MIXED RECYCLING WITH EMULSION AND CEMENT OF ASPHALT
PAVEMENTS. DESIGN PROCEDURE AND IMPROVEMENTS ACHIEVED
R. Mi ó Recasens, F.E. Pé ez Jiménez and S. Cas illo Aguila
Technical Uni e si y o Ca alonia, Spain
ABSTRACT
Cold in place ecycling, as an al e na i e o milling and s anda d eplacemen , shows a
se ies o echnical, economic and en i onmen al ad an ages, which ha e done i s use o g ow
in Spain, especially om 1990 onwa ds. Ne e heless, hese ac ions ha e e ealed ce ain
aspec s and limi a ions ha p e en cold ecycling om being conside ed a ully consolida ed
echnique nowadays.
The use o aguely de ined c i e ia o he design o he ecycled mix, he lack o
c i e ia o cons uc ion con ol as well as o speci ica ions abou he end p oduc , and he
igno ance o he e olu ion o he ma e ial pe o mance wi h ime ha e gi en cold ecycling
some echnical insecu i y.
In his a icle, he p oblems a ising om he s anda d me hodology used o he design
o cold ecycled mixes ha e been analysed i s ly, as well as he e ec ha ce ain a iables,
compac ion and cu ing especially, ha e on hei p ope ies. Secondly, he e ec ha he use
o bo h emulsion and cemen du ing ecycling has on he mix p ope ies has been s udied,
compa ing he esul s wi h hose ob ained by means o he s anda d p ocedu es whe e only
emulsion o cemen a e used. Finally, a new me hodology o he design and con ol o he
ecycled mix has been sugges ed.
RÉSUMÉ
Le ecyclage à oid en place comme al e na i e au aisage e éposi ion con en ionnel
p ésen e une sui e d'a an ages echniques, économiques e en i onnemen aux, qui on ai que
leu u ilisa ion en Espagne ai augmen é p og essi emen , su ou depuis 1990. Cependan ,
ces mêmes ac i i és on mis en é idence ce ains aspec s e limi a ions qui empêchen le
ecyclage à oid d'ê e conside é, à p ésen , comme une echnique de éhabili a ion
consolidée.
L'u ilisa ion de c i è es de dessin de l’en obé ecyclé peu dé inis, la manque de c i è es
de con ole d'exécu ion ainsi que de spéci ica ions su le p odui inal, e la méconnaissance
de l'é olu ion du compo emen du ma é iel a ec le emps, on en ou é le ecyclage à oid
d'une ce aine insecu i é echnique.
Dans ce a icle on analyse, p emiè emen , les p oblèmes que pose la mé hodologie que
l'on u ilise d'habi ude dans le dessin des en obés ecyclés à oid e l'in luence que ce aines
a iables, compaci é e endu cimen spécialemen , on su leu p op ié és; en deuxième lieu,
on a é udié l'e e su les p op ié és de l’en obé de l'u ilisa ion conjoin e d'émulsion e cimen
pendan le ecyclage, que l'on a compa é a ec celles ob enues lo sque l’on n'u ilise que de
l'émulsion ou que du cimen e , inalemen , on a p oposé une nou elle mé hodologie de
dessin e con ole de l’en obé ecyclé.
1
MIXED RECYCLING WITH EMULSION AND CEMENT OF ASPHALT
PAVEMENTS. DESIGN PROCEDURE AND IMPROVEMENTS ACHIEVED
R. Mi ó Recasens, F.E. Pé ez Jiménez and S. Cas illo Aguila
Technical Uni e si y o Ca alonia, Spain
1. INTRODUCTION
The euse o bi uminous ma e ials emo ed om aged pa emen s canno be conside ed
o be a new echnique as a as main enance and ehabili a ion o pa emen s a e conce ned
since i s use, mo e o less widesp ead, began in 1973 as a consequence o he oil c isis. Cold
in place ecycling, as an al e na i e o milling and s anda d eplacemen , shows a se ies o
well known echnical, economic and en i onmen al ad an ages: imp o emen o s uc u al
capaci y and o pa emen egula i y, dec ease in he use o agg ega es and bi umen, lesse
ene gy consump ion, quick execu ion, was e disposal, does no cause smoke pollu ion, e c.,
while being a ela i ely inexpensi e ope a ion ha p o ides a longe pa emen se ice li e,
which is also en i onmen ally iendly.
