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The Marshall Mix design is one of the most widely used methods for designing and evaluating hot asphalt mixes globally, and the main Marshall Test focuses are stability and flow. Two standard curing methods are normally followed to elevate the temperature of testing samples; these involve immersing the samples in 60°C water or placing the samples in an oven at 60°C. These standard curing methods may not simulate the actual state of heating of asphalt pavement in the field, however. In this research, a new curing method that includes insulating the samples before immersion in hot water is thus introduced and compared with the two standard curing methods. During immersion, the water temperature is increased to 60°C and the core temperature of the insulated samples determined. Three sets of Marshall Samples were prepared and cured using the outlined methods; each set consisted of 18 specimens of 101 mm diameter and 63.5 mm height. All specimens were tested using the Marshall Test for stability, flow, and Marshall Stiffness. The set mean results showed that the oven cured samples demonstrated the highest stability values, followed by the standard water cured samples, while the insulated samples exhibited the lowest stability values. The oven cured samples also exhibited higher Marshall Stiffness Index (MSI) values than the other curing methods. However, one-way ANOVA (single factor) testing demonstrated that these differences were not statistically significant.

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IOP Conference Series: Materials Science and Engineering

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The Influence of Curing Methods on Marshall Stability and Flow

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3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

IOP Publishing

doi:10.1088/1757-899X/671/1/012132

The Influence of Curing Methods on Marshall Stability and

Flow

Talal H. Fadhil1 , Rahel Khalid Ibrahim2 , and Hardi Saadullah Fathullah3

1 Faculty of Engineering, University of Anbar, Ramadi, Anbar, Iraq

Email talalmudadi1@gmail.com

2 Faculty of Engineering, Koya University, University Park, Kurdistan Region of Iraq

Email: rahel.khalid@koyauniversity.org

3 Faculty of Engineering, Koya University, University Park, Kurdistan Region of Iraq

Email: hardi.saadullah@koyauniversity.org

Abstract. The Marshall Mix design is one of the most widely used methods for designing and

evaluating hot asphalt mixes globally, and the main Marshall Test focuses are stability and flow.

Two standard curing methods are normally followed to elevate the temperature of testing samples;

these involve immersing the samples in 60°C water or placing the samples in an oven at 60°C. These

standard curing methods may not simulate the actual state of heating of asphalt pavement in the field,

however. In this research, a new curing method that includes insulating the samples before

immersion in hot water is thus introduced and compared with the two standard curing methods.

During immersion, the water temperature is increased to 60°C and the core temperature of the

insulated samples determined. Three sets of Marshall Samples were prepared and cured using the

outlined methods; each set consisted of 18 specimens of 101 mm diameter and 63.5 mm height. All

specimens were tested using the Marshall Test for stability, flow, and Marshall Stiffness. The set

mean results showed that the oven cured samples demonstrated the highest stability values, followed

by the standard water cured samples, while the insulated samples exhibited the lowest stability

values. The oven cured samples also exhibited higher Marshall Stiffness Index (MSI) values than

the other curing methods. However, one-way ANOVA (single factor) testing demonstrated that these

differences were not statistically significant.

Keywords: Asphalt concrete, Curing methods, Insulated samples, Marshall test, and Marshall

stiffness

1. Introduction

The Marshall Mix design concept was developed initially by a highway engineer in the

Mississippi Highway department named Bruce Marshall in 1939; it was then modified by the

USA Corps of Engineers in 1948 and standardized by the American Society for Testing and

Materials (ASTM) under the designation ASTM D1559 in 1958 (Preston, 1991, Brown et al.,

2001). The main standard test was later divided into two standard tests, ASTM D6926, used to

prepare the moulds for asphalt concrete, and ASTM D6927, which determines the stability and

flow of bituminous mixtures using Marshall apparatus. The main outputs from Marshall

apparatus testing are stability ratings, which indicate the maximum resistance of an asphalt

concrete sample to an external diametrical load applied at a rate of 50.8 mm/min (2 in/min), and

flow, recorded in 0.25 mm (0.01 in) increments, which represents the plastic deformation of the

sample at the maximum applied load (Institute, 2007).

