Effect of the Al content and the Ca/Si ratio on the structure and reactivity of calcium aluminosilicate glasses used as model SCMs

Since the reactivity of SCMs is affected by different specific properties, it is crucial to understand their impact. This study, therefore, focuses on how the Al content and Ca/Si ratio affect the structure and reactivity of calcium aluminosilicate glasses. The glasses were synthesized amorphous in 2 series with Al contents ranging from 5 to 40 wt% (Ca/Si mass ratio = 1:1) and Ca/Si ratios ranging from 0.21 to 1.00 (Al 2 O 3 content = 15 wt%). Structural analysis by FTIR, 27 Al and 29 Si MAS NMR, and theoretical NBO/T calculations showed an increasing degree of polymerization with increasing Al content or decreasing Ca/Si ratio. The reactivity, examined by the R 3 test and in cement pastes, was less affected by the degree of polymerization but more by the Al content. These findings provide insights into the dependence of structure and composition on the reactivity of model SCMs that may help in the search for new SCM sources in the future. • Structural analysis of 2 series of CAS glasses with varying Al content or Ca/Si ratio • Reactivity of artificial SCMs increases with their Al content. • Ca/Si ratio seems to have a minor impact compared to Al content regarding reactivity. • Comparison of the phase assemblage in the R 3 test and cement pastes (up to one year)