design of cold recycled emulsified asphalt mixtures using...

International Journal of Modern Research in Engineering & Management (IJMREM)

||Volume|| 1||Issue|| 10 ||Pages|| 63-74 || November 2018|| ISSN: 2581-4540

www.ijmrem.com IJMREM Page 63

Design of Cold Recycled Emulsified Asphalt Mixtures Using Portland

Cement as A Partial Replacement of Aggregate Mineral Filler

1Engr. Abdul Qudoos Malano, 2Prof. Dr. Naeem Aziz Memon, 3Engr. Gulzar Hussain Jatoi and 4Engr. Abdul Hafeez Memon

1,2,3,4Department of Civil Engineering, MUET Jamshoro, Sindh, Pakistan.

------------------------------------------------ABSTRACT----------------------------------------------------------- Cold Recycling is getting popularity in research sector and construction industries because it overcomes all the

issues of Hot Mix Asphalt of more consumption of natural resources, high production energy, central plant

recycling, effect of greenhouse gases and non-feasibility in colder regions. In this research study, a cold recycled

mixture is designed and compared in terms of mechanical and volumetric properties with control hot mix asphalt

mixture, using 60% RAP (reclaimed asphalt pavement) aggregates and 40 % virgin aggregates to fulfill gradation

requirements. Asphalt emulsion for cold recycled mixtures is used as a binder with varying five contents (4.3%,

4.8%, 5.3%, 5.8% and 6.3%). Also, a modified cold recycled mixture is prepared at optimum emulsion content of

control cold recycled mixture by partially replacing conventional aggregate mineral filler with three different

contents of Portland cement (2%, 3% and 4%) of total dry mass of aggregates. Marshall mix design procedure

was adopted to calculate the optimum (bitumen, emulsion and filler content) for control hot mix asphalt, control

cold recycled mixture and modified cold recycled mixtures respectively. Mechanical properties of each of these

mixtures were compared with each other and it was found that modified cold recycled mixtures were better than

controlled cold recycled mixture and comparable in properties to hot mix asphalt mixtures and Optimum filler

content of Portland cement for modified cold recycled mixture was found to be at 4%.

KEYWORDS: Asphalt Emulsion, Cold Recycling, Hot mix asphalt, Marshall mix design and Marshall mix

properties.

----------------------------------------------------------------------------------------------------------------------------- ---------

Date of Submission: Date, 16 November 2018 Date of Accepted: 21 November 2018

------------------------------------------------------------------------------------------------------------------------------ --------

I. INTRODUCTION HMA is almost world widely used for the construction of flexible pavement because of early developed superior

strengths and rapid availability to serve traffic loading soon after the construction. Besides, these merits HMA

consumes more natural resources like (Aggregates, bitumen, high energy required for the production etc.)

Recycling in case of HMA is done as a central plant recycling in which recycled material is mixed with fresh

materials (i.e. Aggregates and bitumen) in the central plant and then transported to the site consuming energy,

transport and labor cost. Also, the production of HMA adversely effects the environment due to the emission of

toxic greenhouse gases.

Due to the additional consumption of natural resources in HMA mixtures a new trend in the research and

construction industries is being adopted for other feasible alternatives. Cold Recycling in this aspect is considered

to be on the top of list. Cold Recycled Mixtures (CRM) reuse existing pavement materials, which is milled and

mixed (with some portion of new aggregates if required) at the place i.e. (In Place Recycling) Unlike HMA. That

reclaimed material contains aggregates and bitumen, which means cold recycling saves natural resources of

aggregates and also favors less quantity of binder to be used in the mixture. CRM also saves energy required for

the production because it is produced at ambient temperature due to the application of binders like Asphalt

Emulsion, foamed bitumen and cut back etc. In HMA mixtures heat is required to lower the viscosity of the binder

and hence, increase the workability of bitumen to be handled and mixed easily with aggregates and provide proper

coating for the strong bonding and ultimately maximum stability. But Binders like Asphalt Emulsion, foamed

bitumen and cut back etc. reduce or eliminate the need of heat. Binder like, Asphalt emulsion is a mixture of about

60% bitumen, 38 to 39% of water and 1 to 2% of emulsifier agent.

Therefore, water present in emulsion reduces the viscosity of bitumen and eliminates the use of heat for the

production. Therefore, it is environmentally friendly it decreases greenhouse effect and facilities the construction

in cold regions. Even after all such benefits over HMA, CRM are only used for the small duties works like

reinstatement works, repair work, patching works, paving of footpaths and are used for small and medium traffic

roads.

