Laying of crumb rubber asphalt in Solo-Kertosono Toll, 2017 (Doc. PPK PJBH Solo-kertosono 1 Colomadu-Karanganyar Section 1)

Environmentally Friendly Technology
Innovations in the field of kebinamargaan continue to bring up something new, one of which is the use of rubber waste that is processed into Crumb Rubber. This innovation aims to improve the quality of infrastructure in addition to considering the importance of environmentally friendly technology.
Crumb Rubber is one of the results of processing (grated) waste of used tires. Used tire processing can be in the form of recycled rubber and reclaimed rubber (Adhikari, De, and Maiti 2000 in Mulyani, Hamdani 2017). This can reduce the amount of rubber waste that is wasted in the environment.
Crumb Rubber is then used in the construction world in the form of Asphalt Modified Crumb Ruber (Mod-CR). One application is as Thin Asphalt / Very Thin Overlay which is a mixture of hot asphalt with hard asphalt or natural asphalt modified with Crumb Rubber, graded open with a maximum aggregate size of 12.5 mm. This asphalt mixture is used for preservation of asphalt pavement or concrete pavement, which is referred to as VTO Mod-CR. If it is spread on a paved layer, the minimum thickness of solid is 2.5 cm, if it is spread on concrete pavement, the minimum thickness is 2.0 cm.

Improvements Due to IRI Values
This Very Thin Overlay (VTO) is also used at several handling points in the Solo-Kertosono (Soker) Toll Road Colomadu-karanganyar section.
With its unique thin characteristics (2 cm), VTO does not have a structural value because it is only a surface layer, which is to improve the road surface.
"We use VTO to refine surface smoothing only. This is to improve the IRI (International Roughness Index for Road) above 4. Because of the rules in the NSPM toll road for rigid, the maximum IRI is 4. For this VTO is only applied in spots where IRI has exceeded 4 "Said Syahputra Amal Ginting, Field Supervisor Coordinator at the PPK Solo-Kertosono 1 Colomadu-Karanganyar Toll Road Section 1, when met by Media-7 in front of the Kartosuro Junction.
According to him this is because some of the toll road sections in the Solo-Kertosono Toll Road have indeed been built and have been run for a long time. One of the sections on the blacktop was built and restructured in 2012 so that at some point there were cracks.

Rigid Characteristics and Crack Vulnerability
"In (Soker) toll road (Solo-Kertosono), there are several locations that are in accordance with the design that must be black top. So the design from the beginning rigid (concrete) then paved. Initially it was going to use conventional asphalt, but reflected from experience in other places, especially on the toll road and in the Pantura, if rigid then coated with conventional asphalt, there would be a reflection crack or segmental crack "Said Bedru Cahyono, PPK Construction of the Solo-Kertosono 1 Colomadu Freeway -Karanganyar Section 1.

 Effect of joint on pavement due to load (source: https://azanurfauzi.blogspot.co.id/2010/06/rigid-pavement.html

 

Bedru then explains the rigid character per segment, and between segments there is a joint (connection). And this will move due to shrinking and moving because there is a burden. Although in the middle there is a dowel (plain steel rod connecting the two structural components), but its function is not to strengthen but to distribute the load.
"Asphalt on rigid is continuous (not segmental). Therefore, when underneath it is moving and above it, there must be cracks in the moving place. That is what happens if we use conventional asphalt "continued Bedru.

one rigid lane that has been "Blacktop" and one lane that has not been blacktop (Doc. PPK PJBH Solo-kertosono 1 Colomadu-Karanganyar Section 1)
Conventional asphalt is the design of Asphalt Concrete-Wearing Course (AC-WC) or the highest layer of pavement and usually has relatively lower bitumen content so that it is rigid and hard.

The decision making process uses VTO Crumb Rubber
"We consulted with several experts from the Directorate and Research and Development Center for Roads and Bridges (Pusjatan) that there was an opportunity or experience to eliminate the cracks caused by the joint with a thin layer. At that time the options were twofold, namely: one, all thicknesses of 10 cm and above, so he reflected from the bottom no longer felt; or the second, thin but only surfacing with a flexible material and asphalt with a gradation so that the asphalt content is high so that it becomes relatively more flexible. That is the first reason. "Said Bedru explained the reasons behind the VTO election.
"Then the second reason, in Bina Marga there are many options for thin layers. VTO itself there is a VTO with conventional asphalt, as well as with Crumb Rubber. At that time the specifications that were ready at Bina marga were VTO with Crumb Rubber "

Laboratory Test

As with other material mixtures that will be used for the construction process and must go through a series of laboratory tests to ensure the levels of material used are in accordance with specified specifications, the VTO Crumb Rubber also goes through laboratory testing.
"Therefore, to apply the VTO requires time because the requirements for asphalt are quite strict from the specifications. Among them must be tested with special tools, and in Indonesia that has these tools is the Laboratory in Cikampek owned by BBPJN VI. Considering this VTO product is not generally different from bitumen A or B which can be bought on the market. This means that the producer does not specifically produce this. Because this is by request, they concoct a composition and then we test it, if the results match, that's what we use. So we need time. "
Bedru said that he also checked Crumb Rubber to the mixing place (concocting composition) in the laboratory.
"Crumb Rubber is an innovation 5 years ago from Bina Marga. This innovation is used to strengthen or make the viscosity (thickness) of the better asphalt. This means that if the temperature is hot he is not too runny, if the temperature is cold he is not too thick so that the flexibility is high. When applied as a layer on top of the rigid, it automatically follows the movement so that no cracks occur, "Bedru said.
Biro and Bence (2005) (in Sri Mulyani, Hamdani, 2017) compared rubber asphalt with other modified asphalt, the results concluded that all samples containing Crumb Rubber showed superior aging performance compared to other modified asphalt. An important reason for this is the carbon content of Crumb Rubber.

VTO Crumb rubber texture although it is more rough but its flexibility is high compared to conventional asphalt (Doc. Humas BBPJN VII)

Obstacles encountered
Bedru regretted that at the same time understand that not all segments were coated with VTO. This is due to limited supply and the ability of the tool itself.
"Because to mix VTO, the device must be modified, the tank is special, the asphalt is also special. The material production is also different from the ordinary asphalt, so it takes longer, because the average material requirements are also small. "
The required VTO asphalt storage tank must be equipped with a heater that can be controlled effectively and reliably. Heating must be done through steam coils, electricity or other means so that the fire does not directly heat the asphalt tank. In addition, the tank must be equipped with a thermometer to monitor the asphalt temperature. A tap must also be installed in the pipe coming out of each tank to collect the test specimens, as well as various other requirements.
"Therefore, not all of the total 10 Km planned to be blacktop, only 6 Km uses VTO, the remaining 4 Km uses conventional asphalt. All of this will be trial, what will be the difference, "he concluded. (LU / CK)

Author: Lia Ursula, S.AP, MT.
Reviewing Publication Sub Division of Personnel, Law and Public Communication,
Administrative Section, BBPJN VII Semarang

Reference:

1. Pavement Design Manual 2017

2. Road Maintenance Procedure