Strength, permeability and micro-structural characteristics of low-calcium fly ash based geopolymers

The paper presents the properties of low-calcium fly ash based geopolymer concrete in which fly ash was partially replaced (0, 10, 20 and 30%) with ordinary Portland cement (OPC). Tests were conducted for workability, compressive strength, split tensile strength and rapid chloride permeability (RCPT) up to the age 28 days. SEM, EDS and XRD analysis were also carried out. Test results indicate that workability of low-calcium fly ash based geopolymer concrete decreased with increase in OPC content. Further, inclusion of OPC enhanced the compressive strength and reduced the permeability at all ages (3, 7 and 28 days). However optimum results were obtained for geopolymers with 20% OPC. SEM, EDS and XRD analysis confirmed the modifications in matrix making it denser, compact and less permeable. (C) 2017 Elsevier Ltd. All rights reserved.