Influence of the activating solution and aggregates in the physical and mechanical properties of volcanic ash based geopolymer mortars

The physical, mechanical and microstructural properties of volcanic ash based geopolymer mortars by alkaline activation (with NaOH and Na(OH) + Na₂SiO₃ solutions) using different aggregates (Peruvian sand and standard sand) were studied. For the synthesis of geopolymers, a liquid:solid ratio of 0.1 and an ash:sand ratio of 1:1 were selected, and 25% of sodium silicate was added to the Na(OH) solution. The samples were compacted, toughened and cured at 80°C for 48 h. The dissolution of volcanic ash particles and the formation of the geopolymeric matrix increase with Na(OH)+Na₂SiO₃ solution and standard sand while the local sand promotes better geopolymerization with NaOH solution. The compression strength of volcanic ash based geopolymer mortar reported values from 18.93 MPa to 23.28 MPa at 6 months of curing, which determines the use of these geopolymers as a construction material.