Ind ian Journal of Engineering & Materi als Sciences Vo l. 9, April 2002. pp. 147- 152

Influence of altered basalt on the burnabiIity of portland cement clinker

EI- Sayed Ali EI-A lfi

Refractori es, Cera illi cs and Bu il ding Materi als Departillent , Nati onal Research Center. Dokk i, Cairo, Egy pt

Received 24 Ocrober 2000; revised received 3 Jllly 2001

Synthesis of portl and ceillent clinker fro lll ceillent raw Illi xes containing altered basalt was studied . The clay of the raw Illi x of portl and ceillent was substituted by basalt in ratios 0, 15. 30, 45 and 60 wt.%. The ingredients of the Illi xes were int imately homogeni zed, Ill ixed. moulded into a cOlllpact mass and fired at 1200, 1250. 1300, 1350 and 137SOC for two hours soak ing tillle. The burn ability of each raw Illi x was in vestigated by the determination of in solu ble residue. free li llle contents and the phase cOIll Pos it ion of the fired products. The results show that the clinker forillation was cOlllpleted at I 300°C in the presence of 30-60 wt. % basalt.

Of the three major steps by which cement is manufac­tured, the raw materi al process ing utili zes about 10% of the total energy, pyroprocess ing 83% and finish grinding 7%. The most energy consumption in the clinker manufacture is about 80% from the total

f . I energy 0 pyroprocess lng.

Hi gh cost of energy and the consumption of almost above three steps of the net theoretical heat required in clinkering process continue to be a cute problem faced by the cement industr/. Therefore, a potential for energy conservation which coul d be rapidly and economicall y accompli shed if the temperature of the burning zone within the kiln could be reduced. This could be brought about by maintaining high homo­geneity and optimum raw mi x composition I , substan­tially decreasing particle size of raw mix 3.4 and using mineralizers and flu xes to lower the melting piont of clinker liquid phase5

-7

. The third method is the most effec ti ve and attracti ve for lowering the clinkering temperature. This could result either in a decrease of the required kiln temperature or in an increase of the clinker production rate.

The natural pozzolana of volcani c origin , as volcanic ashes, tuffs, basalt etc., contains silica in reactive fonns.9. The weathered basalt is an inter­mediate stage of alteration of the fresh basalt into cla/ D

.I t . The chemical composition of basalt lies

within the system CaA I2Si20 s, NaAISi30 s and CaO. MgO.FeO.Si02. It mainl y consists of plageoclase, one or more of the ferromagnesium minerals (oli vines), pyroxenes, amphi boles and someti mes boi ti tes 12.

Basalt is one of the flu xing materi als, which lowers the maturing temperature of the cb y-basalt bathes. It

has a hi gh alka li and/or alkaline earth ox ide contents, its flu xing acti on was found to increase with the alkaline minerals. The presence of basalt plays an important role in the maturing temperature of the clay -basa lt mi xes as well as a good quality of verificati on parameters of the fired samples l3

.

The physicochemi cal studi es to sy nthesis portl and cement clinker at lower temperature conditi ons by using basaltoid containing raw mi xes in combinat ion with composite minerali zers were inves tigated. It was found that in the presence of composite minerali zer clinker formation was completed at the temperature of 1250-1 2800C 14.

The ai m of the present work is to study the effect of partial substitution of clay by altered basalt as flu xing materi al on the clinkerability of portl and cement raw mixes.

Experimental Procedure The materi als used in thi s study; namely, limestone

and clay were received from Helwan Portland Cement Company and basalt was received from Abu-Zaabal Quarries, Egypt. The raw mix was ground in a laboratory steel ball mill to pass through B.S. 200 mesh ' sieve. The particle size distribution of the ground clay and basalt was determined by using sedimentation method l5

. The raw materials were investigated using the chemical, DT A and XRD techniques. The free silica can be determined as described elsewhere l 6

. 0.5 g of dried sample at 150 mesh grain size was mi xed wi th 10-15 g potassium pyrosulphate in silica crucible, then gently heated up to 1000°C to prevent loss of S02 to give homo­geneous melt. Dissolve the cooled crucible in 150-

148 INDI AN J. ENG. MATER. SC I. , APR IL 2002

200 mL of hot distill ed water and add about 12 g NaOH pellets to di sso lve the precipi tated sili ca. Digest on hot water for \12 h at 8S -90°C, then fi Iter and wash the peaker to insure comp lete transfer of sili ca. Wash lOti mes wi th hot disti lied water and then S-I ° times w ith hot di l HCI ( I: I ). Ign i te the fi l ter paper and weigh the res idue to ca lculate the free si I ica. To prepare the portl and cement cl inker (according to the ASTM speci ficati oll C I SO-68 and B.S . : 1370: 199 1), the ingred ients or the mixes were homogenized, mixed w ith 7% water, moulded in to SOx SOx20 mm samples . The samples were fired using a rate of heat ing SOC/min at 1200, 12S0, 1300, 13S0 and 137SoC with 2 h soaking time.

