AIP Conference Proceedings 2114, 040012 (2019); https://doi.org/10.1063/1.5112441 2114, 040012

© 2019 Author(s).

Skid resistance performance againsttemperature change of hot-mix recycledasphalt pavement with added crumb rubberCite as: AIP Conference Proceedings 2114, 040012 (2019); https://doi.org/10.1063/1.5112441Published Online: 26 June 2019

Audy Dwi Putra, Sigit Pranowo Hadiwardoyo, and Raden Jachrizal Sumabrata

Skid Resistance Performance against Temperature Change of Hot-Mix Recycled Asphalt Pavement with Added Crumb

Rubber

Audy Dwi Putra1, Sigit Pranowo Hadiwardoyo1, a), and Raden Jachrizal Sumabrata1

1Department of Civil Engineering, Universitas Indonesia, Depok, West Java, Indonesia

a) Corresponding author: sigit@eng.ui.ac.id

Abstract. Skid resistance is the result of friction between the road surface and vehicle tires. Vehicle safety is affected by the skid resistance value, and increased road surface friction can be achieved at a high slip resistance. In the present study, crumb rubber (CR) and Refined Buton Asphalt (RBA) blend is examined as additives for recycled asphalt mixtures, known as reclaimed asphalt pavement (RAP) in gap-graded aggregates. The percentages of CR used were 0% and 1.0%, with two sample types namely before and after being crossed by the vehicle wheel. Skid resistance testing was carried out using a British pendulum tester at temperatures of 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C, which are the most common road surface temperatures in Indonesia. The test values were derived from the British pendulum number and skid number (SN). The effect of the CR on the SN value is not significant, with an increase in the SN value at a temperature of 45°C, which then decreases at a higher temperature. The addition of CR affects the SN value only at low temperatures. This is consistent with the performance of the gap-graded RAP mixture, particularly in terms of the Marshall stability compared to the asphalt mixture without CR. The RAP mixture with the gap-graded aggregate and the addition of CR exhibits no impact on the SN value of the wheel trajectory resistance owing to temperature changes.

INTRODUCTION

Flexible road pavement surfaces created by asphalt concrete mixtures may have different surface roughness, depending on the asphalt and aggregate composition. Vehicle safety on highways may be evaluated according to several parameters, including road resistance to slippage, which is an important indicator [1]. The safety of road users must be of particular concern so that the road functions and roles are optimally beneficial. Skid resistance describes the contribution of the road surface to the friction force on the road pavement with vehicle tires. It can be defined as the vertical and horizontal forces occurring as a result of the sliding of a tire along the road surface [2], and skid resistance that undergoes an increase in temperature exhibits a decreased Skid Number (SN) [3].

Numerous land transportation accidents in Indonesia occur during the rainy season. This phenomenon has become a topic of major interest to road engineers in wet, tropical regions. In order to minimize the incidences of road accidents in wet weather, institutions involved in road construction are responsible for regular maintenance of the road network, including measuring the pavement slip resistance and activating preventive or corrective measures if necessary to maintain the road pavement as well as safety for driving in wet weather [4].

In dry pavement surface conditions, the existing surface roughness can eliminate the amount of slip in most situations. However, when the pavement surface is wet, skid resistance will be reduced significantly depending on the pavement conditions, or the pavement may not have sufficient skid resistance to overcome certain conditions. Therefore, road safety testing and research procedures related to the latest skid resistance measurements focus on the pavement in wet conditions [5].

The skid resistance value is an important pavement evaluation parameter because [6]: 1. Inadequate slip resistance may cause accident incidents related to slipping conditions. 2. Most road management institutions have an obligation to provide road safety for users.

Exploring Resources, Process and Design for Sustainable Urban DevelopmentAIP Conf. Proc. 2114, 040012-1–040012-8; https://doi.org/10.1063/1.5112441

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3. The measurement of skid resistance can be used to evaluate various material types in road construction practices.

The Reclaimed Asphalt Pavement (RAP) is a residual material derived from the results of stripping damaged road surfaces for maintenance and rehabilitation purposes [7]. RAP is being used increasingly with the aim of preserving the environment against the needs of road pavement materials such as asphalt and aggregates. The recycling of road pavement materials may result in new methods of pavement design by saving material, money, and energy. Aggregates and binders from old asphalt pavements may be used as valuable materials even though the road pavement has reached the end of its service life. A pavement that has been used for several years can be combined with aggregates and virgin asphalt to produce a new asphalt mixture. This method has proven to be economical and effective, and offers benefits in preserving the environment [8].

