Directory UMM :Data Elmu:jurnal:E:Environmental Management and Health:Vol08.Issue1.1997:
Utilization of controlled cement dust as a concrete
material in the United Arab Emirates
Kamal T. Hindy
Re se arc h Pro fe sso r and He ad o f De partme nt o f Air Po llutio n, Natio nal Re se arc h
Ce ntre , Cairo , Egypt
Investigates the characterization of cement dust collected
by electrostatic precipitators
and fabric fi lters to study its
ability to be used as a concrete material. The study
includes 26 cement dust
samples collected from different points on dry process
lines in four of the major
cement plants in the United
Arab Emirates. The collected
samples were subjected to
detailed physical tests and
chemical analyses. Results
obtained were compared with
the British Standard Specifi cations set for ordinary Portland cement. Finds that eight
samples show comparable
physical properties and
chemical as well as mineral
composition.
The author is grateful to
the UAE University for
fi nancing this work through
the project “ Study of Local
Raw Materials” . The friendly
and skilful co-operation of
Eng. Mohammed M. Manna,
Production Manager, Ajman
Cement Company, UAE is
highly appreciated.
Enviro nme ntal Manage me nt
and He alth
8 / 1 [ 1997] 2 0 –2 7
© MCB Unive rsity Pre ss
[ ISSN 0956-6163]
[ 20 ]
Introduction
An exten sive in vestiga tion of th e effect of
electr osta tic pr ecipita tion a n d fa br ic fi ltr a tion on th e ph ysica l a n d ch em ica l pr oper ties
of th e con tr olled cem en t du st w a s u n der ta k en
by Hin dy a n d Attia (1988; 1993). Its r esu lts
in dica te th a t th e cem en t du st leavin g th e
electr osta tic pr ecipita tor s a n d fa br ic fi lter s
h a s a m a ss m edia n dia m eter less th a n th a t
en ter in g th e two m ea n s of th e cem en t du st
con tr ol (Hin dy a n d Attia , 1988). On th e oth er
h a n d, th e stu dy on ch a n ges in ch em ica l com position of cem en t du st du e to collection by
electr osta tic pr ecipita tor s a n d fa br ic fi lter s
r ea ch ed th e follow in g two con clu sion s:
1 r ela tively low r edu ction va lu es in m eta l
con cen tr a tion in cem en t du st is obser ved
du e to collection by th e two con tr ol m ea n s;
and
2 m eta l con cen tr a tion r edu ction is a lw ays
a ssocia ted w ith a n in cr ea se in th e < 20 µm size por tion in cem en t du st leavin g th e
con tr ol device (Hin dy a n d Attia , 1993).
Th is r eflects two fa cts: th e fir st is th a t th e
electr osta tic pr ecipita tion a n d fa br ic fi ltr a tion dim in ish th e dia m eter of th e cem en t du st
pa r ticles, a n d th e secon d is th a t th e two con tr ol pr ocesses do n ot ca u se a n a ctu a l ch a n ge
in th e m eta l con ten t of th e con tr olled m a ter ia l. Th is m ea n s th a t th e ph ysica l ch a r a cter istics of th e cem en t wh ich a r e m a in ly depen den t on its pa r ticle size a r e im pr oved by th e
two con tr ol m ea n s; besides, th e ch em ica l
com position s of th e cem en t do n ot sh ow a n y
ch a n ge a fter a pplyin g th e sa m e two m ea n s.
Accor din g to th e for e goin g fin din gs, it is
expected th a t th er e is a h igh pr oba bility for
th e u tiliza tion of th e con tr olled cem en t du st
for bu ildin g pu r poses. Th er efor e, it w a s n ecessa r y to ca r r y ou t th e pr esen t in vestiga tion
wh ich a im s pr in cipa lly a t a ssu r in g th is
expecta tion .
Th e in vestiga tion in clu des sa m ples collected fr om fou r of th e m a jor cem en t fa ctor ies
in th e Un ited Ar a b E m ir a tes (UAE ). Th ese a r e
loca ted in fou r differ en t E m ir a tes; Du ba i,
F u ja ir a h , Ajm a n a n d Ra s Al Kh a im a h (see
F igu r e 1).
Facility description
With in a per iod of ten yea r s fr om 1975, som e
n in e cem en t com pa n ies h a d been esta blish ed
in th e UAE , w ith a tota l in sta lled clin k er
ca pa city of som e 4.9 m illion ton n es per
a n n u m a n d th e fa cilities to gr in d som e n in e
m illion ton n es of cem en t a n n u a lly (In ter n a tion a l Cem en t R eview , 1992). Th e clin k er a n d
cem en t ca pa cities of th e in vestiga ted fou r
cem en t com pa n ies a r e sh ow n in Ta ble I.
Cem en t is m a n u fa ctu r ed in th e fou r pla n ts by
th e dr y pr ocess. In th is pr ocess th e r aw m a ter ia ls a r e gr ou n d a n d blen ded a s dr y pow der s.
Th en th ey pa ss th r ou gh th e pr eh ea ter a n d
k iln wh er e th ey a r e con ver ted to cem en t
clin k er. Th is clin k er is th en gr ou n d a fter
m ixin g w ith gypsu m to for m Por tla n d
cem en t. Ta ble II sh ow s th e type a n d a n n u a l
con su m ption of th e r aw m a ter ia ls u sed in th e
fou r pla n ts.
Th r ee of th e fou r pla n ts, n a m ely F u ja ir a h ,
Un ion a n d N a tion a l Cem en t Com pa n ies pr odu ce both clin k er a n d cem en t, wh er ea s th e
fou r th , i.e. Ajm a n Cem en t Co., depen ds on th e
clin k er pr odu ced by oth er fa ctor ies (e.g.
Un ion Cem en t Co.) for th e pr odu ction of
cem en t.
Control equipment
E ver y oper a tion in th e cem en t pr odu ction
pr ocess, by its n a tu r e, pr odu ces du st. Du st
em ission s ca n occu r wh en ever dr y m a ter ia ls
a r e m in ed, cr u sh ed, con veyed, tr a n sfer r ed or
pr ocessed. Th e m a jor sou r ces of du st in th e
cem en t in du str y ca n be cla ssified a s:
• poin t sou r ces, in clu din g th e m a in k iln
sta ck , fi n ish m ill ven t sta ck a n d th e pa ck in g
pla n t ven ts; a n d
• fu gitive sou r ces, su ch a s equ ipm en t lea k s,
qu a r r y oper a tion s, a n d th e con veyin g,
sta ck in g, stor in g a n d pa ck a gin g of dr y
m a ter ia ls.
Histor ica lly, electr osta tic pr ecipita tor s h ave
been th e pr edom in a n t ch oice of th e cem en t
in du str y for con tr ollin g th e poin t-of-sou r ce
em ission s. Th e r ecen t tr en d w ith in th e in du str y, h owever, is tow a r ds th e u se of fa br ic
filter s.
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Figure 1
Lo c atio n map o f Unite d Arab Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
Table I
Clinke r and c e me nt c apac itie s o f the
inve stigate d c e me nt c o mpanie s in Unite d Arab
Emirate s
Clinker
Cement
capacitya capacitya
Company
Emirate
Ajman Cement Co.
Fujairah Cement Co.
Union Cement Co.
Ajman
–
Fujairah
0.520
Ras
Al-Khaimah 0.990
Dubai
0.495
National Cement Co.
Note:
a Million tonnes per annum
Source: International Cement Review (1992)
0.750
0.790
1.270
2.000
Sepa r a tion of su spen ded pa r ticu la te m a tter
fr om a ga s str ea m by h igh volta ge electr osta tic pr ecipita tion r equ ir es th r ee ba sic steps:
1 electr ica l ch a r gin g of th e su spen ded m a tter ;
2 collection of th e ch a r ged pa r ticu la te m a tter on a gr ou n d su r fa ce; a n d
3 r em ova l of th e pa r ticu la te m a tter to a n
exter n a l r ecepta cle.
Th e ch a r ge is a pplied by pa ssin g th e
su spen ded pa r ticles th r ou gh a h igh -volta ge,
dir ect-cu r r en t cor on a . Th e cor on a is esta blish ed between a n electr ode m a in ta in ed a t
h igh volta ge a n d a gr ou n ded collectin g su r fa ce. Th e pa r ticles th er eby becom e h igh ly
[ 21 ]
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Table II
Type and annual c o nsumptio n o f raw mate rials
use d in the inve stigate d fo ur c e me nt
c o mpanie s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
Company
Raw material
Ajman
National
Gypsum
Limestone
Bauxite
Iron oxide
Limestone
Silic a
Bauxite
Iron oxide
Gypsum
Limestone
Marl
Alluvium
Bauxite
Iron oxide
Gypsum
Union
Fujairah
Annual consumption
(tonnes)
10,000
1,338,826
446,177
40,000
28,000
50,000
490,000
189,000
187,000
8,700
134,000
11,000
ch a r ged w ith in a fr a ction of a secon d a n d
m igr ate tow a r ds th e gr ou n ded collectin g su r fa ce. Th e pa r ticu la te m a tter is dislodged fr om
th e collectin g su r fa ce by m ech a n ica l m ea n s,
su ch a s vibr atin g w ith r apper s. Th e collected
pa r ticu la te m a ter ia l fa lls to a h opper fr om
wh er e it is r em oved by m ech a n ica l m ea n s.
With a fa br ic filter, th e du st-bea r in g ga s is
pa ssed th r ou gh a gla ss or n eedlefelt fa br ic in
su ch a m a n n er th a t du st pa r ticles a r e r eta in ed
on th e u pstr ea m or dir ty-ga s side of th e fa br ic,
wh ile th e ga s pa sses th r ou gh th e fa br ic to th e
dow n str ea m or clea n -ga s side. Du st is r em oved
fr om th e fa br ic by gr avity a n d/ or m ech a n ica l
m ea n s su ch a s r a pper s or via a ir pu lses.
Th e over a ll collection efficien cy of electr osta tic pr ecipita tor s, in m a n y ca ses, is h igh er
th a n 99 per cen t (Br a u er a n d Va r m a , 1981).
Th e over a ll collection efficien cy of th e fa br ic
filter w a s fou n d to be a r ou n d 99 per cen t
(Hin dy, 1989). However, du st su ppr ession by
th e two m ea n s on th e dr y pr ocess lin es fa ces a
specia l pr oblem r ela ted to th e disposin g of th e
collected cem en t du st. Con tr olled cem en t
du st in th r ee of th e in vestiga ted fou r cem en t
pla n ts is disposed of on th e su r fa ce of th e
open deser t. Th is m ay ca u se ser iou s en vir on m en ta l pr oblem s, su ch a s a ir a n d gr ou n d
w a ter pollu tion .
