Issue 78

C. S. Karadumpa et alii, Fracture and Structural Integrity, 78 (2026) 146-167; DOI: 10.3221/IGF-ESIS.78.09

The environmental assessment is limited to the binder production stage, with emphasis on the reduction in Ordinary Portland Cement (OPC) consumption achieved through the use of composite cement containing GGBS and Fly Ash. Consequently, the reported reduction in CO ₂ emissions should be interpreted as an indicative embodied-carbon comparison rather than a complete life-cycle evaluation. The environmental impacts associated with GO production, CNT production, nanomaterial dispersion, and processing energy were not included in the present assessment. However, it should be noted that the dosages of nanomaterials used in this study were extremely small, with maximum additions of 0.05% GO and 0.3% CNT by weight of binder. These correspond to only a few hundred grams of nanomaterials per cubic meter of concrete, whereas the reduction in OPC content involves several tens of kilograms of cementitious material.

Control Concrete (OPC)

Hybrid Nano-Modified

Reduction / Improvement

Parameter

Calculation Basis

Cement content (kg/m³)

450

410

–8.8%

Mix design (Tab. 3)

Composite cement contains 55–60% OPC 0.9 kg CO ₂ per kg cement

OPC equivalent (kg/m³) Direct CO ₂ emissions (kg/m³) 405 28-day compressive strength (MPa) Carbon intensity (kg CO ₂ /MPa) 14.46 Embodied energy (MJ/m³) 2025 450 28.0 (control concrete)

246

–45.3%

246

–39.2%

34.5 (GO 0.03%)

+23.2%

Tab. 6 CO ₂ ÷ strength

7.13

–50.7%

1230

–39.3%

Cement production energy

Circular economy

Industrial waste utilization

0%

40–50%

GGBS + Fly Ash

Nanomaterial dosage (kg/m³) Minimal GO + CNT Note: Assumes OPC CO ₂ factor = 0.9 kg CO ₂ /kg, GGBS = 0.05 kg CO ₂ /kg, Fly Ash = 0.01 kg CO ₂ /kg, Composite cement effective factor = 0.6 kg CO ₂ /kg. Table 11: Environmental impact and carbon footprint analysis. 0 0.164 0.04% total

C ONCLUSIONS

C

onsidering the combined performance in terms of workability, compressive strength, tensile strength, flexural strength, microstructural refinement, and environmental benefits, the hybrid mixture incorporating GO 0.03% and CNT 0.1% is recommended as the most balanced formulation among the investigated mixtures. Although GO 0.03% produced the highest compressive strength and CNT 0.1% provided the greatest enhancement in tensile and flexural properties, the hybrid system achieved consistently improved performance across all measured parameters while maintaining acceptable workability. The hybrid mixture also exhibited a denser microstructure, improved interfacial transition zone characteristics, and reduced estimated carbon intensity due to the use of SCM-based composite cement. Therefore, for practical structural applications requiring a balance between mechanical performance, durability potential, and sustainability, the hybrid GO 0.03% + CNT 0.1% concrete can be considered the optimum material among the investigated formulations. This study systematically investigated hybrid nano-modified composite cement concrete integrating GGBS, Fly Ash, Graphene Oxide, and Carbon Nanotubes, providing comprehensive experimental evidence linking nanomaterial dosage optimization, microstructural evolution, mechanical performance, and environmental sustainability. The following conclusions are drawn:  This study investigated the influence of Graphene Oxide (GO) and Carbon Nanotubes (CNTs) on the performance of SCM-based composite cement concrete containing GGBS and Fly Ash. The results demonstrate that nano modification can effectively enhance the mechanical performance of SCM-based concretes while mitigating their inherent limitations in early-age strength development.  The addition of Nano reinforcement in cement increased the workability of the concrete. Particularly addition of GO has increased the flowability by 75-85 % compared to the control mixture.

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