Syn hesis and cha ac e iza ion o beli e calcium
sul oalumina e cemen s p oduced by oxy uel combus ion
esidues
A. Telesca*1, M. Ma occoli2, N. Ib is3,
T. R., Naik4, C. Lupiáñez5, L. I. Díez6, L. M. Romeo7 and F. Mon agna o8
1-3School o Enginee ing, Uni e si à degli S udi della Basilica a, ITALY.
(E-mail: an onio. [email protected] , milena.ma [email protected] , nelu a.ib[email p o ec ed] )
4Depa men o Ci il Enginee ing and Mechanics, Uni e si y o Wisconsin, USA
(E-mail: a [email protected])
5-7Mechanical Enginee ing Depa men , Uni e sidad de Za agoza, SPAIN.
(E-mail: ca los.lupianez@uniza .es, luisig@uniza .es, luismi@uniza .es)
4 Depa men o Chemical Sciences, Uni e si à degli S udi di Napoli Fede ico II, ITALY.
(E-mail: abio.mon agna [email protected] )
ABSTRACT
In his wo k, he possibili y o eusing ashes issued by an oxy uel combus ion p ocess
(OC) as a sou ce o ma e ial in he p oduc ion o beli e calcium sul oalumina e BCSA
cemen s has been in es iga ed. OF p ocess is one o he mos p omising combus ion
echnologies o CO2 educ ion om powe plan s. Combus ion es s we e ca ied ou
in an oxy uel bubbling luidized bed pilo plan . Fou BCSA clinke -gene a ing aw
mixes we e hea ed in a labo a o y elec ic o en in he empe a u es ange 1150°-
1350°C: one included only na u al ma e ials (limes one, clay, bauxi e and gypsum),
he o he s con ained OC ashes as o al subs i u e o clay.
X- ay di ac ion (XRD) analysis on he bu ning p oduc s showed high con e sion o
eac an s owa d he main BCSA clinke componen s (C2S and C4A3$), especially a
1200° o 1250°C. Mo eo e , physical-mechanical es s associa ed wi h XRD and
di e en ial he mal- he mog a ime ic analyses accomplished on all he cemen s
(ob ained by adding na u al gypsum o he clinke s p oduced a he bes syn hesis
empe a u es) gene ally displayed a simila hyd a ion beha iou .
Keywo ds: Oxy uel combus ion esidues, clinke , beli e calcium sul oalumina e.
INTRODUCTION
The apid g ow h o Wo ld popula ion, he ene gy demand inc ease, he global
wa ming (GW) ha e pushed go e nmen s and in e na ional au ho i ies o se on he
pa h owa ds sus ainable de elopmen . The e is no doub ha GW ep esen s he mos
signi ican challenge o achie ing sus ainable de elopmen ; his phenomenon is
caused by he emission and accumula ion in he a mosphe e o g eenhouse gases
* Co esponding au ho . T: +39 0971 205225. E-mail: an o[email p o ec ed].
Fi h In e na ional Con e ence on Sus ainable Cons uc ion Ma e ials and
Technologies. h p://www.claisse.in o/P oceedings.h m
(GHGs) which a e mainly eleased by he bu ning o ossil uels, land clea ing,
ag icul u e- ela ed and o he human ac i i ies [Benhelal e al., 2013; De Rich e e al.,
2016; Szulejko e al., 2017; Telesca e al., 2017]. Ca bon dioxide is blamed o be he
main esponsible o GW; he e o e, sea ching o p omising app oaches o mi iga e
CO2 emissions ep esen s he p io i y o s udies aimed a alle ia ing he h ea o
clima e change. In his ega d, he ca bon cap u e and s o age (CCS) echnology has
he po en ial o almos comple ely elimina e CO2 [Boo -Hand o d e al., 2014; Leung
e al., 2014; Telesca e al., 2014a; Telesca e al., 2017]. CCS indica es a g oup o
echnologies de eloped o ob ain CO2- ich lue gases eady o be s o ed by injec ion
in o geological s a a wi h speci ic ea u es. Among he di e en CCS p ocesses (e.g.,
chemical abso p ion, chemical and calcium looping), oxy uel combus ion (OC) is o
g ea in e es due o i s concep ual simplici y [Diez e al., 2015]. In OC a blend o
nea ly pu e oxygen and pa o exhaus gas (employed as O2 diluen o sa e y easons),
is used o combus ion, hus lowe ing bo h N2 and NOx con en s in he exhaus gas
[Buh e e al., 2005; Lupiáñez e al., 2013a; Lupiáñez e al., 2014]. In absence o he
mos ele an diluen o CO2 and a e u he ea men s, i is possible o ob ain
s eams >90% CO2- ich. The CO2- ich s eam is hus eady o inal p ocessing and
geological s o age.
