Effects of alkaline solution/binder and Na2SiO3/NaOH ratios on fracture properties and ductility of ambient-cured GGBFS based heavyweight geopolymer concrete

Abstract

In designing and modelling of nuclear facilities and gravity-based structures constructed with the ambient-cured ground granulated blast furnace slag (GGBFS) based heavyweight geopolymer concrete (ACGHWGC) based on fracture mechanics, it is necessary that fracture parameters of this new material be determined at the first stage. In the present study, effects of alkaline solution to binder ratio (Al/Bi) (i.e. 0.65, 0.75 and 0.85) and Na2SiO3 to NaOH solution ratio (SS/SH) (i.e. 0.25, 0.5 and 0.75) on the fracture properties of the ACGHWGC have been investigated. The fracture parameters of the ACGHWGC including total fracture energy (GF), initial fracture energy (Gf), fracture toughness (KIC), characteristic length (Lch), effective size of the process zone (Cf), critical effective crack-tip-opening displacement (δc) and the brittleness number (β) are determined using work of fracture method (WFM) and size effect method (SEM) and the results obtained are compared. The results show that the Al/Bi ratio has more effects than that of the SS/SH ratio on the fracture properties of the ACGHWGC. The results indicate that as the Al/Bi ratio increases from 0.65 to 0.85, the fracture energy as well as the fracture toughness decrease and the ductility increases. Moreover, maximum fracture energy and fracture toughness and the highest brittleness are obtained from the samples with the SS/SH ratio of 0.5. The results indicate that as the compressive strength increases, the fracture energy, the fracture toughness, and the brittleness are enhanced. In all samples, as both the GF in the WFM and the Gf in the SEM increase, the GF/Gf ratio decreases. In addition, minimum ratio of the GF/Gf (equal to 3.1) is obtained from the ACGHWGC with the Al/Bi and the SS/SH ratios of 0.65 and 0.5, respectively.