At present, alternative materials are used as additives for road pavements from asphalt mixtures, including Crumb Rubber (CR), commonly known as Crumb Rubber Modifier (CRM). The increased use of CRM in asphalt pavements requires an improved understanding of its effects on the physical, chemical, and performance properties of CRM binders. In general, the addition of CRM to asphalt binders is intended to improve certain properties, such as reducing the temperature susceptibility of adhesion to the binder [9]. The use of zeolite additives has demonstrated benefits for warm asphalt mixtures. A warm mix asphalt with zeolite as an additive obtained a higher SN value than mixes without zeolite [10].

Hot climates and heavy traffic occur on various roads in Indonesia, which often results in extensive fatigue cracking and permanent deformation. In such cases, it is necessary to modify the asphalt mixture to overcome this extreme condition. Modification of asphalt mixtures can be achieved by using polymer materials, but this approach is very expensive. Another alternative that can be selected is the use of Refined Buton Asphalt (RBA), which is a modified material processed from natural rock asphalt available on the Buton Island, Indonesia [11].

Based on this understanding, this research was conducted to evaluate the skid resistance performance of hot asphalt recycled mixtures between asphalt and aggregate, with the addition of CR and RBA. Tests were carried out on temperature changes, so that the goal of developing sustainable materials in road pavement construction can improve road safety.

MATERIALS AND METHODS

In the present study, several material types were combined in hot asphalt mixtures, consisting of new aggregates, RAP aggregates, asphalt from RAP, CR, and RBA.

Aggregates

New aggregates were obtained from the stone breaking process in the Sudamanik quarry, West Java, Indonesia. This aggregate quality refers to the aggregate property standards issued by the Directorate General of Highways and Indonesian National Standards (SNI). It consists of three aggregate types: coarse, medium, and fine as shown in Table 1.

Reclaimed Asphalt Pavement (RAP)

The RAP was obtained from the process of stripping the Asphalt Concrete Wearing Coarse (AC-WC) layer on the Jakarta Outer Ring-Road (JORR) toll road in the Jakarta area. In this RAP, two materials are used as recycled asphalt and aggregate materials. Recycling of the hot-mix asphalt in this study uses aggregate, asphalt, and fillers from the road pavement layer that has been passed by a number of vehicles loads so that the aging process is demonstrated; therefore, it is necessary to replace the asphalt and aggregate processes. The RAP process aims to achieve a road pavement mixture with characteristics close to the previous hot-mix asphalt.

The use of RAP provides a mixture of aggregate asphalt with certain characteristics, and in general, old asphalt in the RAP is characterized by low penetration and high softening points, which means that its cohesiveness is lower than that of new asphalt. Certain methods are required to compensate for this aging phenomenon. It is necessary to add new asphalt that is very soft in order to produce a road pavement mixture that has a binder so as to be accepted by specifications, and in certain conditions, it is even necessary to increase the material characteristics [12].

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TABLE 1 Aggregate characteristics No. Laboratory test Method New aggregate RAP aggregate

Coarse/medium aggregate 1 Bulk specific gravity (Gsb) SNI 03-1969-1990 2.608 2.625 2 Surface saturated dry gravity (SSD) SNI 03-1969-1990 2.653 2.636 3 Apparent specific gravity (SG) SNI 03-1969-1990 2.732 2.656 4 Absorption (%) SNI 03-1969-1990 1.741 0.450 5 Los Angeles abrasion (%) ASTM C 131 25.36

Fine aggregate 1 Bulk specific gravity (Gsb) SNI 03-1979-1990 2.252 2.218 2 Surface saturated dry gravity (SSD) SNI 03-1979-1990 2.288 2.288 3 Apparent specific gravity (SG) SNI 03-1979-1990 2.337 2.386 4 Absorption (%) SNI 03-1979-1990 1.626 0.032 5 Passing no. 200 (%) SNI 03-1968-1990 20.00 10.84

Crumb Rubber (CR)

CR is the result of processing rubber material from used tires, and in certain uses, it is mixed with bitumen and known as CRM. CR is one type of pavement material that has been popular because it offers numerous advantages, including a decreased susceptibility to temperature; increased pavement age; reduced pavement damage, traffic noise, maintenance costs, and pollution; and improved environmental quality [13].