The Marshall Method has acquired great significance as a method for design and evaluation of

the Hot Mix Asphalt (HMA) used in airports and highways. Alongside its suitability for different

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

IOP Publishing

doi:10.1088/1757-899X/671/1/012132

types of gradations such as dense graded and stone matrix asphalt, its applicability in both

laboratory mix design and field control processes is also relevant (Roberts et al., 2004). Due to its

application breadth, the Marshall Method, despite some shortcomings, is the most widely used

mix design method in the world (NHI, 2014, Sadid et al., 2010).

In order to determine the stability and flow of an asphalt concrete sample, whether prepared in lab

or extracted from the field, the temperature of sample needs to must be elevated to a standard

value of 60°C, which is intended to represent the maximum pavement temperature that may be

reached in summer (Roberts et al., 2004). For this purpose, two standard curing methods (where

curing refers to elevating the asphalt concrete samples to standard testing temperature of 60±1 ᵒC)

are generally recommended. The first, which is the prevalent standard method (PSM) used

worldwide, involves the specimen being immersed in a water bath with a constant temperature of

60±1 ᵒC (140±2 ᵒF) for 30 to 40 minutes. In the second method, the samples are cured in the oven

with a standard temperature of 60±1 ᵒC (140±2 ᵒF) for 120 to 130 minutes (ASTM D6927, 2015).

The influence of water presence in asphalt concrete samples (lab conditions) or in asphalt

pavement (field conditions) differs. In the laboratory, the tested samples are immersed in hot

water of 60 °C for 30 to 40 minutes and then directly loaded at a continuous constant rate up to

failure. During the immersion time, some of the hot water naturally intrudes inside the tested

specimens, which may affect the results of Marshall Stability testing. The effect of water in the

field, however, basically depends on the reaction of the water to cyclic loading. When an asphalt

concrete pavement is saturated, it is subjected to an increasing and decreasing in pore pressure

due to the cyclic loading and unloading from the motion of vehicles (Islam clic and Tarefder,

2014). In asphalt concrete pavement, some of the pores are interconnected, permitting the water

to move through the pavement. Dynamic traffic loads can thus cause high water pressure within

all pores that are filled by water, as shown in Figure 1 (Carl Thodesen and Hoff, 2010).

Figure:1. Pore pressure development in asphalt concrete pavement due to vehicle motion (Varveri et al., 2014)

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

IOP Publishing

doi:10.1088/1757-899X/671/1/012132

The heating process for asphalt pavement in the field in summer is mainly due to direct sun heat

on the surface layer of the pavement, while the parts below the surface are heated by conductivity

without direct contact with the hot air. In the lab, heating is conducted by immersing the tested

samples in hot water for 30 to 40 minutes prior to commencing loading. Both the heating methods

and loading intensity are thus different from site to lab, so the idea of heating the insulated

samples in the lab without allowing direct contact with hot water to better simulate the real

conditions in the field by allowing all the parts of the sample to be heated by conductivity seems

to offer a reasonable alternative to the two standard curing methods, in which the tested samples

suffer from direct contact of hot water or hot air.

In this research, three methods of curing were thus used to elevate the temperature of samples to

60 °C (standard test temperature):

1. Immersing the samples in water for 30 to 40 minutes (Standard Marshall Procedure, also

known as the Prevalent Standard Method (PSM)).

2. Putting the samples directly in the oven for 120 to 130 minutes (Alternative standard

procedure).

3. Immersing insulated samples (IS) in water for 45 minutes (Proposed procedure).

2. Aim of the Study

The aim of this research is to compare Marshall Test results to determine the influence of the three curing

methods on the Marshall stability and flow values of tested samples.

3. Materials and Experimental Work

3.1 Materials

The materials used in this research include aggregate with different particle sizes, filler, and

asphalt. The source of the aggregate was the Ifraz query in Erbil, Iraq. The physical properties of

the aggregates used in this research are listed in Table 1. Limestone dust was used as a filler in this

work, as this is commonly used for HMA production in Erbil; its properties are shown in Table 2.

