Proceedings of the First Makassar International Conference on Civil Engineering (MICCE2010), March 9-10, 2010, ISBN 978-602-95227-0-9

CHARACTERITICS OF HOT MIX ASPHALT WITH OILY-SLUDGE-MODIFIED BUTON ROCK ASPHALT

M. Hermadi1 and K. A. Zamhari2

ABSTRACT: A number of studies on natural rock asphalt in the past indicate that an addition of Buton rock asphalt into conventional hot mix asphalt may increase the stiffness of the mixture. As a result, the ability of the mixture as part of the pavement structure to distribute the wheel load throughout the pavement will improve. However, the stiffness increment may reduce the ability of mixture to accommodate repeated excessive flexural deflection which may lead to crack initiation. Current practice of the Indonesian Directorate General of Highway is to limit the stiffness hot mix asphalt made of Buton rock asphalt to 2.5 times the stiffness of ordinary hot mix asphalt. The maximum amount of asbuton should be set based on this criterion. This paper describes the laboratory determination to increase rock asphalt proportion in the mix whilst maintained the target stiffness by utilizing oily sludge. The latter is otherwise considered as hazardous waste material which is expensive to dispose. The study aims to (i) reduce the use of petroleum bitumen and maximize the use of locally available natural asphalt and, (ii) utilize crude petroleum oil waste by product. The study reveals that fluxing asbuton with oily sludge may increase the penetration of its bitumen. Despite its small paraffin content, residue of oily sludge also acts as part of the binder. The wheel tracking test results show that the addition Buton rock asphalt and oily sludge significantly increase the dynamic stability of hot mix asphalt.

Keywords: Hotmix Asphalt, Buton rock asphalt, Oily Sludge

INTRODUCTION

The petroleum bitumen that commonly used as the binder in hot mix asphalt in tropical country, such as Indonesia, generally is of penetration grade 60/70 or 80/100. As the price of crude petroleum oil is continuously increased, the price of the petroleum bitumen is also increase accordingly. Therefore, a lot of efforts have been made to utilise the use of locally available material such as rock asphalt as an alternative.

Buton rock asphalt is a natural deposit of lime-stone-rock filled with asphalt found in Buton Island of Indonesia. In the past, this rock asphalt was not used widely as the substitution of petroleum bitumen because of its high transportation cost. Nevertheless, since most of the bitumen of rock asphalt is hard, it can be utilised as an additive in hot mix asphalt. The material usually used for that purpose comes from Kabungka Region of the island. It is locally known Kabungka Buton Rock Asphalt or Kabungka-BRA for short.

The addition of rock asphalt increases the stiffness of the hot mix asphalt and improves its rutting resistance. However, the increase of stiffness should be limited to ensure that the mixture is not susceptible to cracking. The Indonesian’s construction specification of road

restricts the stiffness of hot mix asphalt with BRA to 2.5 times of the ordinary hot mix asphalt or equivalent to a maximum of 3800 MPa. It means that the amount of BRA in the mix should also be restricted. If the amount should be increased, as was aimed by the government, the bitumen of BRA should be softened in the first place.

This paper presents some finding on the study on the use of BRA modified with oily-sludge in hot mix asphalt. The study aims (i) to increase the use of BRA in hot mix asphalt while maintained the stiffness within the allowable limit and, (ii) to utilise the oily sludge in achieving the first aim.

MATERIALS AND METHODS

Buton rock asphalt

The current Indonesian’s specification for rock asphalt classifies rock asphalt based on its bitumen content and penetration. It is designated as x/y whereas x and y indicate the penetration and bitumen content respectively. Four grades of BRA are recently specified, those are BRA Grade 5/20, 15/20, 15/25 and 20/25 (Directorate General of Highway, 2006). Most of the Kabungka is BRA grade 5/20.

