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PHOSPHOGYPSUM WASTE LIME AS A PROMISING SUBSTITUTE OF
COMMERCIAL LIMES: A RHEOLOGICAL APPROACH
M.I. Rome o-He mida
a
, A.M. Bo e o-López
b
, F.J. Alejand e
c
, V. Flo es-
Alés
c (*)
, A. San os
d
, J.M. F anco
b
, L. Esqui ias
a
a
Dp . Física de la Ma e ia Condensada, Uni e sidad de Se illa.
A da. Reina Me cedes s/n, 41012 Se illa, Spain.
b
P o
2
TecS – Chemical P oduc and P ocess Technology Cen e . Dp . Ingenie ía Química.
Uni e sidad de Huel a.
Campus de “El Ca men”. Uni e sidad de Huel a. 21071 Huel a. Spain.
c
Dp . Cons ucciones A qui ec ónicas II, Uni e sidad de Se illa.
A da. Reina Me cedes nº4, 41012 Se illa, Spain.
d
Dp . de Ciencias de la Tie a, Uni e sidad de Cádiz.
Campus Uni e si a io de P o. Real 11519, Pue o Real, Cádiz, Spain.
(*) CORRESPONDING AUTHOR. Email lo [email protected]
ABSTRACT
This pape p esen s he heological p ope ies o h ee ypes o lime pu y, speci ying he
in luence o hei o igin. The s udy aims o compa e a special lime pu y p epa ed om
phosphogypsum wi h a comme cial lime powde and an aged lime pu y. The esul s ob ained in
e ms o chemical composi ion, c ys alline s uc u e, g ain size and heological cha ac e iza ion,
(linea iscoelas ici y, shea a e and ime-dependen low beha iou ) a e p esen ed in he s udy.
Pu ies s udied p esen a simila heological esponse, which mainly depends on he pa icle size
and wa e con en . Lowe alues o he linea iscoelas ic unc ions and iscosi y we e ound
o he phosphogypsum lime pu y, in ag eemen wi h he highe pa icle size. T ansien low
es s e eal a p edominan elas ic esponse wi h no signi ican shea -induced s uc u al
pe u ba ions. Howe e , ei he a hickening phenomenon o e ime, i.e. heopexy, a ou ed a
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low shea a es, o a iscosi y dec ease, i.e. hixo opy, a ou ed a high shea a es, was
obse ed.
KEY WORDS: phosphogypsum; ca bona a ion; lime, heology
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1. INTRODUCTION
The e ilize manu ac u ing indus y in he p o ince o Huel a (SW Spain) is based on an
impo an p oduc ion o phospho ic acid by a we p ocessing o he phospho ic ock, o med
mainly by he apa i e mine al (Ca
5
(PO
4
)
3
OH)), wi h sulphu ic acid. An indus ial was e called
phosphogypsum (PG) esul s om his p ocess, which is mainly composed o calcium sulpha e
dihyd a e [1]. The PG is aken o a suspension wi h wa e and pumped o s o age a s, whe e i
decan s and d ies ou . Cu en ly, he ma e ial s o ed eaches 120 million ons and occupies an
a ea o 1,200 hec a es in a ma sh a ea nea he es ua y o med by he union o he Tin o and
Odiel i e mou hs(Fig.1) [2].
This was e, in whose composi ion appea s oxic me allic impu i ies and adionuclides o na u al
o igin, has been accumula ed o e he yea s in he open ai wi h he consequen social and
en i onmen al con lic s. The adionuclides con en o his was e makes i be conside ed as
"Na u ally Occu ing Radioac i e Ma e ial" (NORM). In pa icula , his was e concen a es
impo an quan i ies o iso opes such as
226
Ra,
238
U,
230
Th and
210
Pb-
210
Po, which p ecipi a e wi h
phosphogypsum due o hei simila i y wi h calcium [3] and whose p esence mus be conside ed
in i s managemen and ea men [4,5].
In such scena io, i is c ucial o ind al e na i es o a be e PG was e managemen . In he
con ex o he need o ad ance in a scien i ic echnology ha allows i s ea men as a by-
p oduc o o he indus ial p ocesses, a simple p ocedu e has been de eloped by ea ing he PG
wi h a sodium hyd oxide solu ion, ob aining sodium sulpha e and a p ecipi a e o slaked lime
(po landi e)
[6,7]
.