Th e pr esen t in vestiga tion tr ies to fi n d ou t a
su ita ble m ea n s, n ot on ly for disposin g of th e
con tr olled cem en t du st in th e fou r fa ctor ies,
on ly a lso for its u tiliza tion a s a u sefu l bu ildin g m a ter ia l.
Experimental work
In a ccor da n ce w ith th e r equ ir em en ts of th e
pr esen t in vestiga tion wh ich is lim ited to th e
[ 22 ]
u tiliza tion of cem en t du st collected by th e
electr osta tic pr ecipita tor s (E SP ) a n d fa br ic
filter s (F F ), th e exa m in ed sa m ples wer e ta k en
fr om 21 pla ces. Th ese a r e listed in Ta ble III.
Th e collected sa m ples wer e th en su bjected to
ph ysica l tests a n d ch em ica l a n a lysis.
Physical tests
P h ysica l tests in clu ded in th e pr esen t stu dy
wer e su r fa ce a r ea , 45 µm -sieve r esidu e, 90µm sieve r esidu e, settin g tim e (in itia l a n d fi n a l),
a n d settin g tim e (th r ee-day, seven -day a n d 28day tests). Testin g pr ocedu r es developed for
Por tla n d cem en t wer e a pplied for th e cem en t
du st.
P r ocedu r es of ch em ica l a n a lysis in volve
deter m in in g in solu ble r esidu e a n d th e loss on
ign ition . Th e la tter r equ ir es ign itin g th e
dr ied sa m ple to a con sta n t weigh t in a m u ffle
fu r n a ce a t 800°C u sin g u n cover ed por cela in
cr u cible. Requ ir ed ch em ica l deter m in a tion s
a r e th en m a de u sin g pr ocedu r es wh ich a r e
th e sa m e a s th ose u sed in testin g Por tla n d
cem en t a n d depen d on X-r ay flu or escen ce
qu a n tom eter plu s com pu ter, wh ich pr ovides
ch em ica l a n a lysis a n d da ta pr in tou t of n in e
elem en ts in less th a n th r ee m in u tes. Th ese
elem en ts a r e ca lciu m (Ca ), silicon (Si), a lu m in iu m (Al), ir on (Fe), sodiu m (N a ), pota ssiu m (K), su lph u r (S), m a gn esiu m (Mg) a n d
ch lor in e (Cl).
Results and discussion
Physical properties
Th e su r fa ce a r ea (fin en ess), settin g (h a r den in g) tim e, a n d com pr essive str en gth a r e th e
th r ee pr in cipa l ph ysica l pr oper ties wh ich
sh ou ld be ta k en in to con sider a tion wh en
eva lu a tin g th e cem en t m a ter ia l. Th e r esu lts
of th e ph ysica l tests of th e con tr olled cem en t
du st sa m ples com pa r ed w ith th e Br itish Sta n da r d r equ ir em en ts of or din a r y Por tla n d
cem en t (OP C) a r e given in Ta ble IV.
F r om th e r esu lts pr esen ted, th e follow in g
m ay be n oted.
Surfac e are a
Th e su r fa ce a r ea of th e exa m in ed sa m ples
r a n ges fr om < 50m 2/ k g in sa m ple N o. 25 to >
700m 2/ k g in sa m ple N os 11, 12, 16, 18, 19, 20,
21, 23 a n d 26. With th e exception of sa m ple
N os 13, 22 a n d 25, a ll oth er exa m in ed sa m ples
h ave a su r fa ce a r ea m or e th a n th e BS r equ ir em en t (225m 2/ k g).
Th e a bove r esu lts a r e m a in ly a ssocia ted
w ith th e electr osta tic pr ecipita tor s a n d fa br ic
filter s u sed in th e in vestiga ted fou r cem en t
pla n ts for th e sepa r a tion of th e cem en t du st
fr om th e ga s str ea m .
F in en ess of th e fly a sh h a s a sign ifica n t
in fl u en ce on its per for m a n ce in con cr ete.
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
Resu lts of tests by ASTM C430, N o. 325 (45µm )
sieve fin en ess (ASTM, 1983) h a d been u sed a s
a m ea n s to cor r ela te th e fin en ess of fl y a sh
w ith cer ta in pr oper ties. Th e da ta in dica te
th a t con cr ete str en gth , a br a sion r esista n ce,
a n d r esista n ce to fr ee zin g a n d th aw in g a r e
dir ect fu n ction s of th e por tion of th e fly a sh
fin er th a n N o. 325 (45µm ) sieve. It cou ld be
con clu ded th a t fin en ess is a m or e con sisten t
in dica tor of fly a sh per for m a n ce in con cr ete
a n d th a t per for m a n ce im pr oves w ith
in cr ea sed fin en ess (ACI Com m ittee 226, 1987).
In th e pr esen t in vestiga tion , th e cem en t
du st coa r ser th a n (45µm ) sieve w a s fou n d to
r a n ge in per cen ta ges fr om 0.00 in sa m ple N o.
17 to 78.07 in sa m ple N o. 25. Seven sa m ples
h ave a (45µm ) r esidu e less th a n 1 per cen t, 14
sa m ples h ave a (45µm ) r esidu e less th a n 10
per cen t a n d 20 sa m ples h ave a (45µm ) r esidu e
less th a n 20 per cen t (Ta ble IV). Th ese r esu lts
r eflect th e h igh fin en ess of th e exa m in ed
sa m ples.
F in en ess of exa m in ed sa m ples h a s been
fu r th er sh ow n by (90µm ) sieve a n a lysis.
Resu lts ava ila ble in dica te th a t collected
cem en t du st coa r ser th a n 90µm r a n ges in
per cen ta ge fr om 0.00 in sa m ple N os 10,16, 17,
18, 20, a n d 26 to 52.35 in sa m ple N o. 25. Th e
r esu lts a lso in dica te th a t 16 ou t of th e 25
exa m in ed sa m ples h ave a 90µm r esidu e less
th a n 1 per cen t, 21 sa m ples h ave a 90µm
r esidu e less th a n 5 per cen t a n d 24 sa m ples
Table III
Co lle c tio n po ints o f sample s studie d fro m the fo ur c e me nt c o mpanie s
Sample
no.
Company
Process
M eans of
control
Sample
type
Sample
location
OPC intake area
OPC bin
7CS-1 air separator
7CB-1 separation
produc t
7CS-2 air separator
7CB-2 separation
produc t
Mill 2 produc t
Mill 1 produc t
OPC silo
SRC silo
Main kiln
Raw mill
Cement mill II
Main by-pass
Main kiln by-pass
Main kiln
Cement mill II
Raw mill
After nodulizer
Kiln 1
Kiln 1
1
2
3
4
Ajman
Ajman
Ajman
Ajman
Clinker feeding
Clinker feeding
Separation
Separation
FF
FF
FF
FF
Outlet
Outlet
Outlet
Outlet
5
6
Ajman
Ajman
Separation
Separation
FF
FF
Outlet
Outlet
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Ajman
Ajman
Ajman
Ajman
National
National
National
National
National
National
National
National
National
Union
Fujairah
Cement pumping
Cement pumping
Silo loading
Silo loading
Clinker produc tion
Silo homogenizing
Silo dedusting
FF
FF
FF
FF
ESP
FF
ESP
ESP
ESP
ESP
ESP
FF
Outlet
Outlet
Outlet
Outlet
Inlet
Inlet
Outlet
Inlet
Outlet
Outlet
Outlet
Outlet
Clinker produc tion
Clinker produc tion
ESP
ESP
Outlet
Outlet
Clinker produc tion
Clinker produc tion
Clinker produc tion
h ave a 90µm r esidu e less th a n 10 per cen t.
Th is r efl ects on ce m or e th e h igh de gr ee of
fin en ess of th e in vestiga ted sa m ples.
It sh ou ld be n oted th a t th er e a r e n o Br itish
Sta n da r d r equ ir em en ts r e ga r din g th e 45µm
a n d 90µm r esidu e tests.
Se tting time
Th e settin g ch a r a cter istics of con cr ete a r e
in fl u en ced by a m bien t a n d con cr ete tem per a tu r e; cem en t type, sou r ce, con ten t, a n d fi n en ess; w a ter con ten t of th e pa ste; solu ble a lk a lis a n d u se of oth er a dm ixtu r e (ACI Com m ittee 226, 1987).
Th is m ea n s th a t oth er fa ctor s th a n th ose
a ssocia ted w ith th e pr oper ties of th e cem en t
m a ter ia l a r e r espon sible for deter m in in g th e
settin g tim e of th e exa m in ed sa m ples.
Th e r esu lts obta in ed sh ow th a t a ll th e
exa m in ed sa m ples h ave a n in itia l settin g
tim e th a t exceeds th e BS r equ ir em en t (45
m in u tes m in im u m va lu e) by sever a l tim es.
However, n in e of th e sa m e sa m ples do n ot
m eet th e BS r equ ir em en t (600 m in u tes m a xim u m va lu e) for th e fin a l settin g tim e. Th ese
a r e sa m ple N os 11, 12, 16, 18, 19, 20, 21, 23 a n d
26 (Ta ble IV).
Co mpre ssive stre ngth
Str en gth a t a n y given a ge a n d r a te of str en gth
ga in of con cr ete a r e a ffected by th e ch a r a cter istics of th e cem en t. Th er efor e, com pr essive
str en gth m ay give som e gu ide to th e poten tia l
of th e cem en t for pr odu cin g str en gth in con cr ete.
Test r esu lts of th e investiga ted cem en t du st
sa m ples (Ta ble IV) in dica te th a t on ly ten of
th ese sa m ples cou ld be su bjected to a com plete com pr essive str en gth tests (sa m ple N os
1-10). Th e r esu lts fin a lly in dica te th a t cem en t
du st sa m ples given N os 3-10 m eet th e BS
r equ ir em en ts of OP C. Th ese sa m ples wer e
collected fr om on e cem en t pla n t (Ajm a n
Cem en t P la n t).
Chemical and mineralogical composition
Cem en t du st is com plex in its r a n ge of ch em ica l a n d ph a se com position s. It con sists of
h om ogen eou s com bin a tion of gla ssy a n d
cr ysta llin e ph a ses.
