Experimental study on eco-friendly one-part alkali-activated slag-fly ash-lime composites under CO2 environment: Reaction mechanism and carbon capture capacity

Abstract

This work studied the reaction mechanism and carbon capture capacity of novel type eco-friendly one-part alkali-activated slag-fly ash-lime composites (SFL) based on the change in SFL under CO2 environment from the macroscale to the microscale. Experimental results showed that SFL had a higher carbonation rate and led to the formation of carbonates (calcite, vaterite, aragonite), gypsum, amorphous calcium carbonate, and alumino-silicate gel. The carbonation reaction of SFL can be generally divided into three periods. In period 3, Al from the decomposed aluminum-bearing hydrates was gradually incorporated into the amorphous silica phase in the form of tetrahedral Al(-SiO)4 sites, which finally resulted in the formation of an alumino-silicate gel. The mass ratio of carbon capture in the complete carbonation zone of SFL is approximately 13%. Due to a large amount of CO2 binding in hydrates in a wider carbonation zone, the actual total capacity of carbon capture in SFL under CO2 environment was slightly lower than that in Portland cement. Thus, SFL had a better and adjustable capacity for CO2 capture compared to other low carbon binder materials.