Reuse of iron ore tailings for production of metakaolin-based geopolymers

Mining tailings are becoming more and more abundant and consequently it has been shown to be a material of great concern, especially after the dam failures in Brazil, Bento Rodrigues, 2015 and Brumadinho, 2019. In this work, iron ore tailings (IOT) were used as an aggregate in the production of geopolymers based on metakaolin used as a precursor and activated in alkaline solution. The alkaline solution was produced from a commercial solution of sodium silicate Na2SiO3 (SS) and a 10 M solution of sodium hydroxide NaOH (SH) prepared from solid flakes (3:1 mass ratio of SS:SH). Two syntheses were carried out, one by mixing metakaolin (MK) with the activator solution (AS) (1:1 mass ratio of MK:AS), called matrix, and another with the addition of aggregate (AG) to the matrix (1:1:2 mass ratio of MK:AS:AG), called geopolymer. XRD, FTIR, Mössbauer and SEM were used to analyze the inputs and materials produced, in addition to the analysis of compressive strength. The matrix reached a strength of 45.88 MPa with 7 days of curing, while the addition of IOT generated an increase in strength to the material, reaching values between 59.59 and 64.90 MPa also with 7 days of curing.