Effect of blast-furnace slag on physicochemical properties of pozzolan-based geopolymers

This research focuses on the synthesis and characterization of geopolymers based on French pozzolan (P) by adding two types of blast-furnace slags with different chemical compositions (L1 and L2). The slags amount varied between 0% and 50%. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) were used as the alkaline activator. The physicomechanical properties of the synthesized geopolymer cements were evaluated. Complementary studies using X-ray diffractometry (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) were also performed. The results found proved that adding the two slags to the pozzolan led to considerable improvement in the geopolymers' physicomechanical properties. In comparison, the L1 slag addition, more magnesian than L2, favored the formation of more quantity of amorphous phase and also the mineral phase of hydrotalcite-type, which justifies the high geopolymers’ physicomechanical characteristics based on L1 slag (series 1) compared with those synthesized from L2 slag (series 2) obtained at 28 days of curing. [Display omitted] •Geopolymers from volcanic pozzolan (P) and two blast-furnace slags (L1 and L2) were prepared.•Mechanical properties of pozzolan-based geopolymers increased with the increase of blast-furnace slags added.•The 50% L1 slag addition, which is more magnesian than L2 slag, resulted in high compressive strength of 105 MPa.•The synthesized geopolymers are ecological and mechanically efficient to replace traditional building materials.