This eac ion has a double ad an age, on he one hand, i causes he p ecipi a ion o he iso opes
p esen in he PG and, on he o he hand, i p o ides lime pu y as esul ing by-p oduc , wi h
in e es o he cons uc ion indus y. P e ious esul s ha e shown a high pe o mance in he
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p ecipi a ion eac ion o calcium hyd oxide and he ans e o impu i y aces o he solid
p oduc , so ha an in e es ing deg ee o s abiliza ion is achie ed, compa ed o he dange posed
by hei p esence in he luid s a e wi h he consequen isk de i ed om leaching [8]. An
addi ional ad an age o his p ocess is he g ea po en ial capaci y o ca bona ion o he
hyd oxide ob ained, ep esen ing a posi i e en i onmen al con ibu ion due o he mine al
seques a ion o CO
2
om a po en ially haza dous was e.
In e ms o applica ion, he plas ici y o he pulps ob ained om he indus ial p ocess desc ibed
is a e y impo an ac o in he possible use as a subs i u e o con en ional comme cial pu ies.
The iabili y o he p oduc ob ained o be inco po a ed in o mo a s o used as a pas e in
cons uc ion applica ions equi es an adequa e wo kabili y, simila o ha o he p oduc s
usually employed. The e o e, he co ec knowledge o he heological beha iou , in compa ison
wi h simila p oduc s ha can be ound in he ma ke , is necessa y be o e alida ing any
possible applica ion. The concep o wo kabili y o he p oduc s ob ained is closely linked o he
pa icle size and size dis ibu ion, o he ex en ha his size dis ibu ion o he po landi e
c ys als in luences he iscosi y o lime suspensions.
A co ec assessmen o he heological beha iou o lime pu y needs o comp ise he analysis
o bo h he linea iscoelas ic and iscous low esponses, he la e including possible shea a e
and ime e ec s ( hixo opy o heopexy), which ep esen he mechanical beha iou unde
s a ic and s essed condi ions, espec i ely. In gene al, ull heological cha ac e iza ions o lime
pu y a e sca cely ound in he li e a u e, no mally limi ed o he low beha iou . In mos cases,
hese s udies e eal a shea - hinning beha iou o lime pu y [9,10], whe e he appa en
iscosi y is mainly dependen on pa icle size and consequen ly on pa icle olume ac ion [11-
15]. In addi ion, some s udies poin ed ou a yielding low beha iou [9,16], wi h a cha ac e is ic
yield s ess which can be es ima ed by i ing he low cu e o he Bingham model [9,17].
Howe e , in mos o hese s udies he shea a e ange applied is ce ainly limi ed o ex apola e
a easible yield s ess alue. On he o he hand, he ime dependence unde shea ing mus be
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e alua ed in o de o be co ela ed wi h he wo kabili y and possible applica ions [18]. The
ime-dependen low beha iou can be s udied by means o shea a e hys e esis loops [9,12] o ,
p e e ably, s ess (o iscosi y) g ow h cu es a cons an shea a e [11,13,15]. Rega ding
ansien low p ope ies, some con o e sy and con adic o y esul s can be ound in he
li e a u e, ob aining bo h hixo opic and heopec ic beha iou s depending on he ype o lime
pu y and p ocessing [8,12,16]. Rega ding he linea iscoelas ic esponse, only a ew s udies
epo ed he dynamic iscoelas ic moduli as a unc ion o s ess (o s ain) ampli ude, in o de o
de e mine he ex ension o he linea iscoelas ici y egime [11], o as a unc ion o ime a
cons an ampli ude [16], whe e a p edominan elas ic beha iou was appa en o di e en lime
pu y.
