Nanozeolite Synthesis and Application in a Metakaolin-Based Geopolymer

Abstract

Alkali-activated cementitious cement such as geopolymers represent an alternative that allows to reduce the carbon footprint in the construction industry due to the CO₂ emissions to the atmosphere that occur during the manufacture of portland cement (CP). During the synthesis of geopolymers, zeolites (mainly faujasite) are formed, which contribute to the improvement of strength and durability. In this work, faujasite type NaY was synthesized from Sodium Hydroxide (NaOH), soluble Sodium Silicate (Na₂SiO₃) and Sodium Aluminate (NaAlO₂). The nanozeolite was added to a metakaolin-based geopolymer, activated with an alkaline solution composed of NaOH and Na₂SiO₃. The geopolymer was prepared by varying the molarity of the NaOH in the alkaline activating solution (AAS). Two types of zeolites were used: natural clinoptilolite-type faujasite and synthesized NaY-type faujasite. The hydration process was analyzed using Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM). According the results, increasing the molarity of the NaOH of the alkaline activator (AA) promotes the dissolution of bonds, favoring the formation of aluminum-rich species and a higher degree of polymerization.