Design of Cold Recycled Emulsified Asphalt Mixtures…


This is because of the facts that Cold Mixes are considered inferior in properties than HMA due to Low

development of early strength, high porosity or air voids and long time required for curing (i.e. evaporation of

water from the CRM and break of emulsion) to achieve full strength for maximum performance. Another

hindrance in the adoptability of Cold mixes and CRM is the lack of proper standard design procedure. Presently,

number of researches have contributed to use cold mixes and CRM in structural layers and this research also aims

to use CRM in high duty pavements i.e. in structural layers in Pakistan. Strength of CRM depends upon the

bonding of aggregate and emulsion which can be achieved after the breaking of emulsion which means the

evaporation of the trapped water from the mixtures. In order to accelerate the process of breaking of emulsion i.e.

evaporation of the water from the mix, additives are to be used which would reduce the porosity, time for curing

and help in development of high early strength. Among various additives Portland cement is found out to be more

effective as suggested by number of researches. When Portland cement is used in emulsion mixtures, it helps and

accelerates emulsion breaking process by utilizing emulsion trapped water for the process of hydration i.e. water

loss favors strength of the mix and secondly, Portland cement acts as a secondary binder i.e. additionally it imparts

strength to the mixture of CRM and therefore problems of low early developed strength and longtime of curing

are mitigated. Therefore, partial replacement of aggregate mineral filler is carried out by ordinary Portland cement

used in three contents i.e. (2%, 3% and 4%) by mass of dry aggregates, total 9 specimens are prepared for modified

CRM after finding the optimum emulsion content for CRM containing 60% RAP.

II. LITERATURE REVIEW In this research, experimental investigation was carried out to estimate and improve the properties of Cold

Emulsion Mixtures. Properties of mixture under consideration were repeated load axial creep, indirect tensile

stiffness modulus (ITSM) and fatigue. After estimation, comparison of these properties was carried out with

control HMA mixture at 2000 MPa targeted (ITSM). The results of tests suggested that even in the absence of

cement, when mixtures were efficiently designed and cured showed approximately the same stiffness as HMA

mixtures. Further, when 1-2% cement was added in the cold mixtures, its performance was enhanced by means

of strength gain, creep resistance and (ITSM). But fatigue performance was yet dominating in HMA mixtures. (I.

N. A Thanaya Beng, 2009).

This research work was done on the topic of “Characterize Cold Bituminous Emulsion Mixtures Incorporated

Ordinary Portland Cement Filler for Local Surface Layer.” Objective of this study was to enhance the properties

of Cold Bituminous Emulsion Mixtures (CBEM) i.e. Mechanical and durability properties for the hope of using

it as a structural layer. In a trial, conventional filler was replaced by the three percentages of ordinary Portland

cement; 0, 50%, and 100%. Mechanical properties of CBEM mixtures were determined in terms of Marshall

stability, Flow, ITS and Wheel Track Test and the damage caused due to moisture was evaluated by Marshall

Retained Stability. It was evaluated from the results of test that specimens with 100 % addition of OPC as a filler

efficiently improved mechanical and durability properties of CBEM and 100 % OPC seemed promising for the

use as structural layer, also there was the enhancement of mixtures about 1.9, 1.78, 9.4, 4.85 and 2.6 times than

the untreated CBEM. It was also observed that CBEM with 100 % OPC was comparable to HMA and in terms of

rutting resistance it performed 6.2 times higher than HMA. (MUSTAFA AMOORI KADHIM, SHAKIR FALEH

AL-BUSALTAN AND RAID RAHMAN ALMUHANNA 2016.)

“Performance Characteristic of Cold Recycled Mixture with Asphalt Emulsion and Chemical Additives.” The

objective of this research was to see the effects of three different chemical additives i.e. Portland cement (PC),

Hydrated lime (HL) and combined HL and ground-granulated blast furnace slag (GGBF), and investigation of

these effects on (CREAM) by volumetric, strength, moisture susceptibility, rutting and low temperature bending

tests along with microstructure images by environmental scanning electron microscope (ESEM). Additionally, A

design procedure was proposed for a cold Recycled Mixture based on the selection of (OPWC) and (OEC). Design

of cold recycled mixture was carried out by Modified Marshall mix design method. In RAP Premix water was

added before introducing emulsified asphalt, then different additives were mixed i.e. CPC content was adapted

from 1.5% to 3.5% at 1% intervals and the mass ratio of HL to GGBF was 1: 3. Specimen were prepared by 75

Marshall hammer blows and were cured for 24 hours in the mold and then specimen were cured in an oven at 600

C for 72 hours and then cooled at the room temperature for 24 hours. Asphalt emulsion was assumed as 4% for

the determination of OPWC, specimens were prepared with premix water contents ranging from 1.5% to 3.5% at

