The hydration of fast setting spray binder versus (aluminum sulfate) accelerated OPC

Lukas G. Briendl, Florian Mittermayr, Rudolf Röck, Florian R. Steindl, Marlene Sakoparnig, Joachim Juhart, Fatemeh Iranshahi, Isabel Galan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Abstract: The (early) hydration mechanisms of two different binder systems used for shotcrete were investigated: the so far almost unexplored low sulfate binder (spray binder), used in the field of dry-mix shotcrete; and ordinary Portland cement, accelerated by aluminum sulfate, widely used for wet-mix shotcrete. The basis for the fast setting of the spray binder is the rapid dissolution of C3A and the subsequent formation of flaky CO3-AFm phases. Thereby induced high aluminum concentrations in the pore solution lead to a blockage of alite dissolution during the first hours of hydration. At later stages, higher amounts of portlandite are formed in the dry-mix, compared to the wet-mix system. The lower calcium availability for portlandite formation in the wet-mix system is explained by an enhanced formation of C–A–S–H phases with a higher Ca:Si ratio. Additionally, wet-mix systems show lower porosity and higher compressive strength after 1 d of hydration and beyond. Graphical abstract: [Figure not available: see fulltext.]

Original languageEnglish
Article number74
JournalMaterials and Structures
Issue number2
Publication statusPublished - Mar 2022


  • Accelerator
  • Hydration
  • Pore solution
  • Shotcrete

ASJC Scopus subject areas

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


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