Encou aged by hese ad an ages, he use o cold ecycling in Spain has been g adually
g owing, especially om 1990 onwa ds, emulsion ecycling being he mos widely used,
accoun ing o a 2.4
x
10
6
m
2
o he ecycled su ace up o now, ollowed by cemen ecycling,
wi h abou 0.8
x
10
6
m
2
, Ruiz [1]. Ne e heless, hese ac ions ha e e ealed ce ain aspec s and
limi a ions ha p e en cold ecycling om being conside ed a ully de eloped and
consolida ed echnique nowadays.
The use o aguely de ined c i e ia o he design o he ecycled mix, he lack o c i e ia
o cons uc ion con ol as well as o speci ica ions abou he end p oduc , and he igno ance
o he e olu ion o he ma e ial pe o mance wi h ime ha e gi en cold ecycling some
echnical insecu i y, causing oad adminis a ions o dis us he use o his echnique.
2
The aim o his a icle is o con ibu e o he cla i ica ion o some o hese issues. I
shows he esul s o a s udy abou cold ecycling o asphal pa emen s, ca ied ou a he
Road Resea ch Labo a o y in he T anspo a ion Depa men a he Technical Uni e si y o
Ca alonia, ollowing he moni o ing o some o he ac ions unde aken in Ca alonia (Spain).
F om his s a ing poin , he p oblems a ising om he s anda d me hodology used o
he design o cold ecycled mixes ha e been analysed i s ly, as well as he e ec ha ce ain
a iables, compac ion and cu ing especially, ha e on hei p ope ies. Secondly, he e ec
ha he use o bo h emulsion and cemen du ing ecycling has on he mix p ope ies has been
s udied, compa ing he esul s wi h hose ob ained by means o he s anda d p ocedu es
whe e only emulsion o cemen a e used. Finally, a new me hodology o he design and
con ol o he ecycled mix has been sugges ed, which is compa ible wi h and complemen a y
o he cu en me hodology.
2. ANALYSIS OF PROPORTIONING AND CONTROL PROCEDURES FOR THE
RECYCLED MIX
The s anda d p ocedu e o he p opo ioning o he ecycled mix is based on he
P oc o es o de e mining he op imal compac ion luids con en and in he s anda d es
me hod o e ec o wa e on comp essi e s eng h -imme sion es - o he mechanic
cha ac e isa ion o he mix and he selec ion o emulsion con en .
A e cha ac e ising he milled ma e ial emo ed om he aged pa emen (g ada ion o
milled ma e ial and ex ac ed agg ega e, pe cen age and cha ac e is ics o he o iginal
bi umen), he op imal pe cen age o compac ion humidi y is de e mined, by means o he
Modi ied P oc o compac ion es . Then, a coa ing es is pe o med wi h an ini ial pe cen age
o emulsion and wa e , he addi ion o bo h being equal o he P oc o humidi y con en .
3
I he coa ing is good, specimens o he imme sion es a e p oduced -as appea s in he
Spanish no m NLT-162/84 [2]-, while inc easing and dec easing he emulsion pe cen age in
espec o he one ini ially ixed, bu keeping he compac ion luids cons an . A e keeping
he specimens in an o en a 60 ºC o 72 hou s, hey a e es ed a simple comp ession
de e mining he d y and a e wa e imme sion (1 day a 60 ºC) esis ance.