Two types of CR exist in the asphalt mixture, namely those resulting from the dry and wet processes. Conventionally, the dry process is achieved by adding CR as a material to the heated aggregate at ambient temperature prior to incorporating asphalt into the mixing process [14]. In this study, the CR is mixed using the dry process. The CR type used in this study is the results of refining granules of used rubber tires, which are then filtered with nos. 50, 100, and 200.

Retona

In the present study, natural asphalt from Buton Island, Indonesia is used. Buton is an island located in the southeast of Sulawesi, with natural rock asphalt resources known as Asphalt Buton. There are 300 million tons of Asphalt Buton supplies, spread over an area of 70,000 hectares. Asphalt Buton has an asphalt content of 20 to 30%, and the remainder is other minerals. This type of asphalt can be used directly or through a screening process to separate the asphalt from other minerals. This process begins with blasting rocks using dynamite, which produces material granules of approximately 20 mm in size.

One of the Asphalt Buton screening processes for obtain asphalt is known as RBA. This material is crushed with a hammer mill to reduce the particle size to 2.5 mm, and then forwarded to the chemical plant for bitumen extraction [15]. During this plant process, an acid-alkali chemical reaction occurs, whereby Asphalt Buton is processed with the help of the reaction process of inorganic compounds in order to obtain RBA (natural bitumen and filler) with different characteristics, according to user demands. Various types of bitumen RBA production are available, but depending on the number of inorganic compounds used in the process, the production cost increases [11].

Asphalt mixtures

The first testing process carried out consisted of the RBA and Virgin Asphalt tests, which continued with CR gradation testing. The RAP asphalt extraction test was conducted to separate the aggregate and bitumen so that each characteristic of the two materials could be established. The extraction tool used was the reflux extractor test, by means of the RAP being inserted into a heated tube filled with liquid Tricloro Etylen (TCE).

During the RAP mixing process with other additional materials, the RAP was softened by machine lubricant waste with a weight ratio of 11:4 in order to increase the penetration value. This softening process is referred to as seven days curing, wherein the RAP material is mixed with engine lubricant waste. The next process involved asphalt mixtures at 160°C, where all RAP material that had been conditioned to a certain penetration was mixed to

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obtain the optimal asphalt mixture. The mixture type used in this study was the specification of the gap-graded hot rolled sheet-wearing course (HRS-WC). The asphalt content used in this asphalt mixing included the addition of asphalt virgin 1.5 and RAP 6.1% asphalt, and the CR levels added were 0% and 1%.

TABLE 2 Asphalt characteristics Laboratory test Method Unit RBA RAP Penetration at 25oC, 100 g, 5 s SNI 06-2456-1996 0.1 mm 59.67 8.70 Penetration TFOT SNI 06-2456-1996 0.1 mm 52.68 Penetration asphalt with oil (4/11) SNI 06-2456-1996 0.1 mm 61.70 Softening point SNI-06-2434-1991 oC 50 72 Ductility at 25oC SNI-06-2432-1991 cm >100 4.20 Ductility TFOT SNI-06-2432-1991 cm >100 Specific gravity SNI-06-2441-1991 g/cm3 1.081 1.061 TFOT weight loss SNI-06-2440-1991 % 0.107 Solubility at TCE SNI 06-2434-1991 % 76.94 Viscosity (mixing temperature / temperature compaction) SNI 7729:2011 oC 152 / 140

Skid resistance test

The skid resistance represents the relationship between the vertical and horizontal forces that occur when a vehicle tires move along a pavement surface. The friction force between the tires and pavement surfaces is an essential component of pavement interaction for vehicle safety. Skid resistance provides the ability for vehicles to accelerate, maneuver, turn, and stop safely, including making a major contribution to reducing the risk of wet pavement surfaces and accidents arising from reduced road surface roughness [16]. Low-level friction is known to be one of the contributing factors to vehicle accidents. Movement at the tire rotation speed and the road surface characteristics at a certain friction level result in the possibility of tire slippage. A direct consequence of slippage is the loss of the vehicle ability to brake and maneuver, so that it may cause property damage and accidents [2].

