Behavior of metakaolin-based potassium geopolymers in acidic solutions

This work studies the behavior of a metakaolin-based potassium geopolymer immersed in HCl solution (pH = 2). The polymer was attacked in three different ways to determine the effects of the immersion time, successive acid attack and the S/V value (sample mass/volume of solution) on the released elements and on pH. XRD, SEM and compressive strength studies showed that the basic geopolymer network remains intact regardless of the attack method. pH monitoring and FTIR demonstrated the existence of KHCO3 and K2CO3, likely resulting from the excessive KOH after the geopolymer samples react with atmospheric CO2. These basic species were considered the main products of the initial immersion in HCl solutions.