Impact of different types of polycarboxylate superplasticisers on spontaneous crystallisation of ettringite

Markus R. Meier, Alexander Rinkenburger, Johann Plank

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

The spontaneous crystallisation of ettringite from combined calcium hydroxide (Ca(OH)2) and aluminium sulfate (Al2(SO4)3) solutions was investigated in the presence and absence of three different kinds of polycarboxylate superplasticisers. The crystallisation period was limited to 10 s only to study the initial crystals, which provide the anchoring sites for most admixtures in cement. It was found that, in the absence of polycarboxylate polymers, only few, but large (l∼3.5 μm), hexagonal, prismatic ettringite crystals exhibiting numerous defects on their surfaces were formed. However, when polycarboxylate polymers were present during the crystallisation, then the crystal sizes decreased to ∼0.5-2.1 μm. Generally, crystal sizes were found to decrease with increasing specific anionic charge of the same kind of polycarboxylate polymer. Apparently, polymers exhibiting a higher affinity to the crystal surfaces of ettringite inhibit its growth more strongly and produce smaller crystals. Furthermore, the specific chemistry (base monomers) of the polycarboxylate also has an impact on the size of ettringite crystals.

Original languageEnglish
Pages (from-to)310-319
Number of pages10
JournalAdvances in Cement Research
Volume28
Issue number5
DOIs
StatePublished - 1 May 2016
Externally publishedYes

Keywords

  • Admixtures
  • Electron microscopy
  • Solution chemistry

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