The tool used in this research was the British Pendulum Tester (BPT), for measuring the friction characteristics from the pavement surface. BPT produces low-speed shear contact forces between standard rubber sliders with pavement surfaces, and calculates the friction properties by determining the kinetic energy loss from the slider when making contact with pavement surfaces [17]. The loss of kinetic energy is converted into friction force, which is then referred to as pavement friction and expressed by the British Pendulum Number (BPN). BPT offers ease of use and can provide friction and microtexture indicators at low speeds such as 10 km/h for all pavements, in both the field and laboratory. In this study, testing using BPT tools was carried out in the laboratory by modifying tools and samples [3].

The skid resistance testing using BPT tools was adjusted to the SNI 4427:2008 standard [18]. The test object was derived from the compaction of a wheel-tracking machine (WTM) with a size of 300 × 300 × 50 mm as shown in Fig. 1, and the test was carried out in the Pusjatan Bandung laboratory. The skid resistance test was conducted utilizing the WTM test results, by cutting the sample from the test into a smaller part with a size of 50 × 100 × 50 mm as shown in Fig. 2. The skid resistance testing was carried out in the Structure & Materials Laboratory, Civil Engineering Department, Faculty of Engineering, Universitas Indonesia. There were four sample types, namely asphalt mixture samples without CR, asphalt mixture samples with additional CR, asphalt mixture without CR crossed by WTM wheels, and asphalt mixture samples with additional CR crossed by WTM wheels. Each BPT sample type was tested using temperature variations of 25oC, 30oC, 35oC, 40oC, 45oC, and 50oC. The test was conducted by conditioning the sample in a water immersion bath from BPT modification until the sample surface temperature reached the measured temperature as shown in Fig. 3. Each test was carried out five times so that the average value of the skid resistance data could be obtained with the temperature variations.

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FIGURE 1. Compactor tool for WTM samples.

FIGURE 2. Forming sample size.

FIGURE 3. Modified British Pendulum Tester.

RESULTS AND DISCUSSION

The SN is a unit of road surface resistance, so a higher SN indicates greater pavement skid resistance. The SN is obtained from the conversion of the BPN, which is a number obtained from testing using the BPT. The BPN value needs to be corrected based on the standard deviation and temperature before being converted to the SN, which can be achieved by using equation (1).

9.69 - (BPN) 286.0SN (1)

Where, SN = Skid Number BPN = British Pendulum Number

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TABLE 3. BPT test results (before and after passing WTM test)

Test no.

Temperature (°C)

RAP RAP+CR Test no.

Temperature (°C)

RAP RAP+CR BPN SN BPN SN BPN SN BPN SN

1 26

42.00 26.51 65.00 46.34

1 26

55.00 37.72 53.00 36.00 42.00 26.51 66.00 47.20 53.00 36.00 53.00 36.00 41.00 25.65 67.00 48.06 55.00 37.72 54.00 36.86 42.00 26.51 65.00 46.34 55.00 37.72 53.00 36.00 42.00 26.51 65.00 46.34 55.00 37.72 53.00 36.00

Average 41.80 26.34 65.60 46.86 Average 54.60 37.38 53.20 36.17

2 30

58.00 40.31 66.00 47.20

2 30

58.00 40.31 63.00 44.62 59.00 41.17 66.00 47.20 58.00 40.31 63.00 44.62 58.00 40.31 70.00 50.65 59.00 41.17 62.00 43.75 56.00 38.58 70.00 50.65 58.00 40.31 62.00 43.75 58.00 40.31 66.00 47.20 58.00 40.31 63.00 44.62

Average 57.80 40.13 67.60 48.58 Average 58.20 40.48 62.60 44.27

3 35

70.00 50.65 70.00 50.65

3 35

62.00 43.75 64.00 45.48 69.00 49.79 72.00 52.37 62.00 43.75 65.00 46.34 67.00 48.06 73.00 53.24 63.00 44.62 65.00 46.34 67.00 48.06 71.00 51.51 63.00 44.62 64.00 45.48 69.00 49.79 70.00 50.65 62.00 43.75 63.00 44.62