0.5% intervals. OEC was determined using 3.0% to 5.5% range of emulsion content at 0.5% intervals. Results of

tests concluded that the proper CPC can improve the ITS and lower the asphalt content, rutting and moisture

resistance were proportional to CPC content, for anti-rutting and moisture damaged it was recommended to use

CPC content or combination of HL and GGBF. (SHAOWEN DU 2015)



Research was conducted on the “Effect of Portland cement (PC) and lime (HL) additives on properties of cold in-

place recycled mixtures with asphalt emulsion.” These properties included, stability, durability, resilient modulus,

permanent deformation and tensile strength. Objectives of this research were to the analyze and compare the

effects of individual additive i.e. PC and HL on CIR emulsified mix, another objective was the evaluation of

optimum PC and HL. Different asphalt emulsion contents and water content were used varying from (2.5 to 4.5)

in 0.5% increments. Finally, optimum asphalt and water content were selected as 3.5 % and 3.6 %. It was

summarized from the test results that PC and HL addition in recycled mixture enhanced stability, tensile strength,

resilient modulus and bulk specific gravity, and decreased air void and flow. Both MSR and TSR outcomes

indicated that both additives improved resistance to moisture damage. Creep test indicated that use of additives

reduced rut depth. Though, both additives had better results but difficulty of lime slurry production compelled to

use Portland cement. (Y. NIAZI, M. JALILI 2008.)

In this investigation the effects of cement on Emulsified Asphalt Mixtures (EAM). Objectives of this research

were to evaluate the influence of cement on (EAM) and enhance the mechanical properties of the mixtures and

hoped to use (EAM) in structural layer. For that purpose, various laboratorial tests were conducted on (EAM) i.e.

strength, water damage, temperature susceptibility, creep and permanent deformation. It was shown from results

of tests that all the mechanical properties of EAM i.e. temperature susceptibility, water damage, creep, resilient

modulus and permanent deformation were improved with inclusion of cement in the mixtures. Further, after curing

rate of resilient modulus increased along with cement content up to 6%, creep, permanent deformation and

resilient modulus were improved by cement addition and were comparable to HMA. Resilient modulus in HMA

decreases with the increase of temperature and same trend is noticed in control EAM but in cement modified

EAM, resilient modulus increases with increased cement content and decrease as temperature decreases.

Unmodified EAM failed less than 30, 000 cycle this indicated poor resistance to permanent deformation. (Seref

Oruc, 2007).

This research was carried out to thoroughly analyze the effects of ordinary Portland cement (OPC) on bitumen

emulsion mixtures. Dense graded mixtures were used for laboratory tests i.e. modulus of stiffness, resistance to

fatigue cracking and permanent deformation. For vivid understanding of enhanced properties of mixtures

measurement of rate of coalescence of bitumen droplet with aggregate was carried out and also various blends of

emulsion with OPC and hydrated lime were analyzed. DSR tests of various blends were carried out to see the

stiffening effects of OPC and HL and also electron microscopy was utilized to study crystalline structures of

completely cured samples with and without OPC. It was concluded that the addition of OPC content up to 4%

increased all the fore mentioned mechanical properties of the mixtures and those all were comparable to HMA

mixes and these were increased due to the effect of hydration of cement, increased rate of coalescence and

increased binder viscosity. (Brown and Needham, 2000)

In this experimental work mechanical properties of modified emulsion mixtures with ordinary Portland cement

(OPC) were investigated. Cold Bitumen Emulsion Mixtures (CBEM) were designed by replacement of filler with

OPC and tested for mechanical properties like stiffness modulus, temperature sensitivity and moisture damage. It

was concluded from the results of tests that addition of OPC increased the stiffness modulus and the maximum

OPC content to be utilized is up to 6% and also faster curing was observed in CBEM mixtures at 6% OPC content.

Resistance to water damage was also increased at 6% OPC content. Also, addition of OPC at 3% and 6% content

in CBEM showed lower figs of temperature sensitivity than conventional mixtures. (Hayder Kamil Shanbara,

2018) This research was based on producing and characterizing the behavior of cold recycled asphalt pavement

with high float emulsion and Portland cement. Objective of this research was to analyze the effect of Portland

cement on the mix and determination of optimum emulsion and cement content. Testing was done on samples to

evaluate the properties of mixtures i.e. soaked and un-soaked stability and for that samples were prepared at four

different contents of Portland cement namely, 0%, 1%, 2% and 3% and at 3 different emulsion contents i.e. 1.5%,

2% and 2.5% and at 2% water. It was concluded from results of tests that both soaked and dry stability of mixtures

increased with increase of cement content but under soaked condition effect were more. High dry stability was

achieved with cement addition in mixtures with high content of emulsion but in mixes without cement stability

decreases with increased emulsion content. Cold Recycled mixture with 2 % water, 2% high float emulsion and

1-2% cement content showed optimum performance in terms of properties than control Cold Recycled mixtures.

