Effect of sulfate content on the porosity distribution and resulting performance of composite cements

The results demonstrate that the sulfate content influences the ettringite content and impacts the porosity distribution. The ettringite stabilization by the sulfate added results in a higher solid volume and thus in a lower total pore volume. However, this phenomenon cannot explain the experimental observations of strength loss for high sulfate contents. Dynamic vapor sorption results reveal that there are fewer coarse capillary pores and more fine gel pores as the sulfate content increases. The mechanical model reflecting both aforementioned phenomena enables the reproduction of the strength evolution typical for the sulfate optimization experiments, i.e. the initial increase of the strength with the increasing sulfate content followed by the maximum and strength decrease.