Alth ou gh th e con stitu en ts a r e typica lly n ot
pr esen t a s oxides, it is cu stom a r y to expr ess
th e r esu lts of th e ch em ica l a n a lyses of th e
m a ter ia ls in ter m s of th e oxides of th e elem en ts, e.g. silica (SiO 2 ), a lu m in a (Al 2O 3),
fer r ic oxide (Fe 2O 3), ca lciu m oxide (Ca O)
m a gn esiu m oxide (MgO), a n d su lph u r tr ioxide (SO 3), besides th e a lk a lis (K 2O a n d N a 2O).
Com pou n d com position of cem en t m a ter ia l,
e.g. Tr i-ca lciu m silica te (C 3S), di-ca lciu m
silica te (C 2S), a n d tetr a -ca lciu m a lu m in iu m fer r ite (C 4AF ) a r e ca lcu la ted by Bogu e For m u la e (Bogu e, 1929), u sin g th e obta in ed
[ 23 ]
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
[ 24 ]
Table IV
Re sults o f physic al te sts o f c o ntro lle d c e me nt dust sample s c o mpare d with the British Standard re quire me nts o f o rdinary Po rtland c e me nt
Sample no.
Test
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
area (m2 / kg)
(12)
>
>
240
335
365
267
314
274
285
321
502
568
700
13.33 22.33 14.79
11.80
1.47
0.25
1.65
0.97
0.6
0
25 26.25
26.25
34
BS
(13)
(14)
(15)
(16)
700
205
355
357
700
7.01
28.80
45.27
13.08
1.72
1.40
10.99
5.26
3.44
45 27.50
22.50
25
–
>
>
160
24
24
hr
hr
Surface
(11)
(22)
(23) (24) (25) (26) Requirement
(18)
>
>
>
395
700
700
700
700
120
0.65
0 0.78 3.45
0.23
0.31
13.44
1.03 – 78.07
0.36
0.20
0.00
0
0
0.07
0.82
0.08 – 52.35
0.00
61.50
37.50
>
(19)
(20) (21)
(17)
>
>
700
–
<
>
Min.
50
700
225
Residue
45 µm %
6.05 1.17 10.58 32.86
Residue
90 µm %
0.87 0.17
0.59
6.55
1.27
26 24.25
26
3.57
0 0.44
Standard
consistency %
–
–
Setting
time (min.)
–
–
170
205
160
210
175
170
145
initial
>
>
280
24
24
hr
hr
41.7
–
Setting
time (min.)
–
–
210
265
225
250
240
220
195
final
225
–
15
225
55 28.75
>
>
115
24
12
12
hr
hr
hr
>
>
>
155
24
12
12
hr
hr
hr
–
–
–
>
270
–
30.00
8
hr
47 36.25
>
37.50 34.50 31.25 – 37.75 35.00
>
24
>
350
24
>
–
260
24
Min.
45
hr
hr
hr
>
>
>
24
390
hr
24
–
260
hr
24
Max.
hr
600
Compressive
strength
( N/ mm2 )
Cubes
Min.
14.7 22.3
35.8
23
34.5
24.3
30
31.8
44
–
11
–
–
–
–
3 day
7 day
20.6
25
52.2
34
51.2
35
45
47
51.3
48
–
–
19.8
–
–
–
–
–
–
–
28 day
31.1 30.4
73
56.2
71.0
57.4
64
67.9
53.3
57.9
–
–
–
–
–
–
–
–
–
–
Note:
– Not determined
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
23
Min.
41
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
ch em ica l a n a lyses. In th e sa m e m a n n er, som e
fa ctor s, e.g. lim e sa tu r a tion fa ctor (LSF ), lim e
com bin a tion fa ctor (LCF ), silica r a tio (SR),
a n d a lu m in a r a tio (AR) a r e a lso ca lcu la ted.
Ca r bon con ten t is u su a lly n ot deter m in ed
dir ectly, bu t is often a ssu m ed to be a ppr oxim a tely equ a l to th e loss on ign ition (LOI);
h owever, ign ition loss w ill a lso in clu de a n y
com bin ed w a ter or ca r bon dioxide (CO 2 ) lost
by decom position of h ydr a tes or ca r bon a tes
th a t m ay be pr esen t.
F r ee lim e (Ca O) wh ich is n ot in com bin a tion in a n y com pou n d is ca lcu la ted by a pplyin g th e Bogu e For m u la e (Bogu e, 1929).
Resu lts of ch em ica l a n a lyses of th e in vestiga ted cem en t du st sa m ples com pa r ed w ith
th e Br itish Sta n da r d specifica tion s a r e given
in Ta ble V.
It seem s im por ta n t a t fir st to k n ow h ow th e
m eta l oxides for m th e a ctu a l com pou n ds in
th e cem en t. Th is w ill be discu ssed n ext.
Wh en a ca r efu lly pr opor tion ed a n d blen ded
r aw m ix is fed in to th e k iln , th e ca lciu m ca r bon a te, Ca CO 3 fr om th e ch a lk or lim eston e is
con ver ted to lim e, Ca O, or C in cem en t
ch em ists’ n ota tion :
Hea t
Ca CO 3 → Ca O + CO 2
Th is com bin es w ith th e silica , a lu m in a a n d
fer r ic oxide fr om th e sh a le or clay (C+ S + A +
F ) to for m cem en t clin k er, a m ixtu r e of
m a in ly fou r com pou n ds ea ch h avin g u n iqu e
pr oper ties (C 3S+ C 2S + C 3A+ C 4AF ). Th e
poten tia l pr opor tion of ea ch of th ese com pou n ds in th e clin k er m ay be ca lcu la ted fr om
for m u la e su ggested by Bogu e (1929).
Th e m ost im por ta n t com pou n d is tr ica lciu m silica te, C 3S (3Ca O. SiO 2 ) in cem en t
ch em ists’ n ota tion . Th e cr ysta llin e m a ter ia l
a s it a ctu a lly occu r s in clin k er in clu des im pu r ities a n d is ca lled a lite.
Tr i-ca lciu m silica te for m s m or e th a n h a lf of
Por tla n d cem en t clin k er a n d it is r espon sible
for m u ch of th e str en gth of con cr ete u p to 28
days; th e ph ysica l pr oper ty by wh ich cem en ts
a r e often com pa r ed. Th er efor e, it is im por ta n t to m a xim ize C 3S con ten t, given th e lim ita tion s im posed by m a r k et r equ ir em en ts, th e
r aw m a ter ia ls a n d th e pr ocess con dition s.
Th e secon d com pou n d is di-ca lciu m silica te, C 2S (2Ca O. SiO 2 ) or belite in its im pu r e
sta te. Alth ou gh pr esen t in sm a ller qu a n tities
th a n C 3S, C 2S, it a lso h a s str en gth givin g
pr oper ties a n d is th er efor e a n im por ta n t
con stitu en t of cem en t.
Alth ou gh C 3S is pr efer r ed, C 2S is still a n
im por ta n t str en gth -givin g com pou n d. It
h ydr a tes m or e slow ly th a n C 3S a n d ten ds to
m a k e its con tr ibu tion to con cr ete str en gth
developm en t a t 28 days a n d beyon d.
Th e th ir d com pou n d, tr i-ca lciu m a lu m in a te, C 3A (3Ca O. A12 O 3) h a s n ot gen er a lly
been con sider ed to con tr ibu te to con cr ete
str en gth . However, it is m u ch m or e r ea ctive
th a n eith er C 3S or C 2S. It m ay, th er efor e,
im pr ove ea r ly str en gth .
Alth ou gh C3A is pr esen t in sm a ller qu a n tities, it h a s a n im por ta n t in flu en ce on th e ea r ly
h ydr a tion r ea ction s wh ich deter m in e wor k a bility a n d settin g beh aviou r. Wor k a bility is
th e ea se w ith wh ich con cr ete ca n be h a n dled
a n d pla ced a fter m ixin g h a s ta ken pla ce.
Th e fou r th com pou n d is tetr a -ca lciu m a lu m in o-fer r ite, C 4AF (4Ca O. A12O 3. Fe 2O 3)
wh ich im pa r ts th e ch a r a cter istic gr ey colou r
to th e Por tla n d cem en t; h en ce th e n eed to
r edu ce th e a m ou n t of th is com pou n d wh en
m a k in g wh ite cem en t. Lik e C 3 A, C 4AF m a k es
little con tr ibu tion to con cr ete str en gth .
F r om th e for e goin g elu cida tion , it ca n be
seen th a t th e r aw m a ter ia ls pr ovide a sou r ce
of lim e, silica , a lu m in a a n d fer r ic oxide a n d
th a t th ese oxides com bin e in th e k iln to for m
fou r com pou n ds: C 3S, C 2S, C 3A a n d C 4AF. It
ca n a lso be seen th a t C 3S a n d C 2S a r e th e
com pou n ds in cem en t wh ich give con cr ete its
str en gth .
Th e ava ila ble r esu lts of ch em ica l a n d m in er a l com position of th e in vestiga ted cem en t
du st sa m ples (Ta ble V) ca n be lim ited to sa m ple N os 3-10. Th ese h ave sh ow n ph ysica l ch a r a cter istics m eetin g th e Br itish Sta n da r d
r equ ir em en ts, a s pr eviou sly discu ssed.
Th e eigh t sa m ples gave C 3S com pou n d
per cen ta ges r a n gin g between 45.60 for sa m ple
N o. 4 a n d 54.10 for sa m ple N o. 10, a n d th e
a r r a n gem en t of th e sa m ples a ccor din g to
th eir con ten t of C 3S is: 10 > 7 > 3 > 9 > 8 > 5 > 6
> 4. Th e cor r espon din g per cen ta ges of C 2S
con ten t r a n ge between 14.10 for sa m ple N o. 10
a n d 28.70 for sa m ple N o. 4, a n d th e
cor r espon din g a r r a n gem en t of th e sa m ples
a ccor din g to th eir con ten t of C 2S is: 4 > 6 > 8 >
5 > 7 > 3 > 9 > 10. Th is m ea n s th a t th er e is
n ea r ly a n in ver se r ela tion sh ip between th e
sa m ples’ con ten t of C 3S a n d th a t of C 2S.
