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Influence of polymer type and structure on polymer modified asphalt concrete mix.



Two low-density polyethylene (LDPE LDPE
abbr.
low-density polyethylene
) resins and two ethyl ethyl (ĕth`əl), CH3CH2, organic free radical or alkyl group derived from ethane by removing one hydrogen atom.  vinyl acetate Vinyl acetate, also known as VAM for vinyl acetate monomer, has the chemical formula CH3COOCH=CH2 and is a colorless liquid with a sweet flavor. Systematic names include 1-acetoxyethylene and acetic acid ethenyl ester.  (EVA) polymers were used to modify asphalt binder, and then mixed with asphalt concrete Asphalt concrete, normally known simply as asphalt, is a composite material commonly used for construction of pavement, highways and parking lots. It consists of asphalt binder and mineral aggregate mixed together then laid down in layers and compacted.  according to according to
prep.
1. As stated or indicated by; on the authority of: according to historians.

2. In keeping with: according to instructions.

3.
 Marshall Method of mix design (ASTM ASTM
abbr.
American Society for Testing and Materials
 D 1559). Effect of weight average molecular weight The weight average molecular weight is a way of describing the molecular weight of a polymer. Polymer molecules, even if of the same type, come in different sizes (chain lengths, for linear polymers), so we have to take an average of some kind.  ([M.sub.w]) of LDPE and vinyl acetate (VA) content of EVA was studied by performing Marshall Stability, moisture susceptibility (AASHTO T 283-89), resilient modulus ([M.sub.R]) and permanent deformation (rutting) tests. EVA with low VA content showed lower stability loss in Marshall Stability test and improved resistance in moisture susceptibility test susceptibility test Antimicrobial susceptibility test, see there  in comparison to hot mix asphalt concrete mix (HMA (High Memory Area) In PCs, the first 64K of extended memory from 1024K to 1088K, which can be accessed by DOS. It is managed by the HIMEM.SYS driver. It was discovered by accident that this area could be used by DOS, even though it was beyond the traditional ) and other polymer modified asphalt concrete mixes (PMAMs). Higher [M.sub.R] and better rutting resistance were observed for PMAMs than that of HMA. This elastic behaviour of modified asphalt correlates very well with the [M.sub.R] and rutting resistance properties of PMAM.

On a utilise deux resines de polyethylene (LDPE) de faible masse volumique et deux polymeres d'acetate d'ethyl vinyl (EVA) afin de modifier (programming) modifier - An operation that alters the state of an object. Modifiers often have names that begin with "set" and corresponding selector functions whose names begin with "get".  le liant asphaltique, puis de le melanger avec du beton asphalte selon la methode de Marshall de conception des melanges (ASTM D 1559). On a etudie l'effet du poids moleculaire ([M.sub.w]) moyen du LDPE et de la teneur en acetate de vinyle (VA) de l'EVA au moyen de divers tests : stabilite de Marshall, susceptibilite a l'humidite (AASHTO T 283-89), module d'elasticite ([M.sub.R]) et deformation permanente (ornierage). L'EVA de faible teneur en VA montre une perte de stabilite moindre dans le test de stabilite de Marshall et une meilleure resistance dans le test de susceptibilite a l'humidite, comparativement au melange mé·lange also me·lange  
n.
A mixture: "[a] building crowned with a mélange of antennae and satellite dishes" Howard Kaplan.
 beton asphalte melange a chaud (HMA) et d'autres melanges de beton asphalte modifie par des polymeres (PMAM). On observe un meilleur [M.sub.R] et une meilleure resistance a l'ornierage pour les PMAM que pour les HMA. Le comportement elastique de l'asphalte modifie montre une tres bonne n. 1. A female servant charged with the care of a young child.  correlation avec les proprietes de [M.sub.R] et de resistance a l'ornierage des PMAM.

Keywords: asphalt concrete mix, Marshall Stability, moisture susceptibility, resilient modulus, permanent deformation

INTRODUCTION

Although 4-6 wt.% of asphalt binder is used with hot mixed asphalt concrete mix (HMA), it improves pavement performance significantly (Al-Dubabe et al., 1998). The most commonly observed types of distress in asphalt concrete pavements are rutting, fatigue cracking, low temperature cracking, aging, ravelling and stripping.