The minimum emulsion pe cen age is es ablished acco ding o he simple comp essi e
s eng h, which has o be o e 1,500 kg, and o he e ained s eng h, equal o o e 75%,
ecommending no o ha e less han 2% by mass o esidual binde e en hough he e ained
s eng h is o e 75%, because he possible homogenei y di e ences in milling du ing he
oad wo ks could p o oke supe icial s ipping in hose a eas wi h a highe quan i y o ines.
Al hough hese c i e ia, backed up by expe ience, ha e been used he e is no speci ica ion
abou hem, bu in he las yea s di e en alues acco ding o a ic ca ego y ha e appea ed
as well as equi emen s on he alue o s eng h a e imme sion, Fe nández del Campo [3].
Howe e , his p ocedu e poses se e al p oblems. The i s and mos impo an one is
ha he op imal emulsion pe cen age is selec ed on a mo e compac ma e ial han he one
achie ed du ing wo ks. The eal densi y ob ained om co es, ex ac ed wi hin 30 and 60 days
a e he execu ion o se e al asphal laye s in place ecycled wi h emulsion, is abou 93% o
he alue ob ained wi h he co esponding specimens p oduced in labo a o y, using he s a ic
compac ion o 17,000 kg s anda d speci ied.
Consequen ly, he p ope ies o he mix p oduced in labo a o y can be sligh ly di e en
om he ones ha he compac ed mix will ac ually ha e. Fig. 1 shows he changes in
comp essi e s eng hs o he ecycled mix specimens in espec o he compac ion ene gy
used, no ing ha he mos simila densi ies o he ones ob ained du ing wo ks (2.27 g/cm
3
on
co es) a e achie ed wi h a 6,000 kg compac ion load.
The second p oblem ha his p opo ioning p ocedu e poses is ha comp essi e
s eng h is e alua ed o a p e-es ablished pe iod o ime and cu ing condi ions, igno ing he
s eng h deg ee ha will be achie ed immedia ely a e he execu ion -which is a e y

4
impo an alue since he ecycled mix laye is open o a ic once he compac ion is o e - as
well as a he end o he ma u a ion pe iod, once he wa e excess coming om he emulsion
b eakage is supp essed. Figs. 2 and 3 e eal ha he s eng hs ob ained on specimens cu ed in
o ens a 60 ºC o 3 days a e qui e highe han hose ob ained a a e y sho e m and ai ly
lowe han he ones ob ained a a longe e m when specimens a e cu ed a oom empe a u e.
Thi dly, he imme sion es is use ul o e ealing he e ec o wa e on he mix,
adhesi eness, bu i is a he ine ec i e in o de o cha ac e ise i mechanically. The es is by
no means he mos app op ia e o de e mining he duc ile and ough cohesion p o ided o he
milling by he bi uminous emulsion; an inc ease in he emulsion con en usually b ings abou
a dec ease in comp essi e s eng h, Pé ez Jiménez [4].
On he o he hand, he echnique o cold in place ecycling has in i sel an addi ional
disad an age: he di icul y o con olling he densi y du ing wo ks.
The nuclea de ice usually con ols he densi y du ing wo ks, which should be aimed a
being he highes possible. Ne e heless, wi h his p ocedu e, he humidi y measu emen
could no be accu a e, gi en he ac ha he bi umen exis ing in he old mix as well as he
added one h ough he emulsion can be measu ed as wa e . The e o e, he eco ded humidi y
is no eal and could be abou wice he eal one. Consequen ly, he d y densi ies ob ained
h ough he nuclea de ice do no co espond o he eal ones, being a ound 86 and 90%,
depending on he di e en cases, o he ones ob ained om co es.
Besides, he densi ies measu ed in si u wi h he nuclea equipmen e ol e wi h ime, as
wa e coming om he emulsion b eakage is los , h ough e apo a ion o il a ion, a mo e o
less di icul p ocess depending on wea he condi ions, hickness o he compac ed laye and
condi ion o he oad base.
