Polymer Modified Asphalt Emulsion

111806-3434 IJCEE-IJENS © December 2011 IJENS

Polymer Modified Asphalt Emulsion

M. A. Shafii1, M. Y. Abdul Rahman2, and J. Ahmad2

1

Postgraduate, Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia. 2_{Faculty of Civil Engineering, Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia.}

In road paving industry, asphalt emulsion is used for cold mix application such as chip seal, slurry seal, microsurfacing, cold recycled mixture and etc. Asphalt emulsion has several advantages compared to normal asphalt such as eco-friendly, easy to handle at ambient temperature and energy saving material because it does not need any heating process in its application. The history of asphalt emulsions and its application in road construction begin in the early part of 20th century. Due to the increasing number of traffic loads and volume, the used of normal asphalt emulsion is not enough to prevent the pavement from deterioration. Nowadays, polymer modified asphalt technology is used by researcher and manufacturer in asphalt emulsion to improve the performance of asphalt emulsion. Various types of polymers can be used to prepare polymer modified asphalt emulsion such as styrene butadiene styrene (SBS) block copolymer, ethylene vinyl acetate (EVA), polyvinyl acetate (PVA), styrene butadiene rubber (SBR) latex, epoxy resin and natural rubber latex. Polymer can be added into asphalt emulsion in three ways: 1) pre-blending method, 2) simultaneous-blending method and 3) post-blending method. The blending method has important influence on polymer network distribution and will affect the performance of polymer modified asphalt emulsions. The absence of an agreed protocol has allowed various techniques to be used by testing laboratories in order to obtain asphalt emulsion residue. This paper presents an overview of the researches which have been conducted on polymer modified asphalt emulsions using various types of polymer and performance of its application.

Keywords: Asphalt Emulsion, Polymer, Blending, Residue, Performance, Application

I. INTRODUCTION

In the past, unmodified asphalts were able to cope with the traffic volumes and loads exerted on them. Nowadays, the burden placed upon road system has reached a critical stage in many developed and developing countries where the increased volume in heavy vehicles coupled with an appreciable increase in allowable axle weights for these vehicles has lead to a dramatic increase in level of stresses exerted on asphalt surface. Due to the sharp increased of stresses exerted on asphalt surface, most of the road system experience distress and deteriorate before it can achieve the design service life. The use of polymer modified asphalt offer a promising way to improve pavement performance hence it can prolong the service life of the road system even though the road experience unexpected increasing number of traffic volume. Polymer modified asphalt pavement exhibits greater resistance to rutting and thermal cracking and decreased fatigue damage, stripping and temperature susceptibility. Typically, polymer modified asphalt are more viscous compare to unmodified asphalt and tend to show improved adhesive bonding to aggregate particles.

Asphalt emulsion consists of small asphalt droplets suspended in water. It can be produced by mixing hot asphalt with water containing emulsifying agent in a colloid mill. Asphalt emulsion that normally used for cold application has several advantages compared to normal asphalt or asphalt cutback such as eco-friendly, easy to handle at ambient temperature and energy saving material because it does not need any heating process in its use. Currently, polymer modified technology is used in asphalt emulsions to improve its physical properties, performance, and durability. Polymer modified asphalt emulsions offers improvements in mitigation of pavement distress and reduced life cycle costs when compared to unmodified asphalt emulsions [1]. In addition, polymer modified asphalt emulsions also exhibit reduction in

rutting and thermal cracking related problem and increased resistance to many forms of traffic-induced stress.

II. HISTORY, USE AND BENEFITS

The history of asphalt emulsions and its application in road

construction begin in the early part of 20th century. Today, up

to 10% of paving-grade asphalt is used in emulsified form [2-3]. However, the use of polymer modified asphalt started earlier than that where in 1843, the process of asphalt modification using natural and synthetic polymers were patented [4]. Nowadays, polymer modified asphalt technology is used by researcher and manufacturer in asphalt emulsion to improve the performance of asphalt emulsion. Polymer modified asphalt emulsion is used for cold mix especially for

chip seal, slurry seal, surface dressing and microsufacing.The

use of polymer modified asphalt emulsion was recorded by Texas Department of Highway and Public Transportation in June 1982 where it was used in placement of a seal coat on a section of State Highway 327 near Silsbee [5]. There are no problems were encountered during the application of styrene-butadiene block copolymer emulsified asphalt for seal coat [5].