Many investigations were performed on polymer modified asphalt (PMA PMA (papillary-marginal-attached),
n a system of epidemiologic scoring of periodontal disease devised by Schour and Massler in which the symbols denote the areas involved in gingival inflammation.

PMA Progressive muscular atrophy
), where asphalt binder is modified by different types of polymers. Goodrich (1988) related asphalt binder and PMA performance to the performance of asphalt concrete mix. It was observed that the performance of PMA such as temperature susceptibility, force ductility ductility, ability of a metal to plastically deform without breaking or fracturing, with the cohesion between the molecules remaining sufficient to hold them together (see adhesion and cohesion). Ductility is important in wire drawing and sheet stamping. , and low temperature ductility didn't correlate with the performance of the mixes with modified binders. It was concluded that tests that involve very high strains didn't correlate conventional asphalt binder tests to the performance of HMA. In another study, Anderson et al. (1999) studied the relationship between low-temperature binder stiffness and HMA stiffness and poor correlation was reported. However, many researchers (Panda and Mazumder, 2002; Chen et al., 2004; Airey et al., 2004; Hansen and Anderton, 1993; Parker and Brown, 1992; Perdomo et al., 1992; Zoorob and Suparma, 2000; Zhou et al., 1997; Amirkhanian and Williams, 1993; Iqbal et al., in press) investigated the properties of HMA and PMAM, and improvement in performance among asphalt concrete mixes was compared. Moreover, some researchers studied modelling of HMA behaviour like viscoelastic Adj. 1. viscoelastic - having viscous as well as elastic properties
natural philosophy, physics - the science of matter and energy and their interactions; "his favorite subject was physics"
 properties, permeability, etc. (Berthelot et al., 2003; Krishnan and Rao, 2001).

Murphy et al. (2001) modified asphalt binder using recycled polymers like polyethylenes, polypropylenes, polyetherpolyurethane and rubber. The performance was evaluated by measuring viscosity, penetration, softening point, aging and rheology. Moreover, mix tests like indirect tensile stiffness and rutting resistance were performed. In that study, rutting performance was appeared to reflect the binders melt rheology. Therefore, there are different reports about the correlation between the properties of PMA and their mixes.

In a recent publication (Hussein et al., 2005), our group studied the influence of the weight average molecular weight ([M.sub.W]) of low-density polyethylene (LDPE) and vinyl acetate (VA) content of ethyl vinyl acetate (EVA) on the properties of PMA. It was found that EVA with low VA content (19.5 wt.%) showed the best storage stability and reduced temperature In thermodynamics, the reduced temperature of a fluid means the actual temperature, divided by its critical temperature.



It is often used in thermodynamical formulas, e.g.
 susceptibility as well. Moreover, EVA modified asphalt extended the window of the performance grading (PG) and improved viscoelastic behaviour of base asphalt binder. In addition, the influence of the [M.sub.W] of LDPE on the properties of PMA was studied.

In this study, the effect of polymer type and structure on polymer modified asphalt concrete mix (PMAM) was investigated. Effect of polymer structure was observed by studying influence of molecular weight of low-density polyethylene (LDPE) and the VA content of EVA on the properties of PMAM. On the other hand, properties of LDPE PMAM and EVA PMAM were compared to observe the effect of polymer type. These observations were based on Marshall Stability test, moisture susceptibility (stripping) test, resilient modulus and permanent deformation measurements. Moreover, correlation between PMA and PMAM was investigated.

EXPERIMENTAL

Material

Two LDPEs of different [M.sub.w] and two EVA polymers of different VA contents were used to modify asphalt binder. This modification was done with 4% polymer as this concentration satisfied the required PG (76-10) in the Arabian Gulf Arabian Gulf: see Persian Gulf.  region (Hussein et al., 2005). The PG was evaluated according to Strategic Highway Research Program (SHRP SHRP School of Health Related Professions
SHRP Strategic Highway Research Program
SHRP Society for Human Resource Professionals
SHRP Small Habitat Restoration Program
SHRP Scientific Human Resources Board
) specification. Table 1 shows the properties of the polymers used in this study as well as the PG for PMAs, where asphalt binder was mixed with 4% of each polymer. The polymer resins were supplied by ExxonMobil, Belgium. Supplier data are presented in Table 1. Moreover, [M.sub.w] and molecular weight distribution (MWD MWD Metropolitan Water District of Southern California
MWD Measurement While Drilling (oil drilling)
MWD Morgan Stanley Dean Witter (stock symbol)
MWD Molecular Weight Distribution
MWD Military Working Dog
) are reported, which were measured by gel permeation chromatography Gel permeation chromatography (GPC) is a separation technique based on hydrodynamic volume (size in solution). Molecules are separated from one another based on differences in molecular size. This technique is often used for polymer molecular weight determination.  (WATER GPC (1) A PC that uses the Linux-based gOS operating system. See gOS.

