Civil Engineering and Architecture 9(6): 1698-1716, 2021 http://www.hrpub.org DOI: 10.13189/cea.2021.090604 Mechanical Properties and Microstructure of Geopolymer Binder Based on Umeanyar Slatestone Powder Ni Kadek Astariani 1,2,* , I Made Alit Karyawan Salain 3 , I Nyoman Sutarja 3 , Ida Bagus Rai Widiarsa 3 1 Doctoral Program Engineering Science, Udayana University, Denpasar, Indonesia 2 Faculty of Science and Technology, Ngurah Rai of University, Denpasar, Indonesia 3 Department of Civil Engineering, Udayana University, Badung, Indonesia Received June 12, 2021; Revised July 12, 2021; Accepted August 22, 2021 Cite This Paper in the following Citation Styles (a): [1] Ni Kadek Astariani, I Made Alit Karyawan Salain, I Nyoman Sutarja, Ida Bagus Rai Widiarsa , "Mechanical Properties and Microstructure of Geopolymer Binder Based on Umeanyar Slatestone Powder," Civil Engineering and Architecture, Vol. 9, No. 6, pp. 1698-1716, 2021. DOI: 10.13189/cea.2021.090604. (b): Ni Kadek Astariani, I Made Alit Karyawan Salain, I Nyoman Sutarja, Ida Bagus Rai Widiarsa (2021). Mechanical Properties and Microstructure of Geopolymer Binder Based on Umeanyar Slatestone Powder. Civil Engineering and Architecture, 9(6), 1698-1716. DOI: 10.13189/cea.2021.090604. Copyright©2021 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract This research focuses on the mechanical and microstructure properties of geopolymer binder with slatestone waste as the base material. This geopolymer binder comes from industrial waste crushing slate in the Umeanyar area. This waste is processed into stone powder (USSP) which contains SiO 2 (49%), Al 2 O3 (11%), CaO (11.2%). This USSP uses a sodium hydroxide (SS) activator with a concentration of 14 M. The proportion of the mixture of precursor and activator (P/A) is 70%: 30%; 75%: 25%; 80%: 20% and alkaline activator Na 2 SiO 3 : NaOH (SS/SH) of 1:1; 1.5:1; 2:1, by weight. Samples of specimens were made in the form of a cube with a side of 50 mm and tested at the age of 7 and 28 days. Mechanical properties tested include density and compressive strength based on ASTM-C39. Meanwhile, the microstructural analysis used X-Ray Diffraction (XRD) and Scanning Electronic Microscope-Energy Dispersive X-Ray (SEM-EDX) analysis. The results of the density test were 1.90g/cm 3 and 1.85g/cm 3 respectively and the compressive strength test results were 7.40 MPa and 12.73 MPa at the age of 7 and 28 days, respectively. Keywords Compressive Strength, Density, Microstructure, Geopolymer Binder, Slatestone, SEM-EDX, XRD 1. Introduction Concrete is one of the materials needed in the construction sector. The constituent materials of concrete generally consist of cement, aggregate, and water, if necessary there are materials added to change certain properties of the concrete [1]. The use of Portland cement as a concrete-forming material, in its production, requires a very large amount of energy due to heating to a temperature of 1500°C [2-9]. The cement-forming materials consist of limestone (CaCO 3 ), silica sand/clay (SiO 2 and Al 2 O 3 ), and iron oxide (Fe 2 O 3 ). These raw materials are processed through heating and calcination to release carbon dioxide gas (CO 2 ) which is the main contributor to greenhouse gas emissions in the atmosphere [10]. The product in the form of granules in the form of gray marbles with a diameter of about 2 cm is called Portland cement clinker The production of each tonne of cement clinker including its fuel is almost equivalent to one ton of CO 2 gas released into the atmosphere [2,5]. In recent years, the world's cement production has been recorded at 4 billion tons per year, which means about 4 billion tons of CO 2 gas has been released into the atmosphere every year [9,10]. With the results of CO 2 gas emissions that are quite large and have harmed the environment, the mitigation action that can be taken is to reduce the use of cement in the manufacture of concrete.