Compare to unmodified asphalt emulsion or hot applied polymer modified asphalt, polymer modified asphalt emulsion have several advantages. Emulsifying of polymer modified asphalt leads to a dried binder film that is more homogeneous and has a better polymer distribution which can improve the binder properties, particularly the ability of the binder to develop consistent cohesion strength and to have a better stone retention [6]. Moreover, study conducted by Forbes et al found that emulsifying of polymer modified asphalt show a good compatibility of polymer network distribution within asphalt compare to polymer modified asphalt [6]. Polymer modified asphalt show incompatibility as the polymer has coalesced into localized agglomerations. Compatibility can be defined as the state of dispersion between two dissimilar components [7]. The compatibility of the polymer within asphalt is important for optimum binder performance.

111806-3434 IJCEE-IJENS © December 2011 IJENS Research also show that polymer modified asphalt

emulsion performs at least as well as modified hot mix binders [1]. In 1992, Anderson et al use three types of polymers such as Neoprene, Butadiene-Styrene (SBS) and Styrene-Butadiene-Rubber (SBR) to study the rheological properties of polymer modified asphalt emulsion residue [8]. From his study, it was found that the polymer modification had little effect on the low temperature stiffness of the emulsion residue. Anderson et al also concluded that some of the polymer modification emulsions slightly increase the consistency of the residue at high temperature [8]. Overall, the benefits of polymer modified asphalt emulsions over unmodified asphalt emulsions can be summarized as follows [1][5]:

• More resistant to rutting and thermal cracking.

• More resistant to flushing or bleeding.

• Increase in traffic‐induced stress resistance (fatigue

cracking).

• Increase in stone retention.

• Faster setting (minimizes land closures and traffic

delay).

• Longer life_‐cycle with same equivalent cost

III. SPECIFIC POLYMER/MODIFIERS

Polymers are very large molecules made by chemically reacting smaller molecules together. The physical properties of polymers are determined based on starting molecules which are called monomers. When two or more different monomers are combined, the resulting compound is termed a “copolymer.” The structure of copolymers may be random, or may repeat in blocks of polymers (block copolymers) as illustrated in Figure 1 [9].

Fig. 1. Example of Copolymers [9]

There are two basic types of polymer that are used in modifying asphalt for road applications [1]:

• Plastomer

• Elastomer

Plastomer polymers attain very high strength at a rapid rate, but are brittle and resistant to deformation at low temperature. An example of plastomer material is ethylene vinyl acetate (EVA). Unlike plastomer, elastomer polymers is a flexible polymer that can be stretched up to ten times without breaking and quickly return to its original shape once the load has been removed. Styrene butadiene rubber (SBR) latex is an example of synthetic elastomer. Plastomer modify asphalt by forming a tough, rigid, three-dimensional network to resist deformation, while elastomer have a characteristic of high elastic response and therefore, it can resist permanent deformation by stretching and recovering their initial shape [10]. The quality of material properties of the polymer modified asphalt emulsion prepared does not only depends on uniformity of the mixture, but also relates greatly to the type, status and nature of polymer or modifiers [11].

1) Natural Rubber Latex

Natural rubber latex (NRL) is an elastomeric hydrocarbon polymer that exists as a natural milky sap produced by several species of plants. The ‘sap’ has a water-based colloidal structure. Natural rubber is produced from natural rubber latex by coagulation to form a solid material [1]. In 1929, the first ever application of natural rubber latex in road construction took place in Singapore [3]. In UK, Europe and USA, the use of natural rubber latex (NRL) in asphalt modification had been studied extensively in the 1950’s and 1960’s [3]. In 1970’s a patented process known as ‘Ralumac’ process was develop to modify asphalt emulsion with natural rubber latex. This process involves mixing anionic natural rubber latex in aqueous phase with cationic asphalt emulsions during asphalt emulsification [3]. Natural rubber latex modification of asphalt since its original introduction has been found to enhance the thermal stability of asphalt in two fundamental ways [3]:

i. Natural rubber latex at high temperatures increases

the bitumen’s viscosity (thickening) making road surface more resistant to deformation under heavy loads during hot weather.

ii. At low temperatures the natural rubber reduces

thermal cracking associated with asphalt.

Study conducted by Malithong and Thongpin show that pre-vulcanized natural rubber latex could be added to modify asphalt emulsion and improve properties of asphalt better than natural rubber latex [12]. Moreover, pre-vulcanized natural rubber latex modified asphalt emulsion could provide asphalt emulsion that possesses acceptable properties of modified asphalt emulsion for highway construction application [12].

