Influence of the activating solution on the mechanical properties of compacted volcanic ash based geopolymers

Abstract

This work studies the mechanical properties of volcanic ash based geopolymer mortars. The geopolymer mortars were made with volcanic ashes from Ubinas volcano using mixtures of Na2SiO3 and 12 M NaOH as alkaline activator. Solutions with different concentrations of silicate (0-25 % by wt.) were used. The geopolymer mortars were compacted at 15 MPa and cured at 80°C for three different periods of time. The results show the influence of the concentration of Na2SiO3 in the compression strength and wear resistance, raising highest compression strengths for 20-25% of Na2SiO3 while the wear resistance was higher at concentrations over 20% of Na2SiO3. In this optimal ratio, for 20% Na2SiO3, a compression strength up to 52.3 MPa was recorded at 7 days. Considering the overall performance analysis, the synthesis of geopolymers with volcanic ash promises a solution for sustainable mortar production and natural waste disposal.