1 Ph.D. Student, Universiti Tun Hussein Onn Malaysia (UTHM), Parit Raja 86400, Malaysia.2 Assoc. Professor, UTHM, Locked Bag 101 - Parit Raja 86400, Malaysia

Figure 1 indicates the recommended proportion of BRA in hot mix asphalt to achieve the target stiffness (Directorate General of Highway, 2006). It shows that to keep the stiffness below 3800 MPa the maximum allowable BRA 5/20 and BRA 15/25 in the mix are 5 and 8.5 percent respectively. It suggests that provide the consistency of BRA 5/20 can be modified to penetration 15, the amount of BRA of this grade that can be added into the mixture can be increased by almost 60 percent.

Figure 1 Maximum use of the BRA (Directorate General of Highway, 2006)

In order to increase the proportion of Kabungka-BRA in the mix, the bitumen of BRA should be soften. For this purpose, oily sludge should be added as such to modify consistency bitumen of Kabungka-BRA from grade 5/20 to be similar with that of 15/25. Grade 15/25 was selected because, as the past experience has shown, BRA of higher grade was too soft and easy to clot so that it was difficult to mix properly with hot mix asphalt. The characteristics of the raw BRA 5/20 that used in this study are shown in Table 1.

Tabel 1 Characteristics of BRA Type 5/20

CharacteristicsTest

ResultsSpec. *

Water content; % 1.2 ≤ 2Bitumen content; % 21.5 18 – 23Penetration of bitumen at 25oC, (100 g, 5 sec); dmm

3 ≤ 10

Wax content in bitumen; % 0.18 -Maximum particle size No 16 -

* Special Specification of Asbuton (Directorate General of Highway, 2007)

Oily sludge

Oily sludge is a waste product from the activity of mining, transporting, storing, and refining of crude oil. Oily sludge is categorised as hazardous waste materials. The handling of such material should follow the tight environmental regulation and therefore very costly. For example, the current cost of handling of oily sludge in Indonesia is around US $ 70 per litre.

Oily sludge that used in this study is the waste of local crude oil from Cepu (East Java) and Balongan (West Java). Generally, the wax content of these crude oils is higher than those from the Middle East. The characteristics of the oily sludge are shown in Table 2.

The oily sludge consists of three main substances i.e. oil, water and mineral. It can be used as BRA modifier because of its oil content (volatile and non-volatile). The non-volatile fraction can be used as a modifier to soften the bitumen of BRA. The volatile fraction should be evaporated for safety reason. The water should be evaporated as well because of its detrimental effect to the mixture. The mineral can be used as mineral filler.

Tabel 2 Characteristics of Oily Sludge Type of Test Origin*

OS-1 OS-2Distillation test until 360oC: Percentage of water 34.15 17.65 Percentage of oil distillate 16.00 2.53 Percentage of Residue 49.85 79.82 Solubility in CH2CL3 of residue 83.37 86.76 Penetration of residue 115 ~Wax content of residue 4.89 4.82

* OS-1: Cepu Oily sludge; OS-2: Balongan Oily sludge

Toxicity of oily sludge from Cepu and Balongan were assessed and the results are shown in Table 3. It indicates that all of heavy metals content the oily sludge is well below the maximum allowable limit. Therefore, it may conclude that the sludge can safely be used in road construction.

Table 3 Toxicity Characteristic of Oily Sludge

Heavy MetalsOily Sludge (mg/L) Upper limit*

(mg/L)OS-1 OS-2 Arsenic 0.002 0.002 5.0Barium 0.26 0.31 100.0Boron 0.33 0.42 500.0Cadmium < 0.005 < 0.005 1.0Chromium < 0.05 < 0.05 5.0Copper < 0.03 < 0.03 10.0Free Cyanide < 0.01 < 0.01 20.0Flouride 0.20 0.20 150.0L e a d 0.05 0.07 5.0Mercury < 0.001 < 0.001 0.2Nitrate+Nitrite 2.11 2.39 1000.0Nitrite < 0.03 < 0.03 100.0Selenium < 0.007 < 0.007 1.0Silver < 0.003 0.05 5.0Zinc 0.18 0.24 50.0

* Technical Requirement of Processing Hazardous Materials (Environmental Impact Management Agency, 1995)

The oily sludge was pre-processed by heating and stirring until 130oC to evaporate water and volatile oil. The non-volatile oil of the pre-processed oily sludge as well as impregnated bitumen of BRA was extracted and blended. After a number of trial and error, the right proportion of the extracted oily-sludge to get softer BRA bitumen of 15 dmm penetration was determined. This proportion was used to modify consistency of BRA 5/20.

