h v a l u e s a r e i d e n t i f i e d a n d t h e i r e f f e c t s on the u l t i m a t e m e c h a n i c a l properties of cement are discussed. It is a l s o a n t i c i p a t e d t h a t the c o m p o s i t i o n a l v a r i e t y of t a i l i n g s m a y a l s o h a v e other beneficial effects on long-term cement behavior such as resistance to s u l f a t e attack.

Introduction

This paper describes the d e v e l o p m e n t of P o r t l a n d cement from a non- c o n v e n t i o n a l raw feed composed of copper-nickel t a i l i n g s as a r e p l a c e m e n t to a r g i l l a c l o u s components in a c o n v e n t i o n a l cement feed.

Limestone and iron bearing taconite t a i l l n g s are used as c a l c a r e o u s and ferruginous components, respectively.

Background

In northern M i n n e s o t a lie vast deposits of copper-nickel ore known as the D u l u t h gabbro which are estimated to contain 28 m i l l i o n metric tonnes of copper and 8 m i l l i o n m e t r i c tonnes of nickel (I).

In the event of the d e v e l o p m e n t of these deposits a l a r g e amount of tailings, exceeding 90% of the b u l k ore, w i l l be produced containing among other discarded minerals, some amount of f i n e l y disseminated fibrous amphi- b o l e s as a p o t e n t i a l p o l l u t a n t of w a t e r a n d air, t h u s p r e s e n t i n g b o t h disposal and p o l l u t i o n p r o b l e m s in c l o s e proximity to an e n v i r o n m e n t a l l y s e n s i t i v e l o c a t i o n known as the Boundary Water Canoe Area (2).

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The m i n e r a l o g i c a l composition of these taillngs, g i v e n in T a b l e I, TABLE I

Mineralogical C o m p o s i t i o n of the Copper-Nickel Taillngs (% Wt.)

Plagioclase 43.03

Olivine 19.54

Pyroxene 18.18

Biotite 3.18

Opaques (ilmenite, magnetite, Cu-Ni sulfides) 9.55

Locked Particles 1.33

i d e n t i f i e s , h o w e v e r , t h a t t h e s e t a i l i n g s c a n be a s o u r c e of s o m e u s e f u l minerals, p a r t i c u l a r l y the p l a g l o c l a s e which constitutes o v e r 43% of the tailings. P l a g i o c l a s e s are a unique source of a l u m i n o - s i l i c a t e s and h a v e among other uses a p o s s i b l e direct use as a r g i l l a c i o u s components in the m a n u f a c t u r i n g of h y d r a u l i c cements. By so doing it w i l l not o n l y introduce a n e w s o u r c e of r a w f e e d for c e m e n t - a c o m m o d i t y w h i c h is c u r r e n t l y n o t produced in M i n n e s o t a - but a l s o reduce the disposal p r o b l e m of the tailings.

Ferruglnous a d d i t i v e needed for the cement raw feed w i l l be p r o v i d e d by another t a i l i n g source - the iron bearing taconites - which are a l s o present in large amounts in the adjacent areas of Northern Minnesota.

T h e p r e s e n t i n v e s t i g a t i o n is t h e r e f o r e a i m e d at m a k i n g u s e of t h e s e t a i l i n g s in order to d e v e l o p h y d r a u l i c cement and c r i t i c a l l y testing the products to assess e n g i n e e r i n g behavior.

Plagioclase as a Component for Cement Feed

C o n v e n t i o n a l l y a h y d r a u l i c cement is obtained by heating to 1450°C a ground mixture of limestone and clay or other mixture of s i m i l a r composition (3) and intergrinding the r e s u l t i n g clinker with a s m a l l proportion of gypsum.

The copper~nickel tailings, when upgraded to p l a g i o c l a s e (anorthite) h a v e a chemical composition c l o s e to that of a c l a y used in cement making, i.e., it is an a l u m i n o s i l i c a t e of t h e l i m e type. A t y p i c a l p l a g l o c l a s e concentrate obtained from the Cu-Ni t a i l i n g contains n e a r l y 57% SiO 2 and 27% A 1 2 0 3 i d e n t i f y i n g it to be a p r i m e s o u r c e for s i l i c a a n d a l u m i n a . A d e t a i l e d ~ n a l y s i s is g i v e n in T a b l e 2.

TABLE 2

Chemical C o m p o s i t i o n of Plagloclase Concentrate (Anorthite) (% Wt.)