Figu e 1. Loca ion map o he phosphogypsum s o age a s (Sou ce: Google Maps)
The objec o his wo k is ocused on he heological cha ac e iza ion o a lime pu y ob ained as
a by-p oduc om he ea men o phosphogypsum was e wi h a solu ion o Na(OH). I has
been named as
lime pu y om phosphogypsum (PLP)
. Toge he wi h his, he heological
p ope ies and g anulome ies ha e been compa ed wi h hose o wo simila comme cial
p oduc s: a comme cial lime pu y wi h i e yea s o aging, designed as aged lime pu y (ALP),
and ano he lime pu y made in he labo a o y om a comme cial lime powde (LLP).
2. METHODOLOGY
2.1 C ys al mo phology. A pa ame e
Po landi e is o med by p ecipi a ion [19] gi ing ise o hexagonal shee s wi h a pe ec basal
ex olia ion. I is possible o make a s udy o he p edominan mo phology in hese c ys als
(p isma ic and plana ) o po landi e o ien ed agg ega es, compa ing he Rela i e in ensi ies o
he p e ious e lec ions using pa ame e A (0001) [20].

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A0001=I0001
I1011
I (0001) in ensi y (in eg a ed a ea o each peak) o he e lec ion a 2θ = 18º
I (1011) in ensi y (in eg a ed a ea o each peak) o he e lec ion a 2θ = 34º
The second one is usually o highe in ensi y wi h espec o he i s one.
Se e al au ho s ha e indica ed ha pa ame e A (0001) indi ec ly ga e a deg ee o he e olu ion
o aging o lime pu y [21-23], in such a way ha he highe he alue o A, he e a e mo e
po landi e c ys als in he o m o pla ele s, since as hey age he o iginally p isma ic c ys als
sepa a e in o hinne hexagonal pla es, said sepa a ion occu s along he planes (0001), which a e
he planes o ex olia ion o said mine al.
2.2 X- ay luo escence and X- ay di ac ion
Fo he PLP sample, he majo and mino chemical componen s o he plas e we e analysed by
X- ay luo escence (XRF) using an Axios Panali ycal spec ome e . The sample cha ac e iza ion
was con inued wi h he iden i ica ion o he mine alogical phases by X- ay powde di ac ion
(XRD) using a B uke -AXS D8 Ad ance di ac ome e equipped wi h coppe anode Cu Kα
(λ=1.5405Ǻ), wi h a B agg-Ben ano θ-θ con igu a ion, a nickel il e , and a LynxEye linea
de ec o , and he XRD pa e ns we e ob ained using he powde echnique, a an angle o 2θ, a
ange o 3º o 70°, and a 0.03° s ep scan wi h a 1s s ep.
2.3 G anulome y
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The mo phology o he di e en lime pu y samples was cha ac e ized by ield-emission gun
scanning elec on mic oscopy (SEM-FEG), wi h a Hi achi S5200 mic oscope, a 5 kV
accele a ing ol age.
The g anulome ic analysis was pe o med by lase di ac ion in a Mal e n Mas e size
equipmen which allows o know he pa icle sizes and he g anulome ic dis ibu ion o we
dispe sions acco ding wi h he wo king eal condi ions as pu ies. G anulome ic dis ibu ion o
c ude solid phosphogypsum sample (PG) was also de e mined in d y dispe sions.
The ollowing p o ocol o we dispe sions based on ha p oposed by Rosell (2013) has been
ollowed [24]:
A small sample aliquo is placed in a beake whe e i is dispe sed in a small amoun o dis illed
wa e o homogenize he sample, and hen placed in an ul asound ba h a maximum in ensi y o
a oid pa icle agglome a ion. The ul asonica ion ime applied in di e en expe imen s was 5
min (42 KHz). A ce ain amoun o he al eady homogenized sample was pipe ed and dispe sed
wi h a shake , a a speed o 2500 pm, in a bucke wi h 100 ml o dis illed wa e . Once he
sys em was s abilized, pa icle size dis ibu ion was ead h ough he equipmen so wa e and
he esul s we e eco ded wice consecu i ely, using he a e age o he measu emen s as he
inal esul .
The adjus men pa ame e s o he Mas e size we e: a) Dispe sing wa e wi h e ac i e index
RI = 1.33, b) Re lec ion a e: 1.5; c) Abso p ion index: 0.01. The heo e ical models applied on
da a analysis a e hose de ined by F aunho e and Mie, conside ing ha he i s o hem is mo e
in line wi h heo e ical models o con i ma ion o sphe ical pa icles and he second, o
elonga ed pa icles.
