Rosman, Effect of Incorporating Super Bond Additives on Volumetric and Mechanical Characteristics of Cold Mix Asphalt Concrete using Asbuton Effect of Incorporating Super Bond Additives on Volumetric and Mechanical Characteristics of Cold Mix Asphalt Concrete using Asbuton

Asbuton is the natural asphalt of Buton Island, Southeast Sulawesi. Asbuton has substantial reserves with deposits estimated at between 150 to 300 million tons. Asphalt mixture using Asbuton can be done with a cold mix. This mixture requires a rejuvenating agent that serves to soften and rejuvenate the asphalt properties contained in Asbuton. The rejuvenation process that is less than optimal results in the low quality of the asphalt mixture. Therefore, it is necessary to conduct a study to imprfove the performance of cold mixtures using Asbuton. In this study, super bond additives were used. This study aims to determine the extent to which the performance of asphalt-concrete mixtures using Asbuton with the addition of super bond additives in the rejuvenating agent is increased. The addition of additives was varied with levels of 0.0%, 0.2%, 0.3%, and 0.4%, so that the impact could be known. The best asphalt concrete mix characteristics were obtained at the addition of 0.4% additives. Where, for volumetric characteristics the values obtained are: Void in the Mix (VIM) 5.08%, Void in Mineral Aggregate (VMA) 19.6% and Void Filled with Bitumen (VFB) 74.0%. While the mechanical characteristics are: Stability 609 kg, Flow 2.7 mm and Marshall Quotient 223 kg/mm. Only the Marshall Quotient value does not meet the minimum requirements, because it is < 250 kg/mm.


INTRODUCTION
One source of Indonesia's natural wealth that is quite potential is natural asphalt, which is found on the Indonesian island of Buton. So this asphalt rock is known as Asbuton (Buton asphalt). It is estimated that at least about 670 million tonnes are deposited in limestone formations and bitumen residues of ancient petroleum. The bitumen in the rock is between 15% and 35% of the total rock weight. If extracted, it is predicted that there will be around 160 million tons of pure bitumen. These reserves can guarantee the supply of bitumen for Indonesia for at least 100 years [1]. However, its existence has not been proportional to the percentage of its use, because the implementation of road pavement works in Indonesia is still dominated by petroleum asphalt which tends to be more expensive than Asbuton. The low stability value compared to mixtures that use petroleum asphalt is one of the reasons [2]. The weakness of Asbuton as natural asphalt is that the asphalt content is hard and not homogeneous. Asphalt that is not soft causes the bond is not optimal. Inhomogeneous asphalt content affects the homogeneity of the asphalt mixture. The bitumen present in the granular asbuton is very difficult to separate from the minerals, so it cannot wrap and bind between the aggregates [3]. Seeing these conditions, pure asphalt must be separated from Asbuton minerals so that asphalt can be used widely and economically and can replace the country's dependence on imports [1]. Research and implementation of mixed using Asbuton to get good quality has been done for a long time in Indonesia. Until the 1987's, Lasbutag and Latasbum were known for mixing asphalt with conventional grain asphalt. The properties of asphalt contained in Asbuton are softened and rejuvenated by using rejuvenating agents such as bunker oil or flux oil. However, this is very difficult to achieve, because the fluffier in the form of bunker oil cannot remove the bitumen and then keep it soft. It takes 254 days for the fuel oil type refining agent to reach the bitumen asbuton in the granules, and as a consequence, a good asphalt mixture is not achieved [3].
Rosman, Effect of Incorporating Super Bond Additives on Volumetric and Mechanical Characteristics of Cold Mix Asphalt Concrete using Asbuton Asbuton can also be treated with hot, warm or cold mixed systems. Energy consumption for mixing in a warm or cold way is smaller than the hot method which is usually done in asphalt concrete mixes (asphalt concrete). The use of cold mixed Asbuton can reduce production costs because aggregates and binders can be mixed, stored and compacted without energy consumption. Because it is made without heating, it is considered a green pavement, and is friendly to the environment [4]. Compared to Hot Mix Asphalt (HMA), especially at its low energy requirements, Cold Mix Asphalt (CMA) offers many environmental and economic advantages. However, generally less superior in performance [5]. The addition of 0.3% Wetfix-BE additive to improve the performance of the cold asphalt mixture with Asbuton was able to speed up the asphalt setting time. This can be seen from the time required for the asphalt softening process in Asbuton where as long as needed, 3x24 hours, but in this research, optimal results were obtained for materials with Marshall characteristics according to the 2010 Bina Marga Specification, without curing [6]. With a large number of reserves, Asbuton has the potential to be developed as an asphalt mixture for road pavements, especially in Indonesia. The use of Asbuton as an asphalt mixture needs to be increased to meet the needs of road construction programs in Indonesia. This utilization must be accompanied by efforts to improve performance through research. In this regard, a study was conducted on the use of Asbuton as a cold asphalt mixture by adding super bond additives. The research objective was to obtain volumetric and mechanical values of cold asphalt mixture using Asbuton with the addition of super bond additives. So that recommendations can be given whether the composition of the mixture and the addition of additives meet the requirements. Or provide recommendations both in terms of mixture composition or the percentage of addition of super bond additives, so that they meet the requirements as road pavement materials.