2) Styrene Butadiene Rubber (SBR) Latex

111806-3434 IJCEE-IJENS © December 2011 IJENS increasing polymer content [13]. Asphalt emulsions modified

with 3 percent SBR latex performed significantly better than did unmodified emulsions or neat non-emulsified asphalt [1]. From the study conducted by Qinqin et al, it was found that the temperature susceptibility of SBR latex modified asphalt emulsion became lower, which was more favourable for practical application, such as slurry seal and micro-surfacing [14]. Furthermore, the increase of equivalent softening point indicated that the thermal stability and the heat resistance of asphalt were significantly enhanced by SBR modification. Compared to unmodified asphalt emulsion, the increase of 5 °C ductility and decrease of equivalent brittle point revealed that anticracking performance of asphalt was also enhanced considerably by SBR modification [14]. Study conducted by Zhang and He on the performances of the asphalt emulsion modified by compound of water-epoxy resin emulsion and SBR latex show that, in the aspects like low-temperature cracking, high temperature stability, adhesion and durability, it obviously exceeds ordinary asphalt emulsion [11].

3) Styrene Butadiene Styrene (SBS)

SBS block copolymers are classified as elastomers that increase the elasticity of bitumen and they are probably the most appropriate polymers for bitumen modification [15]. SBS copolymers derive their strength and elasticity from physical cross-linking of the molecules into a three dimensional network [16]. Serfass et al found that emulsified SBS modified asphalts show excellent adhesion to various types of aggregate compare to hot applied SBS modified binder and it can even be sprayed on damp surfaces [17]. Moreover, emulsified asphalt applications also show to tolerate higher SBS dosing levels than modified hot mixes, resulting in improved stone retention, cohesion and viscoelasticity, especially in crack sealing applications [17]. Generally, random SBR polymer modified asphalts elongate more (have better ductilities, especially at very low temperatures) than SBS block copolymers because of the double bond structure, but SBS block copolymer modified asphalts show more strength at elongation (elastic recovery, especially at high temperatures) because of the structure of the styrene blocks [1].

4) Ethylene Vinyl Acetate (EVA)

EVA is a commonly used as plastomeric modifier which represents a copolymer of ethylene and vinyl acetate. EVA polymers have been used in road construction for more than 20 years in order to improve both the workability of the asphalt during construction and its deformation resistance in service [10]. There has not been much record on polymer modified asphalt emulsion using EVA. Normally, EVA is used in asphalt modification that is purposely used for hot application. Study conducted by Panda and Mazumdar confirmed that asphalt mixture using EVA modified asphalt increased the value of Marshall stability and air voids and at the same time decreased the flow and unit weight value [18].

5) Polyvinyl Acetate (PVA)

Polyvinyl acetate is one of the clear, water-white, thermoplastic synthetic resins produced from its monomer by emulsion polymerization. The degree of polymerization of polyvinyl acetate typically is 100 to 5000. PVA has the advantage over the other resinous adhesives in that it is available in the form of an emulsion that is readily diluted with water, is easily applied, and is safe to use because it contains no flammable solvents [19]. Study conducted by Chavez-Valencia et al show that the compressive strength of the cold mix that use asphalt emulsion modified with PVA was not improve with regards to the cold mix with unmodified asphalt emulsion [20]. However, for the cold mix where the aggregates were coated with a diluted PVA emulsion before blended with asphalt emulsion modified with PVA, the compressive strength was improved in 31% relative to the unmodified cold mix [20].

IV. METHOD TO ADD POLYMERS

Polymer modified asphalt emulsion is a product made from asphalt emulsion that has been modified with polymer emulsion or a product made by means of emulsifying asphalt that has been modified by polymer. Several techniques can be used to produce polymer modified asphalt emulsion. The polymers or modifiers may be added into hot asphalt before emulsification process take place, added to the finished emulsion product or “co-milled” at the colloid mill with the various component streams during production. The blending method to add polymer has important influence on polymer network distribution and will affect the performance of polymer modified asphalt emulsions [11]. Forbes et al studied the effect of polymer modification techniques on asphalt binder microstructure at high temperatures [6]:

i. Pre-blending – The polymer modifier is added

directly to the bitumen prior to emulsification. This method is required for solid forms of polymer.

ii. Co-milling – Separate streams of polymer, bitumen,

and emulsifier solution (soap) are co-milled together simultaneously.

iii. Soap Pre-batching – The polymer modifier is added

to the soap solution (water and emulsifier) prior to milling with the bitumen.

iv. Post-blending – The polymer modifier is added to the

final asphalt emulsion either at the plant or in the field.

