Experimental study on the synthesis and characterization of volcanic rocks (pozzolan and perlite)-based geopolymers

Abstract

The geopolymer preparation based on natural pozzolan is a promising route. Thus, improving the physicochemical properties of these geopolymers by adding other volcanic rocks merits investigation. The present work aims to study the effect of perlite addition, as an acidic volcanic rock, on the physico-chemical and microstructural properties of geopolymers based on pozzolan (basic volcanic rock). The perlite proportion varied between 0 and 50%. A mixture of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) was used as an alkaline activator. The perlite effect on the physico-mechanical properties of the synthesized geopolymers was evaluated by the compressive strength (Rc), P-wave velocity (Vp), bulk density (D), and porosity (P). The microstructural aspects have been explored by X-ray Diffractometry (XRD), Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray spectroscopy (EDS). The results highlight the possibility of obtaining an eco-efficient geopolymer, with compressive strength of up to 50 MPa at 28 days by partially replacing the pozzolan by 40% of the perlite, due to the formation of more amorphous N-A-S-H type gel. However, the excessive content (over 40%) of perlite had a negative effect on the development of the compressive strength and microstructure of the pozzolan-based geopolymer, which was related to the formation of zeolitic phases in the geopolymer matrix. This study confirms the promise of using pozzolan-perlite-based geopolymers as sustainable building materials, which could significantly promote the development of geo-resources and environmental protection in the construction sector.