Performance of asphaltic concreate binder course (AC-BC) using gilsonite modified asphalt

The road pavement structure is the most important part of the design and manufacture of highways, so there is a need for innovation in designing pavement to get a type of pavement that has good quality and is efficient in its design. At this time, many road pavements have suffered damage caused by poor quality. Gilsonite is a natural asphalt that has a relatively high asphalt content compared to other additives, which is 70.9%. In addition, Gilsonite has a maltene content of 27% and 2% oil, then has a nitrogen content of 3.2%. After that, to carry out this test, a test object was made with the addition of Gilsonite Resin using 3 variations of the addition, namely 6%, 7%, and 8%, and compared to the mixture without Gilsonite. The mixture using the addition of Gilsonite (6%, 7%, 8%) an increase in the stability value of the mixture using the addition of Gilsonite, but the flow becomes increased so the properties of the mixture have large deformations. From all the tests that have been carried out, the optimum Gilsonite content is 8%


Introduction
Bitumen is defined as a tarlike mixture of hydrocarbons derived from petroleum naturally or by distillation and used for road surfacing and roofing [1] .Asphalt is a solid or semi-solid material that is black to dark brown has a cementious nature and will soften and melt when heated.According to Sukiman, asphalt is thermoplastic, that is, it melts when heated and re-freezes when the temperature drops.This property of asphalt is used in the road construction process and is known as hot mix asphalt.
Current conditions indicate an increasing traffic load, so the quality improvement of pavement materials must be able to meet these conditions.To improve pavement quality, pavement engineers often add additives to bitumen to improve asphalt properties and use alternative materials (substitutes) in asphalt mixtures [2].Based on where it is obtained, asphalt is divided into natural asphalt and oil asphalt.Natural asphalt is asphalt that is found in nature and can be used as it is obtained or with a little processing, while oil asphalt is asphalt which is the residue of petroleum refining.Asphalt produced from the crude oil refinery industry is known as residual bitumen, which is produced from crude oil through a distillation process.
Asphalt additive is a material used to be added to the asphalt.The use of asphalt additives ranges from types of synthetic rubber and also from rubber that has been processed (for example: used tires), and also from plastic materials.The use of rubber additives can change the characteristics of asphalt.Research on rubber shows that the increasing levels of natural rubber sap, the harder the asphalt and not sensitive to temperature.This is caused by the content of natural rubber latex which is non-bituminous and elastic [3] Gilsonite has a high asphaltene content (70.9%) when compared to other additive materials, in addition to other mineral content, namely 27% maltene, 2% oil, and 3.2% nitrogen, it is expected that this material can improve aggregate adhesion and water stripping [4].Research conducted on the addition of gilsonite to 60/70 penetration bitumen turned out to be able to change the properties of asphalt, namely penetration, softening point flash point, and burning point so that asphalt with gilsoniteadded material becomes hard [5] Asphalt mixture testing with variations of Gilsonite additives was carried out.the results of testing the use of gilsonite in asphalt mixtures can increase the stability of the mixture with an asphalt content of 5.5% with an optimum content of 6.8% Gilsonite [6].Tests on the ac-wc mixture obtained a gilsonite content of 8% which in the conditions of the Marshall test parameters were met [7].Research on the use of Gilsonite in other types of mixtures was also carried out, one of which was porous asphalt.This mixture is an asphalt mixture with a uniform gradation type so this mixture forms larger cavities compared to other types.The addition of gilsonite to the modified porous asphalt mixture lowers the permeability coefficient where the low permeability value is caused by the small cavity in the mix (VIM) value.[8] Based on the issue above, it is necessary to develop research into the latest gradation mixtures, one of which is AC-BC.This layer is part of the surface layer between the top bearing (base course) and the wear layer (wearing course) which aggregate grades continuously, generally used for roads with heavy traffic loads [9].By analyzing the Marshall characteristics of the Gilsonite-modified AC-BC mixture, and reviewing the durability of the AC-BC mixture using Marshall immersion.

Material and Research Methodology
Gilsonite Resin is a hydrocarbon mineral with a high content of resin, asphalten, and nitrogen, and mixes easily with asphalt.Gilsonite Resin is a kind of mineral bitumen that resembles asphalt known as asphaltites.Gilsonite Resin when mixed with aggregate and asphalt mixture is expected to increase the stability of flexible pavement.The content of Gilsonite Resin has 70.9% higher asphaltene compared to other additives as well.contains 27% maltene and 2% oil.The materials used in this study were asphalt pen 60/70, Gilsonite resin, and coarse and fine aggregates.
Mixing Gilsonite resin with asphalt pen 60/70 and testing the properties of asphalt.In testing 3 variations of the use of Gilsonite Resin, namely 6%, 7%, and 8% by weight of asphalt.Tests for these mixes were carried out by the standard tests for hot mix asphalt.The design of the hot mix pavement uses the intermediate layer Laston gradation (AC-BC).To obtain the optimum asphalt content (OAC) value using the Marshall method to measure stability, melting, and cavities in the mixture and test residual strength using the Marshall immersion method.After the Marshall test, an analysis was carried out to determine the optimal gilsonite content.The research flow process can be seen in Figure 1.