The asphalt cement used, which has a penetration of 40 to50, is from the Dora refinery, Baghdad;

its physical properties are tabulated in Table 3.

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

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doi:10.1088/1757-899X/671/1/012132

Table:1. Physical properties of the used aggregate

Crushed Fine Agg.

< Sieve No.4

Los Angles Abrasion value %

*Iraqi Standard Specifications for Roads and Bridges

Table: 2. Properties of the used filler

100 100

ASTM D546-05

0.600 [No.030]

Other Engineering properties

* Iraqi Standard Specifications for Roads and Bridges

Table:3. Properties of asphalt cement

Units

Test designation Test Properties No.

40/50 49

Penetration, 25 °C,100g,5sec 1

Ductility at 25°C ,5cm/min

* Iraqi Standard Specifications for Roads and Bridges

3.2 Experimental Work

A Job Mix Formula (JMF) was prepared from the materials noted above as shown in Table 4.

Aggregate gradation was determined according to the midpoint of gradation in ASTM D3515-

01(D-5), being the same gradation of the surface course Type IIIA of Iraqi Standard Specifications

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doi:10.1088/1757-899X/671/1/012132

for Roads and Bridges (ISSRB) (SORB, 2003). Figure 2 shows the gradation used in this research.

The steps of the experimental procedure are exhibited in the flow chart shown in Figure 3.

Table:4. Job Mix Formula Properties

Property Results

AASHTO Criteria &

SORB2003

Optimum Asphalt Content (% of total mix)

Figure: 2. Gradation of job mix formula ( ASTM D3515-01(D5) & SORB, 2003)

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

IOP Publishing

doi:10.1088/1757-899X/671/1/012132

Figure: 3. Flow Chart of Experimental Procedure Steps

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

IOP Publishing

doi:10.1088/1757-899X/671/1/012132

3.2.1 Preparation and Testing of the Standard Marshall Samples

Three sets of asphalt concrete samples were prepared according to ASTM D6926 - 10. Each set

consisted of 18 specimens of 101 mm in diameter and 63.5 mm in height (4 in. diameter and 2.5

in. height) compacted by using 75-blow/face compaction. Every set was divided into two groups:

Group No.1 (G1) was comprised of 12 samples prepared only from crushed aggregate, in order to

understand the effect of changing any fractions of crushed aggregate on the results of stability and

flow, while group No.2 (G2) consisted of six samples prepared by replacing crushed materials with

those passing 2.38 mm (No. 8) and 0.3 mm (No. 50) sieves with natural sand. The bulk specific

gravity for the specimens was determined according to ASTM D 2726 – 10.

Finally, each sample in each set was cured using one of the three different curing methods

mentioned above and all specimens were subjected to the Marshall testing machine to determine

their Marshall Stability and flow according to ASTM D 1559– 82. The air voids of specimens were

calculated by applying the Rice method or theoretical maximum specific gravity as per ASTM

D2041 – 03 procedures.

3.2.2 Insulated Samples (IS)

In order to discover how much time was sufficient to elevate the temperature of the core of

tested samples to standard test temperature (60°C), an additional nine asphalt concrete samples

were prepared according to JMF specifications. The centres of these samples were drilled with

holes of 4mm diameter up to the mid distance of the total sample height, thus reaching the core.

Thermo-couple probes were embedded inside the hole touching the bed of the hole (at depth of

32mm from the surface) and then the hole was refilled with molten asphalt. These samples which

wrapped in cling film to create an insulated sample (IS), including a thermo-couple probes,

before being immersed in 60°C water. The temperature with respect to time was recorded each 5

minutes using a digital thermometer, as shown in Figure 4.

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

IOP Publishing

doi:10.1088/1757-899X/671/1/012132

Figure: 4. Drilling and embedding thermo-couple in the core

of insulated asphalt concrete sample prior to wrapping.

The average recorded temperature rise versus time for all IS are shown in Figure 5. From this

figure, it can be determined that for the inside temperature for the IS to reach 60°C, 40 to 45

minutes of immersion is required. This duration was thus adopted for curing all IS in 60°C water

baths in this research. Once this time is was determined, 18 asphalt concrete samples were

compacted and wrapped in cling film to ensure the complete isolation of the samples from the

heating water (Fig.6). Before conducting the Marshall test, the insulation film was removed from

the insulated and heated samples.