(Rita I, Musharraf M.Z, Gerald & L. Senkowski, 2001)

III. MATERIALS USED Aggregates : The aggregate for this research was obtained from Noori-Abad quarry which is crushed limestone.

Reclaimed asphalt pavement (RAP) material was collected from M9-motorway Hyderabad, Pakistan. Three types

of mixtures were used for this research. Mix1 which is controlled HMA, Mix2 is CRM which consist of 60% RAP



and 40% virgin aggregates and aggregate above 25mm was removed form RAP. Mix3 is modified CRM in which

partial replacement of aggregate mineral filler of CRM is done with Portland cement. Gradation of aggregate for

(Mix1, RAP extracted aggregate, and Mix2) is carried out according to ASTM C 117,136 given in the table 1.

Physical properties of aggregates (coarse, fine and RAP) are given in table 2.

Table 1. Gradation of All the mixtures

SIEVE SIZE Percentage Passing %

Inch mm Control

HMA Mix

RAP Extracted

Aggregate

Control

CRM

Midpoint

specification

Specification

limit

1 ½ “ 38.1 100 100 100 100 100

1” 25.4 100 100 100 100 100

3/4” 19.1 96 84.8 91 95 90- 100

1/2” 12.7 79.3 45.5 67 --- ---

3/8” 9.52 63.9 28.6 57 63 56-70

#4 4.76 41.8 7 41.5 42.5 35-50

#8 2.40 30.2 1.9 30.5 29 23-35

#50 0.30 7.9 0.6 8 8.5 5-12

#200 0.075 2.8 0.3 3 5 2-8

Fig 1. particle size distribution of all mixtures

Table 2. Results of various test of Aggregates

Test Particulars Results obtained from tests

Los Angeles Abrasion Value % 21

Aggregate impact value % 22.3

Water Absorption % 1.17%

Specific gravity of Coarse Aggregate 2.613

Specific gravity of fine Aggregate 2.615

Specific gravity of RAP Aggregate 2.498

RAP contained 2.5 % asphalt binder by RAP weight according to the results of Rotavapor extraction test.

Properties of aged RAP binder are given in table 3.

0102030405060708090

100

0.01 0.1 1 10 100

Cu

mu

lati

ve %

Pas

sin

g

Particle Size in (mm)

Particle Size Distribution Curve

Upper

Mid point values

lower

Control HMA

RAP Extracted Aggregate

Control CRM



Table 3. Properties of Extracted Bitumen from RAP

Properties Results

Bitumen Content % 2.5

Penetration at 25 0C, 0.1 mm 55

Ductility at 25 0C, cm 101

Softening point, 0C 58

Specific gravity at 25 0C 1.04

Bitumen : Bitumen used as a binder for the controlled HMA mixture was of 60/70 Grade which was obtained

from Karachi refinery. After various tests, physical properties of bitumen were known which are presented in

table 4.

Table 4. Properties of Bitumen used in HMA

Properties Results

Penetration at 25 0C, 0.1 mm 66

Ductility at 25 0C, cm 130+

Softening point, 0C 46

Flash point, 0C 3190

Fire point, 0C 3630

Specific gravity at 25 0C 1.006

Emulsion : In order to determine the type of emulsion to be used in the CRM whether cationic or Anionic

emulsion, consideration of aggregate type is important. Aggregate reactivity depends upon proportion and

distribution of negative charges. In case of acidic aggregates containing high silicon (SiO2) have negative charge

on surface. These negative charged acidic aggregates show strong adhesion bonding with Cationic emulsion. In

this research aggregates containing high silicon content were used and for better bonding with aggregates than

other types Cationic Slow set emulsion was used namely (CSS-1h). After tests results of various properties are

given in the table 5.

Table 5. Properties of Cationic Slow Set Emulsion

Properties Results

Viscosity, Saybolt-Furol, 25 0C SFS 24

Particle Charge test Positive

Specific gravity 1.0185

Residue by Distillation, % 60

Penetration, 25 0C, 100gm, 5s mm 62

Ductility, 25 0C, 5cm/min, cm 100

Solubility in trichloroethylene % 98.5

Mineral Filler : Those aggregate materials having particle size less than 75 micron (No. 200 standard sieve) are

known as mineral fillers and their function is to fill voids in aggregates and provide stability to the mixture against

loads and failures. In this research work partial replacement of conventional aggregate mineral filler with Portland

cement was done for modified CRM by three percentages namely (2%, 3% and 4%) by mass of total dry

aggregates. Properties of conventional filler and ordinary Portland cement are given in the table 6.