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The s a is ics o he dis ibu ion a e calcula ed by he equipmen om he esul s ob ained using
he de i ed diame e s d(m,n), an in e na ionally ag eed me hod o de ining he mean and o he
momen s o pa icle size:
,=∑





∑








,=
∑





∑







whe e V
i
is he ela i e olume in class i wi h mean class diame e o d
i
, d(0,5), d(0,1) and
d(0,9) a e s anda d pe cen ile eadings om he analysis: d(0, 5) is he median o he olume
dis ibu ion, d (0,1) is he size o pa icle below which 10% o he sample lies and d(0,9) is he
size o pa icle below which 90% o he sample lies. d(4,3) is he Volume Weigh ed Mean o
Mass Momen Mean Diame e and d(3,2) is he Su ace Weigh ed Mean, also known as he
Su ace A ea Momen Mean Diame e o Sau e mean.
2.4 The mog a ime ic analysis (TGA)
The mog a ime ic analysis aimed o de e mine wa e con en o he di e en lime pu y
s udied. They we e pe o med using a Q50 (TA Ins ume s, Wa e , USA) appa a us ollowing a
cons an inc ease o 10ºC/min up o 600ºC s a ing a oom empe a u e (a ound 20ºC).
2.5 Rheological es s
Each pu y was heologically analysed a ou di e se wa e con en s, i.e. 45, 50, 60 and 70%.
LLP samples we e di ec ly ob ained by dispe sing he d y powde in dis illed wa e up o he
desi ed concen a ion. None heless, as phosphogypsum and aged limes we e hold in pas es wi h
a ound 50% wa e con en , TGA was used o de e mine he exac con en o wa e in o de o
adjus wi h dis illed wa e he desi ed concen a ion. To ob ain lowe wa e concen a ions (45
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and 50%), a ce ain amoun o wa e was p e iously emo ed by cen i uga ion o he limes,
pe o med du ing 15 minu es a 4200 pm, and hen he same p o ocol o he adjus men o
concen a ion was ollowed. The pu pose o using cen i uga ion o dec ease he ini ial wa e
con en is o a oid any al e a ion ha he d ying p ocess in a s o e migh p oduce in limes
c ys allini y.
Fo each lime sample, s ess g ow h expe imen s in ansien shea low, a ou selec ed shea
a es, i.e., 0.1, 1, 10 and 100 s
-1
, we e pe o med in a con olled-s ain ARES heome e
(Rheome ic Scien i ic, U.K.) i ed wi h a special mixing geome y dealing wi h a cylind ical
essel and a helical ibbon e y con enien o a oid pa icle sedimen a ion and wall slip e ec s
du ing he measu emen [25]. These es s allow o moni o he e olu ion o he iscosi y wi h
shea ing ime. Mo eo e , iscous low measu emen s we e also ob ained by applying a shea
a e-s epped amp om 0.03 o 100 s
-1
, wai ing ime o 2 min in each s ep, using he same ane
geome y. On he o he hand, small-ampli ude oscilla o y shea (SAOS) es s wi hin he linea
iscoelas ic egime we e ca ied ou in a MARS (Haake, The mo Scien i ic, Ge many)
heome e , using a 50 mm pa allel se a ed pla e-pla e geome y, in a equency ange o 0.03-
100 ad/s. The linea iscoelas ic ange was p e iously de e mined by means o s ess sweep
es s a 1 Hz. All heological measu emen s we e pe o med as soon as samples we e p epa ed,
in o de o ob ain eliable esul s acco ding o he di e en concen a ions.