The clay of portland cement was partially substituted by altered basalt in the fo llow ing rati os 0, I S, 30, 4S and 60% respecti vely . The clinker moduli ; li me saturation factor (LSF), sili ca rati o (SR) and alumina rati o (AR), fo r each batch were calculateds. The clinkerability of each mix was tested by the free lime and inso luble res idue contents at different firing temperatures . Al so, the burnability of some selected fired raw mixes was investi gated by XRD technique.

Results and Discussion The chemical analys is of the raw materials is given

in Table I.

It is ev ident that the clay is generall y or th e low grade sample. It con tains higher total si l ica (70%) and lower AI20 :1 contents (9 .1 7%) in compari son wi th th ose of high-grade clays. A lso, it has higher amounts of free sil ica l6 (S2 %) in add ition to small amounts of Fe20 :1 , Ti02 and other fluxing ox ides, namely alkali earth ox ides. Basalt contains tota l react i ve sili ca about 47 % and no free sili ca as detected by XR D as well as chemical anal ys is wh ich leads to increase the contents of A1 20 3, total iron ox ide, Ti02, alka li and alka line earth flu xing ox ides. These are the main ox ides fo rming the plageoc lase and pyroxene minerals.

Table 2 shows particle size distribution of the ground clay and basalt as determind according to the sedimentati on technique IS.

It is not only the chemical ox ide of the main component of the raw mi x is important but also the physica l forms play an important role in both quality of product and operati on of the f iring process. Due to the vari ous degree of hardness of the raw materi als, after grinding they show different particle size distributions. So that, as the free silica content increases in the cemen t raw mi x, it would be very difficult to react w ith lime in limited time. From T able 2, it is evident that the clay is mainly composed of coarse and medium silt as well as sand grains.

Table I- Chemical ox ides of starting raw material s (wt. %)

Sample Si02 AI1O, Fe20) Ti02 CaO MgO SO) Nal0 K20 LOL

Limestone 1.37 0.98 0.45 0.Q7 53 .1 4 0.95 0.34 0.05 0.07 41.06

Clay 69.96 9.1 7 3.9 1 1.02 4.5 1.09 1.71 1.68 1.08 4 .1 5

Basa lt 47.06 15.35 12.76 3.37 10.52 6.09 2.40 0.7 1.02

Table 2- Grain size d istributi on of the clay and basa lt raw mate ri als

Sample

Clay

Basalt

l-' >-' <l

100

Cloy

Bosol l

300 500

100-63 11m

22.45

16.50

o 0> <J'>

700 900

Temperat ure, ·C

63-30 11m

32. 10

29.5 1

Fig. I- DT A cu rves of clay and basalt raw material s

30- 10 )l1l1

45.46

15.57

lOa

10-2 pill

25.97

Cloy

300 500 700

Temperolurl?, ·c

< 2 ~lIll

12 .95

900

Fig. 2-TG curves of c lay and basalt raw materi als

1'--

EL-ALFI: INFLUENCE OF ALTERED BASALT ON PORTLAND CEMENT CLINKER 149

Also, the basalt has different ratios o f s ilt, c lay in

addition to sand . The DT A curves of the c lay and a lte red basalt

samples are shown in Fi g. I . The clay ex hibits intense small endothermic do uble peaks at 107 and 140°C attributed to the dehydrati o n of absorbed and inter­layer water of montmori 1I0 nite and i IIi te s tructure. Another small endothermi c peak at 590°C is due to dehydroxy lation of c lay minera ls. A lso, small S­shaped endothermic-exothermi c reac ti on peak is detected at about 800 and 1000°C due to the formation of new phases , e.g ., SiOr rich spinal crys­talli zation at the expense of the destructed c lay­mineral structures " . On the o ther hand , the DT A curve of basalt shows only a small endothe rmic peak at about lOO°e. Thi s peak indicates the presence of some hydrated metas ilicate phase which is probab ly due to the alteration product of the 0 livine l7

.

