Construction and Building Materials 29 (2012) 108–113

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Construction and Building Materials

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The effects of initial conditioning and ambient temperatures on abrasion lossand temperature change of porous asphalt

Meor Othman Hamzah a,⇑, Mohd Rosli Mohd Hasan a, Martin van de Ven b, Ahmad Shukri Yahaya a

a School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Pulau Pinang, Malaysiab Faculty of Civil Engineering and Geosciences, Department Design and Construction, Section of Road and Railway Engineering, Delft University of Technology,2628 CN Delft, The Netherlands

a r t i c l e i n f o

Article history:Received 8 March 2011Received in revised form 12 August 2011Accepted 16 August 2011Available online 24 November 2011

Keywords:Porous asphaltInitial conditioning temperatureAmbient temperatureSpecimen skin temperatureTemperature changeAbrasion loss

0950-0618/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2011.08.050

⇑ Corresponding author. Tel.: +60 4 5996210; fax: +E-mail addresses: cemeor@yahoo.com, cemeor@en

a b s t r a c t

This paper investigates the effects of initial conditioning and ambient temperatures on abrasion loss andtemperature change of porous asphalt after subjected to 300 rotations in the Los Angeles drum. Identicalspecimens were tested at Universiti Sains Malaysia (USM) and Delft University of Technology (TU Delft),the Netherlands. Specimen temperature change decreased as the initial conditioning temperatureincreased. Temperature inside the drum remained unchanged. The abrasion loss of samples tested atTU Delft were higher than those tested at USM. Therefore for meaningful comparison of test resultsworldwide, the ambient temperature at which a Cantabro test is performed must be specified.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Porous asphalt is widely used in developed nations for its noisereduction potential. It was initially developed to promote trafficsafety. During rain, the safety benefits of a properly designedporous mix include the elimination of hydroplaning, reducedsplash and spray and reduced roadway light reflection due to theimproved drainage, thus providing better visibility. However, theservice life of porous asphalt is limited, primarily due to ravellingand clogging.

Porous asphalt is the preferred asphalt mix for use on motor-ways in the Netherlands. The main problem associated with porousasphalt is its short service life, which is primarily due to ravelling.Ravelling, or the loss of aggregate from the wearing course, is aform of fatigue that occurs in the surface layer of the pavementstructure [1]. In the United States, ravelling has been the majorcause of pavement distress in several regions, although a greatmajority of the states have had good experience with the use ofporous asphalt that includes a polymer-modified binder [2].Kandhal and Mallick [3] reported that temperature is one of thefactors that may affect the performance of asphalt pavement.

Ravelling refers to a pavement surface distress that takes placedue to the dislodgement of aggregate particles from the surface ofthe mix. Kneepkens et al. [4], described ravelling as a process that

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60 4 5941009.g.usm.my (M.O. Hamzah).

typically begins after 7–9 years in service. It starts with the re-moval of the first stone, creating a gap, followed by a domino-likeeffect, with the loss of more stones at a higher rate. When the firststone is removed by a vehicle wheel, the remaining stones aroundthe gap lack support in at least one direction. This type of pave-ment distress occurs due to ageing, which causes the binder to be-come stiffer at a lower temperature, and the adverse effects ofmoisture. The nature of the open mix with high air voids promotesoxidation of the binder, resulting in binder hardening and exposureto moisture. The ageing of bitumen is one of the factors contribut-ing to the reduction of its adhesion and cohesion properties andthe ravelling of porous asphalt [5–7]. When the asphalt binderreaches a certain age, the mixture begins to deteriorate and failsrapidly during cold weather. In some cases, the entire pavementlayer can ravel in a few weeks [8].

In some countries, modified bitumen has been used to lengthenthe lifespan of porous asphalt. Nielsen et al. [9] reported that highviscosity styrene–butadiene–styrene (SBS) modified binders wereused in cold regions to overcome distress due to rutting and ravel-ling. Among the 19 states in the USA that have reported havinggood experiences with porous asphalt, 15 states have used modi-fied binder. Of the 14 states that reported bad experiences, 2 and12 states used modified and unmodified binders, respectively [8].However, the Netherlands has reported successful application ofconventional binder 70/100 with porous asphalt on its motorways.

For many years, the resistance to disintegration of porousasphalt has been evaluated by the Cantabro test, which involves

Table 2Specimen mixing and compaction temperatures.

Binder Temperature

Mixing (�C) Compaction (�C)

60/70 165 155PG 76 180 170

Table 1Properties of aggregate and asphalt binders.