(2) (GPC Group) Originally the Graphics Performance Characterization committee of the NCGA, the GPC Group is now part of Standard Performance Evaluation Corporation (SPEC) and oversees the following
2000). Details of this measurement are described elsewhere (Hussein et al., 2005).

Asphalt binder of PG 64-22 was used in this study. The asphalt binder was obtained from Saudi Aramco Saudi Aramco, the state-owned national oil company of Saudi Arabia, is the largest oil corporation in the world and the world's largest in terms of proven crude oil reserves and production.  Riyadh Refinery. Low [M.sub.w] LDPE was labelled as LDPE1 and the high [M.sub.W] LDPE as LDPE2. On the other hand, EVA with 19 wt.% VA content was represented by EVA1 and the 27.5 wt.% VA content of EVA by EVA2. The two EVA resins had the same melt flow index The Melt Flow Index is a measure of the ease of flow of the melt of a thermoplastic polymer. It is defined as the weight of polymer in grams flowing in 10 minutes through a capillary of specific diameter and length by a pressure applied via prescribed alternative gravimetric  (MFI MFI Microfinance Institution
MFI Money Flow Index
MFI Melt Flow Index
MFI Median Family Income
MFI Malaria Foundation International
MFI Massachusetts Family Institute
MFI Multi-port Fuel Injection (automobile) 
). Aggregates, used to prepare mix samples, were obtained from local sources (details are given in Table 2). Comparison of the two LDPEs will reveal the influence of [M.sub.w]. Similarly, the effect of VA content will be obtained by comparing the two EVA resins. Moreover, LDPE1 and EVA1 mixes have similar MFI, which might provide insight on whether LDPE or EVA (similar MFI, see Table 1) provide better PMAMs.

Polymer and PMA Sample Preparation

25 mm diameter and 2 mm thick flat discs of as received polymer were prepared in a carver press for rheological rhe·ol·o·gy  
n.
The study of the deformation and flow of matter.



rheo·log
 tests. A mould temperature of ~20[degrees]C above the melting point melting point, temperature at which a substance changes its state from solid to liquid. Under standard atmospheric pressure different pure crystalline solids will each melt at a different specific temperature; thus melting point is a characteristic of a substance and  of each polymer was selected. Polymer resins were charged between two platen of the carver press and pressure between the platens was raised gradually up to 7 metric tons and kept for 5 min. Water flow was allowed to cool the platens to room temperature, and disc shaped polymer samples were collected.

PMA samples were prepared by blending pre-weighed polymer with asphalt binder at 160[degrees]C in a high shear blender (~2500 rpm) at optimum blending time (OBT), which was 30, 20, 15 and 20 min for LDPE1, LDPE2, EVA1 and EVA2, respectively. Determination of OBT was mentioned elsewhere (Hussein et al., 2005). In addition, asphalt binder was treated under similar conditions up to 50 min to give similar processing conditions. After blending, samples were collected in a rubber mould and used to perform frequency sweep tests in an ARES rheometer rhe·om·e·ter
n.
An instrument for measuring the flow of viscous liquids, such as blood.
. A temperature of 50[degrees]C and a strain of 20% (in linear viscoelastic region) were used in frequency sweep tests. The purpose of frequency sweep test is to compare frequency response of polymer modified asphalt binder with that of modified asphalt mix.

Mix Design

The mix design was done according to Marshall Method (ASTM D 1559) of mixed design. Wearing course was used as mix code. The details of the mix design for base asphalt mix are given in Table 2 and similar design was used for PMAM. The standard cylindrical shaped Marshall specimen of 100 mm x 62.5 mm was prepared for HMA and PMAM. The prepared specimens were used for the following tests.

