The use of high calcium wood ash in the preparation of Ground Granulated Blast Furnace Slag and Pulverized Fly Ash geopolymers: A complete microstructural and mechanical characterization

Abstract

As concern regarding global environmental issue grows, there is an emerging interest to substitute conventional ordinary Portland cement by using geopolymer composite as binder matrix in concrete. However, there are two main components that become a barrier in industrialization of geopolymer are the high content of chemical activator and requirement for post fabrication heat treatment which is an energy intensive process. The study investigate the hybridization of three industrial byproducts namely Ground Granulated Blast Furnace Slag, High Calcium Wood Ash and Pulverized Fly Ash activated with reduced level of alkaline activator and produced without any thermal treatment and possesses adequate mechanical performance mortar for industrial application. Besides, the properties of low energy hybrid geopolymer mortar were assessed based on the mechanical and microstructure aspects. Test specimens were evaluated in terms of standard consistency, setting times, compressive strength, flexural strength, ultrasonic pulse velocity, dynamic modulus of elastic, and microstructure development. The inclusion of Pulverized Fly Ash at the content of 10–60% by binder weight does reduce the water demand and significantly prolonged the setting times of hybrid geopolymer paste. Enhanced modulus of elasticity, ultrasonic pulse velocity, compressive and flexural strength were observed for hybrid geopolymer concrete with Pulverized Fly Ash content of 40–80% by binder weight compare to control mixture, 0% PFA. Besides, from Scanning Electron Microscope micrograph and Energy Dispersive X-ray analysis geopolymer paste matrix indicated the formation of geopolymeric products of C-A-S-H and N-A-S-H that contributes to the early strength development on geopolymer mixture contains 0% up to 60% percentage of Pulverized Fly Ash.