Table 6. Properties of Filler used

Filler Specific Gravity

Aggregate Mineral Filer 2.615

Ordinary Portland cement 3.11

IV. Research Methodology Mix1 which is controlled HMA was designed using Marshall mix design procedure for that purpose five varying

bitumen contents namely (3%, 3.5%, 4.0%, 4.5% and 5.0%) three replicated of each so, total 15 samples were

prepared for HMA. For preparing specimen a mixture of 1200gm containing (aggregates, filler, and bitumen) was

taken. Aggregates and filler were heated to a temperature of 175 to 190OC, bitumen was heated to 121 to 125OC


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and asphalt (aggregates, filler and bitumen) were mixed at the temperature of 154 to 160OC. Mixture was placed

in preheated mold having 10 cm dia and 7.5 cm height at the temperature of 138 to 149OC and compacted with 75

Marshall hammer blows on both sides of specimen. After compaction, specimen was placed at room temperature

for 24 hours and then volumetric properties of mixture were determined. In order to determine physical properties

of specimen (i.e. stability and flow) specimen was maintained at 60OC in water bath for 1 hour and then tested for

stability and flow test. Optimum bitumen content (OBC) was determined taking average of three parameters

(Maximum stability, unit weight of mix and air voids at 4%).

For designing Mix2 which is controlled CRM a blend of 60% RAP and 40% virgin aggregates was mixed to fulfill

gradation requirements ASTM C 117,136. Three mix design procedures were reviewed for CRM design namely

Asphalt Institutes Manual Series MS (14), 1989, Asphalt Institutes Manual Series MS (19) 1997 and Asphalt

Institute Manual Series MS (21), 2007. In order to removing the complexity in the design method, Asphalt

Institutes Manual Series MS (14) was followed up to the determination of optimum total liquid content (OTLC)

and Variation of Residual Asphalt content (RAC). Following are the steps involved for the determination of OTLC

and RAC.

Step:1 Gradation of aggregates using asphalt institute manual MS (14), 1989 for Dense Graded Mix.

Step:2 Determination of initial residual asphalt content (IRAC) and initial emulsion content (IEC).

IRAC is designated as P (% of IRAC) which is calculate by the following empirical formula.

P = (0.05 A + 0.1 B + 0.5 C) × (0.7) ----------- (1)

Where A = % of aggregate retained on 2.36 mm sieve (8 no. sieve)

B = % of aggregate passing 2.36 mm sieve and retained on 0.075 mm sieve and

C = % of aggregate passing 0.075 mm sieve. (For Mixtures without RAP)

Pnb = P - (100− 𝑟)×𝑃𝑠𝑏

100 (For mixtures containing RAP)

(Asphalt Institute Manual Series MS (21), 2007.)

Where,

Pnb = Quantity of new emulsion asphalt to be added as (% of total aggregate weight)

Psb = Asphalt content in RAP

r = % of new aggregate to be added in CRM

Initial emulsion content is calculated by the following equation.

IEC = ( P/ X ) [%] ------------- (2)

Where X is the asphalt content of emulsion in our case it is 60%.

Table 7. Calculation of Pnb and IEC

Initial Residual

asphalt content (P)

%

RAP % % of new

aggregate (r)

New asphalt

emulsion (Pnb) %

Initial emulsion

content (IEC)

6.8 60 40 5.3 9

Step: 3 Coating Test : For determine % coating based on visual observation specimen of 1200gm at IEC is dry

mixed at room temperature with aggregates, RAP, filler and pre-wetted varied amount of water and afterward

emulsion content is added and mixed for 2 to 3 minutes to obtain even coating. Different pre-wetted water contents

starting from (2%, 2.5%, 3%, 3.5%) by weight of total mix and varied by (0.5%). Pre-wetted water content which

gives best coating of emulsion with aggregate surface (with less amount of water) based on the visual observation

is considered to be Optimum pre-wetted water content (OPWWC) which is 3% in our case.

Step: 4 Determination of optimum total liquid content (OTLC) at compaction level.

AT IEC and OPWWC specimen are compacted by 75 blows of Marshall hammer. Specimen at OPWWC are varied

at compaction by 1% step by air drying i.e. (8, 7 and 6%) then specimens are tested for dry density. OTLC is

consider on that mixture which contains maximum dry density. In our case OTLC was found out at 7%.

Step: 5 Determination of variation of Residual Asphalt Content (RAC)

Maintaining OTLC value, Residual asphalt content (RAC) was varied two points above and below by 0.5% step.