Material Properties Specification Result

Aggregate Abrasion loss (%) Max 25 [17] 23.6Aggregate crushingvalue (%)

Max 25 [17] 21.5

Flakiness index (%) Max 25 [17] 21.8Water absorption (%) Max 2 [17] 0.7Polished stone value Min 50 [17] 51.8Flat and elongated ratio5:1 (%)

Max 5 [18] 1.88

Flat and elongated ratio3:1 (%)

Max 20 [18] 15.99

Conventional binder60/70 pen. grade

Specific gravity (g/cm3) – 1.030Penetration at 25 �C(dmm)

60–70 [19] 63

Softening point (�C) 48–56 [19] 49Ductility at 25 �C (cm) Min 100

[19]>100

Viscosity at 135 �C(Pa s)

– 0.594

Viscosity at 165 �C(Pa s)

– 0.175

Modified binderPG 76

Specific gravity (g/cm3) – 1.055Penetration at 25 �C(dmm)

– 45

Softening point (�C) Min 60 [17] 64Ductility at 25 �C (cm) – 88.8Viscosity at 135 �C(Pa s)

Max 3 [17] 2.650

Viscosity at 165 �C(Pa s)

– 0.610

Table 3Mix designations.

Gradation Binder Designation

Grading A 60/70 A6PG 76 AP

Grading B 60/70 B6PG 76 BP

M.O. Hamzah et al. / Construction and Building Materials 29 (2012) 108–113 109

tumbling asphalt samples in a rotating drum. To a certain extent,the Cantabro test indicates the bond strength between binderand aggregates. Australia, South Africa and some European coun-tries use the Cantabro test to design porous asphalt mixtures[10]. Poulikakos et al. [11] reported that the test is commonly usedin Japan to evaluate the resistance of porous asphalt to particle lossunder winter conditions. However, the manner in which the spec-imens are subjected to stresses when undergoing rotation in thedrum appears to bear little relation to the stress caused by traffic.Nevertheless, for comparative purposes, the Cantabro test is rapid,inexpensive and simple to perform [12].

Test standards differ; the European Union, for instance, man-dates an ambient temperature of 20 ± 5 �C, whereas the EuropeanStandard 12697-17 [13] for the Cantabro test recommends a testtemperature between 15 �C and 25 �C. These temperatures maybe ideal for temperate countries; however, for countries in the tro-pics, the ambient temperature is generally higher than 25 �C. Fromdaytime temperature monitoring at the USM, the average ambienttemperature hovers around 30 �C [14]. Maintaining the specimentemperature at 18 �C or 20 �C or 25 �C throughout the Cantabro testunder local climatic conditions would thus be an arduous task. Thisscenario was the background motivating this study. The mainobjective of the work was to evaluate the influence of initial condi-tioning temperature (ICT) on the abrasion loss of porous asphaltand the change in specimen skin temperature from the ICT afterbeing subjected to 300 drum revolutions. The study was limitedto porous asphalt prepared using conventional bitumen 60/70and modified bitumen PG 76.

2. Materials and methods

2.1. Raw materials

The aggregates that were used in our study consisted of granite obtained from alocal asphalt mixing plant. Both the conventional bitumen (60/70) and modifiedbitumen (PG 76) used in our study were supplied by Shell, Ltd. The two aggregategradations, which were designated as Grading A and Grading B, that were used inthis study differ in terms of their breakpoint locations, corresponding to the sievesizes 2.36 mm and 5 mm, respectively, as shown in Fig. 1. The material propertiesare listed in Table 1.

2.2. Malaysian laboratory ambient temperature

Daytime laboratory ambient temperature was established by monitoring thetemperature fluctuations in the laboratories in the vicinity of the Los Angeles steeldrum over a period of 3 months. It was established that the average ambient tem-perature of the laboratory is about 30 �C. The highest and lowest temperatures re-corded were 34 �C and 26 �C, respectively [14].

2.3. Specimen preparation

Cylindrical specimens were prepared in a standard Marshall mould. Bitumenand aggregates were preheated to the specified temperature and mixed uniformly.Blended loose mix was conditioned in an oven for 2 h at the compaction tempera-ture to allow for asphalt binder absorption, as suggested by the Asphalt Institute[15]. The mixing and compaction temperatures were selected from the rotationalviscosity test results and are tabulated in Table 2. During compaction, each speci-men was subjected to 50 blows per face. Specimens were prepared at binder con-

Fig. 1. Aggregate gradations adopted in this study.

tents ranging from 4.0% to 5.5% in increments of 0.5%. Specimens were allowed tocool overnight before undergoing ICT. To simplify the mix identification, a designa-tion system was adopted, as shown in Table 3.

