Characteristics of Asphalt Mixed Using Mountain Stone

Aggregate is the main thing in asphalt mixtures with a percentage of about 70% to 80%. The aggregate used should meet the Indonesian National Standard (SNI) before being used in the asphalt mixture. East Kalimantan Province is one of the provinces in Indonesia which always brings in aggregates from outside the region for road construction. This study aims to analyze the modulus of stiffness of the AC-WC mixture using local aggregate of East Kalimantan Province and petroleum bitumen grade 60/70 as a binder due to water immersion. This research is experimental in the laboratory. The variation of the petroleum bitumen content used was 4.5, 5.0, 5.5, 6.0 and 6.5%. Water immersion was carried out at the age of 3, 5 and 7 days. The results showed that at 3 days of immersion, the resilient modulus values obtained at petroleum bitumen content of 4.5, 5.0, 5.5, 6.0 and 6.5% were 421.0, 506.0, 872.5, 747.0 and 648.5 MPa, respectively. At 5 days immersion, the resilient modulus values obtained were 383.5, 386.0, 915.5, 561.0 and 555.5 MPa, respectively. Whereas for the 7 days immersion, the resilient modulus were 290.5, 425.5, 1369.0, 547.5 and 525.0 MPa, respectively. It can be seen that water immersion greatly affects the stiffness modulus of the asphalt mixture. This stiffness will cause the asphalt mixture to be easily damaged or cracked. This can be caused by the influence of the sub-standard aggregates used, namely Senoni stone and Mahakam sand.

269 specific gravity, plasticity value, absorption and abrasion which will affect the level of adhesion of the aggregate to asphalt in the asphalt mixture [5]. The problem that can arise due to the use of sub-standard aggregate is the release of asphalt aggregate (stripping) which will result in premature damage and reduced road function [6].
The construction of pavement construction generally uses standard materials derived from natural materials such as stone and sand [7]. This material is used as a material for road foundation layers without or with binder or for asphalt mixtures [8]. In order for construction costs to be minimized, other than that the use of local or local materials needs to be considered and thought out carefully. However, it is necessary to make efforts to optimize the use and utilization of this substandard material [9].
In addition, the increasing demand for road materials cannot be matched by the availability of material sources, especially aggregates [10,11]. To meet the aggregate needs in an area by bringing in the aggregate from other places which of course will increase the unit price of road construction costs [12,13]. To overcome this, it is necessary to carry out technical engineering in the use of materials so that local substandard materials or industrial waste materials can be optimized for use on road pavements, both in asphalt mixtures and for road foundation layers [14,15].
The hot asphalt mixture that is often used for road surface layers in Indonesia is Asphalt Concrete (Laston) or Asphalt Concrete (AC), which is a mixture of bitumen or asphalt material with coarse aggregate and fine aggregate which is processed at very high temperatures [16][17][18]. Laston has three kinds of mixtures, namely Asphalt Concrete Wearing Course (AC-WC) as a wear layer, Asphalt Concrete Binder Course (AC-BC) as an intermediate layer and Asphalt Concrete Base (AC-Base) as a foundation layer [19,20].
A road pavement surface layer has the ability to act as a wear layer and also when there is no change in shape that remains in its service life. One of the causes of damage or not reaching the service life of these roads is the increase in the level of traffic congestion. According to Tayfur et al. (2005) and Birgisson et al. (2007) [21,22], repetition of traffic loads as a result of traffic density causes the accumulation of permanent deformation in the asphalt concrete mixture so that it has decreased road performance in its service life. To solve this problem, one way is to use additives to the mixture.
The stress conditions that occur due to wheel loads on the pavement layer can be tested in the laboratory but by simplifying many factors [23,24]. In actual conditions the pressure or load is applied in three dimensions [25,26]. Therefore, a number of simplified tests were introduced to be able to test certain aspects of in-situ behavior. The test is divided into three groups [27,28]. The first test group is the basic test of the repeated load triaxial test, the unconfined static uniaxial creep compression test, the repeated load indirect tensile test, the dynamic stiffness and fatigue test. Stiffness and fatigue tests). The second group of tests is simulative laboratory testing: the wheel-tracking test and the third testing group is the empirical test using the Marshall tests [29,30]. Basically, East Kalimantan Province has abundant local aggregate reserves, but so far it is considered as non-standard (sub-standard) aggregate to be used as road pavement material. To overcome this, it is necessary to carry out technical engineering in the use of materials so that local materials which are substandard or industrial waste materials can be optimized for use for road pavement, both for asphalt mixtures and for road foundation layers. The objective of this study was to reveal the characteristics of coarse aggregate, fine aggregate (Mahakam sand) and filler, combined aggregate gradation, and Resilient Modulus of asphalt mixed (horizontal deformation of 3, 5 and 7 days due to water immersion). This study aims to analyze the modulus of stiffness of the AC-WC mixture using local aggregate of East Kalimantan Province and petroleum bitumen grade 60/70 as a binder.