The TG curves of Fig . 2 confirm the results of DT A for the clay and basalt. The former shows continuous weight loss up to 4.5 wt. % on heating fro m room temperature up to about 750°C mainly due to the gradual dehydration of adsorbed, interlayer and latti ce water of the clay minerals. On the o ther hand, basalt sample exhibits o nly a weight loss of about 2 % at 100-150°C, which accompanies the dehydration of basalt mineral s.

Fig. 3 exhibi ts the XRD patte rns of c lay and basalt. It is shown that the c lay sample composes mainl y of quartz and some weak lines indi cating the presence of the clay minera ls such as kao linite, illite and mon t · mori llo nite. The differenti at ion between these clay minerals cannot be done using such powder dif.· frac tion patterns because of the randomly o ri entat io n

i >-.;;; c ~ c

o

60

o 9.uartz • Plagioclase • Agu i li c pyroxene

o

50

Cloy

Basalt

• •

40

29(Cu-K .. )

o

30 20

Fig . 3-XRD patterns of clay and basalt raw materi als

Table 3-Raw mix compositi on (wt. %) and calculated clinker modulus

Sample Limestone Clay Basalt LSF SM AM

Mix I 80.65 19.35 97.53 3.97 2.29

Mix 2 80. 10 16.82 3. 17 97.79 3.40 1.99

Mix 3 79.04 14.66 6.3 96.21 2.98 1.79

Mix 4 78. 12 12.50 9.38 94.98 2.66 1.67

Mix 5 77.24 10.36 12.40 93.64 2.40 1.56

Table 4-The chemical ox ides of the raw mixes

Constituent wt. % MIX I MIX2 MIX3 MIX 4 MIX5

Si02 22.7 1 22. 18 2 1.95 2 1.71 2 1.76

Free Si02 16.96 13.88 12.01 10.32 8.53

AI20 3 3.98 4.34 4.72 5.09 5.53

Fe201 1.74 2. 18 2.64 3.07 3.55

Ti02 03 0.43 0.55 0.67 0.80

CaO 67.78 67.21 66.23 65.37 65.43

MgO 1.52 1.78 2.02 2.28 2.58

Na 20 0.57 0.64 0.68 0.74 0.8 1

K20 0.4 1 0.44 0.52 0.56 0.59

SO) 0.9 1 0.83 0.77 0.71 0.6 1

ISO INDIAN J. ENG. MATER. SCI. , APRIL 2002

of the clay-mineral particles . Also, basalt composes mainl y of p lageoc lase and feldspar and aug iti c pyroxene, whi ch compri ses hi gh content of CaO, MgO, and Fe20 1 as fluxing ox ides.

Tabl e 3 illustrates both the raw mix composition (wt. %), and calcul ated lime sa turati o n factor (LSF), sili ca modulu s (S M) and a lumina modulus (A M) of the prepared mi xes. The res ults show that the substitution of c lay by basalt in the preparation of raw mix of cement clinker, the s ili ca and a lumin a mod ulus sharpl y decrease . Thi s leads to the best c1inkerability and maximum amount of liquid phase at lower poss ible temperatu re. Sintering has a large impact ion in determining the burn ing zone, rate of c linker formation and compositi on. The amou nt of AI 20 3

governs the combination of CaO and Si02 at lower sintcring temperature. Iron ox ide (Fe20 ) , magnes ia (MgO), titani a (Ti02) and alka li es (K20 and N(20) are considered as flu xes in cemen t raw mix. All these flux es govern the amount of liquid phase at the c linkering temperature. The hi gher percentage o f the liquid at thi s temperature, the eas ie r will be the burnability of the raw mix .

The calculated che mical ox ide of the raw mixes is shown in Table 4.

The results illustrate that as the basalt content increases, the free silica content decreases and the tota l fluxing ox ides enhances. On the o ther side, as

16r-------------,

'" c ~ c 8 ~

14

12

10

~ 6 ~ ~

~

o 1200

o Mi:t 1

2 .. 3

• 4 D .. 5

1250 1300

Firing temperature . -C

1400

Fig. 4--Free lime conter"lS of raw cement mi xes fired at d ifferent temperatures

the basalt cont nt inc reases the mixes a re rich in iron , titan ia, magnes ia, and the flu xi ng o xides namel y Na20 , K20, Fe20 " Ti02 and MgO. The presence o f these fluxin g ox ides tends to lower the c linkering temperature with reducing the melting poi nt o f the liquid phase. Also, the amount of SO, dec reases with basa lt content due to its disappearance in basalt .