2.4. Cantabro test

The Cantabro test was performed on specimens that had been initially condi-tioned at the designated temperature for at least 4 h, either in a draft oven or anincubator. A specimen was placed in the Los Angeles drum and tumbled for 300rotations without steel balls. The mass of the specimen before and after the testwas noted. An infrared thermometer was used to determine the temperatures ofthe specimen skin and the internal walls of the Los Angeles drum. The skin temper-ature refers to the surface temperature. The infrared thermometer used was able todetermine only the surface or skin temperature. It was not able to measure thespecimen core temperature. Before the test commenced, the specimen skin temper-ature was measured. Then, the specimen was subjected to 300 rotations at 30–33 rpm in the Los Angeles drum. The test took approximately 10 min to completeand during that time, the sample was subjected to impact and frictional forces,causing the specimen skin temperature to change. The specimen skin temperaturewas measured immediately after the test ceased. Hence, after the test has ended,there will be differences in the specimen skin temperatures before and after test.The difference between the two skin temperatures was defined as the specimen

Table 4One-way ANOVA of factors affecting the abrasion losses of the porous mixes.

Source SS df MS F p-value

Binder type 315.993 1 315.993 7.599 0.007Error 3243.709 78 41.586Total 3559.702 79Binder content 1146.414 3 382.138 12.034 <0.001Error 2413.288 76 31.754Total 3559.702 79ICT 1793.555 4 448.389 19.041 <0.001Error 1766.147 75 23.549Total 3559.702 79STC 1793.555 4 448.389 19.041 <0.001Error 1766.147 75 23.549Total 3559.702 79

110 M.O. Hamzah et al. / Construction and Building Materials 29 (2012) 108–113

temperature change (STC). The term drum temperature change (DTC) was definedin exactly the same manner as the STC, that is, temperature difference of Los Ange-les drum internal walls before and after a specimen was subjected to 300 drumrotations.

To investigate the effects of ambient temperature, specimens were also pre-pared in Malaysia and tested at the Delft University of Technology (TU Delft), theNetherlands, where the ambient temperature when the Cantabro test was per-formed was about 24 �C. The specimens were subjected to similar ICT as at the Uni-versiti Sains Malaysia (USM) before testing for abrasion loss.

3. Results and discussion

3.1. Effects of initial temperature conditioning on abrasion loss

The abrasion loss test results for all specimens tested at theUSM are shown in Fig. 2. In general, the abrasion loss for all mixesdecreased as the ICT and binder content was increased. Using theabrasion loss at ICT 15 �C as the baseline, the abrasion losses ofspecimens initially conditioned at 20, 25, 30 and 35 �C decreasedby 16.8%, 39.9%, 57.9% and 65.0%, respectively. Obviously, the ICThad a marked effect on the abrasion loss of porous asphalt. At low-er temperatures, bitumen becomes brittle and become more proneto disintegrate when subjected to external forces.

The experimental data were further analysed statistically to testthe effect of binder type, binder content, ICT and specimen skintemperature change (STC) on the abrasion loss of the porous mixes.The analysis was performed for each explanatory variable usingOne-way Analysis of Variance (ANOVA). The results of the analysisare shown in Table 4. Generally, all of the above factors had signif-icant effects on the abrasion loss of porous asphalt. The results ofthe independent samples t-test of binder types showed that themodified binder (PG 76) resulted in a higher resistance than didthe conventional binder (60/70). Duncan’s Multiple Range testindicated that the higher binder contents (5.0% and 5.5%) and high-er initial ICT (above 30 �C) yielded the lowest abrasion loss values.However, higher STC resulted in higher abrasion loss values.

3.2. Temperature changes of specimens and inside the steel drum

Fig. 3 summarises the average temperature changes of the spec-imen skins in the Cantabro test performed at the USM. These re-sults indicate that the specimen skins became warmer at the endof the test than their ICTs. The temperatures of all specimen skins

Fig. 2. Abrasion losses at various

tested increased to varying degrees. However, the magnitude oftemperature change was reduced as the ICT was increased. Speci-mens tested at the lowest ICT (15 �C) exhibited the highest STC,averaging 11.17 �C, 11.20 �C, 10.95 �C and 11.32 �C, respectively,for the A6, AP, B6 and BP mixes. Specimens conditioned at thehighest temperature (35 �C) became warmer by less than 1 �C. Itis obvious that a greater difference between the ICT and the ambi-ent temperature led to a greater temperature change during thetest. Duncan’s Multiple Range test here indicated that the highestICT (35 �C) yielded the lowest STC. However, the One-way ANOVAresults, listed in Table 5, show that binder type and binder contentdid not have significant effects on the STC.