Cemen p oduc ion is one o he mos la ge-scale aw ma e ials consuming as well as
ene gy-in ensi e manu ac u ing p ocesses and ep esen s one o he majo indus ial
sec o s gi ing ise o CO2 emission. In ac , he Wo ld’s annual cemen p oduc ion
cu en ly accoun s o abou 4.7 billion ons [Ac i i y epo 2016, 2017] and i s
con ibu ion o he global an h opogenic CO2 emission is es ima ed as high as 7%
(abou 26% o he indus ial CO2 emission) [T egambi e al., 2018]. I is he e o e
widely accep ed he need o inc ease he sus ainabili y o cemen mainly o ien ed a
mi iga ing he CO2 impac .
Po land cemen (PC) is he mos widely used binde all o e he Wo ld; i is ob ained
by in e g inding PC clinke (PCC) wi h a ew pe cen o calcium sul a es (mos ly
gypsum). Fo each kg o PCC p oduced, abou 0.87 kg o CO2 a e eleased [Ba celo
e al., 2014]; ca bon dioxide comes om bo h limes one he mal decomposi ion (abou
60% o he o al CO2 emission) and uel combus ion. The e o e, one app oach o lowe
CO2 emissions is ela ed o he limes one educ ion in he clinke -gene a ing aw meal
[Telesca e al., 2016]. In his ega d, beli e ich-cemen s a e conside ed
en i onmen ally iendly binde s inasmuch as hey can allow a CO2 educ ion as much
as 10% [Pim aksa e al., 2009; Cube os e al., 2010]; mo eo e , he p esence o
calcium sul oalumina e (C4A3$) in he cemen clinke can bo h compensa e he lowe
eac i i y o beli e ( ela i e o ali e) and u he educe he limes one equi emen in
he aw eed [Quillin, 2001]. Beli e calcium sul oalumina e (BCSA) cemen s gene ally
display physical and mechanical p ope ies compa able o OPC [Selçuk e al., 2010];
in ac , hei echnical beha iou mos ly depends on he abili y o C4A3$ and C2S, o
espec i ely gene a e, upon hyd a ion, C6A$3H32, e ingi e (a ea ly ages) and CSH
(a medium and longe ages). Mo eo e , BCSA cemen s a e in e es ing hyd aulic
binde s om he en i onmen al poin o iew inasmuch as hei manu ac u ing
p ocess, compa ed o ha o OPC, displays a p onounced en i onmen ally iendly
cha ac e mainly associa ed o (a) he ela i ely low syn hesis empe a u e, (b) he
dec eased speci ic uel consump ion [Ma occoli e al., 2010a], (c) he easie
g indabili y and (d) he g ea e usabili y o indus ial was es and by-p oduc s whose
u iliza ion is gene ally complica ed [Ma occoli e al., 2009; Ma occoli e al., 2010b;
Ma e al., 2014; Shen and Qian, 2015]. BCSA cemen s a e gene ally p oduced by
bu ning a aw mix composed by limes one (L), bauxi e (B), clay (C) and gypsum (G)
a empe a u es anging om 1250°-1350°C [Xue e al., 2016].
In his pape , esidues gene a ed du ing an OC p ocess, ca ied ou in a pilo -scale
luidized bed (FB) eac o , we e es ed as subs i u es o clay in he BCSA clinke -
gene a ing aw mix.
