Issue 78

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

The convergence of nano-modified and control strengths at extended ages—where relative advantages decreased from 69 77% at 7 days to 0.3-11.4% at 56 days (Tab. 6)—reflects that nanomaterial nucleation effects are most pronounced during early stage of hydration, while long-term strength increasingly reflects total cementitious content and ongoing pozzolanic matrix densification. However, this convergence does not negate nanomaterial value; rather, the critical advantage is early age acceleration (69-77% at 7 days), enabling faster construction schedules, rapid formwork removal, and earlier load application while achieving equivalent or superior final strength— potentially advantageous for time-sensitive applications such as precast production and accelerated construction timelines.

Figure 2: Compressive strength comparison with dosage of GO. Figure 3: Compressive strength comparison with dosage of CNT.

% vs Control

28 Days (MPa)

% vs Control

56 Days (MPa)

% vs Control

Mix ID

Mix Description

7 Days (MPa)

Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6 Mix 7 Mix 8

Control (0%)

12.50 18.10 21.13 15.73 22.06 21.13 21.86 21.20

—

28.00 32.80 34.50 24.96 33.53 32.10 32.80 33.90

—

35.10 38.30 39.09 31.47 36.50 33.20 35.20 36.50

—

GO 0.01% GO 0.03% GO 0.05% CNT 0.1% CNT 0.2% CNT 0.3%

+44.8% +69.0% +25.8% +76.5% +69.0% +74.9% +69.6%

+17.1% +23.2% − 10.9% +19.8% +14.6% +17.1% +21.1%

+9.1% +11.4% − 10.3% +4.0% − 5.4% +0.3% +4.0%

Hybrid (GO 0.03% + CNT 0.1%)

Table 6: Compressive strength test results.

Split tensile strength Split tensile strength measures concrete's resistance to cracking under tension—critical for structural members experiencing bending, shrinkage, or temperature stresses. The tested specimen for split tensile strength is shown in Fig. 4.

Figure 4: Split tensile strength specimen test. Tab. 7 presents split tensile strength results across all curing ages. Nano-modified concretes demonstrated dramatic tensile enhancements across all ages, particularly for the CNT formulations. CNT 0.1% achieved exceptional performance: 1.87

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