Wh en exa m in in g th e tota l con ten t of sa m ples of C 3S a n d C 2S, it ca n be seen th a t th e
su m of C 3S plu s C 2S per cen ta ges r a n ges
between 68.20 for sa m ple N o. 10 a n d 74.40 for
sa m ple N o. 8. Th e sa m ples ca n be a r r a n ged
a ccor din gly a s: 8 > 4 > 7 > 6 > 5 > 3 > 9 > 10.
Su ch a r r a n gem en t m ay r eflect th e pr ior ity of
u sin g th e in vestiga ted cem en t du st a s a con cr ete m a ter ia l.
On th e oth er h a n d, th e ava ila ble Br itish
Sta n da r d r equ ir em en ts for ch em ica l a n d
m in er a l com position of OP C a r e con cer n ed
on ly w ith in solu ble r esidu e (IR), m a gn esiu m
oxide (MgO), su lph u r tr ioxide (SO 3), a n d loss
on ign ition (LOI), besides lim e sa tu r a tion
fa ctor (LSF ) (Ta ble V).
With th e exception of sa m ple N o. 10, a ll
oth er sa m ples of cem en t du st a r e su ggested to
be u sed a s a con cr ete m a ter ia l th a t m eets a ll
th e a bove m en tion ed BS r equ ir em en ts.
[ 25 ]
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
[ 26 ]
Table V
Re sults o f c he mic al analyse s (pe r c e nt) o f c o ntro lle d c e me nt dust sample s c o mpare d with the British Standard re quire me nts o f o rdinary Po rtland c e me nt
BS
Sample no.
(1)
0.2
IR
(2)
0.2
0.15
(3)
(4)
(5)
(6)
(7)
0.2
0.25
0.2
0.2
0.18
22.01
21.65
21.84
21.68
21.77
(8)
0.25
(9)
0.25
(10)
(11)
–
–
(12)
0.12
(13)
9.8
(14)
(15) (16)
–
–
8.32
5.8
(17) (18)
–
(19)
(20) (21)
–
–
–
8.32
8.12
–
–
(22)
(23) (24) (25) (26) requirement
–
–
–
–
–
9.53
–
9.51
–
–
14.03
4.4
Max
1.5
SiO2
19.25
17.22 21.5
20.1
19.15
9.3
14.04 21.81
13.04
17.91
Al2 O3
4.38
3.72
5.6
5.69
5.55
5.61
5.52
5.52
5.83
3.9
2.81
3.67
5.6
3.6
3.33
2.82
5.09
3.2
2.91
–
2.06
–
2
–
–
Fe 2 O3
2.6
3
3.7
3.75
3.65
3.7
3.72
3.68
3.46
5.6
1.7
0.7
3.80
1.7
2.67
2.8
3.81
3.15
2.62
–
2.08
–
2.09
–
–
2.12
CaO
63.6
62.9
64.75
64.8
64.75
64.7
64.9
64.85
62.92
55.26 58.59 48.29 60.10 46.36 49.72
–
42.13
– 43.19
–
–
38.05
M gO
0.6
0.6
0.7
0.6
0.7
0.7
0.7
0.9
–
0.54
–
–
–
0.45
61
46.2
43.85 64.31
Max.
0.65
0.8
0.45
0.45
0.9
9.6
0.81
0.86
1.33
0.79
0.85
0.57
4.0
Max.
SO3
2.1
2.14
2.02
1.85
2.2
1.95
2.02
2
3
4.36
1.75
2.11
2.55
0.15
7.38
0.13
0.96
–
2.42
–
3.21
–
–
–
K2 O
0.68
0.52
0.25
0.25
0.2
0.22
0.25
0.25
0.62
0.2
0.03
0.03
0.24
0.68
2.15
0.24
0.88
0.17
0.77
–
3.19
–
2.69
–
–
2.65
Na 2 O
0.18
0.15
0.1
0.11
0.08
0.09
0.12
0.1
0.15
0.08
0.03
0.03
0.14
0.21
1.99
0.25
0.56
0.21
0.58
–
0.34
–
0.3
–
–
0.12
LOI
5.85
8.49
1.07
0.94
1.08
1.05
1.05
1.15
2.2
4.17
27.85 35.89
0.83
21.3
34.12
–
37.4
– 36.15
–
–
–
F.CaO
1.85
11.37
1.68
0.5
0.5
0.45
0.5
0.5
0.45
0.5
–
–
0.45
39.3
–
–
–
–
–
–
–
–
–
–
–
–
–
–
89.8
–
–
–
–
–
–
–
–
–
–
–
–
82.8
89.1
Nil
Nil
2.5 a,3.0 b
Max.
22.73 38.66
3.18 37.7
4.0 c ,3.0 d
Max.
LSF
102.1
LCF
99.07
SR
2.76
91.4
89.6
90.8
90.1
91
90.7
92.7
93.5
91.6
90.4
88.9
90
89.5
90.3
90
92
92.7
2.56
66
2.31
2.33
2.35
2.35
2.35
2.37
2.16
2.02
–
–
–
–
2.32
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
2.15
–
–
–
–
–
–
–
–
–
–
–
–
2.07
43.5
48.7
45.6
48.2
47
49.2
48.5
48.6
54.1
–
–
46.2
–
–
–
–
–
–
–
–
–
–
–
–
–
25
25.9
21
14.1
–
–
27.7
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
8.4
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
11.6
–
–
–
–
–
–
–
–
–
–
–
–
–
1.68
AR
C3 S
112.4
1.24
1.51
1.52
1.52
1.52
1.48
1.50
1.68
C2 S
5.4
16.5
24.9
28.7
25.7
27.1
C3 A
7.2
4.8
8.6
8.7
8.5
8.6
8.3
8.4
9.6
C4 AF
7.9
9.1
11.30
11.4
11.1
11.3
11.3
11.2
10.6
Notes:
– Not determined
a
When C3 A < 5.0
b
When C3 A > 5.0
c
Tropic al
d
Temperate
0.7
0.86
17
–
1.47
102 min.
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
Sa m ple N o. 10 h a s SO 3 a n d LOI m or e th a n th e
BS r equ ir em en ts. A com bin a tion of h igh SO 3
a n d low MgO (a s fou n d in th e stu died sa m ples) in a clin k er m ix m ay be detr im en ta l to
str en gth developm en t. Th is is a ttr ibu ted to
th e eviden ce dr aw n by Gu tt a n d Sm ith (1968)
th a t in th e pr esen ce of C 3A th ou gh n ot of
C 4AF, for m a tion of C 3S is r edu ced by h igh SO 3
con ten t, bu t th is is cou n ter a cted by th e pr esen ce of MgO. Th e r esu lts of ph ysica l tests of
in vestiga ted sa m ples (Ta ble IV), h owever,
in dica te com pr essive str en gth va lu es for
sa m ple N o. 10 h igh er th a n th e BS r equ ir em en ts. At th e sa m e tim e, th e r esu lts of ch em ica l a n a lysis sh ow m a xim u m C 3S con ten t for
sa m ple N o. 10 in com pa r ison w ith oth er su ggested sa m ples (Ta ble V). Th is m ea n s th a t th e
sa m ple ca n be sa fely u sed a s a con cr ete m a ter ia l. On th e oth er h a n d, th e sligh t in cr ea se in
LOI con ten t of th e sa m ple th a n th e BS
r equ ir em en t ca n be con sider ed in effective in
ch a n gin g th e ch a r a cter istics of th e con cr ete.
It sh ou ld be n oted th a t th e a lk a li con ten t of
th e cem en t du st sa m ples su ggested to be u sed
a s con cr ete m a ter ia l is less th a n th e BS specifica tion s, i.e. N a 2O + 0.658 K 2O = < 0.6 per cen t
for low -a lk a li cem en t.
Conclusion
Th e con clu sion th a t ca n be dr aw n fr om th e
pr esen t in vestiga tion is th a t th e cem en t du st
collected by con tr ol m ea n s (e.g. electr osta tic
pr ecipita tor s a n d fa br ic fi lter s) m ay be in vestiga ted fu r th er a s to its u se a s a con cr ete
m a ter ia l.
Th e stu dy r evea ls th a t con tr olled cem en t
du st collected fr om eigh t poin ts on dr y
pr ocess lin es a t a cem en t pla n t in th e Un ited
Ar a b E m ir a tes h a s th e sa m e ph ysica l a n d
ch em ica l specifi ca tion s r equ ir ed for or din a r y
Por tla n d cem en t. Th e con tr ol m ea n s u sed a t
th ese poin ts is th e fa br ic filter a n d th e dr y
pr ocess lin es a r e: sepa r a tion (fou r poin ts);
cem en t pu m pin g (two poin ts); a n d silo loa din g (two poin ts).
References
ACI Com m ittee 226 (1987), Use of Fly A sh in Con crete, ACI 226 3R-87, Am er ica n Con cr ete In stitu te, Detr oit, MI.
ASTM (1983), A m er ica n S ta n d a rd T est M eth od for
Fin en ess of Hyd ra u lic Cem en t b y th e 45-µm
(N o. 325) S iev e, C 430-83.
Bogu e, R.H. (1929), In d . En gn g. A n a lyt. Ed n , Vol. 1
N o. 4, p. 192.
Br a u er, H. a n d Va r m a , Y.B.J . (1981), A ir Pollu tion
Con trol Equ ipm en t, Spr in ger -Ver la g, Ber lin ,
pp. 183-218.
Gu tt, W. a n d Sm ith , M.A. (1968), T ra n sa ction s of
th e B r itish Cera m ics S ociety, Vol. 87, p. 487.
Hin dy, K.T. (1989), “P u lse jet fa br ic filter oper a tion : a n exper im en ta l stu dy”, in Ch er em isin off, P.N. (E d.), En cycloped ia of En viron m en ta l
Con trol T ech n ology. Volu m e 2: A ir Pollu tion
Con trol, Gu lf P u blish in g, Hou ston , TX,
pp. 981-1002.
Hin dy, K.T. a n d Attia , A.A. (1988), Proceed in gs of
3rd In ter n a tion a l Con feren ce on En viron m en ta l Con ta m in a tion , Ven ice (S eptem b er ), CE P
Con su lta n ts Ltd, E din bu r gh , pp. 476-8.
Hin dy, K.T. a n d Attia , A.A. (1993), En viron m en ta l
Ed u ca tion a n d In for m a tion , Vol. 12, p. 35.
In ter n a tion a l Cem en t R eview (1992), Febr u a r y,
pp. 29-42.
