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

Abstract

<jats:sec><jats:title>Abstract</jats:title><jats:p>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 C<jats:sub>3</jats:sub>A and the subsequent formation of flaky CO<jats:sub>3</jats:sub>-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.</jats:p></jats:sec><jats:sec><jats:title>Graphical abstract</jats:title></jats:sec>

Topics

• impedance spectroscopy
• pore
• phase
• atomic force microscopy
• aluminium
• strength
• cement
• porosity
• Calcium
• size-exclusion chromatography