Materials
The materials used to make asphalt concrete mix test specimens are: (1) Asbuton; (2) Aggregate; (3) Rejuvenating agents; and (4) super bond additives. Super bond works by increasing adhesion and bonding and reducing the negative effects of water and moisture resulting in a very sticky surface.

Properties of Asbuton
Asbuton contains asphalt (bitumen) and minerals. Based on the asphalt content, Asbuton can be divided into several types. In this study, Asbuton type B 5/20 was used. Asphalt content contained in Asbuton B 5/20, is known by testing the centrifugal method of extraction using premium as a decomposer. Asphalt content in Asbuton B 5/20 is 19.83% (see Table 1), the rest is fine minerals that will be mixed in the asphalt mixture. This shows that the asphalt content in Asbuton B 5/20 is close to 20% according to the label on the package.

Rejuvenating properties
The rejuvenating agent is a mixture of asphalt, kerosene, and bunker oil. Kerosene is a colorless and flammable hydrocarbon liquid resulting from the fractional distillation of petroleum at temperatures of 150°C and 275°C (carbon chain C12 to C15). The rejuvenating agent is made by heating (diluting) the 60/70 penetration bitumen first. After the asphalt melts, it is then mixed with kerosene and bunker oil. The composition of each ingredient for the rejuvenating agent is 63% asphalt 60/70 penetration, 22% kerosene, and 15% bunker oil. The asphalt used is 60/70 penetration oil asphalt. Table 3 is the result of testing asphalt properties including: penetration, penetration after weight loss, softening point, flash point, ductility specific gravity, and ductility after losing weight.

Specimen manufacture and testing
Making the specimen begins by weighing the asphaltconcrete mixture material according to the design composition. The mixing and compaction process was carried out without heating, at room temperature. Figure 2 is a specimen of the asphalt mixture that has been compacted and is ready to be tested.

Volumetric Characteristics
Volumetric is closely related to voids and density. Density-void analysis was used to determine unit weight, VIM, VMA and VFB [9]. Figure 4, shows the results of the density test (unit weight) of cold asphalt mixture specimens with Asbuton based on variations in the addition of additives. The density of the mixture increases with the addition of super bond additives. This means that the addition of a super bond can reduce the cavity so that the weight of the specimen increases.   The addition of additives showed an effect on the size of the void mixture. The higher the percentage of additive addition, the smaller the value of VMA and VIM ( Figure 5-6). The decrease in the VIM value was caused by an additive reaction that was able to soften the asphalt in Asbuton so that it filled the voids between aggregates (VMA) and enveloped the aggregates. This also causes the VFB value to increase with the addition of additives (Figure 7). Based on the applicable standards in Indonesia [10], the addition of 0.3-0.4% additives meets the volumetric requirements of the mixture. As for the addition of < 0.3% additive, the requirements for VIM and VFB are not met.

Mechanical Characteristics
The Marshall mechanical characteristics measured were the stability and flow of the specimen. Stability is the value of the load at which the specimen fails or has undergone deformation. Flow is the amount of deformation to maximum stability when the sample reaches the limit of collapse [11]. Meanwhile, to determine the stiffness of the asphalt mixture can be known from the value of Marshall Quotient (MQ), namely the ratio of stability to flow. If the specimen loading results have low stability and high flow values, the mixture will tend to deform. On the other hand, if the specimen has high stability and low flow values, the mixture will tend to become brittle and crack when loaded. Figure 8-10 shows the results of stability, flow and MQ testing.  The stability test results show that the increase in the amount of additive addition results in an increase in the stability value. However, the addition of additives <0.4 has not reached the minimum requirements. The addition of additives has an effect on increasing flow, but overall it does not meet the requirements. When viewed from the test results curve, the higher the percentage of additive addition, the performance of the asphalt mixture will increase. So that further research can be done by optimizing the addition of super bond additives to meet all requirements, including MQ which is still < 250 kg/mm.

IV. CONCLUSION
The addition of super bond additives affects the volumetric and mechanical characteristics of the asphalt concrete mixture using Asbuton. Addition of additives with the highest percentage (0.4%) showed the best results. However, not all of the parameters meet the requirements.