3. PHOSPHOGYPSUM AND LIME PUTTIES CHARACTERIZATION RESULTS
3.1 Lime pu y om phosphogypsum (PLP)
3.1.1 Raw ma e ial
C ude solid and d ied phosphogypsum (~ 96% by weigh o CaSO
4
•2H
2
O) was supplied by
Fe ibe ia (Huel a, Spain). The PG was homogenized, g ound and d ied in he o en a 40°C o
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Figu e 11. SEM images o simple pu y p epa ed om PLP. ( op), LLP (middle) and ALP
(bo om)
4.1 Viscoelas ic beha iou
Fig. 12 shows he e olu ion o bo h s o age (G’) and loss (G”) moduli wi h equency o he
di e en lime pu y and wa e con en s e alua ed. As can be seen, as expec ed, he alues o
bo h iscoelas ic moduli inc ease wi h solid con en . Mo eo e , ega ding he equency
dependence, a low wa e con en s ( ypically 45 and 50%), he beginning o he e minal egion,
cha ac e ized by a c osso e poin be ween bo h iscoelas ic unc ions, which de e mines he
low egion, can be clea ly obse ed a low equencies o all pu y samples, along wi h he
pla eau egion, cha ac e is ic o h ee-dimensional in e nal s uc u e esul ing om in e ac ing
pa icles, a highe equencies. None heless, in e es ingly, when inc easing wa e con en , he
pla eau egion is gene ally expanded in de imen o he e minal zone which was only de ec ed
a lowe wa e con en s. In p inciple, his is an unexpec ed esul ha may be explained by an
enhancemen o in e -pa icles in e ac ions and he e o e ma e ial cohesion as a esul o
inc easing hyd ogen bonding and capilla y o ces [30].
Figu e 12. Viscoelas ic moduli o LLP, ALP and PLP limes a di e en wa e concen a ions.
When compa ing he h ee lime pu ies a any gi en concen a ion, he highes alues o SAOS
(Small-Ampli ude Oscilla o y Shea ) unc ions we e shown by ALP, ollowed by LLP,
excep ing G” o he 45% wa e con en (LLP45 and ALP45 samples), whe eas PLP always
5
d(09)=71.57
d(05)=30.204
d(01)=11.824
d(09)=49.611
d(05)=20.819
d(01)=9.057
d(09)=60.460
d(05)=15.404
d(01)=5.581

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exhibi ed no iceably lowe alues o he iscoelas ic unc ions. These esul s can be, in pa ,
explained a ending o he g anulome y o he samples. The mean pa icle size o lime
suspensions, gene ally a ies in e sely wi h he iscoelas ic moduli, i.e. highe pa icle size
leads o a lowe s uc u a ion as a consequence o he lowe numbe o in e ac ing pa icles and
speci ic su ace a ea exposed. As p e iously men ioned, iscoelas ic moduli dec eased when
wa e concen a ion was isen, howe e , he e a e signi ican di e ences among hese d ops
when compa ing he di e en limes. Fo ins ance, he di e ences espec ing he aged lime
which shows he highes alues, became highe and highe when inc easing wa e con en .
These ela i e p og essions a e illus a ed in able 4 o he s o age moduli a 10 ad/s. Finally,
he ela i e elas ici y o he di e en samples can be e alua ed by means o he loss angen ( an
δ = G”/G’). As can be seen in Fig. 13, he alues and e olu ion o he loss angen wi h
equency a e gene ally simila o all he samples, independen ly on he ype o lime and wa e
con en . Ne e heless, some in e es ing poin s can be ema ked. Fo ALP, a lowe an δ was
ob ained o ALP45, which could be expec ed as i is he mos concen a ed sample. Howe e ,
he lowes alues o an δ o LLP we e shown by LLP70, in ag eemen wi h he mo e ex ended
pla eau egion. The same in luence can be obse ed in PLP70 a low equencies.
Table 4. Pe cen age di e ence o G' alues, a 10 ad/s, espec ing he aged lime pu y (ALP).
Wa e con en (%) LLP (%) PLP (%)
45 -9.75 -44.70
50 -58.16 -82.90
60 -79.00 -88.71
70 -85.31 -95.99
Figu e13. anδ o LLP, ALP and PLP a di e en wa e concen a ions.
