Effect of Micro- and Nano-Zeolite/Silica Fume on the Mechanical and Durability Characteristics of Reactive Powder Concrete

Silica fume is an essential additive in Reactive Powder Concrete (RPC), as it promotes hydration and densifies the microstructure. In this research, silica fume was partially or fully replaceded with zeolite, introducing a novel 1:1 calcinated zeolite/silica fume composite. The research examines both complete and partial replacements of silica fume with micro-zeolite and a micro-zeolite/silica fume calcinated composite. Additionally, it explores the replacement of silica fume with nano-zeolite and a nano-zeolite/silica fume calcinated composite, with substitution levels ranging from 1% to 5%. The results indicate that micro-zeolite alone negatively impacts the mechanical and durability properties of RPC, reducing compressive, tensile, and flexural strengths, while increasing sorptivity, water absorption, and acid attack resistance. Conversely, the micro-zeolite/silica fume composite enhanced both strength and durability. The MZS100 mixture showed notable 28-day gains: compressive strength increased by 19.7%, tensile by 28.8%, and flexural by 21.2%.. Additionally, sorptivity, water absorption, and acid attack resistance were reduced by approximately 26.0% compared to the control mix. Similarly, nano-zeolite alone has a limited impact on RPC performance. However, the calcinated composite of nano-zeolite/silica fume significantly enhanced the RPC properties. The optimal mechanical performance was observed at a 4% replacement level, where compressive strength increased by 14.8%, tensile strength by 27.7%, and flexural strength by 19.4%. For durability, the best improvement was observed at a 5% replacement, with a 15.0% reduction in sorptivity, water absorption, and acid attack resistance compared to the control mix.