The mixture characteristics of the hot mix petroleum bitumen with and without the BRA type 15/25 were compared to evaluate the effect of the oily-sludge-modified BRA on the hot mix asphalt. The optimum bitumen content of each mix was determined using ordinary Marshall mix design procedure. Properties of the petroleum bitumen that used in this study are shown in Table 4.

Tabel 4 Characteristics of Petroleum Bitumen

CharacteristicsTest

ResultsSpec.*

Penetration at 25 oC, 100 g, 5 sec; dmm 65 60 - 79Softening point; oC 48.9 48 - 58Flash point (COC); oC 318 ≥ 200Ductility at 25 oC, 5cm/menit; Cm > 140 ≥ 100Specific gravity; 1.034 ≥ 1.0Solubility in C2HCl3; % 99.66 ≥ 99Loss on heating by Thin Film Oven Test (TFOT); % 0.016 ≤ 0.8Penetration after TFOT; % original 84.62 ≥ 54Softening point after TFOT; oC 52.1 -Ductility after TFOT; Cm > 140 ≥ 50Wax content, % 0.24 ≤ 2

* Special Specification of Asbuton (Directorate General of Highway, 2007)

Performance of the mixtures in term of stiffness and resistance to permanent deformation were assessed by using the indirect tensile resilient modulus and the wheel tracking tests respectively. Three types of mix were prepared, those are hot mix asphalt with Cepu and Balongan oily sludge modified BRA, and one with ordinary petroleum bitumen as the control.

RESULTS AND DISCUSSION

Characteristics of oily sludge after pre-processing are shown in Table 5. The effect of these oily sludge on consistency and wax content of the impregnate bitumen of the raw BRA is shown in Figure 2. It implies that the target penetration of 15 dmm can be achieved by adding 15% of Cepu oily sludge or 12% of Balongan oily sludge. At these proportions, the wax content of the related modified impregnate bitumen of BRA is 0.90%

and 0.75% correspondingly. These figures fulfil the maximum wax content requirement of bitumen (i.e. 2%). Characteristics of the modified BRA are shown in Table 6. In this table, BRA-1 and in BRA-2 are refered to BRA plus OS-1 and OS-2 respectively.

Tabel 5 Characteristics pre-processed oily sludge Characteristics Oily Sludge

OS-1 OS-2Distillation test: Percentage of water (%) 0.0 0.0 Percentage of oil distillate

(%) 22.65 2.66

Percentage of Residue (%) 77.35 97.34Solubility in CH2CL3 of distillation residue (%)

83.30 86.74

Penetration of distillation residue at 250C, 100g, 5sec (dmm)

113 ~

Wax content of distillation residue (%)

4.89 4.83

Figure 2 The Effect of Oily Sludge Content on Penetration Value

Figure 3 The Effecty of Oily Sludge on Wax Content

Table 6 Characteristics of modified bitumen of BRA

Characteristics Requirement (BRA 15/25*)

BRA -1 BRA-2

Bitumen content (%) 23 - 27 24.02 23.78Loss on hetaing after TFOT (%) -

0.553 0.437

Flash point (oC) - 195 203Water content (%) Max. 2% 0.518 0.271Bitumen penetration at 250C 100g 5 sec (dmm) 10 – 18

11.4 13.5

Softening pint, oC - 85.4 83.8Ductility at 25 oC 5 cm/min (cm) -

4 4

Wax content (%) - 0.832 0.753Maximum mineral size, mm

1.18 1.18

*) Special Specification of Asbuton (Directorate General of Highway, 2007)

Mixture Characteristics

Aggregate gradation of the hot mix asphalt is shown in Figure 4. Marshall and volumetric properties of the mixtures is shown in Table 8.