Figure:5. Temperature rise via time relationship for the

core of insulated asphalt concrete samples

3rd International Conference on Engineering Sciences

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doi:10.1088/1757-899X/671/1/012132

Figure:6. Wrapping samples in cling film

3.2.3 Oven cured samples

Following the second standard test method, an oven is used to elevate the sample temperature

to 60°C in a dry condition, which creates some difficulties. The main difficulty is adjusting the

temperature inside the lab oven to a constant 60°C, as any opening of the oven door causes a

dramatic drop of the temperature inside the oven and the available lab ovens were insufficiently

accurate to ensure temperature maintenance. Another difficulty was the long time (120 to 130

min) needed to elevate the sample temperatures to the standard value. To overcome some of these

difficulties, a standard manufactured instrument as used for rutting tests, shown in Fig.7 and

made by the MATEST Company, was used for this purpose prior to conducting the Marshall

Test.

Figure:7. MATEST Rutting test instrument used as an oven

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

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doi:10.1088/1757-899X/671/1/012132

4. Results and Analysis

4.1 Stability and flow

Figures 8 and 9 show the mean of stability results for specimens in G1and G2, respectively,

including the error bars of the standard deviation. Table 5 gives the average results for Marshall

Stability and flow for each group .

Figure: 8. Average stability in kN for G1 samples subjected to different curing methods

Figure: 9. Average stability in kN for G2 samples subjected to different curing

methods

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

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Table:5. Means of Test results for tested groups subjected to three curing methods

Properties Oven Cured

( in air)

( in water)

The stability results of specimens in group G1, for specimens cured by oven, PSM, and

insulated curing methods, respectively, were 12.88, 12.49, and 11.9 kN, while, for group G2, the

specimens cured by oven, PSM, and IS produced stability values of 10.06, 9.78, and 9.44 kN,

respectively. The stability results of G1 were higher than those of G2; the main reason for this

variation is due to the use of crushed aggregates in preparing G1 specimens, while in G2

specimens, crushed sand passing 2.36mm and 0.3mm sieves was replaced by natural sand. It is

well known that crushed aggregates with angular ends and rough textures lead to higher

interlocking between aggregate particles than the rounded ends of natural sand, hence giving

lower stability results.

The slightly higher Marshall stability results for oven cured specimens, as compared to PSM,

are due to the direct exposure to hot air inside the oven over a long time (120 to 130 minutes),

which results in the evaporation of some of the volatile materials from the asphalt component,

leading to some aging of the specimens so that they become more stiff and give higher stability

results.

The PSM cured samples, immersed in hot water of 60 °C for 30 minutes prior to the test,

showed quite high stability results as compared to IS. The presence of additional hot water inside

some voids of the PSM samples during Marshall loading may create extra pore pressure, unlike

IS samples whose voids are free from any water, leading to slight increases in the Marshall

Stability values. It should be mentioned that the loading rate for the Marshall machine is 50.8

mm/min, which is high enough that the trapped water inside a sample cannot be drained quickly

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

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doi:10.1088/1757-899X/671/1/012132

and easily during load application. Moreover, the amount of hot water absorbed during the curing

process was 6.59 grams, compared to 4.6 grams of water at 25 °C, as shown in Figure 10.

Figure:10. Comparison between absorption of hot and 25°C water by prepared samples

Another empirical concept determined from the Marshall Test, which is sometimes used to

distinguish and evaluate asphalt mixtures, is known as the Marshall Stiffness Index (MSI) or

Marshall Quotient (MQ) (Chowdhury and Button, 2002; Roberts et al., 2004). MSI is defined as

the ratio of Marshall Stability in kN to the sample's flow in mm. Higher MSI values indicate stiffer

mixtures, offering higher resistance to permanent deformation (Zhang et al., 2004). This concept

is well known and used by some European engineers and is also used as a standard specification

by many transportation agencies including the Ministry of Malaysian Works and the South African

National Roads Agency, which have adopted values of 2000 N/mm and 2500 N/mm as a minimum

allowable MSI of asphalt concrete mixture in their specifications, respectively (Malaysia, 2008,

South African Agency, 2013). Lees (1987) considered that the value of MSI should not be less than

2.1kN/mm, and many researchers have thus adopted this value in their research (Rasel et al., 2011;

Sobhan et al., 2011). Fatih Hattatoglu et al. (2015) further used an Artificial Neural Network tool

to model the MQ of hot mixes.

