Hi all,
I prepared a batch of 40-mm cubic UHPC samples for the compressive test. However, I got a strange failure pattern after the 28-day compressive test. As you can see from my attached photo, instead of the typical failure pattern, the sample broke into three triangular pieces. Could you tell me what are the possible reasons for such failure pattern?
Thank you very much!
Brittle materials in compression fail by shear, which may be explained by the Mohr-Coulomb failure theory. The angle of the fracture plane vs load direction gives the friction coefficient on that plane. Zero friction gives the fracture angle 45 degrees, while smaller angles, as in your case, corresponds to non-zero friction. If you get three pieces (two equally inclined fracture planes) or two (one failure plane) is entirely random. Three pieces requires some symmetry, so I assume two pieces are more common due to irregularities in the material.
Fan Zheng, There are other factors that can lead to your results, they include;
1. Material In-homogeneity: Non-uniform distribution of ingredients, aggregates, or fibers in the UHPC mix can lead to variations in strength and brittleness. This non-uniformity could result in localized stress concentrations and irregular failure patterns.
2. Improper Mixing: Insufficient mixing or inadequate dispersion of fibers and aggregates can result in weak zones within the concrete. These weak zones can lead to localized failure and unusual fracture patterns.
3. High Shear Stress: If the loading conditions during the compressive test induce high shear stress on the UHPC sample, it can result in non-uniform failure patterns, including triangular or irregular pieces.Unfavorable
4. Aggregate Orientation: The alignment or orientation of fibers and aggregates within the UHPC can influence the failure pattern. If the orientation is not optimized or aligned with the principal stress direction, it may lead to unexpected fracture paths.
The failure of the specimen shown in the picture is a shear failure pattern, which might be due to the load distribution and the loading conditions.
The example in the picture is the failure caused by shear, please check whether the clamp is parallel and the force is uniform. If you can, it is recommended to add some steel fibers.
- Badges
- Science topic
- Similar topics
- Biological Science
- Biochemistry
- Biochemical Techniques
- Analytical Chemistry
- pH