IPTEK The Journal for Technology and Science, Vol. 29(3), December. 2018. 2088-2033 (pISSN: 0853-4098) 86 Analysis of Aggregate Gradation to Improve The Characteristics of Geopolymer Based Asphalt Concrete Akhmad Taufik Aditama 1a , Januarti Jaya Ekaputri 1b , Ervina Ahyudanari 1c AbstractThe previous study showed that asphalt concrete using filler geopolymer generate a higher value of stability. On the other hand, the value of flow and the porosity of the asphalt concrete were out of the specification range. This study examines the aggregate gradation analysis to improve the characteristics of mixed asphalt concrete geopolymer. The gradation of aggregate is variated into three following the available specification. The range of specification is then separated into three; those are aggregate gradation upper specifications, middle specification, and lower specification. Filler comes from geopolymer paste, composed of fly ash which is mixed with an activator. Activator is an eight molar concentration of NaOH solution and Na₂SiO₃. The weight ratio of Na₂SiO₃ over the weight of NaOH solution was 1.5. Geopolymer paste waited until reached the age of 28 days, then pounded up to meet the required size of the sieve No. 200. The test of mixture characteristics was conducted to see the comparison of performance from different gradations. The test results showed that middle gradation generating characteristics of the mixture, which is higher than upper gradation and lower gradataion. KeywordsAsphalt Concrete, Geopolymer, Aggregate Gradation, Marshall Characteristics I. INTRODUCTION 1 team Power (PLTU) is a place of producing electrical energy, with the primary fuel is coal. The 50 MWatt power plant requires coal fuel with the amount of 210.1 tons/day and produces solid waste in the form of fly ash up to 17284.65 kg [1]. These wastes can cause health issues and environmental pollution. It must be minimized by conducting research related to the utilization of the waste. Davodovits [2] proposed that geopolymer can be formed from the polymerization of alumina silicate mineral and high alkali solution. One of these minerals is fly ash. Fly ash is a toxic material, with the polymerization process in this geopolymer, a dangerous mix on the fly ash can be controlled. Ekaputri [3] showed that with the process of geopolymerization, fly ash would form a kind of barrier to trap boron on the fly ash. Therefore, geopolymer more environmentally friendly. Boron is an element on the fly ash, which can pose harm to humans and plants if the concentration is high enough [4]. The use of geopolymer materials has several advantages. Some of them are hard, weather resistant, chemical attack, and high temperatures [5]. Geopolymer also can be used as a substitution of cement; therefore, using geopolymer is considered as an environmental conservation. In the process of cement production, CO2 emissions were released into the air. The amount of CO2 equals the production of cement [6]. Other benefits of geopolymer material are its ability to absorb harmful gases from vehicles. Adsorbent made of fly ash can reduce levels of CO and CO₂ emissions of motor vehicles with a maximum contact time of the adsorbent for CO gas is 12 minutes and for CO₂ gas is 14 minutes [7]. The use of nano zeolite-geopolymer as adsorbant managed to absorb Pb₃O₄ and MnO on motor vehicle exhaust gas, which is harmful oxide if inhaled by a human [8]. 1 Department of Civil Engineering, Institut Teknologi Sepuluh Nopember, Surabaya 60111, Indonesia a n E-mail: aditamataufik0@gmail.com b E-mail: januartije@gmail.com c E-mail: ervina@ce.its.ac.id (corresponding author) Geopolymer is a synthesis of alumina silicate (fly ash) and lye (activator). To achieve the desired result, the proportion of both materials should be calculated. Activators that are generally used is a mixture of Na₂SiO₃ and NaOH with concentration 8M to 14M. The ratio between Na₂SiO₃ and NaOH could be selected in the range of 0.4 to 2.5 [9]. The higher the weight ratio of Na₂SiO₃ and NaOH solution does not guarantee to lead to higher tension stress and compression strength. However, the higher molarity is used, the higher the tension stress and its compressive strength[10]. Fly ash is used as geopolymer filler on the mixture of asphalt concrete. There was a study that was using filler geopolymer in asphalt mixture, which produced high stability than ordinary asphalt mixture [11]. Subsequent research [12] showed that the mix of asphalt concrete using filler geopolymer generate better stability than not using filler geopolymer. However, the use of filler geopolymer produced void in the mixture and the void filled with asphalt is less than the specified value. To provide an alternatives improvement on the void in the mixture, there is a need to do some research regarding the analysis of aggregate gradation in the mixture of asphalt concrete geopolymer. The aggregate gradation effects on void volume, which is formed in the mixture. The gradation also affects to workability and stability of the mixture. The changes of aggregate gradation treatment on asphalt concrete mixture affect to characteristics of asphalt concrete mixture [13]. Reducing the percentage of porosity by changing the gradation may increase flexibility and reduce deformation. On the other hand, changing gradation can decrease compressive strength [14]. This study attempts to get a variation on the coarse aggregate gradation. It is expected to provide the best performance on the mixture of asphalt concrete incorporating geopolymer. The second objective of this research is to reduce the waste of coal combustion in order S