Durability of fly ash/GGBFS based geopolymers exposed to carbon capture solvents

Abstract

This paper examines a series of fly ash and ground granulated blast furnace slag binders formulated to examine the effects of composition and mix design on performance and durability when exposed to aggressive environments found in carbon capture facilities (monoethanolamine or concentrated potassium carbonate, as well as distilled water). Ordinary Portland cement and ordinary Portland cement fly ash blends were examined for comparison. The samples are exposed to solvents by immersion under static conditions. Leaching and mechanical strength tests show a wide range of geopolymer performance, depending on the initial mix design and the nature of the aggressive agent. Alkali carbonate solutions are found to be the most aggressive agent among those tested in terms of geopolymer mass and strength loss; nonetheless, the resistance to structural degradation upon carbonation of the geopolymer binder structure is mitigated to a significant extent by the low calcium content of the geopolymer binder. Less porous materials, or materials with smaller and more tortuous pores, show in many cases a markedly higher durability; porosity is shown to hold the key to durability. In traditional cement based binders, strength is lost through chemical attack upon exposure to solvents.