I.e. (4.3%, 4.8%, 5.3%, 5.8% and 6.3%). 3 replicates of each content i.e. total 15 samples were compacted by 75

blows on of Marshall hammer on each side of specimen and then specimen was left in the mold for 24 hours and

then it was extruded and placed in oven at 40oC for 72 hours (which is slightly modified from one day to 3 days)

because of achieving good strength due to evaporation of water and then it was again maintained at room



temperature for 24 hours and finally volumetric properties of specimen were determined and later tests for

mechanical properties were conducted. Then using Marshall design procedure optimum residual asphalt content

(ORAC) was determined in similar way as optimum bitumen content. For design of Mix3, Mix2 was modified by

partial replacement of aggregate mineral filler with three different percentages of Portland cement (2%, 3% and

4%). Rest of the procedure was similar as for above mentioned Mix2.

V. RESULTS After conducting the various tests of physical and volumetric properties for all three types of mixes namely;

Control HMA, Control CRM at 60% RAP and Modified CRM with the incorporation of cement, results and

analysis are discussed in this section.

Results of Controlled HMA. : Volumetric properties of mixtures were evaluated after compacting specimen i.e.

Unit weight, VMA, VFA, and VTM. Afterwards, Marshall mix design equipment was utilized for calculating

physical properties i.e. stability and flow values. Resulted are presented in table 8. The evaluated properties of

mixture are also plotted against bitumen content.

Table 8. Results of HMA Mixtures

Properties Bitumen Content %

3.0 3.5 4.0 4.5 5.0

Stability (Kgs) 1304 1456 1950 1504 1608

Unit weight g/cm2 2.28 2.29 2.37 2.33 2.32

Flow in 0.01” 9.1 10.5 11.3 12.8 13.9

% V.T.M 8.31 8.1 5.82 4.9 2.38

% V.M.A 15.1 14.8 15 15.3 15.5

% V.F.A 55 62 71 80 83

fig 2. variation of unit weight vs bitumen content fig 3. variation of stability vs bitumen content

fig 4. variation of flow values vs bitumen content fig 5. variation of % air voids vs bitumen content

2.26

2.28

2.3

2.32

2.34

2.36

2.38

2.4

2.5 3.5 4.5 5.5

Un

it w

eig

ht

(gm

/cc)

Bitumen Content (%)

Unit weight (gm/cc)

120013001400150016001700180019002000

2.5 3.5 4.5 5.5

Sta

bil

ity

(K

gs)

Bitumen Content (%)

Stability (Kgs)

6.0

8.0

10.0

12.0

14.0

16.0

2 . 5 3 . 5 4 . 5 5 . 5Flo

w V

alu

e (0

.01

")

Bitumen Content (%)

Flow

0.02.04.06.08.0

10.012.0

2.5 3.5 4.5 5.5

Air

Vo

ids

% (

VT

M)

Bitumen Content (%)

VTM



fig 6. variation of VMA vs bitumen content fig 7. variation of VFA vs bitumen content

Fig 2. shows relationship between unit weight of compacted specimen vs bitumen content and it can be observed

that unit weight values increase linearly with the increasing bitumen content up to 4% and maximum unit weight

observed is 2.37. Later beyond 4% content values of unit weight decrease. First rise of the curve is due to the

reduction of the air voids in the mixture and ultimately the reduction in the volume of the mixture and therefore

unit weight increases. Beyond optimum point excessive amount of bitumen fills the voids of mineral aggregates

with the bitumen and thereby bleeding of the mix increases and the sliding of the particles reduces unit weight.

Fig 3. shows the relationship of stability (Kgs) with bitumen content and it can be seen that stability increases

with increased bitumen content and maximum stability values of 1950 kgs is achieved at 4% bitumen content.

Later, further increased bitumen content decreases stability value. Up to the optimum bitumen content point

increasing bitumen favors better coating and ultimately increasing bonding and stability of mix and after optimum

point excessive bitumen content causes bleeding of bitumen and reduce voids of mixture i.e. resulting in the lower

stability value.

Fig 4. shows Flow relationship vs bitumen values bearing liner relationship with bitumen content as it can be seen

from the above fig it linearly increases with increased bitumen content. Maximum flow value is 14 at 5% content.

This linear trend is due to the plastic deformation of the mixture at the failure point and it increases the segregation

of mixture with increasing bitumen content. Fig 5. shows variation of air voids with bitumen content and it can

be seen that air voids linearly decrease with increased binder content. 4% air void is achieved at 4.7 % binder

content. Air voids in the mineral aggregate decreases with the increasing bitumen content because the voids of

aggregates get filled more with the bitumen content and thereby reducing air voids. Fig 6. shows variation of

Voids in mineral aggregate VMA with bitumen content. It can be observed that at 3.5 % binder content VMA is

minimum and later VMA linearly increases with binder content. Fig 7. shows relationship of VFA with bitumen

content. It is clear from the above graph that % of VFA increases continuously as bitumen content increases. Void

in mineral aggregate by increasing bitumen content reduce the voids proportion filled by air and thereby increasing

% VFA.

