Rheological and microstructural properties of FA+GGBFS-based engineered geopolymer composites (EGCs) capable of comparing with M45-ECC as mechanical performance

Abstract

In this study, it has been aimed to obtain the fly ash + ground granulated blast furnace slag (FA + GGBFS)-based engineered geopolymer composites (EGCs) having similar bearing strength and deformation capacity with the engineered cementitious composite (M45-ECC) known as M45. EGCs incorporating 70% FA and 30% GGBFS as binder were developed under three different groups in which the different ratios of alkali liquids/binder (AL/Bi) with the different content of AL + Bi. All of eight FA + GGBFS-based EGCs designed with 2.5 ratio of Na2SiO3/NaOH. FA + GGBFS-based EGCs, which were kept in the mold under laboratory conditions for 24 h immediately after production, were kept in water at 60 °C until the test age. The fresh, rheogical, mechanical and microstructural properties of FA + GGBFS-based EGCs were determined. Test results indicated that FA + GGBFS-based EGCs can be developed with similar or higher compressive strength and ductility than that of M45-ECC. However, the flexural strength of M45-ECC was higher than those of all other composites. In addition, TGA/DTA and FTIR analysis supported that the excessive amount of AL + Bi content would not improve the characteristics of FA + GGBFS-based EGCs after the optimal production of C–S–H and N-A-S-H gels which acquired in geopolymerization. However, ductility continued to improve significantly as the AL + Bi content increased. Moreover, reduction of AL/Bi ratio increased the total gel content and thus, the compressive strength of composites developed.