Durability and Environmental Performance of Nano-SiO ₂ Modified Surface Treatments in Green Concrete Structures

The significant carbon emissions from cement production and the demand for sustainable infrastructure have prompted the development of eco-friendly concrete materials and protective techniques. This research evaluates the durability and environmental performance of Nano- Silicon Dioxide (Nano-SiO 2 ) surface-Treated Green Concrete (GC) incorporating Fly Ash and Silica Fume. Three mixtures, GC-1, GC-2, and GC-3, were prepared using cement moderately exchanged by fly ash (0–100%) and silica fume (0–40%) to decrease ecological effect while sustaining structural performance. A Nano-SiO 2 -based surface treatment was applied to all surface protection and long-term durability under aggressive environmental conditions. Durability tests, including water absorption, sorptivity, rapid chloride permeability (RCPT), and resistance to acid and sulphate attack, were conducted. Microstructural characterization was performed using X-ray Diffraction (XRD) to identify hydration products and Field-Emission Scanning Electron Microscopy (FE-SEM) to observe pore structure, cracks, and matrix densification. Environmental performance was assessed through CO 2 emission reduction analysis. Among the mixes, GC-3 demonstrated the highest performance. Water absorption was 3.60%, sorptivity 0.085mm/√min, RCPT 1500 coulombs, acid weight loss 3.70%, and sulphate strength loss 4.80%, indicating excellent struggle to moisture ingress and biochemical attack. XRD revealed reduced calcium hydroxide (CH) and improved calcium silicate hydrate (C–S–H), confirming enhanced pozzolanic reactions. FE-SEM analysis showed a dense, compact matrix with minimal pores, cracks, and voids. Environmental evaluation indicated a 35% CO 2 reduction for GC-3 compared to GC-1. Overall, the combined incorporation of fly ash, silica fume, and Nano-SiO 2 surface treatment improved durability, microstructural integrity, and environmental performance, providing an effective and sustainable solution for modern concrete structures.