Marshall Stability Test

Stability is an important property of the bitumen bitumen (bĭty`mən) a generic term referring to flammable, brown or black mixtures of tarlike hydrocarbons, derived naturally or by distillation from petroleum.  mixture in the wearing course design. It shows the ability to resist shoving and rutting under traffic (Hinislioglu and Agar Agar, in the Bible
Agar (ā`gər), the same as Hagar.
agar, substance obtained from seaweed
agar (ä`gär, ā`–, ăg`är) 
, 2004). Marshall Stability test of HMA and PMAM was performed in a Marshall testing machine testing machine

Machine used in materials science to determine the properties of a material. Machines have been devised to measure tensile strength, strength in compression, shear, and bending (see strength of materials), ductility, hardness, impact strength (
 at a constant rate of 51 mm/min. Six specimens were immersed into a water bath at 60[degrees]C. After 40 min (initial condition), 3 specimens were tested and the average compressive com·pres·sive  
adj.
Serving to or able to compress.



com·pressive·ly adv.
 load required to break the sample was determined and corrected by multiplying with a stability correction factor to get the initial stability. The remaining 3 specimens were kept for 24 h and the required compressive load was measured in the same way to get the final stability.

Moisture Susceptibility Test (Lottman Test, AASHTO T-283-89)

Moisture susceptibility was evaluated by determining the changes in the mechanical properties of the specimens after conditioning. This test reveals the resistance of compacted bituminous bi·tu·mi·nous  
adj.
1. Like or containing bitumen.

2. Of or relating to bituminous coal.

Adj. 1. bituminous - resembling or containing bitumen; "bituminous coal"
 mixture to moisture induced damage. It is done by measuring the change of diametral tensile strength tensile strength

Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its
 resulting from the effects of saturation and accelerated water conditioning of compacted asphalt mixtures in the laboratory. The results may be used to simulate the long-term stripping susceptibility of the asphalt mixtures. Samples were conditioned in water for 2 h at room temperature. The load was applied on the specimen at a constant deformation rate of 51 mm/min and the load at failure was measured at dry condition. This load is called indirect tensile strength (ITS). For the wet condition, specimens were subjected to vacuum up to a saturation level of 60%, in water at 60[degrees]C for 24 h, then at room temperature for 2 h, and finally ITS was measured. The ratio between the value of the wet ITS and the dry ITS was calculated and expressed in percent form, which is known as tensile strength ratio (TSR (Terminate and Stay Resident) Refers to a program that remains in memory when the user exits it in order that it be immediately available at the press of a hotkey. ).

Resilient Modulus, [M.sub.R] (ASTM D 4123)

Diameter resilient modulus is the measure of pavement response in terms of dynamic stresses and corresponding strains. A static load of about 10 lb was applied to hold the specimen in place. A dynamic load in the elastic range was applied with a frequency of 1 Hz (ASTM D 4123), and the resulting horizontal deformation was obtained at 50[degrees]C. Our interest was to evaluate [M.sub.R] at high temperature (76[degrees]C) since PG in the Gulf region is 76-10, but the maximum attainable temperature in the existing experimental set-up is 50[degrees]C.

Permanent Deformation (Rutting)

Permanent deformation measurements were performed on HMA and PMAM at 50[degrees]C. The controlled stress loading at 150 initial [mu]-strain level, which showed elastic region, was used at 1 Hz. The deformation was measured by linear variable differential transducer and data were stored in a data logger data logger - data logging . The data were collected at every 5 s for the first 100 load repetitions; every 10 s for the next 100 repetitions; then every 15 s for the following 100 repetitions, and finally every 30 s up to the sample failure.

RESULTS AND DISCUSSIONS

Melt Rheology

Rheology is the science of deformation and flow deformation and flow

Alteration in size or shape of a body under the influence of mechanical forces. Flow is a change in deformation that continues as long as the force is applied.
 of materials. Melt rheology means measurement of rheological properties (viscosity and elasticity) of PMA in the melt state. For PMAM the measurement of stress-strain relationship is considered solid-state rheology. Viscoelastic properties of PMA were measured in the melt state. In Figure 1, storage modulus, G', of PMA is shown for the 4 wt.% polymer concentration. Moreover, base asphalt binder was shown for comparison purposes. Addition of polymers increased G' value of base asphalt binder. The highest increase was obtained for EVA1 modified asphalt. At low frequency ([omega]), both LDPEs and EVA2 PMAs showed similar values of G'. At high [omega], G' value for EVA2 modified asphalt was the lowest among other PMAs. In the following sections, we will examine whether the melt rheology of PMA is correlated with the properties of their PMAM.

