Bond Strength and Fracture Toughness of Alkali Activated Self-Compacting Concrete Incorporating Metakaolin or Nanosilica

This study aims to evaluate the effect of nanosilica (NS) and metakaolin (MK) as binder replacement materials on the fresh and hardened characteristics of slag (GGBS)-based alkali-activated self-compacting concretes (A-ASCC). Therefore, nine A-ASCC mixes, with and without metakaolin, were prepared, as well as mixes with and without NS incorporation. In the production of A-ASCC mixes, GGBS was used as a binder material. The fresh properties of A-ASCC were determined using the L-box, V-funnel, T50 value, and slump flow tests, while the hardened properties were examined using compressive strength, bonding strength (pullout test), fracture toughness, and flexural tensile strength tests. A relationship analysis was also conducted on the A-ASCC experimental data. The experimental results showed that NS and MK had a negative effect on the fresh properties of GGBS-based A-ASCC mixtures, whereas metakaolin had a greater influence. The addition of 1% and 2% NS, on the other hand, improved the mechanical performance of the A-ASCC specimens significantly. The use of more than 2% NS had a harmful effect on the mechanical properties of A-ASCC. A 5% replacement ratio of metakaolin improved the mechanical properties of A-ASCC. The use of metakaolin at ratios of more than 5% had a negative effect on the properties of A-ASCC.