Aggregate
Tables 1 to 3 shows the characteristics of coarse aggregate, fine aggregate (sand) and filler, respectively that have been carried out. Based on the test results, the characteristics of coarse aggregate, sand, and filler are shown to meet the Directorate General of Bina Marga, Ministry of Public Works 3 rd Revision, 2010 [26].    Table 4 shows the results of the petroleum bitumen pen. 60/70 that has been carried out. The results of the examination of the characteristics of the 60/70 penetration oil asphalt shown in Table 4 show that the asphalt used in this study has met the specifications required by Directorate General of Bina Marga, Ministry of Public Works 3 rd Revision, 2010 [26].

Research Design
To facilitate the research to be carried out, it is necessary to plan the stages that will be the guidelines for this research, the stages of the process are shown in Figure 1. This study used petroleum bitumen content of 4.5, 5.0, 5.5, 6.0 and 6.5%. Indirect Stiffness modulus (ITSM) testing is carried out after the specimen has been immersed in water for 3, 5 and 7 days.

Indirect Tensile Stiffness Modulus (ITSM) Test
The indirect tensile stress test (ITSM) shown in Figure 1 is used to determine the tensile properties of asphalt concrete which can be further related to cracks that occur in the asphalt mixture, especially the AC-WC mixture. Strain control was used to evaluate the stiffness modulus in which the specimen was subjected to sinusoidal loading axial oscillations in a voltage at a constant amplitude of 5 microstrains. All materials are tested at a temperature of 20˚C, where the sample is subjected to dynamic loads in a certain strain range (linear elastic conditions) with the test configuration. This test is considered a non-destructive test carried out using a Dynapave UTM 30 machine. ITSM testing is calculated by formula and in accordance with the provisions of the British Standard [27].  Measurements are made by placing a load on the upper part of the cylindrical specimen, and by recording computerized strain data that is generated in a plane perpendicular to the plane given the load. If you can know the poisson ratio, the size of the test object and the applied load, the modulus of the asphalt mixture. Equation 1 shows the modulus value generated from the ITSM equipment. Where:

Mixtures Design of AC-WC Mixture
Based on the previous results that analyzed the optimum asphalt content was 5.10%, a mix design was designed to make the test object with various levels of oil asphalt content, namely 4.5%, 5.0%, 5.5% , 6.0% and 6.5% by weight of the mixture. Table 5 shows the composition of the material by weight obtained from the proportion of the aggregate based on the results of the sieve analysis.  Table 6 shows the resilient modulus value of the asphalt mixture with water immersion time for 3, 5 and 7 days. It can be seen that the resilient modulus value increases along with the increase in asphalt content until it reaches the optimal value then decreases after getting the optimal value. In this study, it increased to 5.5% asphalt content both at 3, 5 and 7 days immersion.

Indirect Tensile Stiffness Modulus (ITSM) Results
At the 3-day immersion, the resilient modulus values obtained at the asphalt content of 4.5, 5.0, 5.5, 6.0 and 6.5% were respectively 421. It can be seen that water immersion greatly affects the stiffness modulus of the asphalt mixture. This stiffness will cause the asphalt mixture to be easily damaged or cracked. This can be caused by the influence of the sub-standard aggregates used, namely Senoni stone and Mahakam sand.  Based on the test results, the chemical characteristics of Senoni stone and Mahakam sand contain predominantly calcium, followed by silica and alumina or magnesium or ferrous content. Thus electrostatically, these aggregates have a positive electric charge. This shows that the aggregate should be able to stick tightly to the asphalt because the asphalt is negatively charged. But in reality the aggregate adhesion to asphalt is less than 95%. There are two things that can cause it, namely the lack of positive ions from the aggregate or because the absorption is too small so that the asphalt is difficult to stick to. Figure 4 shows the relationship between the time domain of the test and the horizontal deformation of the AC-WC mixture with water immersion for 3 days using Senoni rock aggregate and Mahakam sand. It can be seen that in all variations of asphalt content, maximum horizontal deformation occurs in about 0.4 seconds. At asphalt content 4.5% horizontal the maximum deformation that occurs is 20.15 mm, at asphalt content is 5.0% horizontal the maximum deformation that occurs is 35.70 mm, at asphalt content is 5.5% horizontal maximum deformation occurs namely 53.10 mm, the maximum horizontal deformation at asphalt content is 6.0%, 17.35 mm and at 6.5% asphalt content, the maximum horizontal deformation is 31.94 mm. Figure 5 shows the relationship between the test time domain and the horizontal deformation of the AC-WC mixture with water immersion for 5 days using Senoni stone aggregate and Mahakam sand. It can be seen that in all variations of asphalt content, maximum horizontal deformation occurs in about 0.4 seconds.

