Multi-Walled Carbon Nanotubes as a Chemical Modifier in Alkali-Activated GGBS Concrete Incorporating Cashew Nut Shell Ash

Abstract

This study examines the performance of ground granulated blast furnace slag (GGBS)-based alkali-activated concrete incorporating cashew nut shell ash (CNSA) as a supplementary binder and multi-walled carbon nanotubes (MWCNTs) as a nano-additive. CNSA replaced 20% of GGBS, while MWCNTs were added at 0–0.4% of binder weight. A 12 M sodium hydroxide solution served as the alkali activator, with a high-pH dispersion method ensuring uniform MWCNT distribution. Tests on workability, density, mechanical strength, electrical resistivity, and durability (water absorption and RCPT) were conducted, supported by SEM microstructural analysis. Results show that CNSA enhances workability, strength, and durability, while MWCNTs further improve mechanical and durability properties and boost electrical conductivity. Optimal performance occurred at 20% CNSA and 0.2% MWCNTs, linked to improved gel formation, matrix densification, and crack-bridging. Excess MWCNTs caused agglomeration, reducing performance. The combined use of CNSA and MWCNTs offers a sustainable route to high-performance alkali-activated concrete.