Rheology and thixotropy of one-part fly ash/slag blended geopolymer pastes

Yazan Alrefaei, Yanshuai Wang, Jian-Guo Dai, Ye Qian

Research output: Unpublished conference presentation (presented paper, abstract, poster)Conference presentation (not published in journal/proceeding/book)Academic research

Abstract

The research area of geopolymer is flourishing vividly. The bulk of currently available research is related to “two-part” geopolymer (i.e. using conventional liquid alkaline activators), while limited research was conducted on “one-part” geopolymer (i.e. using solid activators). The technology of “one-part” geopolymer is promising due to its simple operation (i.e. “just add water”) alike ordinary Portland cement (OPC). However, in order to promote the use of such environmentally-friendly binders as building or repairing materials, their rheological behavior must be clearly identified.
In this study, the rheological and thixotropic behaviors of one-part geopolymer pastes were evaluated. The one-part geopolymer pastes were synthesized using 50% fly ash and 50% slag. The solid activator used was anhydrous sodium metasilicate (Na2SiO3-Anhydrous) and the activator content used was 10% by the mass of binder. The water-to-binder ratio (w/b) was fixed at 0.45. Three rheological protocols were used in this study: 1) constant angular velocity to evaluate thixotropy through stress decay process, 2) step down protocol to obtain the dynamic yield stress and 3) intermediate constant angular velocity to measure the static yield stress. Three samples were tested for each rheological protocol and the average values were reported. It was found that the one-part geopolymer pastes activated using anhydrous sodium metasilicate powder possessed highly thixotropic behavior. The static yield stress was markedly higher than the dynamic yield stress for the achieved one-part geopolymer binders, resulting in a thixotropy index (Rthix = static stress/ dynamic stress) of 4.8. The flocculation state of fly ash/slag alkali-activated gepolymer pastes had slower destructuration rate and stronger bonding in case of using higher activator content, which is directly related to thixotropy. Furthermore, the chemical composition and purity of fly ash highly affected the thixotropy of one-part geopolymer.
Original languageEnglish
Publication statusPublished - Mar 2020
EventRILEM-SC2020 Ambitioning a Sustainable Future for Built Environment: Comprehensive Strategies for Unprecedented Challenges - Guimarães, Portugal
Duration: 10 Mar 202014 Mar 2020

Conference

ConferenceRILEM-SC2020 Ambitioning a Sustainable Future for Built Environment: Comprehensive Strategies for Unprecedented Challenges
Abbreviated titleRILEM-SC2020
CountryPortugal
CityGuimarães
Period10/03/2014/03/20

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