By way o illus a ion, Figs. 4 and 5 ep esen he e olu ion wi h ime o a e age d y
densi ies and humidi ies, measu ed in si u on oad C-1410, oge he wi h hose ob ained om
co es ex ac ed ou o he ecycled laye . The e o e, he d y densi y ob ained in si u a ies
5
om 1,860 g/cm
3
, a e he laye compac ion is comple e, o 1,942 g/cm
3
a e 40 days, a
alue which is s ill dis an om 2,119 g/cm
3
ob ained on co es ex ac ed be ween 1 o 2
mon hs a e i s cons uc ion, o om 2,280 g/cm
3
co esponding o he job mix o mula in
his case.
The es o pa ame e s ha a e usually con olled du ing cons uc ion do no show so
many p oblems. These pa ame e s a e: g ada ion o he milled ma e ial in o de o check he
milling p ocess homogenei y, agg ega e g ada ion a e ex ac ion and bi umen con en o
de ec any a ia ions in he exis ing mix in he aged pa emen , and comp essi e s eng h, d y
and a e imme sion, o he ecycled mix in o de o compa e i wi h he one ob ained in
labo a o y du ing he p opo ioning p ocess.
In iew o hese conside a ions, imp o ing he mechanical cha ac e is ics o he mix is
conside ed, especially in he i s momen s a e i s cons uc ion, by he inco po a ion o bo h
emulsion and cemen in he ecycling, adding new es s and p oduc ion p ocedu es ha allow
o a be e co ela ion be ween labo a o y esul s and wo k esul s.
This double ea men in place wi h bo h emulsion and cemen o ecycling asphal
pa emen was used in 1992 by Sain on e al. [5, 6], wi h he pu pose o simul aneously gi ing
a highe igidi y o he ypical solu ion o emulsion ecycling and a highe lexibili y o he
ea men wi h cemen , hus minimising he issu e p ocesses o he la e . Engbe s e al. [7]
con i m his aspec and, mo eo e , e eal he good a igue esis ance o his mixed mix. Ou
s udy is mainly aimed a he analysis o he e ec o his kind o ea men in he i s s ages
o cu ing.
3. ANALYSIS OF THE MIXED MIX PROPERTIES
The expe imen al s udy has basically consis ed in de e mining he p ope ies, and hei
e olu ion wi h ime, o he cold ecycled mix using bo h emulsion and cemen , compa ing
hem wi h he ones ob ained when only emulsion o cemen is used.
6
The comp essi e s eng h, he indi ec ensile s eng h, and he dynamic moduli o i e
ecycled mixes ha e been analysed: one wi h emulsion, wo wi h cemen and he o he wo
wi h bo h emulsion and cemen , made om he same milling ma e ial, emo ed om he
asphal pa emen o oad C-147, which was ecycled wi h emulsion du ing he sp ing o
1996, Pé ez Jiménez e al. [8] This ma e ial has been used wi h he same g ada ion employed
du ing i s cons uc ion in o de o compa e he labo a o y esul s wi h hose o he co es
ex ac ed.
Table 1 shows he p opo ioning o each mix. The pe cen ages o wa e added o mixes
RE, RC-1, and RC-2 a e he equi ed ones o ob ain he op imal compac ion luids in he
Modi ied P oc o es . The aim has been o main ain hese op imal compac ing luids o
emixed RM-1 and RM-2, modi ying hem sligh ly in o de o ob ain a simila wa e /cemen
a io.
The specimens ha e been p oduced by s a ic compac ion, using a 6,000 kg load in o de
o ob ain densi ies simila o hose ob ained du ing wo ks. The cu ing o he specimens
con aining emulsion has been ca ied ou a oom empe a u e, whils he ones con aining
only cemen ha e been kep in a humid chambe o i s cu ing.