Fou mix u es we e hea ed in a labo a o y elec ic o en in he empe a u es ange
1150°-1350°C: one included only na u al ma e ials ( aken as a e e ence e m), he
o he s con ained OC esidues in a measu e comp ised be ween 24.5 and 56.0% by
mass. The con e sion o eac an s owa ds C2S and C4A3$ was in es iga ed by means
o X- ay di ac ion (XRD) analysis. XRD and di e en ial he mal− he mog a ime ic
(DT−TG) analyses oge he wi h physical and mechanical es s we e employed as
main cha ac e iza ion echniques o ca y ou he in es iga ion.
EXPERIMENTAL
Ma e ials and Oxy uel Pilo Plan
The na u al ma e ials (L, C, B and G) used in his in es iga ion we e aken om
qua ies loca ed in I aly. The OC ashes came om a 95 kW h pilo -scale bubbling
oxy uel luidized bed (FB) eac o (2.5 m high wi h an inne diame e o 21 cm); i is
schema ically epo ed in Figu e 1 and desc ibed elsewhe e [Lupiáñez e al., 2013b].
Figu e 1. Oxy uel luidized bed pilo plan .
The FB eac o (R), cooled by means o a wa e jacke placed a i s bo om and ou
wa e -cooled p obes uni o mly dis ibu ed, was cha ged wi h a bed in en o y o 5 kg
silica sand, luidized a 0.8 ms–1 (wi h a 65% CO2–35% O2 mix u e) and hea ed up o
850°C o 925°C; i was equipped wi h wo di e en de ices o he emo al o ly ash
(ba le chambe , BC, and cyclone, CY, in he o de ) om he lue gas s eam.
A blend o ligni e and biomass co n s o e ed he appa a us in a 70:30 ene gy a io;
mo eo e , o cap u e he SO2 gene a ed du ing he combus ion h ough he in si u
desul u iza ion (calcium, Ca (in he so ben ): sul u , S (in he uel)), wo di e en
limes ones (A and B) we e al e na i ely injec ed in o FBR.
Th ee di e en es s we e pe o med: hei ope a ing condi ions, o he sake o cla i y,
a e summa ized in Table 1. Du ing each es , h ee kind o combus ion esidues we e
collec ed: a bo om ash (BA), ex ac ed om he bo om o FBR, and wo ly ashes
(BCFA, CYFA) wi hd awn along he lue gas ea men line.
Table 1. Ope a ing condi ions o he es s ca ied ou in he in he FBR.
Tes no.
Fuel
Limes one
Ca:S
FBR Tempe a u e, °C
1
Ligni e+Co n s o e
A
2
925
2
“
A
6
850
3
“
B
6
925
The esidues o each es we e hen mixed o p epa e h ee blends (B1, B2 and B3),
p opo ioned consis en wi h he co esponding amoun gene a ed du ing he
expe imen al ac i i y (40%BA-50%BCFA-10%CYFA).
The chemical composi ion (in e ms o majo oxides) o he aw ma e ials, de e mined
by X- ay luo escence echnique (wa eleng h dispe si e BRUKER Explo e S4
appa a us), is shown in Table 2.
Table 2. Chemical analysis o he na u al and was e aw ma e ials, w %
L
B
G
C
B1
B2
B3
CaO
55.16
-
30.10
10.40
49.92
27.13
16.84
SiO2
-
7.20
3.00
54.10
21.35
37.70
44.38
Al2O3
-
56.30
0.90
11.50
4.23
8.62
10.67
Fe2O3
-
6.30
0.30
4.50
3.86
10.54
11.63
SO3
-
-
36.20
-
7.26
6.87
5.51
O he s
-
2.30
3.70
6.40
1.89
3.28
2.97
L.o.i.*
43.40
27.50
24.60
13.10
11.48
5.85
8.00
*Loss on igni ion a 950°C
Mix u es Design and Cemen s P epa a ion
Fou BCSA clinke -gene a ing aw mix u es we e designed acco ding o he modi ied
Bogue equa ions [I in e al., 2011], assuming ha C2S, C4A3$, C4AF and C$ amoun
ell in he ange 45%-60%, 20%-30%, 8%-20% and 4%-10%, espec i ely; mo eo e ,
a ee CaO concen a ion alue lowe han 1.5% was also conside ed. All he mix u es
con ained L, B and G; a e e ence mix (MR) included also clay (C), whe eas he
emaining h ee mix u es (M1, M2 and M3) al e na ely con ained B1, B2 o B3 as o al
subs i u e o C. Table 3 and 4 espec i ely epo he modi ied Bogue po en ial
mine alogical composi ion o he ou clinke s (CLIR, CLI1, CLI2 and CLI3) and he
aw meals p opo ion.