Gilsonite Modified Material
Analysis of pen 60/70 asphalt modified with Gilsonite Resin added to the penetration test of 6%, 7%, and 8% Gilsonite asphalt obtained penetration values of 47.5, 46.5, and 42.5.This means that more Gilsonite additions make asphalt brittle.on testing the flash and burning point of asphalt added to Gilsonite resin 6%, 7%, and 8%, high flash points, and burning points were obtained, approximately, 305°C to 335°C.where Gilsonite resin-modified bitumen has non-flammable properties because the temperature obtained to get the flash point and burning point is very high Testing the softening point modified bitumen with Gilsonite resin added 6%, 7%, and 8% obtained values of 50.2°C, 52.6°C, and 54.3°C, where it makes the asphalt properties harder, meaning the higher the temperature, the lower the penetration because it requires a high temperature to reach its softening point.Testing the ductility of modified Gilsonite asphalt 6%, 7%, and 8%, the results were 697.9, 597.9, and 497.9 cm.From the results obtained the ductility of asphalt added to Gilsonite becomes inelastic or brittle, meaning that Gilsonite has the property of hardening asphalt.Viscosity is an important component in mix planning because viscosity can show asphalt behavior due to temperature changes.To check the viscosity of asphalt added with Gilsonite additives, the viscosity of asphalt was obtained, namely, for Gilsonite additives of 6%, 7%, and 8%, the results were obtained for mixing temperatures of 161-167°C, 162-169°C, and 166-172°C .The solidification temperature is 149-154°C, 150-155°C, and 153-159°C.From the results obtained, the mixing temperature is greater than the compaction temperature, meaning that the mixing temperature is higher because the asphalt will unite with the aggregate at high temperatures.The effect of Gilsonite on the viscosity test is that the higher the Gilsonite content, the higher the temperature obtained to obtain the mixing temperature and compaction temperature.The addition of Gilsonite can cause the density value of the test object to decrease.This is due to the decrease in aggregates in the mixture as the asphalt content increases, the properties of the mixture cannot be compacted anymore, due to the occurrence of bonds between the aggregates with the asphalt content.For Gilsonite content of 6%, 7%, there is an increase in density value but at 8% Gilsonite content the density value is the same as that given by Gilsonite with 7% content.

Figure 3 Density of the Modified Gilsonite Mixture
The addition of 6% Gilsonite content, the VMA value increases, this proves that increasing the percentage of Gilsonite content in the mixed composition will increase the void value in the aggregate.The addition of Gilsonite will cause the inner cavity to enlarge.

Figure 4 VMA of the Modified Gilsonite Mixture
Testing the VFB value for the asphalt mixture with the addition of 6%, 7%, and 8% Gilsonite decreased compared to the asphalt mixture without the addition of Gilsonite or 0% Gilsonite content, this is also because the voids between the aggregates are getting smaller.The lower the percentage of asphalt content in the mixture, the more surfaces and voids in the mixture that are not covered with asphalt so the binding between aggregate and asphalt is not optimal.For the Gilsonite content of 8%, a decrease will cause the mixture to be less impermeable to water and air because the asphalt layer will become thin and will crack easily.

Figure 5 VFB of the Modified Gilsonite Mixture
For a mixture with 0% Gilsonite content, a value of VIM 3.82% was obtained, while for a value VIM with the addition of 6%, 7%, and 8% Gilsonite each had a value of 3.74%, 3.62%, and 3.96 %.Based on the results obtained, the highest number was obtained at the Gilsonite content of 8%, this means that the voids in the mixture are getting larger so that the mixture is porous or absorbs easily, which causes the mixture to become less dense so that water and air easily enter the cavities in the mixture which will cause asphalt easily oxidized, causing the adhesion between aggregate grains to decrease resulting in the release of granules and peeling off the surface of the pavement layer.

Figure 6 VIM of the Modified Gilsonite Mixture
Improving Gilsonite to the mixture with the addition of 6% and 7% will increase the stability value of the mixture compared to the mixture without the addition of Gilsonite.These results also conclude that the mixture with the addition of Gilsonite is more durable and strong in accepting large amounts of vehicle loads.the value obtained for a mixture with a Gilsonite content of 0% is 1357.10kg, then for a mixture with a Gilsonite content of 6%, 7%, and 8% respectively has a value of 1314.58 kg, 1598.42 kg, and 1658.67 kg.

Figure 7 Stability of the Modified Gilsonite Mixture
Flow is affected by asphalt content, viscosity, aggregate gradation, as well as the amount and temperature of compaction of the mixture.The values obtained from the test were 3.8mm for mixtures with 0% Gilsonite content, then 3.32mm, 4.24mm, and 5.61mm for mixtures with 6%, 7%, and 8% Gilsonite content.This also shows that the addition of Gilsonite can increase Flow of the asphalt mixture so that it can cause large deformations when given a load.