Simple comp essi e s eng h
The e olu ion o he comp essi e s eng h o he mixed mix du ing he cu ing pe iod,
de e mined a 20 ºC acco ding o NLT-161/84 s anda d [9], is qui e simila o ha o he
emulsion ecycled mix, al hough he highe he cemen addi ion is, he highe he s eng h
alues a e, as shown in Fig. 6.
In he sho e m -se en days- he comp essi e s eng hs o he emulsion and cemen
o mula ions become qui e simila o hose o he cemen o mula ions o wha e e cemen
con en , and a e 28 days he e ec o a highe o lowe cemen con en s a s o be
7
pe cep ible. In he long un, om 60 days onwa ds, he cemen ecycled mixes a e he ones
showing highe s eng hs.
Comp essi e dynamic modulus
The comp essi e dynamic modulus, NLT-349/90 [10], has been de e mined a 20 ºC and
a a 10 Hz equency.
The emulsion ecycled mix shows he lowes dynamic moduli, and he lowes modulus
inc ease du ing he cu ing pe iod, going om 3,540 o 4,878 MPa in a 7 o 90 day pe iod, as
seen in Fig. 7. The mixed mix eaches highe moduli, and he highe he cemen pe cen age
is, he highe i s inc ease du ing he cu ing pe iod will be. The e o e, a mix wi h 3.5% by
mass o emulsion plus 2.5% by mass o cemen goes om 4,071 o 6,006 MPa, and a mix
wi h 3.5% by mass o emulsion plus 3.5% by mass o cemen goes om 4,484 o 7,907 MPa
in he speci ied pe iod.
The cemen ecycled mixes show he highe moduli; he highe he cemen pe cen age
is, he highe he moduli inc ease du ing he cu ing pe iod will be.
Resilien dynamic modulus
The e olu ion o he ins an aneous esilien modulus, a 20 ºC and 0.5 Hz, NLT-360/91
[11], o he se o analysed o mula ions shows a endency simila o he one p e iously
ob ained o he comp essi e dynamic modulus, bu wi h lowe alues.
The emulsion ecycled mix eaches he lowes alues, he cemen ecycled mix he
highes ones, and he mixed mix shows an in e media e pe o mance. The highe he
pe cen age o cemen is, he highe he inc ease o he esilien modulus du ing he cu ing
pe iod o he cemen o mula ions will be.
14
LIST OF TABLES AND FIGURES
Table 1. P opo ioning o each o he analysed mixes.
Figu e 1. Va ia ion o comp essi e s eng h o labo a o y specimens wi h he compac ion load.
Figu e 2. E olu ion o comp essi e s eng h o labo a o y specimens wi h ime and cu ing
ype. Compac ion 6 .
Figu e 3. E olu ion o comp essi e s eng h o labo a o y specimens wi h ime and cu ing
ype. Compac ion 17 .
Figu e 4. E olu ion o in si u and co e densi ies wi h ime.
Figu e 5. E olu ion o in si u humidi ies wi h ime.
Figu e 6. E olu ion o he comp essi e s eng h o labo a o y specimens o he analysed
mixes.
Figu e 7. E olu ion o he comp essi e dynamic modulus, a 10 Hz, o labo a o y specimens.
Figu e 8. E olu ion o he ins an aneous esilien modulus, a 0.5 Hz, o labo a o y specimens.
Figu e 9. E olu ion o he indi ec ensile s eng h, a 5 ºC, o labo a o y specimens.
Figu e 10. Va ia ion o he indi ec ensile s eng h a 5 ºC wi h he used emulsion pe cen age.

14
Figu e 1. Va ia ion o comp essi e s eng h o labo a o y specimens wi h he compac ion load.
Figu e 2. E olu ion o comp essi e s eng h o labo a o y specimens wi h ime and cu ing ype.
Compac ion 6 .