SiO 2 AI203 CaO Fe203 MgO Na20 K20 SO 3

56.40 27.10 8.80 0.62 0.16 4.5 0.81 0.0

Some e a r l i e r attempts h a v e a l r e a d y shown the use of anorthites in the d e v e l o p m e n t of white P o r t l a n d cement (4,5) and their potential in new high temperature cementing m a t e r i a l s (6).

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Vol. 15, No. 3 503 M I N E R A L WASTES, CEMENT PRODUCTION, TACONITE, STRENGTH

It may be pointed out that both these t a i l l n g s are a v a i l a b l e in ground form r e q u i r i n g l i t t l e of the further grinding otherwise needed in conven- tional cement feed preparation.

M a t e r i a l s and Methods

C o p p e r - n l c k e l t a i l i n g s r e c e i v e d as such were upgraded in anoPthite by methods i n v o l v i n g g r a v i t y and m a g n e t i c separation (1,7). Taconite t a i l i n g s w e r e o b t a i n e d f r o m t h e E r i e C o m p a n y , H o y t L a k e s , M i n n e s o t a (8) a n d t h e i r fractions finer than 200 mesh collected. A mixture of both these t a i l l n g s a l o n g w i t h l i m e s t o n e to p r o d u c e a T y p e I c e m e n t c l i n k e r w a s m a d e w i t h the f o l l o w i n g p r o p o r t i o n s : l i m e s t o n e (74.6%); a n o r t h i t e (12.5%); t a c o n i t e t a i l i n g s (10.9%) a n d a n h y d r l t e (2.0%) (3).

An a m o u n t of 2.0 % a n h y d r i t e w a s a d d e d in t h e c l i n k e r f e e d to r e d u c e the formation of a l k a l i a l u m i n a t e phase in the c l i n k e r due to the presence of e x c e s s i v e N a 2 0 (4.5%) in a n o r t h i t e . A d e t a i l e d c h e m i c a l a n a l y s i s of the c l i n k e r feed is g i v e n in T a b l e 3.

TABLE 3

Chemical Analysis of the Clinker Feed Material D e s c r i p t i o n

Taconite

Anorthite Tailings Limestone Anhydrlte

SiO 2 56.96 58.54 2.17 - AI203 27.57 0.64 0.13 - Fe203 0.62 27.40 0.37 - CaO 8.80 4.40 53.96 41.20 MgO 0.16 3.10 0.33 - SO 3 0.18 0.23 0.00 58.80 L.O.I. 0.40 5.69 42.92 - Na20 4.50 0.03 K20 0.81 0.06 - TiO 2 - - 0.03 - P205 - _ Total 100.00 100.00 100.00 100.00

Any Na20 present without a s u l f a t e b a l a n c e can produce an a l k a l i a l u m i n a t e phase which may cause setting problems. Target amounts of c l i n k e r phases to

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produce a Type I cement clinker using cement chemists notation* were deter- m i n e d to be as f o l l o w s : C 3 S (55-60%); C 2 S (20-22%); C 3 A (8-10%) and C 4 A F

(8-10%).

Preparation and Firing of C l i n k e r Feed

T h e l i m e s t o n e was g r o u n d in a b a l l m i l l u n t i l 85% was p a s s i n g a 200 m e s h sieve. A n o r t h i t e a n d t a c o n i t e r a i l i n g s w e r e a l r e a d y v e r y f i n e a n d therefore required l i t t l e grinding. The three components along with anhy- drite were thoroughly mixed prior to p e l l e t i z i n g with water for the rotary k i l n b u r n i n g . R a w f e e d (I/4 to I/2 i n c h p e l l e t s ) was fed into a 15-ft. long and 5-in. wide pilot plant rotary kiln, fired with natural gas as fuel to a burning temperature of 1450-1480 C with an oxygen l e v e l in the k i l n at 1.5-2.0%. The fired clinker was cooled and c o l l e c t e d for testing.

Analytical Evaluation of the Clinker

Q u a l i t a t i v e X-Ray diffraction analysis shows that the clinker produced from the feed is of quality grade and the l e v e l s of phases estimated from the peak intensities are similar to those of target values (see T a b l e 4).