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4.2 Viscous low measu emen s
All samples demons a ed a shea - hinning beha iou a all he concen a ions s udied wi hin he
shea a e ange s udied, howe e , he e a e se e al di e ences among he di e en lime kinds
ega ding he iscosi y alues and shea a e dependence (Fig. 14). Fo mos o he samples, he
e olu ion o iscosi y can be p ope ly i ed o he powe -law model, as epo ed elsewhe e [9]:
!="·$%

whe e " and  a e he consis ency and low indexes espec i ely. Values o hese i ing
pa ame e s a e lis ed in able 5. In all cases, he low index was simila and close o ze o,
cha ac e is ic o yielding ma e ials [31]. Howe e , o 60 and 70% wa e con en s, comme cial
and phosphogypsum lime pu ies shown a endency o each bo h ze o- and high-shea a e
limi ing iscosi ies, which needs addi ional i ing pa ame e s, as also ound in o he s udies
[15]. The C oss model can be sa is ac o ily employed o i his e olu ion:
!=!
&
+!
(
−!
&
/1+·$%


whe e !
&
and !
(
a e he inal and ini ial iscosi y alues, whils  is ela ed o ecip ocal shea
a e o he onse o he powe -law e olu ion, and  has a simila meaning han he same
pa ame e in he powe -law model. Values o hese pa ame e s o hese pa icula pu ies a e
also included in able 5.
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Figu e 14. Viscous low measu emen s ( illed poin s) o LLP, ALP and PLP limes a di e en
wa e concen a ions. (hollow poin s e e o equilib ium alues ob ained om s ess g ow h
expe imen s).
Table 5. Cha ac e is ics pa ame e s o he powe -law and C oss models o he lime pu y
s udied.
Sample
E a
0
E a
∞
K(Pa·s
n
)
m(Pa·s
n
) n
PLP45 27.56 0.07
PLP50 18.24 0.1
PLP60 44.37 0.03 62.22 0.06
PLP70 8.48 0.013 40.62 0.05
LLP45 105.67 0.15
LLP50 34.31 0.18
LLP60 103.48
0.09 15.27 0.07
LLP70 38.54 0.09 15.12 0.19
ALP45 321.02 0
ALP50 127.29 0
ALP60 34.32 0.04
ALP70 9.73 0.06
When he h ee lime pu y samples a e compa ed, again ALP clea ly shows he highes iscosi y
alues, whe eas PLP samples always show he lowes alues (see o ins ance K alues in able
5). These esul s a e in ag eemen wi h hose p e iously discussed ega ding he iscoelas ic
esponse. On he o he hand, iscosi y p og essi ely dec eases wi h he wa e con en , ollowing
a powe -law e olu ion, o all he lime pu ies s udied. This ac suppo s ha wa e dependen
in e -pa icle in e ac ions unde low o slaked limes a e quali a i ely simila . Howe e , his
dec ease in iscosi y is mo e d ama ic o LLP and especially o PLP samples (Fig. 15).
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Figu e 15. Va ia ion o he iscosi y alues a 1 s
-1
wi h wa e con en .
4.3 T ansien low
The ansien low beha iou o he h ee lime pu ies was in es iga ed by pe o ming s ess
g ow h expe imen s a cons an shea a es. Fig. 15 shows he ansien low cu es, in he o m
o iscosi y s. ime plo s as a unc ion o he applied shea a e, o all he samples s udied. The
e olu ion o he ansien shea s ess is simila o ha obse ed o o he hixo opic colloidal
suspensions [32], which is he esul o a well-known non-linea iscoelas ic esponse ini ially,
and he ime-dependen shea -induced s uc u al modi ica ion once he maximum shea s ess,
i.e. he s ess o e shoo , was eached. In mos cases, he elas ic de o ma ion is he p e ailing
componen , so ha he s ess o e shoo , which was a ained in seconds, app oxima ely coincides
wi h he equilib ium (s eady-s a e) alue, especially a highes wa e con en s (60 and 70%), as
can be seen in Fig. 15 in e ms o iscosi y. This means ha no signi ican shea -induced
s uc u al pe u ba ions occu o e ime. Howe e , a much mo e complex beha iou is appa en
a lowe wa e con en s. Thus, once he maximum alue was a ained, ei he a hickening
phenomenon o e ime, i.e. heopexy, a ou ed a low shea a es, o a iscosi y dec ease, i.e.
hixo opy, a ou ed a high shea a es, was obse ed. This shea a e dependen beha iou
ound in highly concen a ed pu y may be explained as he esul o a balance be ween a cu ing
kine ics and he shea -induced dis up ion o agg ega es. Excep ionally, bo h phenomena can be
clea ly dis inguished, see o ins ance sample LLP50 a low shea a es. Mo eo e , some
dis u bances a high shea imes and/o sudden d ops in iscosi y can be occasionally de ec ed
(see o ins ance samples LLP45 and ALP45 a ela i ely high shea a es), which mus be
a ibu ed o shea -induced ac u e phenomena.
