Rheology, Setting Time, and Compressive Strength of Class F Fly Ash-Based Geopolymer Binder Containing Ordinary Portland Cement

Arash Nikvar-Hassani, Lino Manjarrez, Lianyang Zhang

Research output: Contribution to journalArticlepeer-review

Abstract

This paper investigates the incorporation of ordinary portland cement (OPC) to adjust/improve the workability, setting time, and compressive strength of Class F fly ash (FA)-based geopolymer binder. The geopolymer binder specimens were produced by mixing OPC with FA at a dosage of 0%, 5%, 10%, 15%, and 20% by weight of FA, respectively, and then mixing the mixture with a blended sodium silicate (SS) and sodium hydroxide (SH) solution at a SH concentration of 5 M and a SS/SH ratio of 1. A water-to-solid (W/S) ratio of 0.35, 0.40, 0.45, and 0.50, respectively, was used in preparing the specimens. The viscosity and setting time of the fresh geopolymer binder were measured by using a coaxial cylinder viscometer and a Vicat apparatus, respectively. The specimens were cured at 35°C in an oven for 7 days before tested to measure the unconfined compressive strength (UCS). The results show that the viscosity of the geopolymer binder increases with higher OPC content and lower W/S ratio. The addition of OPC reduces the setting time. The shortest initial and final setting times of 16 and 46 min, respectively, were obtained at W/S=0.35 and 20% by weight OPC. The incorporation of OPC increases the UCS of the geopolymer binder. The highest UCS of 42.4 MPa was obtained at W/S=0.35 and 20% by weight OPC. Microstructural and chemical analyses including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were also carried out and the results indicate that the addition of OPC produces a denser microstructure by the formation of calcium silicate hydrate (CSH) gel along with geopolymer gel.

Original languageEnglish (US)
Article number04021375
JournalJournal of Materials in Civil Engineering
Volume34
Issue number1
DOIs
StatePublished - Jan 1 2022

Keywords

  • Class F fly ash (FA)
  • Compressive strength
  • Geopolymer
  • Ordinary portland cement (OPC)
  • Setting time
  • Viscosity

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Materials Science(all)
  • Mechanics of Materials

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