Experimental Investigation on Durability Performance of Nano Orion–Modified M35 Grade Concrete

Concrete structures exposed to harsh conditions like sulphates, acids, and chlorides often deteriorate faster, decreasing their lifespan and raising maintenance expenses. Improving concrete durability while supporting sustainable building practices has become a key research area. This study examined the effectiveness of Nano Orion, a nano-silica–based material, as a partial cement substitute in M35 concrete. Nano Orion was added at replacement levels of 0%, 1%, 2%, 3%, 4%, and 5% by weight of cement, with a constant water–binder ratio. Durability was tested through sulphate attack, acid resistance, and chloride resistance, measuring weight loss and residual compressive strength. Results showed significant durability improvements with Nano Orion compared to standard concrete. The mix with 3% Nano Orion performed best overall, showing minimal mass loss and strength reduction under harsh conditions. The durability boost is due to Nano Orion’s pozzolanic activity and fine filler properties, which refine pores, densify the matrix, and generate more secondary C–S–H gel. Levels above 3% slightly decreased performance, likely from nanoparticle agglomeration and dispersion issues. Overall, 3% Nano Orion is identified as the optimal amount for enhancing M35 concrete’s durability. The results suggest Nano Orion–modified concrete can be a durable, sustainable material for structures in aggressive environments.