TABLE 4

Estimated Phase Levels (% Wt.) from XRD Analysis

Free Alkali

C3S C2S C3A C4AF CaO MgO Aluminate

55-60 20-22 8-10 8-10 < I < I none

Optical analysis of the clinker confirms its quality to be from good to e x c e l l e n t a n d s h o w s (as in F i g u r e I) a d i s t r i b u t i o n of w e l l f o r m e d medium sized C3S crystals and clusters of rounded striated C2S crystals. C 4 A F is p r e s e n t as w h i t e b r i g h t a r e a in the i n t e r s t i c e s and m e d i u m s i z e d C3A crystals are also u n i f o r m l y distributed. O n l y traces of CaO and MgO are f o u n d w h e r e a s a l k a l i s u l f a t e s are v e r y r a r e l y present. T h e c l i n k e r a l s o shows good porosity (as the large grey areas in the photomicrograph) a l l o w i n g easy grinding. The q u a l i t y of the clinker predicts good strength development.

Chemical and Physical Testing

T h e c l i n k e r was i n t e r g r o u n d w i t h 5% g y p s u m to a B l a i n e f i n e n e s s of 3500 cm2/g to form the cement used in chemical and physical tests.

Chemical analysis and c a l c u l a t e d compound composition of major phases of the cement produced an oxide composition with the presence of o n l y 0.24% N a 2 0 (see T a b l e 5).

T h e a n a l y s i s s h o w s the c e m e n t to be of g o o d q u a l i t y f r o m w h i c h the production of strong and sound concrete is predicted.

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Vol. 15, No. 3 505 MINERAL WASTES, CEMENT PRODUCTION, TACONITE, STRENGTH

FIG. I

Photomicrograph of the clinker showing well formed C3S crystals; BC2S crystals occurring in clusters; C4AF occurring in the interstices; C3A well distributed within the interstices; CaO and MgO in traces.

TABLE 5

I. Chemical Analysis of Cement (% Wt.) . . . _ . . . SiO 2 20.71 Na20 0.24 A1203 5.07 K20 0.03 CaO 64.01 SO 3 2.30 Fe203 4.63 TiO 2 0.06 MgO 0.86 L.O.I. I .46 . . . _ . . . II. Calculated Compound Composition of Major Phases (% Wt.) . . .

C3S

C2S

C3A

C4AF

56 17 6 14

A c c o r d i n g to the A S T M C 1 5 0 s p e c i f i c a t i o n s (9) for T y p e I c e m e n t s , a s e r i e s of p h y s i c a l t e s t s w e r e c o n d u c t e d on t h e c e m e n t to d e t e r m i n e its soundness; setting time (initial and final); fineness; air content; false set and c o m p r e s s i v e strength. R e s u l t s are shown in T a b l e 6.

Tests for compression strength on some concrete specimens (2.5" cubes at w / c = 0.49) a n d for f l e x u r a l s t r e n g t h on m o r t a r s p r i s m s (I" x 1"x 6" at w/c = 0.49) both prepared from the cement were a l s o conducted. D e t a i l s of the r e s u l t s are g i v e n in T a b l e 7 and Figures 2 and 3.

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TABLE 6

Results from Physical Test on the Cement Produced from Tailings ASTM Specifications

Test Results C 150-83a Type I

Setting Time (Vicat) Initial Final Soundness (Expansion) Fineness (Blaine) Fineness by #325 Sieve Air Content

False Set (Paste Method)

2 hr. 20 min. Not less than 45 min & not more than 6 hr, 15 min

4 hr. 30 min. Not more than 8 hr (C150-78a)

0.03% Maximum 0.80%

3540 Sq. cm/g M i n i m u m 2800 Sq. cm/g 93.6% passing Not specified

9.8% Maximum 12.0%

75% Minimum 50%

Compressive Strength -

I day test 1600 psi -

3 day test 3250 psi Minimum 1800 psi

110 day test 10350 psi -

... ~ ... - - ...

TABLE 7

Flexural Strength and Compressive Strength Values (PSI) for Mortar and Concrete S p e c l m e n s , R e s p e c t i v e l y , M a d e from the Cement Mortar I" x I" x 6" Prism and C o n c r e t e 2.5" x 2.5" x 2.5" Cubes; at W / C =0.49. ... Curing Time (Days) I 3 7 28 110 ... . ... Flexural Strength 306 560 740 820 950 (Mortars) Compressive Strength 1,500 3,200 5,000 7,100 8,900 (Concrete) ... Analysis of Data

R e s u l t s from the physical tests show that the cement adequately meets the A S T M r e q u i r e m e n t for a T y p e I c e m e n t e x c e p t t h a t the c o m p r e s s i v e s t r e n g t h v a l u e s on the n e a t c e m e n t p a s t e s a r e a p p r o x i m a t e l y d o u b l e the required minimum v a l u e s (see T a b l e 6).