Figure 4 Mixture gradation of hot mix asphalt

Table 7 Properties of the mixtures Petroleum Bitumen

MixtureSpec. *)

0% BRA

6%BRA-1

6% BRA-2

Bitumen content optimum (%)

5.8 6.0 6.1 -

Density (g/ml) 2.346 2.304 2.323 -Void in Mix Aggregates (%) 17.0 17.3 17.4 ≥ 15Void fill bitumen (%) 75.4 76.6 76.9 ≥ 65Void in mix (%) 4.2 4.8 4.3 3.5-5.5Void in mix at refusal density (%)

4.0 4.1 3.2 ≥ 2.5

Stability (kg) 1027 1343 1302 ≥1000Flow (mm) 3.9 3.8 3.5 ≥ 3Marshall quotient (kg/mm) 263 347 372 ≥ 250Retained stability (%) 86.7 89.3 86.7 ≥ 75

*) Special Specification of Asbuton (Directorate General

of Highway, 2007)

The proportions of BRA-1 and BRA-2 in the mixtures are not at the maximum border 8.5%. The

proportions are 6% that predicted can improve the mixtures dynamic stability minimum 2500 track/mm.

The finding yield that BRA modified with both Cepu and Balongan oily sludge can improve the Marshall Stability and Marshall Quotient of the mixtures. Performance of the mixtures in term of the resistance to permanent deformation and modulus resilient are also signifantly improved as shown in Table 9. Figure 5 illustrates the rate of deformation of the mixtures at the wheel tracking test at 60oC.

.Table 8 Performance Based Characteristics of Petroleum Bitumen Mixtures

Mixture Characteristics

Petroleum Bitumen Mixtures

Unit0%

BRA6%

BRA-16%

BRA-2Dynamic Stability (60oC) :- Initial Deformation 2.48 1.88 1.99 mm- Deformation rate 0.0320 0.0113 0.0153 mm/min- Dynamic Stability 1312.5 3705.9 2739.1 track/mmResilient Modulus: 25 oC 2950.7 5483.0 4875.0 MPa 35 oC 1066.0 2218.0 1977.0 MPa 45 oC 371.3 1193.0 1058.0 MPa 55 oC 230.5 628.9 536.1 MPa

Figure 5 Deformation characteristics of the mixtures

CONCLUSIONS

The possibility of utilizing oily sludge from Cepu and Balongan as modifier of Buton rock asphalt has been discussed. Toxicity Characteristic Leaching Procedure (TCLP) reveals that the oily sludge is a non toxic material and, therefore, is safe for use in road construction. After pre-procesings by heating to reduce the water and volatile oil content, oily sludge form both sources can be used to modify the consistency of BRA grade 5/20. The modification enables the increase of the allowable proportion of the Kabungka-BRA to be used in hot mix asphalt. The produced mixtures yield a significant improvement. This advanteges are in

agreement with the aim of the government to promote the use of BRA.

ACKNOWLEDGEMENTS

This study is part of the research work on the chemical properties and the physical performance of Buton rock asphalt. The first author hold the scholarship from the University Tun Hussein Onn Malaysia. Some of the data was collected during his term as a researcher at the Institute of Road Engineering Indonesia. Research work at the University Tun Hussein Onn Malaysia is managed by the Centre for Research and Inovation.

The authors would like to thank the Ministry of Higher Education, Malaysia for supporting this research under the Fundamental Research Grant Scheme (FRGS).

REFERENCES

Environmental Impact Management Agency, 1995, Technical Requirement of Processing Hazardous Materials No: Kep-03/BAPEDAL/ 09/1995, BAPEDAL, Jakarta, Indonesia.

Directorate General of Highway, 2006, Technical Guidelines of Utilization of Asbuton Book 1 General No. 001-01/BM/2006, Public Work Department, Jakarta, Indonesia.

Directorate General of Highway, 2007, Special Specification of Asbuton, Public Work Department, Jakarta, Indonesia.