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

Abstract The (early) hydration mechanisms of two different binder systems used for shotcrete were investigated: the so far almost unexplored low sulfate (spray binder), in field dry-mix shotcrete; and ordinary Portland cement, accelerated by aluminum sulfate, widely wet-mix shotcrete. basis fast setting spray is rapid dissolution C 3 A subsequent formation flaky CO -AFm phases. Thereby induced high concentrations pore solution lead to a blockage alite during first hours hydration. At later stages, higher amounts portlandite are formed dry-mix, compared system. lower calcium availability system explained an enhanced C–A–S–H phases with Ca:Si ratio. Additionally, show porosity compressive strength after 1 d beyond. Graphical abstract