Table 3. Bogue po en ial mine alogical composi ion o he clinke s, w %
C2S
C4A3$
C4AF
C$
C
CLIR
56.0
25.9
8.3
5.1
0.1
CLI1
48.7
23.9
12.4
9.7
1.4
CLI2
52.6
20.7
17.9
4.9
0.1
CLI3
50.2
22.8
16.4
7.1
0.1
The aw mix u es we e hea ed in co e ed pla inum c ucibles in a labo a o y elec ic
o en o wo hou s a 1200°, 1250°, 1300° and 1350°C and hen apidly cooled o
oom empe a u e; he ob ained BCSA clinke s we e inely g ound in a F i sch
Pul e ise e 6 (FP6) labo a o y plane a y mill o pass a 90 m sie e and a e wa ds
submi ed o XRD analysis in o de o assess he bes empe a u e o maximizing bo h
C2S and C4A3$ concen a ion.
Table 4. Composi ion o he aw meals, w %
L
B
G
C
B1
B2
B3
MR
53.0
13.0
12.0
22.0
-
-
-
M1
50.0
13.0
5.0
-
56.0
-
-
M2
20.0
16.0
8.0
-
-
32.0
-
M3
52.0
13.5
10.0
-
-
-
24.5
BCSA cemen s (CEMR, CEM1, CEM2 and CEM3) we e hen p epa ed by g inding
he bes ob ained clinke s wi h G in he FP6 labo a o y mill always o pass he 90 m
sie e. The amoun o he added gypsum was de e mined conside ing bo h he C$
al eady p esen in he clinke (calcula ed wi h he modi ied Bogue equa ion) and he
eac ion s oichiome y o he gene a ion o e ingi e (C6A$3H32, he main hyd a ion
p oduc egula ing he echnical beha io a ea ly ages) and aluminium hyd oxide
(AH3) [Manzano e al., 2012; Telesca e al., 2014c], namely:
C4A3$+2C$+38H⇒C6A$H32 +2AH3 (1)
XRD analysis was also employed o he e alua ion o BCSA cemen s hyd a ion
p oduc s; i was pe o med wi h a B uke D2 Phase di ac ome e (CuKα adia ion
and 0.02°2θs-1 scanning a e).
Measu emen s on Mo a s
BCSA mo a p isms we e p epa ed acco ding o he Eu opean S anda d EN 196-1 and
cu ed a e demolding unde wa e a 20°±1°C; hey we e submi ed o comp essi e
s eng h measu emen s a cu ing pe iods anging om 1 o 56 days.
Measu emen s on Pas es
BCSA cemen s we e pas e hyd a ed wi h a wa e /cemen a io equal o 0.5 by mass.
The pas e samples we e cas in o 15-mm-high and 30-mm-diame e cylind ical molds,
and inally placed in polye hylene bags inside a he mos a ic ba h (a 20°C and 95%
ela i e humidi y) o cu ing imes anging om 4 hou s o 56 days. A he end o each
aging pe iod he specimens we e i s c ushed and hen ea ed wi h ace one ( o s op
hyd a ion) and die hyl e he ( o emo e wa e ); he pul e ized samples we e
subsequen ly s o ed in a desicca o o e silica gel–soda lime ( o ensu e p o ec ion

agains H2O and CO2) and inally submi ed o simul aneous DT-TG (NETZSCH-Tasc
414/3 appa a us, hea ing a e 10°C min–1, ope a ing be ween oom empe a u e and
1000°C) and XRD analyses.