Figure 5. The relationship between the time domain of the test and the horizontal deformation of the AC-WC mixture for 5 days immersion
At asphalt content 4.5% horizontal the maximum deformation that occurs is 20.19 mm, at asphalt content is 5.0% horizontal the maximum deformation that occurs is 14.54 mm, at asphalt content is 5.5% horizontal maximum deformation occurs that is, 37.37 mm, the maximum horizontal deformation at 6.0% asphalt content was 21.46 mm and at 6.5% horizontal asphalt content, the maximum deformation occurred was 31.86 mm. Figure 6 shows the relationship between the time domain of the test and the horizontal deformation of the AC-WC mixture with water immersion for 7 days using Senoni rock aggregate and Mahakam sand. It can be seen that in all variations of asphalt content, maximum horizontal deformation occurs in about 0.4 seconds. At asphalt content 4.5% horizontal the maximum deformation that occurs is 20.19 mm, at asphalt content is 5.0% horizontal the maximum deformation that occurs is 14.54 mm, at asphalt content is 5.5% horizontal maximum deformation occurs that is, 37.37 mm, the maximum horizontal deformation at 6.0% asphalt content was 21.46 mm and at 6.5% horizontal asphalt content, the maximum deformation occurred was 31.86 mm. The amount of horizontal deformation is directly proportional to the magnitude of the resilient modulus value. The greater the resilient modulus value that occurs, the greater the horizontal deformation value. In this study, the AC-WC mixture using sub-standard aggregates had small resilient modulus values compared to the resilient modulus values of AC-WC mixtures using standard aggregates. The resulting AC-WC mixture is strong enough but does not have good resistance to water. This is caused by the adhesion of the aggregate to the asphalt which is less than 95% and does not meet the General Specifications 2010 Revision 3 of Bina Marga. In addition, the high absorption capacity of the aggregate which is also accompanied by a large asphalt surface tension which reduces the wetting effect of the asphalt also causes this to occur. To change the ionic charge of bitumen also has to do with laboratory engineering.

Time Relationship with Horizontal Deformation of Immersion in 7 Days
The stiffness of the asphalt mixture is closely related to the stability and flow values. Asphalt mixtures, especially AC-WC have high stability with a small flow value, this makes the mixture stiffer, especially for the test object that has an accelerated aging process both in the field and in the laboratory. As previously explained, the high stability is due to the low penetration of petroleum bitumen. This can also be explained by considering that the VIM value of the asphalt mixture that does not undergo an accelerated aging laboratory process is smaller than that of the asphalt mixture that has undergone an accelerated immersion in the laboratory. The small VIM value indicates that the mixture is denser and the mixture is stiffer which is indicated by the Marshall Quotient (MQ) value on the Marshall characteristics. A high MQ value indicates that the asphalt mixture has higher stiffness [18][19][20][21][22][23][24][25][26][27][28][29][30].

Conclusion
Aggregates used in Based on the test results of the characteristics of coarse aggregate (crushed stone), rock ash, and rock ash filler shown, it can be seen that the aggregate used meets the general specifications in 2010 of Bina Marga for the required road materials. However, coarse aggregate (Senoni stone) is based on the results of the adhesion test of the aggregate to asphalt where the result is <95% so it is classified as non-standard (sub standard) aggregate. However, considering the unfulfilled properties are not natural properties of the aggregate, efforts to improve these properties by engineering the materials in the laboratory can be carried out.
Aggregates from Samarinda, East Kalimantan in the form of Senoni stone and Mahakam sand are very good for use as class A foundation layers but should not be used as aggregates for asphalt mixtures because they have poor adhesion to asphalt and cannot withstand water immersion. At the 3-day immersion, the resilient modulus values obtained at the asphalt content of 4.5, 5.0, 5.5, 6.0 and 6.5% were respectively 421.0, 506.0. 872.5, 747.0 and 648.5 MPa. At 5 days immersion, the resilient modulus values obtained were 383.5, 386.0, 915.5, 561.0 and 555.5 MPa, respectively. Whereas for the 7-day immersion specimen, the resulting resilient modulus values were 290.5, 425.5, 1369.0, 547.5 and 525.0 MPa, respectively. Asphalt mixture using mountain rock aggregates in Senoni, East Kalimantan and asphalt content of 5.5% is resistant to water immersion until the age of 7 days with the largest resilient modulus (stiffness modulus), which is 1369.0 MPa.
Laboratory engineering carried out to optimize the use of substandard aggregate from Senoni rock and Mahakam sand as a material for asphalt mixtures has not been proven on a project scale. For that, a pilot project needs to be carried out and observed for two seasons for further proof. Asphalt Content 6.0% Asphalt Content 6.5%

Data Availability Statement
The data presented in this study are available in article.

Funding and Acknowledgements
This work was not supported by the Indonesian Scholarship Program but it's personal expenses. Most of the research works were conducted in the Eco Material and Concrete Laboratory, Transportation Systems Engineering Laboratory and Road and Asphalt Laboratory, Civil Engineering Department, Hasanuddin University, Makassar-Indonesia.

Conflicts of Interest
The authors declare no conflict of interest.