Referring to the re levant al umina-sili ca fluxin g ox ides tern ary diagrams l 8

, the temper:1ture of initi al liquid phase formati on due to each oxide are , TiOz; 1478°C, MgO; 1425°C, FeO-Fe20 , ; 12 10-1 300°C, N:1z0 ; 1050°C , K20 ; 980°C. Since these flu xes are present together in a ll mi xes, the problem of me lt development i concerned with phase-eq uilibrium in an eight-component sys te m. Therefore, the liquid phase is ex pected to be formed :1t a temperature lower than 980°C, the lower of the above invariant points .

The clinkerability of the raw mixes determining with firing temperature up to 1375°C was studied by dete rmining the free lime and inso lubl e resid ue contents.

Fig. 4 shows that the free lime content sharply decreases as basalt and the firing temperature increases. The raw mixes 3, 4 and 5 g ive the bes t clinkerability and minimum amount of free lime content at 1300°C «0.5%).

During firing the raw mix up to clinkering temperature, the clay minerals loose the ir adsorbed and lattice water up to 600°C giving ri se to a mixture of active amorphous Si02 and A1 20 3. Be tween 600 and 850°C variable amounts of impurity ox ides of iron, titania, alkalies and alkaline earth are liberated together with CaO, Si02 and A120 3. These oxides in addition to the added amount of basalt act at temperatures probably higher than 800°C and onwards, as tluxing material s for the combination of

o~ o Mi). 1

~ 2

'i \ 'i '" D .. 5 C ~

:~ c 8 ~ ~ '0

:~~~.~ 'iii ~ ~

:0 2 ~

'0 '" oS ~~~Q-.-" 0

1200 1250 1300 1350 1400

f iring temperature,·C

Fig. 5- lnsoluble residue of raw cement mi xes fired at different temperatures

(

t

EL-A LFI: INFLUENCE OF ALTERED BASA LT O N PORTLAN D CEMENT C LI NKER 15 1

o CoO • • • Alit€' . • Belile mi x eS)

I ,.. '~ c

'"

i 52 f,f, 3 0 28 20

29 (Cu -K ... )

Fig . 6- XRD pat tern s of 1,3 and 5 cement mi xes fired at 1200°C

CaO and Si02 at lower clinkering temperature. At the same time, the free sili ca from the cl ay resists the action of the flu xing ox ides and persists at hi gher temperatures. Therefore, as the basalt increases the best burnability and max imum amount of liquid phase at lowest possible temperature enhances.

Fig. 5 shows the insoluble residue of the fired mi xes as a functi on of firing temperature from 1200°C up to I 375ae. The results indicate that as the basalt content increases the insoluble res idue decreases at any firing temperature. This is mainly due to that the clay contains higher values of free silica as well as sili ca and alumina moduli , which lead to give hi gher in so luble res idue at any firing temperature. The mixes 3, 4 and 5 give the lower amounts of insoluble res idue at l300ae. The values of the inso luble res idue are in a good agreement with those of free lime contents.

Fig. 6 illustrates the XRD patterns of mi xes I, 3 and 5 fired at 1200ae. It illustrates a singlet peak at 32.22, 37.40 and 53.90 (20-va lues), indicating the presence of free lime in the three mi xes in a decre­as ing order of mi x I > 3> 5. Also, the presence of a si nglet peaks at 29.4, 32.30, and 34.40 (20-va lues), illustrates the presence of alite phase in a small amount in mi x I in compari son with 3 and 5 mi xes. Also, it is clcar that the frcc lime content is sharpl y decreases with basa lt contcnt in mi xes 3 and 5 at the same temperature ( 1200aC).