Fo he expansion–sh inkage measu emen s, eigh pas e samples, shaped as small
p isms (15X15X78 mm), we e i s ai cu ed a 20°C o 4 hou s and hen demolded.
La e on, one se o samples was aged a 20°C unde ap wa e , he o he s o ed in a
con olled humidi y (H) chambe a 70% R.H. and 20°C. The leng h changes we e
de e mined as a e age alues o ou measu emen s wi h a calipe accu a e o ±1 m;
he e e ence leng h o hem was ha e alua ed jus a e demolding [Telesca e al.,
2014b; Valen i e al., 2012].
RESULTS AND DISCUSSION
The in ensi y o he main XRD peaks o C2S and C4A3$ we e aken as a con e sion
index o he BCSA clinke -gene a ing aw mixes owa d hese p oduc s. The “ex e nal
s anda d me hod” [Culli y e al., 2001] was used and, as a e e ence line, he same
e lec ion om pu e C2S and C4A3$ p epa a ions (gene a ed by high- empe a u e
syn hesis o analy ical g ade calcium ca bona e and qua z o he o me and calcium
ca bona e, alumina and gypsum o he la e ) was aken [Telesca e al., 2015]. The
XRD in ensi y (cps) o he C2S and C4A3$ lines is plo ed as a unc ion o he hea ing
empe a u e (Figu e 2 (a) and 2 (b), espec i ely); each cu e displays a maximum
occu ing, o C2S, a abou 1200 °C (MR and M2) o 1250°C (M1 and M3).
Conce ning calcium sul oalumina e, he bes syn hesis empe a u e was he same as
ha o beli e o mix u es M1 and M2, while highe o MR (1250°C) and M3
(1300°C).
Figu e 2. XRD in ensi y (coun s pe second, cps) o he C2S and C4A3$ main peak o
he BCSA clinke s as a unc ion o he syn hesis empe a u e.
F om an o e all examina ion o he XRD da a abou he syn he ic BCSA clinke s i
was ound ha ha , a e e y in es iga ed empe a u e, he con e sion o eac an s was
comple e and C2S and C4A3$ we e he main bu ning p oduc s. Fu he mo e, C4AF,
C2AS and C$ equen ly occu ed as seconda y componen s.
Tempe a u e, °C
1150 1200 1250 1300 1350
Peak in ensi y, cps
0
500
1000
1500
2000
2500
CLIR
CLI1
CLI2
CLI3
Tempe a u e, °C
1150 1200 1250 1300 1350
Peak in ensi y, cps
500
1000
1500
2000
2500
3000
3500
4000
4500
CLIR
CLI1
CLI2
CLI3
Figu e 3 illus a es he XRD pa e ns o mix u es MR, M1, M2 and M3 hea ed a he
bes syn hesis empe a u es. The ou BCSA cemen s ob ained om he syn he ic
clinke s gene a ed by RM, M1, M2 and M3 a hei bes syn hesis empe a u e we e
espec i ely deno ed wi h he symbols CEMR, CEM1, CEM2 and CEM3.
Figu e 3. XRD pa e ns o he BCSA clinke s ob ained om MR, M1, M2 and M3 a
hei bes syn hesis empe a u e. Legend o symbols: Y=C4A3$, A=C$, B=C2S,
G=C2AS, B =C4AF.
Table 5 epo s he comp essi e s eng h de elopmen o BCSA-based mo a s as a
unc ion o cu ing ime; a all he in es iga ed pe iods, he comp essi e s eng h alues
o CEMR, CEM2 and CEM3 based-mo a s we e simila o each o he ; on he
con a y, he comp essi e s eng h alues o CEM1 we e cons an ly lowe han hose
o he o he cemen s.
Table 5. Resul s o comp essi e s eng h measu emen s o CEMR, CEM1, CEM2 and
CEM3 a a ious aging pe iods.