[ 27 ]
material in the United Arab Emirates
Kamal T. Hindy
Re se arc h Pro fe sso r and He ad o f De partme nt o f Air Po llutio n, Natio nal Re se arc h
Ce ntre , Cairo , Egypt
Investigates the characterization of cement dust collected
by electrostatic precipitators
and fabric fi lters to study its
ability to be used as a concrete material. The study
includes 26 cement dust
samples collected from different points on dry process
lines in four of the major
cement plants in the United
Arab Emirates. The collected
samples were subjected to
detailed physical tests and
chemical analyses. Results
obtained were compared with
the British Standard Specifi cations set for ordinary Portland cement. Finds that eight
samples show comparable
physical properties and
chemical as well as mineral
composition.
The author is grateful to
the UAE University for
fi nancing this work through
the project “ Study of Local
Raw Materials” . The friendly
and skilful co-operation of
Eng. Mohammed M. Manna,
Production Manager, Ajman
Cement Company, UAE is
highly appreciated.
Enviro nme ntal Manage me nt
and He alth
8 / 1 [ 1997] 2 0 –2 7
© MCB Unive rsity Pre ss
[ ISSN 0956-6163]
[ 20 ]
Introduction
An exten sive in vestiga tion of th e effect of
electr osta tic pr ecipita tion a n d fa br ic fi ltr a tion on th e ph ysica l a n d ch em ica l pr oper ties
of th e con tr olled cem en t du st w a s u n der ta k en
by Hin dy a n d Attia (1988; 1993). Its r esu lts
in dica te th a t th e cem en t du st leavin g th e
electr osta tic pr ecipita tor s a n d fa br ic fi lter s
h a s a m a ss m edia n dia m eter less th a n th a t
en ter in g th e two m ea n s of th e cem en t du st
con tr ol (Hin dy a n d Attia , 1988). On th e oth er
h a n d, th e stu dy on ch a n ges in ch em ica l com position of cem en t du st du e to collection by
electr osta tic pr ecipita tor s a n d fa br ic fi lter s
r ea ch ed th e follow in g two con clu sion s:
1 r ela tively low r edu ction va lu es in m eta l
con cen tr a tion in cem en t du st is obser ved
du e to collection by th e two con tr ol m ea n s;
and
2 m eta l con cen tr a tion r edu ction is a lw ays
a ssocia ted w ith a n in cr ea se in th e < 20 µm size por tion in cem en t du st leavin g th e
con tr ol device (Hin dy a n d Attia , 1993).
Th is r eflects two fa cts: th e fir st is th a t th e
electr osta tic pr ecipita tion a n d fa br ic fi ltr a tion dim in ish th e dia m eter of th e cem en t du st
pa r ticles, a n d th e secon d is th a t th e two con tr ol pr ocesses do n ot ca u se a n a ctu a l ch a n ge
in th e m eta l con ten t of th e con tr olled m a ter ia l. Th is m ea n s th a t th e ph ysica l ch a r a cter istics of th e cem en t wh ich a r e m a in ly depen den t on its pa r ticle size a r e im pr oved by th e
two con tr ol m ea n s; besides, th e ch em ica l
com position s of th e cem en t do n ot sh ow a n y
ch a n ge a fter a pplyin g th e sa m e two m ea n s.
Accor din g to th e for e goin g fin din gs, it is
expected th a t th er e is a h igh pr oba bility for
th e u tiliza tion of th e con tr olled cem en t du st
for bu ildin g pu r poses. Th er efor e, it w a s n ecessa r y to ca r r y ou t th e pr esen t in vestiga tion
wh ich a im s pr in cipa lly a t a ssu r in g th is
expecta tion .
Th e in vestiga tion in clu des sa m ples collected fr om fou r of th e m a jor cem en t fa ctor ies
in th e Un ited Ar a b E m ir a tes (UAE ). Th ese a r e
loca ted in fou r differ en t E m ir a tes; Du ba i,
F u ja ir a h , Ajm a n a n d Ra s Al Kh a im a h (see
F igu r e 1).
Facility description
With in a per iod of ten yea r s fr om 1975, som e
n in e cem en t com pa n ies h a d been esta blish ed
in th e UAE , w ith a tota l in sta lled clin k er
ca pa city of som e 4.9 m illion ton n es per
a n n u m a n d th e fa cilities to gr in d som e n in e
m illion ton n es of cem en t a n n u a lly (In ter n a tion a l Cem en t R eview , 1992). Th e clin k er a n d
cem en t ca pa cities of th e in vestiga ted fou r
cem en t com pa n ies a r e sh ow n in Ta ble I.
Cem en t is m a n u fa ctu r ed in th e fou r pla n ts by
th e dr y pr ocess. In th is pr ocess th e r aw m a ter ia ls a r e gr ou n d a n d blen ded a s dr y pow der s.
Th en th ey pa ss th r ou gh th e pr eh ea ter a n d
k iln wh er e th ey a r e con ver ted to cem en t
clin k er. Th is clin k er is th en gr ou n d a fter
m ixin g w ith gypsu m to for m Por tla n d
cem en t. Ta ble II sh ow s th e type a n d a n n u a l
con su m ption of th e r aw m a ter ia ls u sed in th e
fou r pla n ts.
Th r ee of th e fou r pla n ts, n a m ely F u ja ir a h ,
Un ion a n d N a tion a l Cem en t Com pa n ies pr odu ce both clin k er a n d cem en t, wh er ea s th e
fou r th , i.e. Ajm a n Cem en t Co., depen ds on th e
clin k er pr odu ced by oth er fa ctor ies (e.g.
Un ion Cem en t Co.) for th e pr odu ction of
cem en t.
Control equipment
E ver y oper a tion in th e cem en t pr odu ction
pr ocess, by its n a tu r e, pr odu ces du st. Du st
em ission s ca n occu r wh en ever dr y m a ter ia ls
a r e m in ed, cr u sh ed, con veyed, tr a n sfer r ed or
pr ocessed. Th e m a jor sou r ces of du st in th e
cem en t in du str y ca n be cla ssified a s:
• poin t sou r ces, in clu din g th e m a in k iln
sta ck , fi n ish m ill ven t sta ck a n d th e pa ck in g
pla n t ven ts; a n d
• fu gitive sou r ces, su ch a s equ ipm en t lea k s,
qu a r r y oper a tion s, a n d th e con veyin g,
sta ck in g, stor in g a n d pa ck a gin g of dr y
m a ter ia ls.
Histor ica lly, electr osta tic pr ecipita tor s h ave
been th e pr edom in a n t ch oice of th e cem en t
in du str y for con tr ollin g th e poin t-of-sou r ce
em ission s. Th e r ecen t tr en d w ith in th e in du str y, h owever, is tow a r ds th e u se of fa br ic
filter s.
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Figure 1
Lo c atio n map o f Unite d Arab Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
Table I
Clinke r and c e me nt c apac itie s o f the
inve stigate d c e me nt c o mpanie s in Unite d Arab
Emirate s
Clinker
Cement
capacitya capacitya
Company
Emirate
Ajman Cement Co.
Fujairah Cement Co.
Union Cement Co.
Ajman
–
Fujairah
0.520
Ras
Al-Khaimah 0.990
Dubai
0.495
National Cement Co.
Note:
a Million tonnes per annum
Source: International Cement Review (1992)
0.750
0.790
1.270
2.000
Sepa r a tion of su spen ded pa r ticu la te m a tter
fr om a ga s str ea m by h igh volta ge electr osta tic pr ecipita tion r equ ir es th r ee ba sic steps:
1 electr ica l ch a r gin g of th e su spen ded m a tter ;
2 collection of th e ch a r ged pa r ticu la te m a tter on a gr ou n d su r fa ce; a n d
3 r em ova l of th e pa r ticu la te m a tter to a n
exter n a l r ecepta cle.
Th e ch a r ge is a pplied by pa ssin g th e
su spen ded pa r ticles th r ou gh a h igh -volta ge,
dir ect-cu r r en t cor on a . Th e cor on a is esta blish ed between a n electr ode m a in ta in ed a t
h igh volta ge a n d a gr ou n ded collectin g su r fa ce. Th e pa r ticles th er eby becom e h igh ly
[ 21 ]
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Table II
Type and annual c o nsumptio n o f raw mate rials
use d in the inve stigate d fo ur c e me nt
c o mpanie s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
Company
Raw material
Ajman
National
Gypsum
Limestone
Bauxite
Iron oxide
Limestone
Silic a
Bauxite
Iron oxide
Gypsum
Limestone
Marl
Alluvium
Bauxite
Iron oxide
Gypsum
Union
Fujairah
Annual consumption
(tonnes)
10,000
1,338,826
446,177
40,000
28,000
50,000
490,000
189,000
187,000
8,700
134,000
11,000
ch a r ged w ith in a fr a ction of a secon d a n d
m igr ate tow a r ds th e gr ou n ded collectin g su r fa ce. Th e pa r ticu la te m a tter is dislodged fr om
th e collectin g su r fa ce by m ech a n ica l m ea n s,
su ch a s vibr atin g w ith r apper s. Th e collected
pa r ticu la te m a ter ia l fa lls to a h opper fr om
wh er e it is r em oved by m ech a n ica l m ea n s.
With a fa br ic filter, th e du st-bea r in g ga s is
pa ssed th r ou gh a gla ss or n eedlefelt fa br ic in
su ch a m a n n er th a t du st pa r ticles a r e r eta in ed
on th e u pstr ea m or dir ty-ga s side of th e fa br ic,
wh ile th e ga s pa sses th r ou gh th e fa br ic to th e
dow n str ea m or clea n -ga s side. Du st is r em oved
fr om th e fa br ic by gr avity a n d/ or m ech a n ica l
m ea n s su ch a s r a pper s or via a ir pu lses.
Th e over a ll collection efficien cy of electr osta tic pr ecipita tor s, in m a n y ca ses, is h igh er
th a n 99 per cen t (Br a u er a n d Va r m a , 1981).
Th e over a ll collection efficien cy of th e fa br ic
filter w a s fou n d to be a r ou n d 99 per cen t
(Hin dy, 1989). However, du st su ppr ession by
th e two m ea n s on th e dr y pr ocess lin es fa ces a
specia l pr oblem r ela ted to th e disposin g of th e
collected cem en t du st. Con tr olled cem en t
du st in th r ee of th e in vestiga ted fou r cem en t
pla n ts is disposed of on th e su r fa ce of th e
open deser t. Th is m ay ca u se ser iou s en vir on m en ta l pr oblem s, su ch a s a ir a n d gr ou n d
w a ter pollu tion .