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FIG. 2

Development of compressive strength of concrete specimen made from: the tailing cement • Type I Portland cement • at w/c = 0.49

. ~

10

8

¢-

ol

.=

.>

U) (0

==

D. E

o

(J

6

4 3 7

28

i

100 Age (days)

FIG. 3 ~ 1 0 Development of flexural ~ 8 strength of mortar specl- 01

m 6

men made from the tailing cement • ; and varia ~

tlon of calculated flexu- ~ 4 al values obtained from

compressive strengths of ~

x

2

the tailing cement O and concrete O using

equation I.

_{1 3 7}

₁₀₀

Age (days)

A

O-

Compression tests on concrete specimen made from the cement also show higher strength development leading to high ultimate strengths when compared to similar specimen from Type I cement tested under identical conditions (see Figure 2 for strength comparisons).

The r e a s o n for s t r e n g t h gain may be a t t r i b u t e d to the p r e s e n c e of r e l a t i v e l y high C3S content in the cement giving a high C3S/C2S ratio of 3.29 as c o m p a r e d to an a v e r a g e of 2.01 for a Type I cement (10). A llst of the c o m p o u n d c o m p o s i t i o n s of some T y p e I cements, g i v e n in T a b l e 8, shows that the C 3 S / C 2 S ratio v a r i e s w i t h c o m p o s i t i o n from 0.94 to 3.06. The C3S c o m p o u n d has h i g h e r s t r e n g t h r a t e s than C2S, and if p r e s e n t in excess, contributes dominantly towards higher strength values in the early periods of hydration. Both C3S and C2S are, however, primarily responsible for strength development of cement. An approximate assumption is that C3S c o n t r i b u t e s m o r e to the s t r e n g t h g a i n d u r i n g the f i r s t m o n t h and C2S in- fluences the strength development from one month onward (11,14).

The presence of C4AF in the cement is also r e l a t i v e l y higher; 14% as c o m p a r e d to an a v e r a g e 7.5% for Type I cements. This would, however, contribute little towards the strength development (12). C4AF on its own

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TABLE 8

Major Compound Composition (% Wt.) and C3S/C2S Ratios for Various Type I Cements.- T y p e I C e m e n t s

C3S

C2S

C3A

C4AF

C3S/C2S

R a t i o I 55 18 11 7 3.06 2 54 23 9 6 2.35 3 47 28 7 9 1.68 4 33 35 14 8 0.94 Mean C3S/C2S Ratio 2.01 Tailing Type I 56 17 6 14 3.29 Cement

hydrates faster, but in the presence of gypsum, which is g e n e r a l l y added to prevent a flash set caused by a v i o l e n t hydration reaction by C~A during m i x i n g of the c e m e n t , it w i l l h a v e a r e g u l a t e d s e t t i n g b e h a v i o r (13). Again, a high C4AF value combined with a low v a l u e of C3A , 6% by weight, is g e n e r a l l y regarded to be useful as it lessens the amount of C3A hydration products, p a r t i c u l a r l y the m o n o s u l f o a l u m i n a t e s which are prone to sulfate a t t a c k (14).

A c o m m o n c o n c e p t is t h a t C 3 A in the p r e s e n c e of g y p s u m h y d r a t e s to calcium s u l f o a l u m i n a t e s known asT'ettrlngite." If the sulfate ions are all consumed before the C3A has c o m p l e t e l y hydrated, the ettringite transforms to m o n o s u l f o a l u m l n a t e s which when brought into contact with a new source of sulfate ions reform to ettringlte once again. This reforming of ettrlngite is the basis for attack when exposed to fresh s u l f a t e ions. With cements l o w in C 3 A but h i g h in C 4 A F c o n t e n t , the f o r m a t i o n of e t t r i n g i t e f r o m m o n o s u l f ~ a l u m i n a t e s does not occur. It may be that iron-substituted mono- s u l f o a l u m i n a t e c a n n o t r e a c t to f o r m e t t r i n g i t e or t h a t the p r e s e n c e of amorphous hydrous oxides of iron and aluminate, which do form during sulfate reaction, may in some way prevent the completion of ettringite forma- t i o n (14,15,16).

