Compressive strength and microstructure of concretes made with supersulfated binders based on volcanic materials exposed to a sulphate environment.

This investigation presents results on concretes fabricated with supersulfated cements (SSC) based on volcanic materials; the binders were composed by pumice (PM), sulfated activators and alkaline activators.  The cementitious content was about 720kg/m³ of concrete. The concretes were cured under  two regimes one for 24 h at 20°C  and other  for 22h at 60°C and then at 25°C. The specimens were exposed to two conditions, dry open conditions in the laboratory and also submerged under water in a solution with 3.5% CaSO4 at 25°C for up to 180 days. After 180 days, the concrete using a binder composed of 5%An-10%CP-10%CaO-75%PM exposed to the CaSO4 solution reached a compressive strength of 46 MPa and 44 MPa under dry laboratory conditions. The microstructure, analyzed by scanning electron microscopy, indicated a relatively dense microstructure. The chemical analysis, by energy dispersive spectroscopy, of the cementitious matrix that the main hydration products were C-S-H and ettringite finely intermixed.