[FIGURE 1 OMITTED]

Marshall Stability Test

The results of Marshall Stability are presented in Table 3. Three samples were used to obtain the average stability and the corresponding standard deviations were reported. It can be observed that the initial stability for HMA was higher than PMAM. All PMAMs showed similar initial stability. The percent stability loss was the highest for HMA and the least for EVA1-PMAM. No significant difference in percent stability loss was observed between LDPE1 and LDPE2. Therefore, increasing [M.sub.w] from 72 to 102 kg/mol had no effect on the stability of LDPE modified asphalt concrete mixes. EVA1 mix showed remarkable retained stability in comparison with EVA2. The reason is likely the presence of lower amount of VA in EVA1. EVA with high VA content has a rigid long molecule that is not compatible with asphalt's constituents as discussed in a previous publication (Hussein et al., 2005). Comparison between polymer types (LDPE1 and EVA1) of similar MFI suggests that EVA1 is more stable than LDPE1.

Moisture Susceptibility Test

The initial and final ITS values were presented in Table 4. The average ITS value for three specimens is shown along with the standard deviation. The TSRs were lower for PMAMs in comparison to HMA except EVA1 mix, which indicates that PMAMs retained less strength due to water saturation in comparison to HMA. LDPE may have physical bond only with asphalt phase. No network behaviour or cross-linking (chemical bond) is expected from such a stable polymer made by free radical polymerization Radical polymerization is a type of polymerization in which the reactive center of a polymer chain consists of a radical.

The polymerization reaction is initiated by three classes of free-radical initiators:
 (Hussein et al., 2000). The physical bonding between PMA and aggregates is expected to be weakened; resulting in loss in ITS. Moreover, these results show that LDPE1 (low [M.sub.w]) PMAM is more water sensitive than that of LDPE2 (high [M.sub.w]) PMAM. The previous rheological results suggest that LDPE2 forms better homogeneous mixture with asphalt binder than that of LDPE1. EVA1 showed excellent network behaviour in PMAM and retained ITS was the best. Values of TSR for EVA2 PMAM are comparable to LDPE PMAMs. Earlier results (Hussein et al., 2005) showed better storage stability for EVA1 modified asphalt over that of EVA2 modified asphalt. Also, the resistance to moisture induced damage of EVA1 is better than LDPE1.

Resilient Modulus, [M.sub.R]

The resilient modulus of HMA and PMAM at 50[degrees]C is given in Figure 2. It was observed that [M.sub.R] for PMAM was higher than that of HMA. These results are in agreement with previous reports (Jew et al., 1986; Metcalf et al., 2000). Both LDPE PMAMs showed almost similar increase in resilient modulus. On the other hand, EVA1 displayed a higher [M.sub.R] in comparison with EVA2, is a consequence of its high G' modulus. Moreover, EVA1 showed the highest increase in [M.sub.R] value among all polymers used in this study. Thus, EVA with low VA content is superior over LDPE (values of G' at a [omega] = 0.1 rad/s were used in this plot). Data of G' at low [omega] are usually used to detect morphological differences (Hussein et al., 2003). These results correlate very well with the G' data of these polymers, where the trend was qualitatively similar. Similar results were reported by the authors for acrylate polymers A group of polymers which could be referred to as plastics generally. They are noted for their transparency and resistance to breakage when compared to conventional window glass. Commonly called as acrylics or polyacrylates, acrylate polymers.  (Iqbal et al., in press). In this case, value of G' has been taken at 0.016 Hz (0.1 rad/s) rather than 1 Hz to show the robustness of the correlation. Therefore, qualitative screening of polymer for their [M.sub.R] values could be obtained from simple measurement of G' of the PMA rather than the PMAM. This means major reductions in testing and savings in resources.