Th e pr esen t in vestiga tion tr ies to fi n d ou t a
su ita ble m ea n s, n ot on ly for disposin g of th e
con tr olled cem en t du st in th e fou r fa ctor ies,
on ly a lso for its u tiliza tion a s a u sefu l bu ildin g m a ter ia l.
Experimental work
In a ccor da n ce w ith th e r equ ir em en ts of th e
pr esen t in vestiga tion wh ich is lim ited to th e
[ 22 ]
u tiliza tion of cem en t du st collected by th e
electr osta tic pr ecipita tor s (E SP ) a n d fa br ic
filter s (F F ), th e exa m in ed sa m ples wer e ta k en
fr om 21 pla ces. Th ese a r e listed in Ta ble III.
Th e collected sa m ples wer e th en su bjected to
ph ysica l tests a n d ch em ica l a n a lysis.
Physical tests
P h ysica l tests in clu ded in th e pr esen t stu dy
wer e su r fa ce a r ea , 45 µm -sieve r esidu e, 90µm sieve r esidu e, settin g tim e (in itia l a n d fi n a l),
a n d settin g tim e (th r ee-day, seven -day a n d 28day tests). Testin g pr ocedu r es developed for
Por tla n d cem en t wer e a pplied for th e cem en t
du st.
P r ocedu r es of ch em ica l a n a lysis in volve
deter m in in g in solu ble r esidu e a n d th e loss on
ign ition . Th e la tter r equ ir es ign itin g th e
dr ied sa m ple to a con sta n t weigh t in a m u ffle
fu r n a ce a t 800°C u sin g u n cover ed por cela in
cr u cible. Requ ir ed ch em ica l deter m in a tion s
a r e th en m a de u sin g pr ocedu r es wh ich a r e
th e sa m e a s th ose u sed in testin g Por tla n d
cem en t a n d depen d on X-r ay flu or escen ce
qu a n tom eter plu s com pu ter, wh ich pr ovides
ch em ica l a n a lysis a n d da ta pr in tou t of n in e
elem en ts in less th a n th r ee m in u tes. Th ese
elem en ts a r e ca lciu m (Ca ), silicon (Si), a lu m in iu m (Al), ir on (Fe), sodiu m (N a ), pota ssiu m (K), su lph u r (S), m a gn esiu m (Mg) a n d
ch lor in e (Cl).
Results and discussion
Physical properties
Th e su r fa ce a r ea (fin en ess), settin g (h a r den in g) tim e, a n d com pr essive str en gth a r e th e
th r ee pr in cipa l ph ysica l pr oper ties wh ich
sh ou ld be ta k en in to con sider a tion wh en
eva lu a tin g th e cem en t m a ter ia l. Th e r esu lts
of th e ph ysica l tests of th e con tr olled cem en t
du st sa m ples com pa r ed w ith th e Br itish Sta n da r d r equ ir em en ts of or din a r y Por tla n d
cem en t (OP C) a r e given in Ta ble IV.
F r om th e r esu lts pr esen ted, th e follow in g
m ay be n oted.
Surfac e are a
Th e su r fa ce a r ea of th e exa m in ed sa m ples
r a n ges fr om < 50m 2/ k g in sa m ple N o. 25 to >
700m 2/ k g in sa m ple N os 11, 12, 16, 18, 19, 20,
21, 23 a n d 26. With th e exception of sa m ple
N os 13, 22 a n d 25, a ll oth er exa m in ed sa m ples
h ave a su r fa ce a r ea m or e th a n th e BS r equ ir em en t (225m 2/ k g).
Th e a bove r esu lts a r e m a in ly a ssocia ted
w ith th e electr osta tic pr ecipita tor s a n d fa br ic
filter s u sed in th e in vestiga ted fou r cem en t
pla n ts for th e sepa r a tion of th e cem en t du st
fr om th e ga s str ea m .
F in en ess of th e fly a sh h a s a sign ifica n t
in fl u en ce on its per for m a n ce in con cr ete.
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
Resu lts of tests by ASTM C430, N o. 325 (45µm )
sieve fin en ess (ASTM, 1983) h a d been u sed a s
a m ea n s to cor r ela te th e fin en ess of fl y a sh
w ith cer ta in pr oper ties. Th e da ta in dica te
th a t con cr ete str en gth , a br a sion r esista n ce,
a n d r esista n ce to fr ee zin g a n d th aw in g a r e
dir ect fu n ction s of th e por tion of th e fly a sh
fin er th a n N o. 325 (45µm ) sieve. It cou ld be
con clu ded th a t fin en ess is a m or e con sisten t
in dica tor of fly a sh per for m a n ce in con cr ete
a n d th a t per for m a n ce im pr oves w ith
in cr ea sed fin en ess (ACI Com m ittee 226, 1987).
In th e pr esen t in vestiga tion , th e cem en t
du st coa r ser th a n (45µm ) sieve w a s fou n d to
r a n ge in per cen ta ges fr om 0.00 in sa m ple N o.
17 to 78.07 in sa m ple N o. 25. Seven sa m ples
h ave a (45µm ) r esidu e less th a n 1 per cen t, 14
sa m ples h ave a (45µm ) r esidu e less th a n 10
per cen t a n d 20 sa m ples h ave a (45µm ) r esidu e
less th a n 20 per cen t (Ta ble IV). Th ese r esu lts
r eflect th e h igh fin en ess of th e exa m in ed
sa m ples.
F in en ess of exa m in ed sa m ples h a s been
fu r th er sh ow n by (90µm ) sieve a n a lysis.
Resu lts ava ila ble in dica te th a t collected
cem en t du st coa r ser th a n 90µm r a n ges in
per cen ta ge fr om 0.00 in sa m ple N os 10,16, 17,
18, 20, a n d 26 to 52.35 in sa m ple N o. 25. Th e
r esu lts a lso in dica te th a t 16 ou t of th e 25
exa m in ed sa m ples h ave a 90µm r esidu e less
th a n 1 per cen t, 21 sa m ples h ave a 90µm
r esidu e less th a n 5 per cen t a n d 24 sa m ples
Table III
Co lle c tio n po ints o f sample s studie d fro m the fo ur c e me nt c o mpanie s
Sample
no.
Company
Process
M eans of
control
Sample
type
Sample
location
OPC intake area
OPC bin
7CS-1 air separator
7CB-1 separation
produc t
7CS-2 air separator
7CB-2 separation
produc t
Mill 2 produc t
Mill 1 produc t
OPC silo
SRC silo
Main kiln
Raw mill
Cement mill II
Main by-pass
Main kiln by-pass
Main kiln
Cement mill II
Raw mill
After nodulizer
Kiln 1
Kiln 1
1
2
3
4
Ajman
Ajman
Ajman
Ajman
Clinker feeding
Clinker feeding
Separation
Separation
FF
FF
FF
FF
Outlet
Outlet
Outlet
Outlet
5
6
Ajman
Ajman
Separation
Separation
FF
FF
Outlet
Outlet
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Ajman
Ajman
Ajman
Ajman
National
National
National
National
National
National
National
National
National
Union
Fujairah
Cement pumping
Cement pumping
Silo loading
Silo loading
Clinker produc tion
Silo homogenizing
Silo dedusting
FF
FF
FF
FF
ESP
FF
ESP
ESP
ESP
ESP
ESP
FF
Outlet
Outlet
Outlet
Outlet
Inlet
Inlet
Outlet
Inlet
Outlet
Outlet
Outlet
Outlet
Clinker produc tion
Clinker produc tion
ESP
ESP
Outlet
Outlet
Clinker produc tion
Clinker produc tion
Clinker produc tion
h ave a 90µm r esidu e less th a n 10 per cen t.
Th is r efl ects on ce m or e th e h igh de gr ee of
fin en ess of th e in vestiga ted sa m ples.
It sh ou ld be n oted th a t th er e a r e n o Br itish
Sta n da r d r equ ir em en ts r e ga r din g th e 45µm
a n d 90µm r esidu e tests.
Se tting time
Th e settin g ch a r a cter istics of con cr ete a r e
in fl u en ced by a m bien t a n d con cr ete tem per a tu r e; cem en t type, sou r ce, con ten t, a n d fi n en ess; w a ter con ten t of th e pa ste; solu ble a lk a lis a n d u se of oth er a dm ixtu r e (ACI Com m ittee 226, 1987).
Th is m ea n s th a t oth er fa ctor s th a n th ose
a ssocia ted w ith th e pr oper ties of th e cem en t
m a ter ia l a r e r espon sible for deter m in in g th e
settin g tim e of th e exa m in ed sa m ples.
Th e r esu lts obta in ed sh ow th a t a ll th e
exa m in ed sa m ples h ave a n in itia l settin g
tim e th a t exceeds th e BS r equ ir em en t (45
m in u tes m in im u m va lu e) by sever a l tim es.
However, n in e of th e sa m e sa m ples do n ot
m eet th e BS r equ ir em en t (600 m in u tes m a xim u m va lu e) for th e fin a l settin g tim e. Th ese
a r e sa m ple N os 11, 12, 16, 18, 19, 20, 21, 23 a n d
26 (Ta ble IV).
Co mpre ssive stre ngth
Str en gth a t a n y given a ge a n d r a te of str en gth
ga in of con cr ete a r e a ffected by th e ch a r a cter istics of th e cem en t. Th er efor e, com pr essive
str en gth m ay give som e gu ide to th e poten tia l
of th e cem en t for pr odu cin g str en gth in con cr ete.
Test r esu lts of th e investiga ted cem en t du st
sa m ples (Ta ble IV) in dica te th a t on ly ten of
th ese sa m ples cou ld be su bjected to a com plete com pr essive str en gth tests (sa m ple N os
1-10). Th e r esu lts fin a lly in dica te th a t cem en t
du st sa m ples given N os 3-10 m eet th e BS
r equ ir em en ts of OP C. Th ese sa m ples wer e
collected fr om on e cem en t pla n t (Ajm a n
Cem en t P la n t).
Chemical and mineralogical composition
Cem en t du st is com plex in its r a n ge of ch em ica l a n d ph a se com position s. It con sists of
h om ogen eou s com bin a tion of gla ssy a n d
cr ysta llin e ph a ses.