111806-3434 IJCEE-IJENS © December 2011 IJENS residue and presents a major advantage with bi-phase

emulsions [6].

Some of the polymers such as SBR latex and natural rubber latex have an advantage in manufacturing polymer modified asphalt emulsion due to its physical form. It can be co-milled, added into emulsifier or even can be post-blended into the prepared emulsion [21]. Sometimes, post-blending method is discouraged due to the need for vigorous, continual and thorough mixing to ensure proper and homogeneous polymer dispersion [1]. Becker et al observed that the phase separation and stability problems associated with using solid polymer modifiers generally necessitate pre-blending the solid polymer in the asphalt at elevated temperatures prior to emulsification process [1]. Because of the importance of uniformity and compatibility for performance, it is recommended that the polymer should be pre-blended into the asphalt or co-milled into the emulsion and not be post-blended with the asphalt emulsion in the field [9].

Fig. 2. Typical Emulsion Modification Process [1]

V. POLYMER DOSAGE RATES

The dosage rates of polymer vary but are generally one to five percent polymer by weight asphalt, two to three percent is the most common dosage rates for chip seal and slurry seal application [9]. Johnston and Gayle stated that the range of polymer content dosing recommended for most applications generally varies between about 2 percent and 10 percent by weight of the residual asphalt content with most research, standard, and manufacturer specifications calling for a polymer concentration of approximately 3 percent to 5 percent [1]. The optimal percent depends upon the specific polymer, specific asphalt and their interaction. Study conducted by Anderson et al shows that the addition of polymer between 2.8% - 3.0% had little effect on the stress-strain response of the emulsion residue at low temperatures and had moderate increases in stiffness of the emulsion at temperatures above 25

°C [8]. Takamura use 3.0-3.5 percent of SBR latex for microsurfacing formulation that consist of 100 parts of aggregates, 8-15 parts of water and 0.5-2 parts of Portland cement [22].

VI. RESIDUE RECOVERY METHOD

Transportation Research Board (TRB) stated that, the main purpose of asphalt emulsion residue recovery process is to determine the amount of non-water phase in the emulsion and to obtain the asphalt residue for further testing [23]. Generally, residue recovery techniques can be categorized based on two basic concepts which are distillation and evaporation. Distillation normally used high temperature of heat compare to evaporation technique. Currently, a variety of asphalt emulsion residue recovery method has been used by US and European countries. The absence of an agreed protocol for recovery of the residue from the emulsion has allowed various techniques to be used by testing laboratories, and these techniques can affect the rheological properties of the recovered binder. For example, in French standard (NF T 66-031), asphalt emulsion is store at temperature of 50 °C for 14 days. In European standard (EN 14895), firstly, asphalt emulsion is store for 24 hours at ambient temperature, then 24 hours at 50 °C (“recovered” binder, short-term aging) and, finally, 24 hours at 85 °C (“stabilized” binder, medium term aging). In Belgian Procedure (08-34), the binder is recovered by evaporating off the aqueous phase of 1 L of emulsion in a 2 L tall beaker heated with a Bunsen burner and stirred continuously. A temperature of 163 °C is reached in the course of the test. The binder is then placed in an oven at 163 °C for half an hour in order to eliminate any remaining traces of water. Spanish Method (NLT 147) consists of heating 50 g of emulsion for 2 hours at 163 °C in a 600 ml beaker. American Society for Testing and Materials (ASTM) stated that there are

four standard methods for recovery of normal emulsion

residue which is Standard Test Method for Residue by

Evaporation of Emulsified Asphalt (ASTM D6934-08), Standard Test Method for Distillation of Emulsified Asphalt (ASTM D6997-04), Standard Test Method for Determination of Emulsified Asphalt Residue by Moisture Analyzer (ASTM D7404-07) and Standard Practice for Recovering Residue from Emulsified Asphalt Using Low Temperature Evaporative Technique (ASTM D7497-09)[24-27]. Waters et al in the report of “Residual Binder Extraction from Emulsions for

Quality Assurance Testing” categorized most of the emulsion

residue recovery methods into three groups as follows [28]:

i.

ii.

iii.