[FIGURE 2 OMITTED]

Permanent Deformation (Rutting)

The accumulated strain vs. repeated load at initial tensile strain level of 150 [mu]-strain and 50[degrees]C is displayed in Figure 3. At low repeating loads, there was no significant difference in deformation between HMA and PMAMs. But this difference was distinguishable at higher repetitions, where HMA showed higher permanent deformation rate than PMAMs. Similar findings were reported in previous studies (Srivastava et al., 1992; Baig and Al-Abdul Wahhab, 1998; Iqbal et al., in press). Regardless of the major difference in [M.sub.w] of the two LDPEs, their rutting resistance is comparable. These results are in agreement with their G' data, where the two LDPE PMAs showed very similar values (see Figure 1). Although rheological tests were performed at small strain and rutting at large strain, both LDPEs showed comparable performance in each case. Moreover, EVA1 with a higher value of G' (more elastic) than EVA2 demonstrated a higher rutting resistance. Although it is difficult to correlate the linear viscoelastic properties of PMA to the non-linear properties of asphalt concrete mixes, the increase in the elasticity of the PMA is reflected on the rutting properties of PMAMs. The EVA with the highest value of G' showed the best rutting resistance and the LDPEs of similar value of G' displayed similar rutting properties. In another paper the authors (Iqbal et al., in press) obtained similar results for Acrylate polymers. Is this a coincidence? In this study, EVAs were generally better than LDPE in asphalt binder modification. Therefore, it is not just the elasticity that plays a major role in the rutting properties. The polymer structure is another important factor. In general, at such high strains both the elasticity of the PMA and the polymer structure are important in determining the rutting properties of PMAMs. EVA2 rutting resistance was less than EVA1. Hence, low VA content is favoured over high VA content polymers for PMAM. With the same MFI (~150), EVA1 showed less permanent deformations in comparison to LDPE1.

[FIGURE 3 OMITTED]

Most interesting behaviour was observed at higher number of repetitions. At these loads HMA failed gradually compare to PMAMs. Due to the presence of vinyl group, EVA is more rigid than LDPE. Hence, sudden failure was most likely and was found for EVA PMAM. EVA2 mix showed rapid failure compared to EVA1 mix. It is likely that high VA content makes asphalt concrete mixes stiffer. Therefore, polymer structure and the rigidness of the molecule directly are suggested to correlate with its accumulated permanent deformation. At large strains, the rheology of polymers is usually very sensitive to molecular structure (strong flow). Table 5 shows anti log of intercept and slope. Slope shows deformation at early life of pavement, which is the smallest for EVA1-PMAM and the highest for HMA. Other PMAMs show deformation in between this. Among two different polymer types, EVA-PMAM showed lower deformation at early life than that of LDPE PMAM.

Endurance limit (total number of repetitions required to complete breakdown of sample) of HMA and PMAMs as shown in Figure 4. PMAMs showed higher endurance limit compared to HMA. Endurance limit for EVA1 modified mix was the highest among all mixes. Accumulated deformation was least for EVA1 mix (Figure 3) and more than 4 x [10.sup.4] cycles were needed to break a sample. This shows that EVA1 asphalt concrete mix is both strong and tough. On the other hand, EVA polymers are generally better than LDPE of similar rheological characteristics. Thus, among all the polymer modified asphalts used in this study, best mix performance was observed for EVA with low VA content polymer within performed tests and for asphalts of high asphaltene content.

[FIGURE 4 OMITTED]

CONCLUSION

In this study, two LDPE polymers of different MFI and two EVA polymers of different VA contents were used to modify asphalt binder. This modification was performed with 4% polymer concentration. Marshall Method of mix design was used to prepare asphalt concrete mix. Following are conclusions of this study:

1. HMA showed high initial stability, but retained stability was the lowest in comparison to PMAMs. Marshall Stability loss was the lowest for EVA1 asphalt mix (7%). In all other mixes the loss was about 30%.

2. Values of TSR indicated that PMAMs are more sensitive to water than HMA. But EVA1 PMAM showed better resistance to moisture induced damage than that of HMA.

3. Polymer modification increased the [M.sub.R] of base asphalt binder. No effect for molecular weight was detected for LDPEs since their G' values were of similar magnitudes. For EVA, the resin with high elastic modulus showed a higher [M.sub.R]. A correlation between [M.sub.R] and G' was suggested.

4. Rutting behaviour of PMAM has improved significantly over that of base asphalt binder by a factor of 1.5-10. Accumulated deformation was very small for EVA1-PMAM. The EVA with the highest value of G' displayed the highest value of rutting resistance and LDPEs of similar G' showed similar rutting resistance. In general, EVA mixes showed less deformation than LDPE mixes.

5. Endurance limit was the highest for EVA1 modified asphalt mix. However, all PMAMs showed higher values than that of HMA.

6. Correlation between G' and [M.sub.R] and rutting properties of asphalt concrete mix should save the time and recourses spent in screening different polymers. However, generalization of the above results to asphalts with very different compositions should be cautioned.

