Effect of alkali-hydroxide on hydration kinetics and microstructure of high-volume fly ash blended cement pastes

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Author(s)

  • Satya Medepalli
  • Tiao Wang
  • Yuqian Zheng
  • Tetsuya Ishida

Detail(s)

Original languageEnglish
Article number107641
Number of pages18
Journal / PublicationCement and Concrete Research
Volume185
Online published12 Aug 2024
Publication statusPublished - Nov 2024

Abstract

The influence of NaOH on pore structure, reaction kinetics, volume, and morphology of reaction products in high-volume-fly-ash mixtures was explored by two mixing methods: (i) direct addition of 0.2 M, 0.5 M and 1.0 M NaOH solution into cement-FA powder, and (ii) pre-dissolving FA into NaOH solution before mixing with cement. The pre-dissolution technique improved early-age mechanical performance by enhancing Si release, aiding the expedited precipitation of extra C-A-S-H gel. Both methods improved the degree of FA reaction and alite/belite hydration. However, 1.0 M NaOH negatively affected the strength and microstructure properties due to undesirable silica-gel formation, C-A-S-H gel carbonation, and increased capillary pore volume. NaOH concentration has affected the packing density of C-A-S-H gel, where high-pH systems exhibit loosely packed sheet-like clusters. Ca/Si of C-A-S-H gel in low and high pH systems evolved with increased curing age, with low pH system exhibiting high Ca/Si at 90 days. © 2024 Elsevier Ltd.

Research Area(s)

  • Alkali-hydroxide, C-A-S-H gel, High volume fly ash (HVFA), Hydration degree, Microstructure, Pre-dissolution of fly ash

Bibliographic Note

Publisher Copyright: © 2024 Elsevier Ltd

Citation Format(s)