However the use of heat at high temperature to obtain residue from asphalt emulsion especially ASTM D6934-08 and ASTM D6997-04 methods are not represents the application temperature of asphalt emulsion at site [24-25]. Moreover, high temperature can also affect the rheological properties of asphalt emulsion residue. For polymer modified asphalt emulsion, the high temperature not only will affect the asphalt residue but also can cause damage to the polymer

111806-3434 IJCEE-IJENS © December 2011 IJENS show that the high temperature used in distillation procedure

can significantly alter or damage themicroscopic structure of

the emulsion and therefore the residues recovered by these

processes do not represent the field conditions where

construction is done in ambient temperatures [29]. They proposed a new residue recovery procedure that uses airflow

under ambient temperatures to simulate field conditions. The

forced air-drying procedure, wherein the emulsion was dried

under ambient temperatures for 5-6 hours, was found to

preserve the microscopic polymer network inthe residue and

this network was stable at temperatures as high as 180 ºC [29]. Donald in his study modified the standard distillation test to obtain residue from SBS polymer modified asphalt emulsion where the maximum temperature was reduced to 350 F (177 °C) to prevent damaging to the polymer [5].

Kadrmas compare the residue recovery methods of 177 °C distillation procedure modified from the ASTM D6997 with BASF evaporation procedure that utilizes a silicone mat to hold emulsions at 25 °C oven temperature for 24 hours followed by a 60 °C oven cure for another 24 hours [30]. The reason for comparing these residue recovery methods is the temperature difference between these methods. The distillation procedure uses a much higher temperature than the emulsion applications see during application and use. The BASF evaporation procedure is much closer to the road temperatures seen during the curing process for emulsion applications. From the dynamic shear rheometer (DSR) test result, it showed that BASF evaporation procedure gives higher overall values for the G*/sin delta than the distillation procedure, which may be an indication of less degradation of the polymer [29]. Salomon and Thompson revealed that the residue recovery method (distillation (ASTM D6997), evaporation (ASTM D6934) and moisture analyzer method (ASTM D7404)) has little affect on the complex shear modulus (G*) of polymer modified asphalt emulsion [31]. From the temperature sweep of the G*, the slope of the graph is same for all three recovery methods which is interpreted to mean that there is no significant differences in the property of these binders regardless of the recovery method [31].

Study conducted by Prapaitrakul et al on “Recovered

Binder Properties Using Three Asphalt Emulsion Recovery Methods” show that recovered binders from the Hot Oven (ASTM D6934-08) and Stirred-Can (TXDOT 0-1710) methods showed no sign of residual water due to their high recovery temperature (163 °C), but small amounts of water were detected in the Warm Oven (ASTM D7494-09) recovered samples, which uses only a moderate recovery temperature of 60 °C [32]. Moreover, the Hot Oven recovery method has the advantages of simple equipment, an inert recovery environment and a fast recovery time compare to Warm Oven method [32]. King et al stated that heating can cause cross-linking and damage to polymer additives. Therefore, it is generally agreed that recovery should simulate field curing [33].

VII. CHARACTERIZATION OF POLYMER

MODIFIED ASPHALT EMULSION

A variety of laboratory tests are used by researchers to characterize asphalt emulsions and their residue. Typical test that are normally used to characterize emulsified and non-emulsified asphalt are summarized as follows [1]:

1. Conventional Test

a) Penetration – to estimate cracking potential

and mixture consistency.

b) Ductility – to estimate the potential for

fatigue and thermal cracking and/or raveling.

c) Ring and Ball – to determine stiffness failure

at high temperature. Usually used as a consistency check on polymer modified asphalt.

d) Elastic Recovery – Elastic recovery (or

elasticity) is the degree to which a substance recovers its original shape following application and release of stress. A degree of elastic recovery is desirable in pavement to avoid permanent deformation.

e) Rotational Viscometry (RV) – used to gauge

cracking susceptibility, and raveling

potential through viscosity measurements.

2. SUPERPAVE Specifications

a) DSR (Dynamic Shear Rheometer) – to

predict rutting resistance and high

temperature susceptibility. Useful for

polymer modified asphalt emulsions

employed in rut-filling applications.

b) BBR (Bending Beam Rheometer) – low

temperature susceptibility and thermal

cracking potential.

c) Rolling Thin Film Oven (RTFO) – to

simulate the effects of aging/oxidation.

d) Pressure Aging Vessel (PAV) – to simulate

the effects of long term field aging.