Alth ou gh th e con stitu en ts a r e typica lly n ot
pr esen t a s oxides, it is cu stom a r y to expr ess
th e r esu lts of th e ch em ica l a n a lyses of th e
m a ter ia ls in ter m s of th e oxides of th e elem en ts, e.g. silica (SiO 2 ), a lu m in a (Al 2O 3),
fer r ic oxide (Fe 2O 3), ca lciu m oxide (Ca O)
m a gn esiu m oxide (MgO), a n d su lph u r tr ioxide (SO 3), besides th e a lk a lis (K 2O a n d N a 2O).
Com pou n d com position of cem en t m a ter ia l,
e.g. Tr i-ca lciu m silica te (C 3S), di-ca lciu m
silica te (C 2S), a n d tetr a -ca lciu m a lu m in iu m fer r ite (C 4AF ) a r e ca lcu la ted by Bogu e For m u la e (Bogu e, 1929), u sin g th e obta in ed
[ 23 ]
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
[ 24 ]
Table IV
Re sults o f physic al te sts o f c o ntro lle d c e me nt dust sample s c o mpare d with the British Standard re quire me nts o f o rdinary Po rtland c e me nt
Sample no.
Test
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
area (m2 / kg)
(12)
>
>
240
335
365
267
314
274
285
321
502
568
700
13.33 22.33 14.79
11.80
1.47
0.25
1.65
0.97
0.6
0
25 26.25
26.25
34
BS
(13)
(14)
(15)
(16)
700
205
355
357
700
7.01
28.80
45.27
13.08
1.72
1.40
10.99
5.26
3.44
45 27.50
22.50
25
–
>
>
160
24
24
hr
hr
Surface
(11)
(22)
(23) (24) (25) (26) Requirement
(18)
>
>
>
395
700
700
700
700
120
0.65
0 0.78 3.45
0.23
0.31
13.44
1.03 – 78.07
0.36
0.20
0.00
0
0
0.07
0.82
0.08 – 52.35
0.00
61.50
37.50
>
(19)
(20) (21)
(17)
>
>
700
–
<
>
Min.
50
700
225
Residue
45 µm %
6.05 1.17 10.58 32.86
Residue
90 µm %
0.87 0.17
0.59
6.55
1.27
26 24.25
26
3.57
0 0.44
Standard
consistency %
–
–
Setting
time (min.)
–
–
170
205
160
210
175
170
145
initial
>
>
280
24
24
hr
hr
41.7
–
Setting
time (min.)
–
–
210
265
225
250
240
220
195
final
225
–
15
225
55 28.75
>
>
115
24
12
12
hr
hr
hr
>
>
>
155
24
12
12
hr
hr
hr
–
–
–
>
270
–
30.00
8
hr
47 36.25
>
37.50 34.50 31.25 – 37.75 35.00
>
24
>
350
24
>
–
260
24
Min.
45
hr
hr
hr
>
>
>
24
390
hr
24
–
260
hr
24
Max.
hr
600
Compressive
strength
( N/ mm2 )
Cubes
Min.
14.7 22.3
35.8
23
34.5
24.3
30
31.8
44
–
11
–
–
–
–
3 day
7 day
20.6
25
52.2
34
51.2
35
45
47
51.3
48
–
–
19.8
–
–
–
–
–
–
–
28 day
31.1 30.4
73
56.2
71.0
57.4
64
67.9
53.3
57.9
–
–
–
–
–
–
–
–
–
–
Note:
– Not determined
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
23
Min.
41
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
ch em ica l a n a lyses. In th e sa m e m a n n er, som e
fa ctor s, e.g. lim e sa tu r a tion fa ctor (LSF ), lim e
com bin a tion fa ctor (LCF ), silica r a tio (SR),
a n d a lu m in a r a tio (AR) a r e a lso ca lcu la ted.
Ca r bon con ten t is u su a lly n ot deter m in ed
dir ectly, bu t is often a ssu m ed to be a ppr oxim a tely equ a l to th e loss on ign ition (LOI);
h owever, ign ition loss w ill a lso in clu de a n y
com bin ed w a ter or ca r bon dioxide (CO 2 ) lost
by decom position of h ydr a tes or ca r bon a tes
th a t m ay be pr esen t.
F r ee lim e (Ca O) wh ich is n ot in com bin a tion in a n y com pou n d is ca lcu la ted by a pplyin g th e Bogu e For m u la e (Bogu e, 1929).
Resu lts of ch em ica l a n a lyses of th e in vestiga ted cem en t du st sa m ples com pa r ed w ith
th e Br itish Sta n da r d specifica tion s a r e given
in Ta ble V.
It seem s im por ta n t a t fir st to k n ow h ow th e
m eta l oxides for m th e a ctu a l com pou n ds in
th e cem en t. Th is w ill be discu ssed n ext.
Wh en a ca r efu lly pr opor tion ed a n d blen ded
r aw m ix is fed in to th e k iln , th e ca lciu m ca r bon a te, Ca CO 3 fr om th e ch a lk or lim eston e is
con ver ted to lim e, Ca O, or C in cem en t
ch em ists’ n ota tion :
Hea t
Ca CO 3 → Ca O + CO 2
Th is com bin es w ith th e silica , a lu m in a a n d
fer r ic oxide fr om th e sh a le or clay (C+ S + A +
F ) to for m cem en t clin k er, a m ixtu r e of
m a in ly fou r com pou n ds ea ch h avin g u n iqu e
pr oper ties (C 3S+ C 2S + C 3A+ C 4AF ). Th e
poten tia l pr opor tion of ea ch of th ese com pou n ds in th e clin k er m ay be ca lcu la ted fr om
for m u la e su ggested by Bogu e (1929).
Th e m ost im por ta n t com pou n d is tr ica lciu m silica te, C 3S (3Ca O. SiO 2 ) in cem en t
ch em ists’ n ota tion . Th e cr ysta llin e m a ter ia l
a s it a ctu a lly occu r s in clin k er in clu des im pu r ities a n d is ca lled a lite.
Tr i-ca lciu m silica te for m s m or e th a n h a lf of
Por tla n d cem en t clin k er a n d it is r espon sible
for m u ch of th e str en gth of con cr ete u p to 28
days; th e ph ysica l pr oper ty by wh ich cem en ts
a r e often com pa r ed. Th er efor e, it is im por ta n t to m a xim ize C 3S con ten t, given th e lim ita tion s im posed by m a r k et r equ ir em en ts, th e
r aw m a ter ia ls a n d th e pr ocess con dition s.
Th e secon d com pou n d is di-ca lciu m silica te, C 2S (2Ca O. SiO 2 ) or belite in its im pu r e
sta te. Alth ou gh pr esen t in sm a ller qu a n tities
th a n C 3S, C 2S, it a lso h a s str en gth givin g
pr oper ties a n d is th er efor e a n im por ta n t
con stitu en t of cem en t.
Alth ou gh C 3S is pr efer r ed, C 2S is still a n
im por ta n t str en gth -givin g com pou n d. It
h ydr a tes m or e slow ly th a n C 3S a n d ten ds to
m a k e its con tr ibu tion to con cr ete str en gth
developm en t a t 28 days a n d beyon d.
Th e th ir d com pou n d, tr i-ca lciu m a lu m in a te, C 3A (3Ca O. A12 O 3) h a s n ot gen er a lly
been con sider ed to con tr ibu te to con cr ete
str en gth . However, it is m u ch m or e r ea ctive
th a n eith er C 3S or C 2S. It m ay, th er efor e,
im pr ove ea r ly str en gth .
Alth ou gh C3A is pr esen t in sm a ller qu a n tities, it h a s a n im por ta n t in flu en ce on th e ea r ly
h ydr a tion r ea ction s wh ich deter m in e wor k a bility a n d settin g beh aviou r. Wor k a bility is
th e ea se w ith wh ich con cr ete ca n be h a n dled
a n d pla ced a fter m ixin g h a s ta ken pla ce.
Th e fou r th com pou n d is tetr a -ca lciu m a lu m in o-fer r ite, C 4AF (4Ca O. A12O 3. Fe 2O 3)
wh ich im pa r ts th e ch a r a cter istic gr ey colou r
to th e Por tla n d cem en t; h en ce th e n eed to
r edu ce th e a m ou n t of th is com pou n d wh en
m a k in g wh ite cem en t. Lik e C 3 A, C 4AF m a k es
little con tr ibu tion to con cr ete str en gth .
F r om th e for e goin g elu cida tion , it ca n be
seen th a t th e r aw m a ter ia ls pr ovide a sou r ce
of lim e, silica , a lu m in a a n d fer r ic oxide a n d
th a t th ese oxides com bin e in th e k iln to for m
fou r com pou n ds: C 3S, C 2S, C 3A a n d C 4AF. It
ca n a lso be seen th a t C 3S a n d C 2S a r e th e
com pou n ds in cem en t wh ich give con cr ete its
str en gth .
Th e ava ila ble r esu lts of ch em ica l a n d m in er a l com position of th e in vestiga ted cem en t
du st sa m ples (Ta ble V) ca n be lim ited to sa m ple N os 3-10. Th ese h ave sh ow n ph ysica l ch a r a cter istics m eetin g th e Br itish Sta n da r d
r equ ir em en ts, a s pr eviou sly discu ssed.
Th e eigh t sa m ples gave C 3S com pou n d
per cen ta ges r a n gin g between 45.60 for sa m ple
N o. 4 a n d 54.10 for sa m ple N o. 10, a n d th e
a r r a n gem en t of th e sa m ples a ccor din g to
th eir con ten t of C 3S is: 10 > 7 > 3 > 9 > 8 > 5 > 6
> 4. Th e cor r espon din g per cen ta ges of C 2S
con ten t r a n ge between 14.10 for sa m ple N o. 10
a n d 28.70 for sa m ple N o. 4, a n d th e
cor r espon din g a r r a n gem en t of th e sa m ples
a ccor din g to th eir con ten t of C 2S is: 4 > 6 > 8 >
5 > 7 > 3 > 9 > 10. Th is m ea n s th a t th er e is
n ea r ly a n in ver se r ela tion sh ip between th e
sa m ples’ con ten t of C 3S a n d th a t of C 2S.
Wh en exa m in in g th e tota l con ten t of sa m ples of C 3S a n d C 2S, it ca n be seen th a t th e
su m of C 3S plu s C 2S per cen ta ges r a n ges
between 68.20 for sa m ple N o. 10 a n d 74.40 for
sa m ple N o. 8. Th e sa m ples ca n be a r r a n ged
a ccor din gly a s: 8 > 4 > 7 > 6 > 5 > 3 > 9 > 10.
