Contribution of Fineness Level of Fly Ash to the Compressive Strength of Geopolymer Mortar

¹ Civil Engineering Department, Faculty of Engineering, Bina Darma University, Palembang 30264, Indonesia
² Civil Engineering Department, Faculty of Engineering, Universitas Sriwijaya, Palembang, 30136, Indonesia

^* Corresponding author: firdaus.dr@gmail.com

Abstract

The development of geopolymers has allowed the flash as the substitution of cement in the application of concrete. Therefore, this will be very useful considering the quite abundant by-product materials from power plants burning coal in South Sumatera. However, the untreated fly ash from the source caused its fineness level unpredictable, whereas the fineness of binder in cementitious material significantly affects the mechanical properties of the harden. Therefore, this study aims to determine the contribution of the fineness level of fly ash to the compressive strength of geopolymer mortar, as well as its excellent composition. Type F fly ash from Tanjung Enim Power Plant was treated by filtering to obtain different fineness levels based on the fall zones of the ash. Activators used in geopolymer mixing were sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) with three activator/fly ash ratios which was 0.25, 0.35 and 0.45. The results showed that the fineness level based on fall zone as well as the activator to fly ash ratio significantly influenced the compressive strength of the geopolymer mortar. The compressive strength of the F4-P4 specimen of geopolymer mortar with zone-4 fly ash and an activator ratio of 0.45 achieved 28.2 MPa at 28 days.