IO, Surabaya – The use of plastic waste as a substitute for and additive to asphalt concrete apparently has positive potential in the midst of current infrastructure construction. As a result, students from Institute Teknologi Sepuluh Nopember (ITS), joined in a Student Creativity Program (PKM) team and conducted research in an attempt to continue to improve the quality of roads.
Team head Thoriqul Huda stated that the use of plastic waste as an aggregate in asphalt concrete increased its hardness and endurance. However, the hydrophilic (polar) nature of asphalt was in opposition with plastic, which is hydrophobic (nonpolar).
It was explained that an indication of agglomeration in the pavement structure of roads was measured by the increase in the Void In Mix (VIM) taken from a Marshall test. “The VIM value tended to increase as the percentage of plastic level rose,” said the ITS Civil Engineering Department student, as quoted from a press release received by the Independent Observer, Friday (19/7/2019).
The VIM value impacted the endurance of the pavement layer. The higher the VIM value, the more porous the mixture became. This results in the asphalt cement more easily absorbing water and air which increases oxidation.
Water dissolves the parts which will then be oxidized and result in an increasing reduction of asphalt in the mixture. This then causes a decrease in adhesion between the construction aggregate, threatening reveling and stripping of the pavement. A coupling agent that must be both hydrophobic and hydrophilic then needs to be added, according to Thoriq.
Previous research compared the use of an epoxy and lignin coupling agent, in a mixture of polyethylene terephalate (PET) and polyolefins (POs), which are polar and nonpolar. The research concluded that the lignin mixture used as a coupling agent could create a mixture which had better distribution and dispersion compared to an epoxy coupling agent.
This research was conducted by Thoriq, together with Moh Firli Firdausi from the Civil Engineering Department and Muhammad Rizal Afif from the Material Engineering Department, joined together in the PKM – Research team; they worked to increase the quality of the AC-BC layer measured by the Marshall stability parameter, as a layer between structures on the surface of roads, using a Polymer Modified Bitumen (PMB), Low Density Polyethylene (LDPE) plastic waste, and lignin as a coupling agent.
Thoriq stated that the aim of the research was to discover the morphology and bonds created as a result of the increase in lignin as a coupling agent to Polymer Modified Ritnen (PMB). “Also, to obtain a recommended proportional mixture for the AC-BC layer which impacts the use of plastic waste and decreases road surface implementation costs,” he said.
From the research, according to Thoriq, an increase in stability of the AC-BC layer of up to 75.8% was found, compared to only using pure asphalt. Another benefit was a reduction in road construction costs of Rp 40,480,625.09 and the use of 3.96 tons of LDPE plastic waste per km.
Thoriq hopes that the research can be used by the Balai Besar Pelaksanaan Jalan National (BBPJN) as in 2018, the related Ministry planned on conducting a 27 km trial of plastic-infused roads. “We hope (they) will be able to use the results from our research for infrastructure managers in the government as a reference or input to the research we have conducted,” said Thoriq. (est)