Su ch a r r a n gem en t m ay r eflect th e pr ior ity of
u sin g th e in vestiga ted cem en t du st a s a con cr ete m a ter ia l.
On th e oth er h a n d, th e ava ila ble Br itish
Sta n da r d r equ ir em en ts for ch em ica l a n d
m in er a l com position of OP C a r e con cer n ed
on ly w ith in solu ble r esidu e (IR), m a gn esiu m
oxide (MgO), su lph u r tr ioxide (SO 3), a n d loss
on ign ition (LOI), besides lim e sa tu r a tion
fa ctor (LSF ) (Ta ble V).
With th e exception of sa m ple N o. 10, a ll
oth er sa m ples of cem en t du st a r e su ggested to
be u sed a s a con cr ete m a ter ia l th a t m eets a ll
th e a bove m en tion ed BS r equ ir em en ts.
[ 25 ]
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
[ 26 ]
Table V
Re sults o f c he mic al analyse s (pe r c e nt) o f c o ntro lle d c e me nt dust sample s c o mpare d with the British Standard re quire me nts o f o rdinary Po rtland c e me nt
BS
Sample no.
(1)
0.2
IR
(2)
0.2
0.15
(3)
(4)
(5)
(6)
(7)
0.2
0.25
0.2
0.2
0.18
22.01
21.65
21.84
21.68
21.77
(8)
0.25
(9)
0.25
(10)
(11)
–
–
(12)
0.12
(13)
9.8
(14)
(15) (16)
–
–
8.32
5.8
(17) (18)
–
(19)
(20) (21)
–
–
–
8.32
8.12
–
–
(22)
(23) (24) (25) (26) requirement
–
–
–
–
–
9.53
–
9.51
–
–
14.03
4.4
Max
1.5
SiO2
19.25
17.22 21.5
20.1
19.15
9.3
14.04 21.81
13.04
17.91
Al2 O3
4.38
3.72
5.6
5.69
5.55
5.61
5.52
5.52
5.83
3.9
2.81
3.67
5.6
3.6
3.33
2.82
5.09
3.2
2.91
–
2.06
–
2
–
–
Fe 2 O3
2.6
3
3.7
3.75
3.65
3.7
3.72
3.68
3.46
5.6
1.7
0.7
3.80
1.7
2.67
2.8
3.81
3.15
2.62
–
2.08
–
2.09
–
–
2.12
CaO
63.6
62.9
64.75
64.8
64.75
64.7
64.9
64.85
62.92
55.26 58.59 48.29 60.10 46.36 49.72
–
42.13
– 43.19
–
–
38.05
M gO
0.6
0.6
0.7
0.6
0.7
0.7
0.7
0.9
–
0.54
–
–
–
0.45
61
46.2
43.85 64.31
Max.
0.65
0.8
0.45
0.45
0.9
9.6
0.81
0.86
1.33
0.79
0.85
0.57
4.0
Max.
SO3
2.1
2.14
2.02
1.85
2.2
1.95
2.02
2
3
4.36
1.75
2.11
2.55
0.15
7.38
0.13
0.96
–
2.42
–
3.21
–
–
–
K2 O
0.68
0.52
0.25
0.25
0.2
0.22
0.25
0.25
0.62
0.2
0.03
0.03
0.24
0.68
2.15
0.24
0.88
0.17
0.77
–
3.19
–
2.69
–
–
2.65
Na 2 O
0.18
0.15
0.1
0.11
0.08
0.09
0.12
0.1
0.15
0.08
0.03
0.03
0.14
0.21
1.99
0.25
0.56
0.21
0.58
–
0.34
–
0.3
–
–
0.12
LOI
5.85
8.49
1.07
0.94
1.08
1.05
1.05
1.15
2.2
4.17
27.85 35.89
0.83
21.3
34.12
–
37.4
– 36.15
–
–
–
F.CaO
1.85
11.37
1.68
0.5
0.5
0.45
0.5
0.5
0.45
0.5
–
–
0.45
39.3
–
–
–
–
–
–
–
–
–
–
–
–
–
–
89.8
–
–
–
–
–
–
–
–
–
–
–
–
82.8
89.1
Nil
Nil
2.5 a,3.0 b
Max.
22.73 38.66
3.18 37.7
4.0 c ,3.0 d
Max.
LSF
102.1
LCF
99.07
SR
2.76
91.4
89.6
90.8
90.1
91
90.7
92.7
93.5
91.6
90.4
88.9
90
89.5
90.3
90
92
92.7
2.56
66
2.31
2.33
2.35
2.35
2.35
2.37
2.16
2.02
–
–
–
–
2.32
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
2.15
–
–
–
–
–
–
–
–
–
–
–
–
2.07
43.5
48.7
45.6
48.2
47
49.2
48.5
48.6
54.1
–
–
46.2
–
–
–
–
–
–
–
–
–
–
–
–
–
25
25.9
21
14.1
–
–
27.7
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
8.4
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
11.6
–
–
–
–
–
–
–
–
–
–
–
–
–
1.68
AR
C3 S
112.4
1.24
1.51
1.52
1.52
1.52
1.48
1.50
1.68
C2 S
5.4
16.5
24.9
28.7
25.7
27.1
C3 A
7.2
4.8
8.6
8.7
8.5
8.6
8.3
8.4
9.6
C4 AF
7.9
9.1
11.30
11.4
11.1
11.3
11.3
11.2
10.6
Notes:
– Not determined
a
When C3 A < 5.0
b
When C3 A > 5.0
c
Tropic al
d
Temperate
0.7
0.86
17
–
1.47
102 min.
Kamal T. Hindy
Utilizatio n o f c o ntro lle d
c e me nt dust as a c o nc re te
mate rial in the Unite d Arab
Emirate s
Enviro nme ntal Manage me nt
and He alth
8 / 1 [1 9 9 7 ] 2 0 –2 7
Sa m ple N o. 10 h a s SO 3 a n d LOI m or e th a n th e
BS r equ ir em en ts. A com bin a tion of h igh SO 3
a n d low MgO (a s fou n d in th e stu died sa m ples) in a clin k er m ix m ay be detr im en ta l to
str en gth developm en t. Th is is a ttr ibu ted to
th e eviden ce dr aw n by Gu tt a n d Sm ith (1968)
th a t in th e pr esen ce of C 3A th ou gh n ot of
C 4AF, for m a tion of C 3S is r edu ced by h igh SO 3
con ten t, bu t th is is cou n ter a cted by th e pr esen ce of MgO. Th e r esu lts of ph ysica l tests of
in vestiga ted sa m ples (Ta ble IV), h owever,
in dica te com pr essive str en gth va lu es for
sa m ple N o. 10 h igh er th a n th e BS r equ ir em en ts. At th e sa m e tim e, th e r esu lts of ch em ica l a n a lysis sh ow m a xim u m C 3S con ten t for
sa m ple N o. 10 in com pa r ison w ith oth er su ggested sa m ples (Ta ble V). Th is m ea n s th a t th e
sa m ple ca n be sa fely u sed a s a con cr ete m a ter ia l. On th e oth er h a n d, th e sligh t in cr ea se in
LOI con ten t of th e sa m ple th a n th e BS
r equ ir em en t ca n be con sider ed in effective in
ch a n gin g th e ch a r a cter istics of th e con cr ete.
It sh ou ld be n oted th a t th e a lk a li con ten t of
th e cem en t du st sa m ples su ggested to be u sed
a s con cr ete m a ter ia l is less th a n th e BS specifica tion s, i.e. N a 2O + 0.658 K 2O = < 0.6 per cen t
for low -a lk a li cem en t.
Conclusion
Th e con clu sion th a t ca n be dr aw n fr om th e
pr esen t in vestiga tion is th a t th e cem en t du st
collected by con tr ol m ea n s (e.g. electr osta tic
pr ecipita tor s a n d fa br ic fi lter s) m ay be in vestiga ted fu r th er a s to its u se a s a con cr ete
m a ter ia l.
Th e stu dy r evea ls th a t con tr olled cem en t
du st collected fr om eigh t poin ts on dr y
pr ocess lin es a t a cem en t pla n t in th e Un ited
Ar a b E m ir a tes h a s th e sa m e ph ysica l a n d
ch em ica l specifi ca tion s r equ ir ed for or din a r y
Por tla n d cem en t. Th e con tr ol m ea n s u sed a t
th ese poin ts is th e fa br ic filter a n d th e dr y
pr ocess lin es a r e: sepa r a tion (fou r poin ts);
cem en t pu m pin g (two poin ts); a n d silo loa din g (two poin ts).
References
ACI Com m ittee 226 (1987), Use of Fly A sh in Con crete, ACI 226 3R-87, Am er ica n Con cr ete In stitu te, Detr oit, MI.
ASTM (1983), A m er ica n S ta n d a rd T est M eth od for
Fin en ess of Hyd ra u lic Cem en t b y th e 45-µm
(N o. 325) S iev e, C 430-83.
Bogu e, R.H. (1929), In d . En gn g. A n a lyt. Ed n , Vol. 1
N o. 4, p. 192.
Br a u er, H. a n d Va r m a , Y.B.J . (1981), A ir Pollu tion
Con trol Equ ipm en t, Spr in ger -Ver la g, Ber lin ,
pp. 183-218.
Gu tt, W. a n d Sm ith , M.A. (1968), T ra n sa ction s of
th e B r itish Cera m ics S ociety, Vol. 87, p. 487.
Hin dy, K.T. (1989), “P u lse jet fa br ic filter oper a tion : a n exper im en ta l stu dy”, in Ch er em isin off, P.N. (E d.), En cycloped ia of En viron m en ta l
Con trol T ech n ology. Volu m e 2: A ir Pollu tion
Con trol, Gu lf P u blish in g, Hou ston , TX,
pp. 981-1002.
Hin dy, K.T. a n d Attia , A.A. (1988), Proceed in gs of
3rd In ter n a tion a l Con feren ce on En viron m en ta l Con ta m in a tion , Ven ice (S eptem b er ), CE P
Con su lta n ts Ltd, E din bu r gh , pp. 476-8.
Hin dy, K.T. a n d Attia , A.A. (1993), En viron m en ta l
Ed u ca tion a n d In for m a tion , Vol. 12, p. 35.
In ter n a tion a l Cem en t R eview (1992), Febr u a r y,
pp. 29-42.
[ 27 ]