Modification of alkali-activated fly ash-granulated blast furnace slag-steel slag: effect of thermodynamic modeling and graphene oxide

Abstract Synthesizing alkali-activated materials (AAM) with multi-component feedstock is a promising technology for resource utilization of massive industrial wastes, and there is an urgent need to develop proportional design methods. A thermodynamic modeling assisted design method was proposed for the fly ash (FA)-granulated blast furnace slag (GBFS)-steel slag (SS) AAM, of which the mechanical properties and multi-scale shrinkage were modified by incorporating graphene oxide (GO). The FA/GBFS mass ratio and SS content had a significant effect on the solid–liquid and crystalline phases, consistent to the thermogravimetric analysis and mechanical performances of the AAM. For the optimized FA:GBFS:SS mass ratio of 3:5:2, the mechanical strengths increased with the increment of GO content, then decreased, while the shrinkages at different stages and scales followed the opposite trend. At a GO dosage of 0.01%, the compressive, flexural, and tensile strengths increased by 9.6%, 67.1%, and 135%, respectively, while the chemical, autogenous, and drying shrinkage were reduced by 43.2%, 26.5%, and 46.1%, respectively. These modifications were mainly attributed to the refined pore structure and decreased micro-cracks of AAM through bridging and filling effects of GO, and the increased formation of C(N)-A-S–H gels thanks to the raised nucleation sites by the high specific surface areas of GO.