ACKNOWLEDGEMENT

The authors would like to thank King Fahd University of Petroleum and Minerals King Fahd University of Petroleum and Minerals (KFUPM or UPM) (Arabic:جامعة الملك فهد للبترول و  for performing this study. The authors are thankful to Al-Dossary Asphalt Plant An asphalt plant is a plant used for the manufacture of asphalt, macadam and other forms of coated roadstone, sometimes collectively known as blacktop.

The manufacture of coated roadstone demands the combination of a number of aggregates, sand and a filler (such as stone
 for providing the aggregates and Willey Leyson of ExxonMobil, Belgium for providing polymer resins.

NOMENCLATURE nomenclature /no·men·cla·ture/ (no´men-kla?cher) a classified system of names, as of anatomical structures, organisms, etc.

binomial nomenclature
 

AASHTO American Association of State Highway and Transportation Officials

ASTM American Standard and Testing Materials

ARES Advanced Rheometric Expansion System

EVA ethylene vinyl acetate

G' storage modulus

HMA hot mix asphalt concrete

ITS indirect tensile strength

LDPE low-density polyethylene

[M.sub.R] resilient Modulus

[M.sub.w] weight average molecular weight

MFI melt flow index

PG performance grading

PMA polymer modified asphalt

PMAM polymer modified asphalt concrete mix

TSR tensile strength ratio

Greek Symbols

[omega] frequency

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n.
1. A small portion of food or a slice, especially of meat.

2. A roll of fat flesh.



[Middle English.
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American Society of Civil Engineers
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adj.
1. Mechanically determined.

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Manuscript received February 14, 2006; revised manuscript received April 24, 2006; accepted for publication April 25, 2006.

Ibnelwaleed A. Hussein (1) *, Hamad I. Al-Abdul Wahhab (2) and Mohammad H. Iqbal (1)

(1.) Department of Chemical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia Saudi Arabia (sä`dē ərā`bēə, sou`–, sô–), officially Kingdom of Saudi Arabia, kingdom (2005 est. pop.  

(2.) Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

* Author to whom correspondence may be addressed.

E-mail address: ihussein@kfupm.edu.sa
Table 1. Characterization of polymers

                 Density          Melting point   MFI
Polymer          (g/[cm.sup.3])   ([degrees]C)    (g/10 min)

LDPE1            0.913            100             155
LDPE2            0.913            100              70
EVA1
(19 wt.% VA)     0.938             81             150
EVA2
(27.5 wt.% VA)   0.950             68             150

                                     PG
                 [M.sub.W]           (asphalt binder + 4% of
Polymer          (kg/mol)    MWD     corresponding polymer)

LDPE1             71.92       9.75   76-16
LDPE2            102.93      12.4    76-10
EVA1
(19 wt.% VA)      45.63       4.71   82-10
EVA2
(27.5 wt.% VA)    40.48       5.4    76-22

Table 2. Mix design

                                       Job mix         Specification
                                       formula (JMF)   limits

1. Optimum asphalt binder content, %
(PG 64-22)                             5.3             5.3  0.3

2. Aggregate grading:
% Passing

1"                                     100             100
3/4"                                   87              80-95
# 4                                    55              48-62
# 10                                   38              32-45
# 40                                   21              16-26
# 80                                   13              8-18
# 200                                  6               4-8

3. Marshall test results
(75 blows, compaction temperature
150[degrees]C)

Stability (kN)                         18.04           8.00 Min.
% Air voids. Total mix                 4.4             4.0-6.0
Flow (mm)                              3.2             2.0-4.0
% Voids filled w/asphalt               74              70-80
Stability loss (%)                     16.2            20 Max.
Void in mineral aggregates (VMA)       16.04           --

Table 3. Marshall Stability test

                                              Average
                         Sample   Stability   stability
Sample ID    Condition   no.      (kN)        (kN)