6.59

4.6

Absorbed Hot

water(gm)

Absorbed Cold

water(gm)

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

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doi:10.1088/1757-899X/671/1/012132

The MSI values for the specimens in this test are shown in Figure 11. Here, the MSI values are

more than 2.1kN/mm and thus within the specification of Ministry of Works Malaysia (Malaysia,

2008) and as recommended by Lees (Lees, 1987). The MSI results indicate that the samples have

appropriate resistance to permanent deformation. However, the oven cured samples showed the

highest MSI values among all curing conditions followed by PSM cured samples, while the

insulated samples had the lowest MSI values.

Figure:11. Marshall stiffness index values for G1 and G2 samples

4.2 Analysis of variance (ANOVA)

In order to verify that the differences observed between the means of the main outputs of the

Marshall Test were actually due to the use of different curing conditions to elevate the

temperature of samples, and not laboratory artefacts or sample preparation, statistical analysis

of variance, ANOVA was conducted using Microsoft Excel with a 95% confidence interval.

Two hypotheses for the two-tailed test were set:

● H1: the curing condition has a significant effect on the output of the Marshall Test

● H0: the different curing conditions produce similar results.

The proposed hypothesis would be accepted if the P -value were smaller than the significance level

(ߙ ), which in this study is 0.05 as long as the F-statistic is greater than the F-critical value.

Otherwise, the null hypothesis is accepted. Tables 6 to 9 present the variance analyses of the

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

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doi:10.1088/1757-899X/671/1/012132

stability and flow of different groups based on curing condition. It can be seen from those tables

that the P -values are greater that the significance level (0.05) and that the F-stat values are smaller

than F-crit. Thus, the proposed hypothesis must be rejected, and the different curing conditions

used to elevate the sample temperatures assumed to not have a significant effect on the output of

the Marshall Test.

Table: 6. ANOVA single factor between the different curing conditions and stability values of G1.

Table: 7. ANOVA single factor between the different curing conditions and stability values of G2.

Table :8. ANOVA single factor between the different curing conditions and flow values of G1.

Table: 9. ANOVA single factor between the different curing conditions and flow values of G2.

3rd International Conference on Engineering Sciences

IOP Conf. Series: Materials Science and Engineering 671 (2020) 012132

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doi:10.1088/1757-899X/671/1/012132

However, replacing the crushed stone with natural sand leads to a significant effect on the stability

and flow values as measured in the Marshall test, as can be seen from the P -values in Tables 10

and 11. The P -values in tables 10 and 11 are smaller than the significance level (0.05), and the F-

stat values are greater than F-crit.

Table:10. ANOVA single factor between the crushed stone and natural sand on stability values.

Table:11. ANOVA single factor between the crushed stone and natural sand on flow values.

5. Conclusions

The following conclusions can be derived from this research:

1- Marshall Test results indicated that oven cured samples show the highest stability values,

followed by PSM cured samples, while the insulated samples exhibited the lowest stability

values. However, ANOVA testing showed that these differences were not statistically

significant.

2- The intrusion of hot water into PSM samples increased the stability values as compared

with insulated samples.

3rd International Conference on Engineering Sciences

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3- The oven cured samples become stiffer due to the evaporation of volatile materials, which

gave higher stability values and lower flow as compared with samples cured by other two

methods, resulting in higher MSI values.

4- The suggested curing method, using insulated specimens, seems to simulate real conditions

in the field by eliminating hot water absorption (in PSM) and hot air effects as in the second

standard curing method .