Based on above results, determination of optimum bitumen content (OBC) is carried out by taking average of

three bitumen content i.e. at maximum stability, at maximum unit weight and at 4% air voids.

OBC = 4+4+4.7

3 ,

Table 9. Results of Various Properties at OBC

14.714.814.9

1515.115.215.315.415.515.6

2 . 5 3 3 . 5 4 4 . 5 5 5 . 5

VM

A (

%)

Bitumen Content (%)

Voids In Mineral

Aggregate (VMA) %

50

60

70

80

90

2 . 5 3 . 5 4 . 5 5 . 5

VF

A

(%)

Bitumen Content (%)

Voids Fi l led With Asphalt

(VFA) %

Properties OBC = 4.23 %

Stability (Kgs) 1750

Unit weight (gm/cc) 2.36

Flow (0.01”) 11.9

VTM (%) 5

VMA (%) 15.2

VFA (%) 76

OBC = 4.23 %



Results of CRM: Applying the same testing procedure for the calculation of volumetric and physical properties

of Cold Recycled mixtures (CRM) as for HMA mixtures mentioned above. Table 10. Shows the results of CRM

properties at varying emulsion content. After obtaining all the properties of CRM i.e. volumetric and physical

properties graphs are plotted for each property against varying emulsion content.

Table 10. Properties of CRM

Properties Emulsion Content %

4.3 4.8 5.3 5.8 6.3

Stability (Kgs) 760 867 1000 912 804

Unit weight

g/cm2

2 2.1 2.2 2.16 2.12

Flow in 0.01” 2.5 3.2 3.9 4.3 4.8

% V.T.M 16.3 11.5 6.6 7.7 8.8

% V.M.A 21.4 17 18.1 20 21.9

% V.F.A 34.1 46 61.5 63.3 65

fig 8. variation of stability vs emulsion content

fig 9. variation of unit weight vs emulsion content

650

700

750

800

850

900

950

1000

1050

3.8 4.8 5.8 6.8

Sta

bil

ity

(K

gs)

Emulsion Content (%)

Marshall Stability (Kgs)

1.98

2.03

2.08

2.13

2.18

2.23

3.8 4.8 5.8 6.8

Un

it W

eig

ht

(gm

/cc)


Unit Weight (gm/cc)



fig 10. variation of flow vs emulsion content fig 11. variation of air voids vs emulsion content

fig12. correlation b/w VMA vs emulsion content fig 13. variation of VFA vs emulsion content

Fig 8. shows stability values linearly increasing with emulsion content up to 5.3% content and at this content

maximum stability of 1000 kgs is achieved and beyond 5.3% emulsion content stability values linearly decrease

with increased emulsion content. Fig 9. shows relationship between unit weight and emulsion content. It can be

analyzed from the graph that unit weight is linearly increasing with increasing emulsion content up to 5.3% content

and beyond this content further increase of emulsion content decreases unit weight value. Maximum value of unit

weight observed is 2.2 gm/ cm3. Fig 10. shows linear increased trend of flow values with varying emulsion content

and it can be seen that maximum flow value is achieved is 4.8 at 6.3% emulsion content.

Fig 11. shows variation of % air voids with emulsion content and air voids linear decrease with increased emulsion

content up to 5.3 % content and further increase of emulsion content increases air voids. But in actual increase of

emulsion content should linear decrease air voids. Fig 12. shows that VMA linear decrease up to 4.8% emulsion

content and further increase of emulsion content increases VMA. Fig 13. show relationship b/w VFA and emulsion

content. It can be seen from above graph that VFA value increases with increasing emulsion content and

Maximum value of VFA is 65 % achieved at 6.8 % emulsion content.

At Optimum Emulsion content (OEC) or Optimum residual emulsion content (OREC) i.e. 5.3 % values of all the

properties are already mentioned in table 10.

