Development and performance evaluation of hybrid nano modified SCM-based concretes

https://doi.org/10.3221/IGF-ESIS.78.09

Concrete production contributes approximately 8-10% of global CO₂ emissions necessitating sustainable alternatives. This study investigates hybrid nano-modified composite cement concrete with Ordinary Portland Cement (OPC) partially replaced by Ground Granulated Blast-furnace Slag (GGBS, 30-35%) and Fly Ash (10-15%) by weight of cement, nano-reinforced using Graphene Oxide (GO, 0.01-0.05%) and Carbon Nanotubes (CNT, 0.1-0.3%) by weight of cement. Eight mixes were designed and evaluated for fresh properties, mechanical performance (compressive, split tensile, and flexural strength at 7, 28, and 56 days), and microstructure (SEM, XRD, and EDAX). Nanomaterials were dispersed using magnetic stirring to ensure uniform distribution. Optimal formulations achieved significant enhancements, specifically, GO 0.03% reached 34.5 MPa compressive (+23.2%) and 15.6 MPa flexural (+108%); CNT 0.1% achieved 33.53 MPa compressive (+19.8%) and 3.23 MPa tensile (+31.8%); the hybrid (GO 0.03% + CNTs 0.1%) demonstrated 33.9 MPa compressive (+21.1%) and 14.92 MPa flexural (+98.9%). Early-age strength improved by 69-77%, compensating for slower pozzolanic reactions associated with GGBS and Fly Ash. Microstructural characterization revealed densified C-S-H gel, refined ITZ (from 20-50μm to 10-15μm), reduced porosity (from 12.3% to 7.8%), enhanced crystallinity, and optimal Ca/Si ratios (1.36-2.14). Environmental assessment showed 39.2% CO₂ reduction and a 50.7% improvement in carbon intensity. The hybrid approach provides a viable route to sustainable, high-performance concrete for infrastructure applications.