Figure 8 Flow of the Modified Gilsonite Mixture
The Optimum Asphalt Content (OAC) is 5.8% for asphalt without added Gilsonite, while the OAC value for mixture with the addition of Gilsonite Resin from 6%, 7%, and 8% content respectively is 6.1%, 6.2%, and 6.0%, from tests that have been carried out that the addition of Gilsonite can increase the Optimum Asphalt Content of the mixture The Marshall immersion test aims to see the mixture resistance to temperature.The Marshall immersion test results for the mixture without the addition of Gilsonite obtained a value of 90.78%, while for the Marshall immersion value in the asphalt mixture with the addition of Gilsonite 6%, 7%, and 8% obtained a value of 91.51%, 93.08 %, and 93.44%.It can be concluded that the mixture with the addition of Gilsonite can increase the Marshall immersion value of the asphalt mixture when compared to the mixture without the addition of Gilsonite Figure 9 Immersion of the Modified Gilsonite Mixture

Gilsonite Content Analysis
The determination of the optimum Gilsonite content was carried out using 2 methods.The first was to review the properties of adding Gilsonite resin to asphalt.This analysis uses a relationship approach between the asphalt test results, namely Penetration, Ductility, and Softening Point.From the analysis of adding Gilsonite to asphalt, it can be concluded that with increasing levels of Gilsonite added to asphalt, the penetration value and the ductility decreases, then the softening point value of asphalt increases.It can also be said that the addition of Gilsonite can make the properties of asphalt brittle or stiff when compared to asphalt without the addition of Gilsonite.
The other method is looking at the characteristics of the mixture added to Gilsonite and reviewing the Marshall test results.Analysis of the characteristics of the mixture of the added Gilsonite examined the stability and melting values of the mixture.Based on Table 2, the Gilsonite modified asphalt mixture uses 6% Optimum Asphalt Content and the results show an increase in the stability value of up to 22% and a melting point of 10%.Analysis of the addition of Gilsonite to asphalt pen 60/70 as well as in mixed testing, it can be said that adding Gilsonite to asphalt and to the mixture can increase the stiffness and strength values of the asphalt mixture itself, along with the many additions of Gilsonite, the stability and melting values also increase.But in this case, if the addition of Gilsonite eats too much it will behave unfavorably towards the asphalt, this can cause the pavement to crack or break easily when loaded.With the addition of Gilsonite the properties of the AC-BC mixture are able to withstand high traffic loads and have high strength.high on the pavement.However, with this addition, the flow value for adding Gilsonite tends to be high for 7% and 8% additions, so a good grade for this addition is 6%.

Conclusion
Based on the analysis and discussion of the addition of Gilsonite to the Characteristics of Asphalt Concrete Intermediate Coating (AC -Binder Course) mixture, the following conclusions are obtained: 1.The use of Gilsonite resin on asphalt pen 60/70 makes asphalt properties harder, this can be seen from the decreased penetration value, increased softening point, and decreased ductility value, this is due to the mineral content in Gilsonite resin which affects the properties of asphalt pen 60/70.2. The results of penetration testing of 6% modified Gilsonite resin asphalt obtained a value of 47.5 mm, the addition of 7% Gilsonite obtained a value of 46.5 mm, and the addition of 8% Gilsonite obtained a value of 42.5 mm.The softening point value with the addition of 6% Gilsonite resin was 50.2 ˚C, 7% Gilsonite resin was 52.6 ˚C, and 8% Gilsonite resin was 54.3 ˚C.The ductility value of the modified asphalt with the addition of 6% gilsonite resin was 697.9 mm, 7% was 597.9 mm, and 8% was 497.9 cm. 3. The Marshall test showed that the addition of Gilsonite to the AC-BC mixture increased the stability and melting characteristics of the AC-BC mixture.The Marshall stability value increased with the addition of 6% Gilsonite at 1314.58 kg, 7% Gilsonite at 1598.42 kg, and 8% Gilsonite at 1658.67 kg.The melting value of the 6% Gilsonite asphalt mixture was 3.32 mm, 7% Gilsonite asphalt was 4.24 mm, and 8% Gilsonite asphalt was 5.61 mm.Based on the results of the analysis, it can be concluded that adding Gilsonite to asphalt and the mixture can increase the stiffness and strength of the asphalt mixture itself, Along with the many additions of Gilsonite, the stability and melting values also increase.However, if you add too much Gilsonite, it will behave less well with the asphalt, this can cause the pavement to crack or break easily when loaded. 4. The characteristics of the intermediate layer mixture (AC-BC), for the provisions of the properties of the final mixture (AC) used can be said to be good, and suitable to be an intermediate layer (AC-BC) if you look at the quality that has been obtained in the mixed test.If you look at the provisions for the properties of the AC-BC mixture, the effect of Gilsonite on the AC-BC layer can be said to

Figure 1
Figure 1 Research Methodology Mixture of Asphalt Modified Gilsonite

Figure 10 Figure 11 Figure 12
Figure 10 Penetration ratio with Gilsonite Content

Table 1
Characteristics of Gilsonite Resin Modified Bitumen

Table 2
Effect of asphalt mixture on gilsonite additives