Enhancing engineering and sustainable properties of alkali-activated concrete with nanomaterials under aggressive environmental conditions

The high carbon footprint associated with Ordinary Portland Cement (OPC) necessitates the development of sustainable alternatives in construction. In this context, alkali-activated concrete (AAC) has emerged as a viable low-carbon binder; however, its widespread application is limited by insufficient understanding of long-term durability. This study investigates the influence of nano-sized industrial by-products nano fly ash (nFA), nano ground granulated blast furnace slag (nGS), and nano bentonite (nBT) on the mechanical, durability, and sustainability performance of ambient-cured alkali-activated nano concrete (AANC). The results indicate significant enhancements in compressive strength, with nFA (9 %), nGS (12 %), and nBT (6 %) mixtures achieving increases of 49.27 %, 45.93 %, and 66.07 %, respectively, at 28 days compared to the control mix. Durability performance under aggressive environments showed that, after 90 days of acid exposure, weight loss ranged from 1.32 to 1.63 % for nGS and 1.49–1.96 % for nFA, while higher losses were observed for nBT (2.10–6.28 %). The lowest compressive strength loss was recorded in nGS-modified AANC (3.78–4.03 %), demonstrating superior resistance. Under sulfate and chloride exposure, nGS-AANC exhibited minimal deterioration and maintained a high residual compressive strength of 59.48 MPa. Microstructural analyses using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) confirmed that the incorporation of nanoparticles, particularly nGS, promoted the formation of dense and stable Calcium Aluminosilicate Hydrate (C-A-S-H) gel, leading to refined pore structure and reduced permeability. Furthermore, sustainability assessment revealed reductions in energy consumption and carbon emissions compared to conventional mixes. The study demonstrates that optimized incorporation of nano-industrial by-products especially nGS significantly enhances the mechanical performance, durability, and sustainability of AANC, making it a promising alternative to OPC-based concrete for durable and eco-efficient construction applications.