5- The Marshall Stability values gained by using the prevalent standard curing method PSM

are higher than those of actual state (insulated) samples by approximately 5% , which is a

considerable percentage considering highway agency requirements.

6. Recommendations:

The main recommendations from this research are thus

1- Further research regarding the effect of curing methods on Marshall stability and

Stiffness Index is highly recommended to consider different types of asphalt mixture

parts such as binder and base course mixes.

2- Using insulation in curing the asphalt concre te specimens in the lab offers more reliable

Marshall Stability results than the other curing methods.

3- If the PSM is used, in order to account for the reduction in stability, it is recommended

to increase the minimum stability values by 1 KN over specification requirements .

7. Acknowledgements

The authors would like to give their thanks and appreciations to the Faculty of Engineering, Koya

University for their support in giving us permission to use the highway engineering labs to

accomplish this work.

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... The stability value is used as an indicator of strength in resisting external loads. Fadhil and Ibrahim [28] proposed that the Marshall test can be used to evaluate asphalt designs, especially HMA, for applications on highways. Its application has also been employed to design asphalt mixtures worldwide [29]. ...

Amin Chegenizadeh
Pak Jing Shen
I S Arumdani
Hamid Nikraz

Bitumen is subjected to cracks and damage during its service life. Adding a material with the potential to increase the durability of bitumen can expand its service life and reduce maintenance costs. Previous studies indicate that adding crumb rubber into asphalt has a positive effect on the performance of the mixture. Using crumb rubber may solve environmental problems due to vehicle tire waste disposal by reducing maintenance costs needed to increase asphalt's strength. Some studies have investigated the effect of bitumen mixed with crumb rubber; however, it seems that the effect of different types of rubber mixtures used has been overlooked. Therefore, this study aims to better understand the effects of the increasing amount of rubber addition in various types of asphalt mixtures and determine the optimal mixture that could be used in road construction. A series of experiment was conducted, incorporating various tests (such as Marshall stability, rutting, and fatigue), to test various mixtures of asphalt in the form of dense-graded asphalt (DGA), fine gap-graded asphalt (FGG), gap-graded asphalt (Stone Mastic Asphalt, SMA), and open-graded asphalt. The amount of added crumb rubber was 25% by weight of bitumen. All mixtures were classified as superior in rutting and fatigue resistance, since they all reached a maximum depth of rutting less than 15 mm and generated two times more failure cycles compared to the conventional asphalt. The most optimal performance asphalt mixture was showed by the SMA10 mixture, resulting in a minimum rut depth of less than 1.2 mm and producing 750% more fatigue cycles than conventional asphalt. The result indicates that the addition of 25% of the rubber particles in the binder can increase the properties and durability of asphalt mixtures.

Soheil Heydari
Ailar Hajimohammadi
Nioushasadat Haji Seyed Javadi
Nasser Khalili

Waste plastics are a growing concern for society and need sustainable strategies to deal with. One of the promising strategies is to use them as a replacement of virgin polymers for asphalt mixture modifications. This article compares the dry and wet methods of asphalt modification with waste plastics to understand the critical factors affecting the modification and shed light on the gaps of knowledge. Marshall test results reveal that both the nature of the waste plastics and the way they are introduced into the asphalt mix have significant impacts on the performance of the resultant asphalt mixture. However, in general, plastic wastes can increase the Stability and decrease the Flow number.

In this paper, a new moisture conditioning protocol which attempts to distinguish the contributions of long- and short-term moisture damage, i.e. moisture diffusion and cyclic pore pressure generation, in asphalt mixtures is presented. The capability of the proposed protocol to rank various asphalt mixtures of known field performance for their short- and long-term sensitivity to moisture is evaluated on the basis of the Tensile Strength Ratio. Asphalt specimens with different types of aggregates and asphalt binders were conditioned by various combinations of water bath immersion and cyclic pore pressures by means of the Moisture Induced Sensitivity Tester. The results show that the proposed conditioning protocol can be used to evaluate the moisture susceptibility of asphalt mixtures and distinguish among mixtures with different moisture damage characteristics. In addition, it is shown that the use of cyclic pore pressures has a significant effect and can be used as an accelerated moisture conditioning procedure.