Days
CEMR
CEM1
CEM2
CEM3
1
12.70.4
8.70.5
10.90.3
12.20.3
2
19.20.3
14.50.2
16.10.5
19.70.2
7
26.40.2
20.40.6
24.50.5
27.90.5
14
32.50.1
24.60.3
30.50.8
33.50.2
28
37.10.5
26.90.1
34.50.7
36.80.4
56
36.90.7
28.40.5
35.10.8
37.10.3
The comp essi e s eng h esul s e e o h ee p isms (six de e mina ions)
The esul s o he expansion–sh inkage es s a e illus a ed in Figu e 4.
Figu e 4: Dimensional s abili y cu es o BCSA-based cemen s (ai and wa e cu ed).
They indica e ha all he in es iga ed BCSA cemen s di e ed e y li le om each
o he , bo h when subme ged unde wa e and cu ed in ai . In pa icula , unde wa e
he maximum expansion alues, eached a e abou 14 days o cu ing, a e comp ised
in he na ow ange o 0.17-0.23%. When cu ed in ai , he in es iga ed pas es showed
a con inuous sh inkage ill 14 days when a minimum leng h change is eached (-0.06%,
-0.05%, -0,08 and -0.07% o CEMR, CEM1, CEM2 and CEM3, espec i ely); since
ha pe iod he alues emained cons an o all he in es iga ed sys ems.
The change o mine alogical phases wi h ongoing hyd a ion was de e mined h ough
XRD and DT-TG in es iga ions. The XRD analysis o all he BCSA cemen s e ealed,
as expec ed, ha a e 4 hou s o hyd a ion e ingi e had al eady o med a he expense
o pa o calcium sul oalumina e and calcium sul a es. A 28 days o cu ing e ingi e
was s ill he main c ys alline phase o hyd a ed cemen s which also e ealed he
p esence o some aces o C4A3$ and ine phases (e.g. gehleni e). A he same cu ing
pe iod, s ä lingi e (C2ASH8), which s a ed o ming al eady a e 1 day o cu ing in
CEMR and CEM1, was e iden oge he wi h ka oi e (C3AH6) in all he in es iga ed
sys ems. These compounds had espec i ely o med om beli e (as silicon sou ce) and
AH3 (as aluminium sou ce) and om he emaining beli e and C2ASH8 acco ding o
he ollowing equa ions [Winne eld e al., 2016]:
C2S+AH3+5H ⇒C2ASH8 (2)
C2S+ C2ASH8 ⇒ CSH2+C3AH6 (3)
Mo eo e , AH3 was no de ec ed a any cu ing pe iod due o i s amo phous na u e. No
signi ican changes we e obse ed a 56 days o cu ing in he ou hyd a ed sys ems.
As an example, XRD pa e ns o CEMR, CEM1 and CEM3 hyd a ed a 4 hou s, 1
and 56 days a e epo ed in Figu e 5.
Tempe a u e (°C)
010 20 30 40 50
Leng h change (%)
-0,10
-0,05
0,00
0,05
0,10
0,15
0,20
0,25
CEMR ai cu ed
CEM1 ai cu ed
CEM2 ai cu ed
CEM3 ai cu ed
CEMR wa e cu ed
CEM1 wa e cu ed
CEM2 wa e cu ed
CEM3 wa e cu ed
Figu e 5. XRD pa e ns o CEMR (le ), CEM1 (middle) and CEM3 ( igh ) hyd a ed o
4 hou s, 1 and 56 days. Legend o symbols: E=C6A$3H32, Y=C4A3$, S=C2ASH8,
K=C3AH6, B=C2S.
The DT−TG analyses almos con i med he mine alogical e alua ions made by XRD.
Th ee endo he mal e ec s we e obse ed and a ibu ed, on he basis o li e a u e da a
[Taylo , 1997], o he ollowing compounds: e ingi e (E) and, con a y o XRD da a,
calcium silica e hyd a e (CSH) and aluminum hyd oxide (AH3); in pa icula , CSH, E
and AH3 we e espec i ely de ec ed h ough he ollowing dehyd a ion endo he mal
peaks: 103°±4 °C, 152°±5°C, 277°±3°C. S ä lingi e could no be iden i ied inasmuch
as i s DT peak was o e lapped by he e ingi e one.
(a)
c
(b)