In contrast, the temperatures inside the steel drum remainedrelatively unchanged regardless of the ICT, with a drum tempera-ture change (DTC) of less than 1 �C (Fig. 4). The temperature insidethe steel drum was more affected by the ambient temperature atthe time the test was performed.

After undergoing the Cantabro test, which took about 10 min tocomplete, the specimen temperature had changed due to friction,impact and abrasive forces between the surface of the sample, thewalls of the steel drum and the disintegrated asphalt materials.When this occurred, heat was generated that subsequently affectedthe temperature of the specimens. This, in turn, influenced the abra-sion loss of the samples tested. However, this did not affect the steeldrum temperature, which registered only a 0.38 �C maximum in-crease in temperature. This was statistically confirmed by a One-way ANOVA with a p-value greater than 0.05, as shown in Table 6.

temperatures for all mixes.

Fig. 3. Specimens skin temperatures before and after testing and temperature changes.

Table 5One-way ANOVA of potential factors affecting STC.

Source SS df MS F p-value

Binder type 0.882 1 0.882 0.057 0.812Error 1204.088 78 15.437Total 1204.970 79Binder content 0.258 3 0.086 0.005 0.999Error 1192.962 76 15.697Total 1193.220 79ICT 1197.130 4 299.282 2862.92 <0.001Error 7.840 75 0.105Total 1204.970 79

M.O. Hamzah et al. / Construction and Building Materials 29 (2012) 108–113 111

The relationship between the percentage difference in STC andDTC versus the ICT is depicted in Fig. 5. The results indicate that thepercentage STC decreased as the ICT was increased. The tempera-ture of the specimen skins initially conditioned at 15 �C increasedby 72.4% after 300 revolutions. The corresponding values for thoseconditioned at 30 �C and 35 �C were 8.9% and 1.1%, respectively. Incontrast, the interior steel drum temperature changed by a maxi-mum of only 0.8% and was therefore considered to be unaffectedby the test.

The effects of the temperature difference between the ICT andambient temperature (AT) on STC and DTC are shown in Fig. 6.The difference between the ICT and the ambient temperature onlyaffected the STC, not the DTC, whereas the STC increased rapidly asthe temperature difference between ICT and the ambient temper-ature increased.

3.3. Influence of ambient temperature

The main difference between the Cantabro tests performed atTU Delft and USM was the ambient temperature. The average

Fig. 4. Interior drum temperature before and

ambient temperature at TU Delft was 6 �C lower than at USM.The abrasion loss and STC results performed at TU Delft exhibitedsignificantly different trends from the USM test results, as shownin Table 7. Given the same ICT, the abrasion loss obtained at TUDelft was higher than at USM. The abrasion loss difference betweenthe specimens tested at the two locations became greater as theICT was increased. For a given ICT, specimens tested at TU Delftregistered a lower temperature change than did those tested atUSM. This probably explains the higher abrasion losses obtainedat TU Delft when initially conditioned at the same temperature.When specimens were initially conditioned at 15 �C, the STC atUSM laboratory was more than two times that at TU Delft. This ef-fect is the result of a mere 6 �C difference in ambient temperaturesat the two locations. The test results conducted at TU Delft alsoindicate that the temperature inside the steel drum is similar tothe ambient temperature. As in the USM test results, the steeldrum temperature remained relatively unchanged throughoutthe test. At USM, all specimens became warmer at the end of theCantabro test. Conversely, at TU Delft only the specimens initiallyconditioned at temperatures below ambient became warmer dur-ing testing; otherwise, the specimens became cooler, as indicatedby the negative values in Table 7.

Fig. 7 depicts the effects of ICT on abrasion loss and STC; higherICT resulted in lower STC and abrasion loss values. The lower STCcontributed to higher abrasion loss values at a given ICT. Whentested at TU Delft, the STC was lower and the abrasion loss washigher compared to the corresponding specimens tested at USM.

The same One-way ANOVA was performed to determine theeffect of ambient temperature on the Cantabro test results basedon a 95% (a = 0.05) confidence level. The results in Table 8 indicatethat ambient temperature had significant effects on the STC, DTCand abrasion loss values. Higher ambient temperature resulted insignificant increase of STC and DTC, which in turn reduced the

after testing and temperature changes.

Table 6One-way ANOVA of potential factors affecting DTC.