3. Others

a) Vialit Plate Shock Test – measures stone

retention characteristics.

b) Wheel-Track Test – used to simulate wheel

traffic loading and unloading to ascertain rutting-resistance.

c) Loaded Wheel Test – used for slurry seals

and microsurfacings to compact the sample as a means of assessing the mixture’s susceptibility to flushing.

d) Wet Track Abrasion Loss – used to measure

the wearing characteristics of slurry seals and microsurfacings under wet track abrasion conditions.

e) Schulze-Breuer-Ruck – used to evaluate the

compatibility between bitumen, aggregate,

filler and polymer modifier in

microsurfacing.

f) Zero Shear Viscosity – proposed as an

alternative to G*/sin δ as a measure of rut

111806-3434 IJCEE-IJENS © December 2011 IJENS mixtures to estimate the degree of polymer

network formation.

g) Infrared Spectroscopy (IR) and Nuclear

Magnetic Resonance (NMR) – used to verify the presence and relative abundance of polymer modifiers.

h) High Performance Gel Permeation

Chromatography (HPGPC) – used to characterize the molecular weight and physical size of polymer modifiers.

Nowadays, most studies used rheological properties test such as DSR and BBR to characterize the residue of polymer modified asphalt emulsion even though some researchers still use conventional test. Conventional test methods perform on asphalt emulsion typically focused on determination of viscosity, penetration, ductility, elastic recovery and softening

point temperature. However, researchers have found that

rheology is the best way to characterize the performance properties of polymeric and high float asphalt gel structures, as well as asphaltic materials. Rheology is the study of deformation and flow of matter, specifically quantifying the viscous and elastic components. The dynamic shear rheometer (DSR) and bending beam rheometer (BBR) are now used for specifying hot mix asphalt, and with some adaptations, are recognized as the most potentially valuable tools for specifying emulsion residues [33]. Takamura and Lubbers used both of DSR and conventional test such as elastic recovery, penetration and softening point to characterize the SBR latex polymer modified asphalt emulsion residue in their study to compare the emulsion residues recovered by forced air flow and RTFO drying method [29]. From the study conducted by Anderson et al, test result of penetration and bending beam shows that polymer modification had little effect on the low temperature properties and significantly increases the temperature of softening point [8]. Salomon and Thompson use DSR by performing frequency sweep and a temperature sweep on the recovered residue to characterize

asphalt emulsion [31]. The preliminary rheological

characterization of the binders performed at 60 °C and 25 °C show that the Complex Modulus, G* can be used to rank the recovery procedure for each emulsion type [30]. Timothy et al also use standard SUPERPAVE test procedure (BBR, DSR and Direct Tension (DT) Tester) to characterize asphalt emulsion residue [34].

VIII. CONCLUSIONS

Overall, the use of polymer modified technology has been proven that it can improve the physical properties, performance, and durability of asphalt emulsion. For example, the used of polymer can improve the temperature susceptibility and rutting performance of cold mix. Certain polymer can be added at higher dosage level in asphalt emulsion compared to hot modified asphalt which means the improvement of polymer modified asphalt emulsion is better than hot polymer modified asphalt.

The method to add polymer is depends on the physical properties of the polymer. Normally, the pre-blended method will be used for solid polymer and post-blended method will

be used for liquid polymer. Even though the pre-blended method is proven to produce a fine polymer network within asphalt emulsion, some researchers suggested that post-blended method should be used for liquid polymer to produce polymer modified asphalt emulsion to reduce the energy used and minimize the effect of heat to the polymer that might be can alter or damage the polymer.

In terms of residue recovery methods, no consistent method has been used all over the world. In general, residue recovery method can be categorized based on two concepts: distillation and evaporation. Distillation method use high temperature of heat and evaporation can be considered use lower temperature than distillation. However, these two methods have their own advantages compared to each other. For example, distillation can produce the emulsion residue in short period of time compare to evaporation method, but the heat used in distillation method can damage the morphology of polymer. Evaporation method require a long period of time to recover the residue and some method can be up to 48 hours to complete the evaporation process. Some manufacturers need a quick technique to recover the residue for quality control test. Research and development (R & D) laboratory normally prefer the evaporation method which can reduce the effect of heat on polymer and asphalt emulsion itself.

DSR and BBR commonly are the preferred method choose by researcher to characterize the residue of polymer modified asphalt emulsion. However, some conventional test such as penetration, ductility and softening point are still used by the researchers and manufacturers to characterize asphalt emulsion. DSR and BBR test can be considered among the best methods to characterized polymer modified asphalt emulsion residue because it can be used to quantify the viscous and elastic components of asphalt emulsion.

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