HMA          Initial     1        20.22       19.81
                         2        19.64       19.81
                         3        19.58       19.81
             Final       1        11.61       13.15
                         2        14.32       13.15
                         3        13.53       13.15
LDPE1-PMAM   Initial     1        16.49       15.33
                         2        14.69       15.33
                         3        14.82       15.33
             Final       1        10.06       10.66
                         2        10.82       10.66
                         3        11.10       10.66
LDPE2-PMAM   Initial     1        15.55       14.40
                         2        12.68       14.40
                         3        14.98       14.40
             Final       1        10.85        9.74
                         2         9.92        9.74
                         3         8.45        9.74
EVA1-PMAM    Initial     1        14.52       14.71
                         2        14.67       14.71
                         3        14.95       14.71
             Final       1        12.85       12.70
                         2        12.01       12.70
                         3        13.26       12.70
EVA2-PMAM    Initial     1        16.62       15.11
                         2        13.76       15.11
                         3        14.95       15.11
             Final       1        10.53       10.37
                         2        10.19       10.37
                         3        10.38       10.37

                                     % decrease
                         Standard    in
Sample ID    Condition   deviation   stability

HMA          Initial     0.35        34
                         0.35        34
                         0.35        34
             Final       1.39        34
                         1.39        34
                         1.39        34
LDPE1-PMAM   Initial     1           30
                         1           30
                         1           30
             Final       0.53        30
                         0.53        30
                         0.53        30
LDPE2-PMAM   Initial     1.52        32
                         1.52        32
                         1.52        32
             Final       1.21        32
                         1.21        32
                         1.21        32
EVA1-PMAM    Initial     0.21         7
                         0.21         7
                         0.21         7
             Final       0.63         7
                         0.63         7
                         0.63         7
EVA2-PMAM    Initial     1.43        32
                         1.43        32
                         1.43        32
             Final       0.17        32
                         0.17        32
                         0.17        32

Table 4. Moisture sensitivity test (Lottman Test)

                                                 Average
Sample ID    Condition   Sample no.   ITS (kN)   ITS (kN)

HMA          Dry         1            10.74      10.77
                         2            10.77      10.77
                         3            10.82      10.77
             Wet         1             6.37       6.69
                         2             7.73       6.69
                         3             5.98       6.69
LDPE1-PMAM   Dry         1            10.48      10.07
                         2            10.00      10.07
                         3             9.90      10.07
             Wet         1             3.45       3.60
                         2             3.98       3.60
                         3             3.38       3.60
LDPE2-PMAM   Dry         1             9.63       9.50
                         2             9.36       9.50
                         3             9.50       9.50
             Wet         1             5.99       5.39
                         2             5.92       5.39
                         3             4.28       5.39
EVA1-PMAM    Dry         1            10.52      10.56
                         2            10.22      10.56
                         3            10.96      10.56
             Wet         1             8.12       8.41
                         2             8.82       8.41
                         3             8.31       8.41
EVA2-PMAM    Dry         1            11.76      11.31
                         2            10.77      11.31
                         3            11.40      11.31
             Wet         1             4.85       5.85
                         2             7.07       5.85
                         3             5.63       5.85

                         Standard
Sample ID    Condition   deviation   TSR

HMA          Dry         0.04        62.11
                         0.04        62.11
                         0.04        62.11
             Wet         0.92        62.11
                         0.92        62.11
                         0.92        62.11
LDPE1-PMAM   Dry         0.31        35.75
                         0.31        35.75
                         0.31        35.75
             Wet         0.32        35.75
                         0.32        35.75
                         0.32        35.75
LDPE2-PMAM   Dry         0.13        56.73
                         0.13        56.73
                         0.13        56.73
             Wet         0.96        56.73
                         0.96        56.73
                         0.96        56.73
EVA1-PMAM    Dry         0.37        79.64
                         0.37        79.64
                         0.37        79.64
             Wet         0.36        79.64
                         0.36        79.64
                         0.36        79.64
EVA2-PMAM    Dry         0.50        51.72
                         0.50        51.72
                         0.50        51.72
             Wet         1.12        51.72
                         1.12        51.72
                         1.12        51.72

Table 5. Rutting coefficients

Mix type     Anti log of intercept   Slope    [R.sup.2]

HMA          0.0045                  0.6876   0.9957
LDPE1-PMAM   0.0082                  0.5277   0.997
LDPE2-PMAM   0.0123                  0.4635   0.975
EVA1-PMAM    0.037                   0.2657   0.9686
EVA2-PMAM    0.0188                  0.3957   0.987
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Author:Hussein, Ibnelwaleed A.; Al-Abdul Wahhab, Hamad I.; Iqbal, Mohammad H.
Publication:Canadian Journal of Chemical Engineering
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Date:Aug 1, 2006
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