An integrated microstructural-nanomechanical-chemical approach to examine material-specific characteristics of cementitious interphase regions

Mahdieh Khedmati, Yong Rak Kim, Joseph A. Turner, Hani Alanazi, Charles Nguyen

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Effective properties and structural performance of cementitious mixtures are substantially governed by the quality of the interphase region because it acts as a bridge transferring forces between aggregates and a binding matrix and is generally susceptible to damage. As alternative binding agents like alkali-activated precursors have obtained substantial attention in recent years, there is a growing need for fundamental knowledge to uncover interphase formation mechanisms. In this paper, two different types of binding materials, i.e., fly ash-based geopolymer and ordinary portland cement, were mixed with limestone aggregate to examine and compare the microstructures and nanomechanical properties of interphase region. To this end, microstructural characteristics using scanning microscopies, nanomechanical properties by nanoindentation tests, and spatial mapping of chemical contents based on the energy dispersive spectroscopy were integrated to identify and investigate the interphase region formed by the case-specific interactions between the matrix materials and limestone. The integrated microstructural-nanomechanical-chemical approach was effective to better understand links between material-specific properties of cementing phases. More specifically, the fly ash-based geopolymer paste was usually well bonded to the aggregate surface with a rich formation of N-A-S-H gel, while interfacial debonding was often observed between aggregate surface and paste in ordinary portland cement concrete. However, when a good bonding between aggregate and paste is formed, interphase region in PCC did not show any considerable difference in nanomechanical properties compared to the bulk paste.

Original languageEnglish (US)
Pages (from-to)154-164
Number of pages11
JournalMaterials Characterization
Volume138
DOIs
StatePublished - Apr 2018

Keywords

  • Cementitious concrete, Geopolymer
  • Chemical mapping
  • Interfacial transition zone (ITZ)
  • Microstructure
  • Nanomechanical properties

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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