Results of Modified CRM

Table 11. Properties of Modified CRM

Properties At Optimum Emulsion Content (OEC) = 5.3 %

2% OPC 3% OPC 4% OPC

Stability (Kgs) 1174 1260 1300

Unit weight g/cm2 2.140 2.148 2.156

Flow in 0.01” 3.2 2.8 2.2

% V.T.M 9.19 8.85 8.51

% V.M.A 20.33 20.03 19.73

% V.F.A 54.78 55.80 56.85

2

3

4

5

3.8 4.8 5.8 6.8

Flo

w v

alu

e


Flow (0.01")

4.0

9.0

14.0

19.0

3.8 4.8 5.8 6.8

Air

vo

ids

(%)


Voids in total mix (VMT) %

15.0

17.0

19.0

21.0

23.0

3.8 4.8 5.8 6.8

VM

A (

%)


Voids in Mineral Aggregate

(VMA) %

30

50

70

3.8 4.8 5.8 6.8

VFA

(%

)


Voids filled with asphalt (VFA) %



From the above results of table 11. it can be analyzed that the addition of Portland cement follows a linear

regression with the values of Stability, unit weight and VFA by increasing the content of cement from 2% to 4%

this is due to the fact that increasing content of cement makes strong bonding due to the hydration process of the

cement and further increasing hydration process utilize water present in emulsion and thereby breaking process

of emulsion is accelerated and both these process results increasing stability, unit weight and further increasing

cement content reduce air trapped in void of mineral aggregate and thereby increases VFA. Further, increasing

cement content reduces the properties of mix i.e. Flow value, VTM and VMA. Increasing cement content from

2% to 4% fill the voids of aggregates and reduce trapped air thereby it reduces air voids of mix, flow value is the

plastic deformation of mixture which is reduced due to the increasing cement content because cement adds rigidity

and thereby flow deformation is reducing. Also, at 4% content of cement, stability and unit weight are found

maximum so, the optimum content Portland cement to be used in the design mix is at 4%.

After analyzing all the three types of the mixtures i.e. HMA, CRM and Cement modified CRM, three main

properties of the mixtures i.e. Stability, unit weight and air voids are compared with each other. Mixture which is

having greater value of stability, unit weight and minimum 4% value of air voids is considered to be better than

other mixtures. HMA mixtures having stability value of 1750 kgs, unit weight of 2.36 gm/cc and 5% air voids at

4.23% optimum bitumen content. Whereas, in CRM at 5.3% optimum emulsion content stability is 1000 kgs, unit

weight is 2.2 gm/cc and air voids are 6.6% and finally for modified CRM at 5.3% optimum emulsion content and

4% optimum filler content of Portland cement, stability achieved is 1300 kgs, unit weight is 2.16 gm/cc and air

voids are 8.5%. It is clear from the above results that though HMA mixtures are rich in terms of properties than

CRM and modified CRM, but results of CRM and modified CRM mixtures are comparable to HMA mixtures.

But due to the more energy consumption requirement for the production, adverse environmental impacts and

higher construction cost, HMA mixtures are not feasible. Whereas cold recycled mixtures are cost effective, saves

natural aggregate resources, lowers binder requirement due to the utilization of aged binder and also, it is

environmentally friendly. Further, cement modified cold recycled mixtures exhibits more increased strength due

to the hydration of cement, it mitigates the lower early strength development problem by accelerating the breaking

process of emulsion and it also, ensures the rapid availability of the pavement to serve traffic loading. However,

problem of more air voids can be mitigated by heavy compaction i.e. applying 150 blows per face of specimen

[1,10 and 11].

VI. CONCLUSION Following conclusions are drawn from this research based on experimental works on volumetric and physical

properties of mixtures.

1- Cold Recycled Mixtures (CRM) favor less consumption of natural resources, save budget and are

environmentally friendly. Also, CRM are equivalent in strengths and durability as HMA. i.e. Cold Recycled

Mixture (CRM) can be used for high duty pavements.

2- CRM based on above mentioned physical and volumetric properties are comparable to HMA mixtures, as it

is evident from the results that CRM and modified CRM are almost fulfilling all the requirements of Marshall

mix design procedure for heavy traffic. i.e. Stability requirement in design is 815 kgs, achieved in CRM is

1000 and in modified CRM is 1300 kgs. Therefore, Modified CRM are preferred over HMA and CRM.

However, air voids are achieved more than 4% so this problem as suggested by [1,10 and 11] is mitigated by

heavy compaction (i.e. 150 blows per face of specimen).

3- Further, the issues of CRM regarding gaining low early strength and long time required for curing are

mitigated by the addition of Portland cement as partial replacement of aggregate mineral filler and it was

found that optimum filler content of Portland cement was found out to be at 4% by weight of dry aggregates

of mixture.

Recommendation

1- This research is based on materials and region of Hyderabad, Sindh, Pakistan. Further it can be conducted in

other areas of the world.

2- This research utilizes only the determination of volumetric and physical properties of the mixtures. Further,

performance-based properties can be evaluated.

3- Marshall mix design procedure was adopted for this research. further, this research can be conducted on

Vheem and performance-based super-pave mix design method.



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