Average 68.40 49.27 71.20 51.68 Average 62.40 44.10 64.20 45.65

4 40

71.00 51.51 70.00 50.65

4 40

68.00 48.93 66.00 47.20 73.00 53.24 72.00 52.37 68.00 48.93 68.00 48.93 73.00 53.24 74.00 54.10 68.00 48.93 66.00 47.20 72.00 52.37 74.00 54.10 68.00 48.93 65.00 46.34 73.00 53.24 74.00 54.10 69.00 49.79 65.00 46.34

Average 72.40 52.72 72.80 53.06 Average 68.20 49.10 66.00 47.20

5 45

73.00 53.24 75.00 54.96

5 45

69.00 49.79 60.00 42.03 73.00 53.24 74.00 54.10 68.00 48.93 61.00 42.89 73.00 53.24 75.00 54.96 67.00 48.06 61.00 42.89 73.00 53.24 74.00 54.10 66.00 47.20 60.00 42.03 72.00 52.37 72.00 52.37 66.00 47.20 61.00 42.89

Average 72.80 53.06 74.00 54.10 Average 67.20 48.24 60.60 42.55

6 50

68.00 48.93 70.00 50.65

6 50

62.00 43.75 59.00 41.17 68.00 48.93 72.00 52.37 62.00 43.75 59.00 41.17 70.00 50.65 70.00 50.65 63.00 44.62 60.00 42.03 70.00 50.65 70.00 50.65 62.00 43.75 59.00 41.17 68.00 48.93 70.00 50.65 62.00 43.75 60.00 42.03

Average 68.80 49.62 70.40 50.99 Average 62.20 43.93 59.40 41.51

Skid resistance before and after passing WTM test

The skid resistance values in the sample before passing of the wheel increased with temperature, in both the asphalt mixture of RAP and asphalt mixture of RAP+CR as shown in Fig. 4. A decrease in the SN value occurred in the two sample types after passing a temperature of 45oC, with the values of the samples being 53.06 and 54.10, respectively. The addition of CR did not have a significant impact on increasing the skid resistance of the gap-graded asphalt mixture for the road surface. The addition of CR only increased the SN value at 25oC and 30oC.

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0.00

10.00

20.00

30.00

40.00

50.00

60.00

20 30 40 50 60

Skid

Num

ber

Temperature °C

RAP

RAP+CR

0.00

10.00

20.00

30.00

40.00

50.00

60.00

20 30 40 50 60

Skid

Num

ber

Temperature °C

RAP

RAP+CR

(a) Before passing of wheel (b) After passing of wheel

FIGURE 4. Skid number with increasing temperature.

Skid resistance of sample with passing wheel

After passing the wheel in the WTM test, the ample skid resistance value of the sample increased owing to the temperature, in both the RAP and RAP+CR mixtures. However, a decrease in the SN value occurred when passing the temperature of 45oC, with the SN values for the samples of 48.24 and 42.55. It demonstrates that CR has no effect on increasing the skid resistance value.

An increase in the SN value of the gap-graded asphalt mixture in line with an increase in the surface temperature is possible because the asphalt content of this mixture is higher than that of a dense-graded asphalt mixture. It indicates that the mixture asphalt content affects the skid resistance value, particularly the increase owing to the temperature increase. At high temperatures, the asphalt will reach its softening point, resulting in bleeding on the surface layer.

CONCLUSION

From this study, it can be concluded that, in the hot-mix gap-graded RAP asphalt, an increase in the SN value occurred owing to an increase in temperature up to 45 oC, with SN values of 53.06 and 48.24 after being crossed. With the addition of CR, the same tendency was exhibited, namely an increase in the SN up to 45oC with values of 48.2 and 42.55, respectively. In the RAP mixture without CR and after wheel crossing, a decrease in the CR value of 9% occurred, while with the addition of CR, a decrease of 11% was determined. It can be concluded that the addition of CR to the RAP in the wheel-tracking test decreases the SN value.

ACKNOWLEDGMENTS

The study is supported by PITTA 2018 Research Grant funded by DRPM Universitas Indonesia No. 2532/UN2.R3.1/HKP.05.00/2018. The authors thank the Pusjatan Bandung Laboratory of the Ministry of Public Works and Public Housing Republic of Indonesia, and the Structure and Material Laboratory of the Universitas Indonesia Civil Engineering Department.

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