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

• Published in: Journal of Building Engineering Vol. 65; p. 105792
• Main Authors: Öz, Hatice Öznur, Güneş, Muhammet, Yücel, Hasan Erhan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.04.2023
• Subjects: FA+GGBFS-based EGCs; Fresh and rheogical properties; M45-ECC; Mechanical properties; Microstructural characteristics; Mechanical properties; Fresh and rheogical properties; Microstructural characteristics; M45-ECC; FA+GGBFS-based EGCs
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2022.105792

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. •A total of 8 FA + GGBFS-based EGCs with different design parameters were developed.•FA + GGBFS-based EGCs showed similar fresh and rheological properties with M45-ECC.•FA + GGBFS-based EGCs with much higher compressive strength and ductility than that of M45-ECC were obtained.•The ductility improved significantly as the AL + Bi content increased.•The test results were supported with the microstructural analysis of EGCs.