Source SS df MS F p-value

Binder type 0.045 1 0.045 2.416 0.124Error 1.457 78 0.019Total 1.502 79Binder content 0.011 3 0.004 0.193 0.901Error 1.491 76 0.020Total 1.502 79ICT 0.139 4 0.035 1.909 0.118Error 1.363 75 0.018Total 1.502 79

Fig. 5. Percentage temperature changes of specimen skins and drum interior.

Fig. 6. Effects of temperature difference between ICT and ambient temperatures onSTC and DTC.

Table 7Temperature changes of specimen skins and inside the steel drums at TU Delft andUSM.

Test location ICT (�C) STC (�C) DTC (�C) AT* (�C)

USM, Malaysia 15 +11.40 +0.10 29.820 +8.00 +0.20 31.025 +5.00 +0.30 30.830 +2.90 +0.10 31.535 +0.70 +0.40 31.2

TU Delft, the Netherlands 15 +5.17 +0.00 23.324 +2.27 +0.20 23.825 +1.40 +0.03 24.130 �1.00 +0.23 24.035 �3.43 +0.17 24.0

* Ambient temperature.

Fig. 7. Comparison of Cantabro test results at USM and TU Delft.

Table 8One-way ANOVA on the effects of ambient temperatures on the Cantabro test results.

Dependent variables Source SS df MS F p-value

STC AT 337.936 8 42.242 90.170 <0.001Error 5.622 12 0.468Total 343.558 20

DTC AT 0.280 8 0.035 4.659 0.009Error 0.090 12 0.008Total 0.370 20

AL* AT 385.250 8 48.156 4.650 0.009Error 124.262 12 10.355Total 509.513 20

* Abrasion loss.

112 M.O. Hamzah et al. / Construction and Building Materials 29 (2012) 108–113

abrasion loss value of the porous mixes. However, the results of theindependent-samples t-test indicated that the drum temperaturechanges at USM and TU Delft were not significantly different (t-sta-tistic = �1.756; p-value = 0.096). It is clear from this result that thetest is very sensitive to ambient temperature or the temperatureinside the steel drum. Therefore, a specific ambient temperatureis required to evaluate mixes in the Cantabro test.

4. Overview of current and future practice

Colonna [16] suggested maximum permitted abrasion losses of30%, 25% or 20% for tests performed at 18 �C, 20 �C or 25 �C, respec-tively. Many researchers have used one of these values to determinethe minimum value of the design binder content of porous asphaltmixes. Subsequently, researchers normally perform the Cantabrotest on specimens conditioned at the chosen temperature and reportthe abrasion loss obtained. Because the test takes approximately10 min to complete, it is very difficult to maintain the specimen tem-perature throughout the duration of the test; we found that speci-men temperature changed to varying degrees during that period.Perhaps the test is too simple, in that the fundamental principle thatthe specimen temperature changes during the test has been ignored,and it went unnoticed that the specimen temperature change ismore pronounced in the case of a wide difference between the ambi-ent temperature and that at which the specimen was conditioned.

The findings from this investigation indicate the wide differencein abrasion loss values and changes in specimen temperature after300 drum rotations caused by a mere 6 �C difference in ambienttemperature. The Cantabro test has been criticised for its lack ofcorrelation with actual ravelling on roads, because it does not accu-rately simulate external forces acting on a porous pavement sur-facing. The test was also found to favour modified mixes, which,according to the experience of some countries such as the Nether-lands, does not correspond to practical results. Still, it has re-mained a popular test due to its simplicity. However, it is clearfrom this study that the test is very sensitive to temperature. Tominimise temperature changes in the specimens, the test is bestperformed at the ambient temperature, which differs from countryto country. Otherwise, coefficients must be formulated to accountfor differences in testing and ambient temperatures.

5. Conclusions

During the Cantabro test, specimens were subjected to impactand abrasive forces between the sample surface and the walls of

M.O. Hamzah et al. / Construction and Building Materials 29 (2012) 108–113 113

the Los Angeles drum and the disintegrated asphalt materials,causing the specimen temperature to change. The magnitude oftemperature change depended on the ICT and the ambient temper-ature. This in turn affected the abrasion loss value. Therefore, with-out specifying the ambient temperature at which the Cantabro testis performed, a worldwide comparison of abrasion-loss values canbe misleading.

Acknowledgements

The authors would like to acknowledge the Malaysian Ministryof Science, Technology and Innovation (MOSTI) who funded this re-search grant through the eScience Fund program and enabled thisstudy to be completed. Many thanks are also due to the techniciansof the Highway Engineering Laboratory at USM. Last, but not least,we thank Professor Molenaar for his kind permission to use thelaboratory facilities at TU Delft, the Netherlands.

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