0
0.5
1
1.5
2
2.5
3
3.5
4
0 2 4 6 8 10 12 14 16 18 20
COMPACTION LOAD ( )
COMPRESSIVE STRENGTH (MPa)
D y
We
d= 2.264 g/cm
3
d= 2.391g/cm
3
d= 2.435g/cm
3
0
1
2
3
4
5
6
0 20 40 60 80 100 120 140 160 180 200
CURING PERIOD (days)
COMPRESSIVE STRENGTH (MPa)
S d y (cu ing 60 ºC)
S we (cu ing 60 ºC)
S d y (cu ing 20 ºC)
S we (cu ing 20 ºC)
15
Figu e 3. E olu ion o comp essi e s eng h o labo a o y specimens wi h ime and cu ing ype.
Compac ion 17 .
Figu e 4. E olu ion o in si u and co e densi ies wi h ime.
0
1
2
3
4
5
6
0 20 40 60 80 100 120 140 160 180 200
CURING PERIOD (days)
COMPRESSIVE STRENGTH (MPa)
S d y (cu ing 60 ºC)
S we (cu ing 60 ºC)
S d y (cu ing 20 ºC)
S we (cu ing 20 ºC)
1.840
1.880
1.920
1.960
2.000
2.040
2.080
2.120
2.160
2.200
2.240
2.280
2.320
0 5 10 15 20 25 30 35 40 45 50 55 60
TIME (days)
DENSITY (g/cm
3
)
COLD RECYCLING WITH EMULSION C-1410, sec ion CARDONA-SOLSONA
IN PLACE NUCLEAR DENSITY ( o 50 mm)
CORES DENSITY
DESIGN DENSITY (IMMERSION TEST)
16
Figu e 5. E olu ion o in si u humidi ies wi h ime.
Figu e 6. E olu ion o he comp essi e s eng h o labo a o y specimens o he analysed mixes.
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0 5 10 15 20 25 30 35 40 45 50 55 60
TIME (days)
MOISTURE CONTENT (%)
COLD RECYCLING WITH EMULSION C-1410, sec ion CARDONA-SOLSONA
IN PLACE NUCLEAR MOISTURE CONTENT( o 50 mm)
0
0.5
1
1.5
2
2.5
3
3.5
4
0 10 20 30 40 50 60 70 80 90 100
CURING PERIOD (days)
COMPRESSIVE STRENGTH (MPa)
3.5 E
3.5 E, 2.5 C
3.5 E, 3.5 C
5.0 C
7.0 C
17
0
2000
4000
6000
8000
10000
12000
0 10 20 30 40 50 60 70 80 90 100
CURING PERIOD (days)
DYNAMIC COMPRESSIVE MODULUS (MPa)
3.5 E
3.5 E, 2.5 C
3.5 E, 3.5 C
5.0 C
7.0 C
Figu e 7. E olu ion o he comp essi e dynamic modulus, a 10 Hz, o labo a o y specimens.
Figu e 8. E olu ion o he ins an aneous esilien modulus, a 0.5 Hz, o labo a o y specimens.
0
2000
4000
6000
8000
10000
12000
0 10 20 30 40 50 60 70 80 90 100
CURING PERIOD (days)
RESILIENT MODULUS (MPa)
3.5 E
3.5 E, 2.5 C
3.5 E, 3.5 C
5.0 C
7.0 C
18
Figu e 9. E olu ion o he indi ec ensile s eng h, a 5 ºC, o labo a o y specimens.
Figu e 10. Va ia ion o he indi ec ensile s eng h a 5 ºC wi h he used emulsion pe cen age.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 10 20 30 40 50 60 70 80 90 100
CURING PERIOD (days)
INDIRECT TENSILE STRENGTH (MPa)
3.5 E
3.5 E, 2.5 C
3.5 E, 3.5 C
5.0 C
7.0 C
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
12345
EMULSION CONTENT (%)
INDIRECT TENSILE STRENGTH (MPa)
D y (cu ing 60 ºC, 3 days)
We (cu ing 60ºC, 3 days)
D y (cu ing 60ºC, 1 day)
We (cu ing 60ºC, 1 day)