Another important engineering property of cement is its bonding behavior w h i c h is c o m m o n l y a s s e s s e d by its f l e x u r a l s t r e n g t h . R e s u l t s f r o m f l e x u r a l t e s t s on the cement, g i v e n in T a b l e 9, s h o w t h a t the c e m e n t possesses e x c e l l e n t bonding properties. For instance, a 28 day f l e x u r a l strength for cement mortar is 820 psi as compared to c a l c u l a t e d flexural v a l u e s of 632 psi and 677 psi for concrete and neat pastes, respectively. These c a l c u l a t e d flexural values are based on a generalized correlation that exists between the flexural and compressive strength as

o f ~ 7.5 (o c )I/2 (I)

where c f is the f l e x u r a l strength and ° c is compressive strength (14). Variations of o b s e r v e d and c a l c u l a t e d flexural values with curing times are also given in Figure 3.

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TABLE 9

Comparison of Observed Flexural Strength (~f) with the Calculated Flexural Strength from Compressive Strength Values (a c of both Cement

and Concrete Specimens Using Equation I. ... Curing Times (Days) I 3 7 28 110 ... - - ... Observed Flexural 306 560 740 820 950 Strengths

Calculated from Cement Compressive Strength

300 428 536 677 763

Calculated from Concrete 290 424 530 632 708

Compressive Strength

...

Another check on the flexural strength is that the ratio of flexural to compression strength should range from about 0.11 to 0.23 (14,17) which h o l d s true for c a l c u l a t e d m e a n r a t i o s of 0.14 and 0.15 r e c o r d e d both for m o r t a r to c e m e n t and m o r t a r to concrete, r e s p e c t i v e l y (see T a b l e 10). C a l c u l a t e d r a t i o s for f r e s h s p e c i m e n s are h o w e v e r higher; 0.19 and 0.20, respectively, for I day o l d specimens, indicating that the cement acquires better bonding strength in the early ages, but compressive strength domi- nates as the h y d r a t i o n p r o g r e s s e s , y i e l d i n g a m u c h h i g h e r u l t i m a t e strength, as referred to above.

TABLE 10

Ratios of Observed Flexural Strengths to Compressive Strength (of/c c) from both Cement and Concrete Specimens

Curing Time (Days) I 3 7 28 110 Mean ~f/~c 0.19 0.17 0.15 0.10 0.09 0.14 (for cement) ~f/~c 0.20 0.18 0.15 0.12 0.11 0.15 (for concrete) - - - - ~ ... - - ... Conclusions

The utilization of copper-nickel and taconite taillngs as a partial r e p l a c e m e n t of r a w feed for c e m e n t m a k i n g is p r a c t i c a l l y possible. The c e m e n t thus p r o d u c e d e x h i b i t s e x c e l l e n t strength properties; adequately meets the required standard specifications and can have marketable potential at l e a s t in the state of M i n n e s o t a w h i c h c u r r e n t l y p r o d u c e s no cements.

This approach of tailing consumption could also simultaneously reduce the impact of tailing disposal around the environmentally sensitive area of northern Minnesota.

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In this w o r k a p p r o x i m a t e l y 24% of the raw feed for the c e m e n t is derived from tailings. Whether this proportion can further be increased without significantly effectlng the cement properties is a matter of further investigation.

Acknowledgements

The a u t h o r s w i s h to thank the C o n s t r u c t i o n T e c h n o l o g y L a b o r a t o r i e s (CTL), Skokie, Illinois, and the Twin City Testing and Engineering Labora- tories, St. Paul, Minnesota for their assistance in certain experimental and t e s t i n g work. T h a n k s are a l s o due to Dr. E.L. Skok of the D e p a r t m e n t of Civil and Mineral Engineering, University of Minnesota, for his advice on various technical matters during this work.

References

I. IN Iwasaki, K.A. S m i t h and A.S. M a l i c s i , " B y - p r o d u c t R e c o v e r y from Copper-Nickel Bearing Duluth Gabbro," Report for the U.S. Dept. of the I n t e r i o r M i n e r a l Institute, U.S. B u r e a u of Mines, W a s h i n g t o n , D.C. 20241, MRRC, 56 East River Road, Mpls, MN 55455 (1982).

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3. J. S k a l n y and K.E. D a u g h e r t y , " E v e r y t h i n g You A l w a y s W a n t e d to K n o w about Portland Cement," p. 38, Chemtech (January, 1972).

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