Issue 72

H. S. Vishwanatha et alii, Fracture and Structural Integrity, 72 (2025) 80-101; DOI: 10.3221/IGF-ESIS.72.07

Figure 7: Load-deflection curves for B-SB75.

The same phenomenon, known as the aggregate blocking effect, is seen for aggregates b-c-d-e-f in Fig.8. Therefore, it can be concluded that the aggregate geometry has the effect of blocking and guiding the crack, while the blocking effect tends to occur in the spherical aggregate model. The results indicated that the geometric properties of aggregates have both blocking and guiding effects on crack development. The present study focuses on medium-strength concrete, where the crack propagation predominantly occurs along the weak interfacial transition zone (ITZ) due to the relatively lower strength of the matrix compared to the aggregate. However, in high-strength concrete, the ITZ is significantly strengthened due to the reduced porosity and improved bonding between the matrix and the aggregate. As a result, the crack is more likely to propagate through the aggregate itself, destroying it and altering its trajectory.

Figure 8: Crack Propagation under TPB test at heterogeneous section (Central part of beam).

I DENTIFICATION OF LOADING STEPS o investigate crack propagation in the fracture procedure, ten steps were selected, as shown in Fig. 9. Based on the results of analysis, the load deflection curve of the TPB with the notch-to-depth ratio of 0.25 plotted, and the results are shown in Fig.9. In Fig. 9, P 1 point selected after initial crack load. At P 1 , cracking starts at the notch tip. As cracking progresses, the load in P 2 approaches the maximum load with a less steep slope than in P 1 . The load at P 2 reaches T

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