A quan i ica ion o he shea -induced s uc u al b eakdown can be done by es ima ing he
“amoun o o e shoo ”, which is de ined as:
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∞
∞
+
−
=
τ
τ
τ
max
S
whe e τ
max
is he s ess o e shoo and τ
∞
is he equilib ium s ess. Conside ing ha , in mos
cases, almos cons an alues o he s ess we e eached be o e agglome a ion o o he
men ioned anomalous e ec s, he equilib ium alues he e conside ed do no ake in o accoun
hose e ec s. The alues o he amoun o o e shoo a e shown in able 6 as a unc ion o shea
a e o all he samples s udied. As can be seen, in gene al, e y small alues we e ob ained in
all he samples, which co obo a es ha he iscoelas ici y is he p e ailing componen and no
signi ican s uc u al b eakdown is no iced. To suppo his ac , he equilib ium iscosi y alues
ob ained om he s ess-g ow h es s we e also added o Fig. 14 and compa ed wi h iscous
low cu es ob ained in s epped-s ess amps. As depic ed in he igu e, hese alues a e
easonably in ag eemen o all he samples and concen a ions s udied.
By analogy wi h he amoun o o e shoo , ano he pa ame e mo e ela ed wi h he applica ions
o lime pu y may be de ined, conside ing he s ess alue a 1 min ins ead o he equilib ium
one, which may be conside ed an app oxima e ime o i s s abiliza ion:
min1
min1max
min1
τ
ττ
−
=
+
S
In his way, all he abo e-men ioned phenomena can ake place a his ime (1 min).. Ei he
impo an nega i e alues o his pa ame e (down o a ound -30% o -50%) o no iceable
posi i e alues can be indis inc ly ound, especially a low wa e con en s and/o low shea
a es, which is a ibu able o dis up ion, agglome a ion and o he e ec s p e iously discussed.
The alues o S
+1min
a e also shown in able 6.

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Figu e 16. T ansien Flow beha iou o he h ee lime pu ies s udied and all wa e
concen a ions (Shea a es o 0.1 s
-1
(■), 1 s
-1
(●), 10 s
-1
(▲), 100 s
-1
(▼)).
Table 6. S
+eq
and S
+1min
o he samples s udied.
Shea a e
(s
-1
) S
eq
S
1min
Shea
a e (s
-1
) S
eq
S
1min
Shea a e
(s
-1
) S
eq
S
1min
PLP45 0.1 0.16 -0.58 LLP45 0.1 0.08 -0.38 ALP45 0.1 0.34 -0.34
1 0.36 0.24 1 0.30 -0.28 1 0.74 -0.17
10 0.00 -0.32 10 0.65 -0.36 10 0.20 0.48
100 0.10 0.11 100 0.05 0.17 100 0.10 0.35
PLP50 0.1 0.10 0.10 LLP50 0.1 0.84 0.25 ALP50 0.1 0.46 -0.19
1 0.00 0.00 1 1.02 0.51 1 0.75 0.00
10 0.04 0.00 10 0.03 0.16 10 0.10 0.09
100 0.05 0.03 100 0.21 0.14 100 0.01 0.01
PLP60 0.1 0.09 -0.37 LLP60 0.1 0.16 -0.15 ALP60 0.1 1.08 0.37
1 0.08 -0.13 1 0.03 0.05 1 0.82 0.49
10 0.09 0.06 10 0.56 -0.28 10 0.04 0.13
100 0.18 0.15 100 0.02 0.02 100 0.03 0.02
PLP70 0.1 0.02 -0.13 LLP70 0.1 0.00 -0.04 ALP70 0.1 0.00 -0.04
1 0.17 0.09 1 0.06 -0.03 1 0.09 0.13
10 0.24 0.12 10 0.13 0.09 10 0.12 0.13
100 0.02 -0.04 100 0.00 -0.01 100 0.02 0.01
5. CONCLUSIONS
The a icle he ein p esen s he heological beha iou o a comme cial lime pu y, and aged lime
pu y and a pu y ob ained om phospogypsum was es o he Huel a p o ince, con i ming ha
PLP does no show any inapp op ia e beha iou ega ding ei he linea iscoelas ici y o
iscous low beha iou ocused on possible applica ions as comme cial-lime subs i uen in
composi e ma e ials o he building and cons uc ion indus y. In addi ion, he slaked lime
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ob aining p ocess om phospogypsum would consequen ly lead o he p ecipi a ion o
haza dous iso opes, emo ing hose om he liquid s a e whe e hei p esence pu in o isk bo h
human being and he en i onmen . Ano he powe ul ad an age is he high ca bona ion capaci y
ha he slake limes possess, a ou ing CO
2
seques a ion.