The XRD patterns of mixes I, 3 and 5 fired at l300DC are show n in Fig. 7. The pattern s illustrate that the amount of alite phase (s inglet peak at 29.40, 32.30 and 34.40 20 -va lues) sharp ly increases in mi xes 3 and 5 with the co mplete disappearance of free lime peaks in compari son with mi x 1. The reac ti vity of each cement raw mi x at different burning tempera­tures vari es fro m one mi x to another depending on the

o Coo • AliiEo' • Belile

t

52

• . • mixeS)

f,f, 30 28 29(Cu ·K .. )

20

Fig. 7-X RD pattern s of 1, 3 and 5 cement mi xes fi red at 1300"C

chemical, physical and mineralogical composition of each mi x. On the other side, the extent of clinker formation depends not only on the amount of the liquid phase fo rmed, but also on its viscos ity and surface tension. As the amounts of flu xing ox ides Fe20 3, Ti20 , MgO, Na20 and K20 in the cement mixes increase, its maturing temperature decreases and liquid phase content enhances. Thus, as the basalt content increases in the mi x, the iron ox ide, titani a, magnes ia and the fluxing ox ides namely Na20 , K20 , Fe20 3, Ti02 and MgO enhance. Therefore, these lead to the best burnability with minimum amount of free lime as well as insolub le residue content at lower possible temperature.

Conclusions From the above findings it is concluded that it is

poss ible to use the waste weathered basa lt from the basa lt quarri es at Abu-Zaabal, Egy pt as flu xing materi al in the sy nthesis of the portl and cement clinker. As the basa lt content increases the mi xcs are ri ch in iron ox ide, titani a, magnes ia and the sum of the alkali es contents whi ch tend to lower the clinkering temperature with reducing the melting point of the liquid phase. On the other side, thc free lime and insolub le res idue contents sharp ly decreased with the basa lt addition. Al so, the mi xes 3, 4 and 5 give the best clinkerabi lity with minimum free lime « 0.5%) and insoluble « 0.4%) contents at l300ae. Portl and cement clinker can be prepared at 1300aC by substituting clay by basalt at ratios between 30-60 wt. % in compari son to about 1450°C when used on ly clay- limestone mi xes.

References 1 Chatterjee A K, Celll elll raw lIlater ia/s alld ralll lIlixes. Part I

Pit and Quarry , ( 1979) 104.

152 INDIAN J. ENG. MATER. SCI., APRIL 2002

2 Sing R A, Prvc A ll Illdia Selllillar all Celllem alld Allied Buildillg Ma/erials, (CR I Puplicati on, New Delhi , India ), II ( 19R I ) 79.

3 Bogue R H, The chellli.l"lI y of pOrllalld celllelll , 2nd ed (Reinhold Pupli shcrs Corp., New York ) 1953.

4 Ludwig U & Ruc ensteiner G, TOllilld-Zlg Keralll RUlldsch, 97 ( 12) 313 ( 1973).

5 Hewlett P C, Lea '.I' Chelllislrv of Celll elll wid COllcrele (John & Sons I nc, New York), 1998.

6 Butt Y M , Tilllashov V V & Malczcnh L T, Proc 5'" 1111

SYIIIP Chelll Celllell ls, Tokkyo I ( 1968) 340. 7 Kn6fe l D, ZClllent Kalk Gips, 30 ( 1977) 19 1. 8 EI-Didarnony H & Taha A S, Zelllelll Kalk Gips. 34 ( 1981)

312. 9 Taha A S & El-Didaillony H, Tallilld ZIg . 106 ( 1982) 64. 10 Searl e A B & Grimshaw R W, Th e chelllislry {///{I phys ics of

clays alld OIher ceralllic lIIalerials, (Ernst Benn Ltd, London), 1959,4 1.

11 Grim R E, Applied clay lIIilleralogy, (McGraw-Hili , ew York ), 1962, 43.

12 Konrad K B, IlIlroduuioll 10 geochelllisll )" 2nd ed (McGraw­Hill , Kogakusha, Ltd ), 1979.

13 EI-A lfi S A. Osman A G & Elwan M, Illd Cerulli. 19(3) 1999, 145.

14 Sanjoasuren R & RYlllyant seu P F, Proc 1(/' 1111 CaliX Chelll Celli , Sweden ( 1997) 37.

15 Plaul T, Tecllllologie del' Grobkeralllik . 8el.l , (Verl ag fur Bauwesen. Berlin), 1964, 272 .

16 Trostel L J & Wynne D J, Alii Ceralll Soc, 23( I) ( 1940) 18.

17 Abdel-Maksoud M A, Pelrological. geological allll phvsical properlie.l' 01' £gyplioll basallic rocks IVil1i special referellce TO Abu-Z(/abal, M Sc Thes is , Fac Sc i Ca iro Uni versity, Ca iro, Egypt, 1965.

18 Wilhelm Hinz, Die Silika/e , vo l. 2 (V EB Ver lag fijr Bauweser, Berlin ), 1970.