Waste PVC that has been used previously as mineral water bottles, pipes, electrical fittings etc. are biologically non-degradable and posed an ominous environmental problem which led to severe environmental impact. But molten PVC has a binding property which can be reused with bitumen to reduce the cost of bituminous mix. At the same time the recycling of waste PVC save disposal sites and to reduce the amount of inert drawn from quarries, which often lead to environmental problems. This paper describes the investigation of the properties of bitumen mixed with PVC (2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5% and 20% by the weight of bitumen) at optimum bitumen content and to check the design criteria of bituminous mixes using this bitumen-PVC binder. The investigation concentrated on the test of strength properties of coarse aggregates and Marshall Design properties of bituminous mixes according to the test procedure specified by AASHTO. Some of the measured properties of bituminous mix with bitumen-PVC binder used in this study were within the acceptable recommended limits. On the basis of experimental results of this investigation, it is concluded that the dense graded bituminous mixes with bitumen containing PVC up to 10% can be used for bituminous pavement construction in warmer region from the stand point of stability, stiffness and voids characteristics.

M.A. Sobhan
S.A. Mofiz
H. M. Rasel

Waste concrete aggregate (WCA) refers to aggregates that have been used previously in cement concrete structures. After many research it had been concluded that WCA can be used in bituminous concrete. In bituminous concrete mix, there is a wide scope for varying the gradation of aggregate to obtain a good mix without affecting the durability of pavement. Bituminous concrete mixes with WCA in accordance with different gradations were studied. Behavior of bituminous concrete mixes with WCA is also investigated with two different compactive energy, one for medium traffic and another for heavy traffic. The research program concentrated on the Marshall design criteria for bituminous mixes. A dense grading with 25 mm maximum size is found to give the most satisfactory result from the stand point of stability, stiffness, deformation and voids characteristics. Test results reveal that the bituminous concrete with WCA can give satisfactory results when they are constructed using dense gradation and medium compaction.

The effect of the Superpaver defined restricted zone on hot-mix asphalt rutting performance was evaluated. One gradation that violated the restricted zone (TRZ) and two gradations that did not violate the restricted zone (BRZ and ARZ) were evaluated. Evaluated mixes represented a range of maximum aggregate sizes (MASs), design traffic levels, and aggregate types. Three laboratory tests—asphalt pavement analyzer, rotary-loaded wheel tester, and Marshall test—were used to evaluate the rutting performance. From the analysis, it was found that mixes with gradations violating the restricted zone performed similarly to or better than the mixes with gradations passing outside the restricted zone with respect to laboratory rutting tests. This conclusion was drawn from the results of experiments with 12.5-, 19.0-, and 25.0-mm MAS gradations at Ndesign (design number of gyrations) values of 100, 75, and 50 gyrations. This conclusion is confirmed and supported by the recently completed NCHRP Project 9-14: The Restricted Zone in the Superpave Aggregate Gradation Specification. The results also showed that rutting performance of mixes having gradations below the restricted zone, which was commonly recognized to be rut resistant, appeared to be more sensitive to aggregate properties than mixes having gradations above or through the restricted zone.

Standard Specifications for Roads and Bridges. R9. Baghdad, Iraq: State corporation for roads and bridges SORB

ISCRB, 2003. Standard Specifications for Roads and Bridges. R9. Baghdad, Iraq: State corporation for roads and bridges SORB.

Standard specification for road works, section 4, flexible pavement

P Malaysia

MALAYSIA, P. 2008. Standard specification for road works, section 4, flexible pavement. Jabatan. Kerja Raya Malaysia, Kuala Lumpur.

Hot mix asphalt materials, mixture design and construction

F L Roberts
P S Kandhal
E R Brown
D.-Y Lee
T W Kennedy

ROBERTS, F. L., KANDHAL, P. S., BROWN, E. R., LEE, D.-Y. & KENNEDY, T. W. 2004. Hot mix asphalt materials, mixture design and construction, MaryLand, USA, NCAT.

Study of Water Effects on Asphalt and Porous Asphalt