Gene ally, he ansien low beha iou was highly dependen on wa e con en . The lime pu ies
de elop an ini ial iscosi y inc ease (due o elas ic e ec s) and a e wa ds ei he emains
cons an o sligh ly dec eases, demons a ing a non-no iceable shea -induced s uc u al change.
Subsequen ly, a highe shea ing imes, wo di e en anomalous beha iou s can be ound,
especially a lowe wa e con en s: ei he a signi ican iscosi y inc ease a low shea a es,
which can be a ibu ed o he o ma ion o agglome a es, o a dec ease in iscosi y,
p edominan ly a high shea a es, due o he dis up ion o agg ega es o ac u e occu ence. I
is wo h no icing ha PLP, al hough exhibi ing lowe iscous alues, displayed mo e s able and
sligh ly hixo opic ansien low a high shea a es han ALP and LLP (compa able o s i ing
condi ions o indus ial pu y applica ion), a oiding he abo e explained anomalous e ec s, hus
a ou ing he wo kabili y o his ma e ial.
Rega ding equency sweeps, all samples exhibi e y simila quali a i e esponse, being he
elas ic con ibu ion mo e impo an han he iscous one, especially a high equencies whe e
he pla eau zone is always no iced. This linea iscoelas ic esponse con i ms a high le el o
s uc u al in e ac ions among calcium hyd oxide pa icles. Mo eo e , LLP and ALP samples
shows e y simila alues o he SAOS unc ions a low wa e concen a ions. None heless,
when wa e concen a ion was aised, di e ences became highe , ALP showing he highes
alues. On he con a y, PLP always exhibi ed he lowes alues o he SAOS unc ions
analysed o all concen a ions s udied.
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Viscosi y low es s demons a e a p onounced shea - hinning beha iou o all samples, wi h
low index alues close o 0, PLP again showing he lowes iscosi y alues. In addi ion, he
iscosi y o PLP samples is mo e a ec ed by wa e con en .
All hese heological p ope ies measu ed we e consis en wi h he g ain size o he samples
s udied.
The po landi e c ys als agglome a ion phenomenon has a ele an in luence on he
heological beha iou o he pas es, independen ly o he c ys alline mo phology. A ending o
he g anulome y, he la ge he mean pa icle size, he lowe he alues o he linea iscoelas ic
unc ions and iscosi y. Thus, a la ge agglome a ion pa icle size de elops a smalle s uc u ing
e ec due o he numbe o in e ac ing pa icles and speci ic su ace exposed. In his way, he
PLP sample always showed lowe iscoelas ic unc ions alues han comme cial pu ies, in
cohe ence wi h he g anulome ic cu es.
ACKNOWLEDGEMENT
The au ho s would like o hank he aid o CITIUS a he Uni e si y o Se ille o he use o
hei labo a o ies o he cha ac e iza ion analyses. A.M.B.-L. has ecei ed a Ph.D. Resea ch
G an om he Minis e io de Educación, Cul u a y Depo e (FPU16/03697)
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