A 2026 study of eight granodiorite specimens from the El-Bakriya ring complex in eastern Egypt found substantial differences in their density, strength, stiffness and gamma-ray attenuation. GB4 performed best for attenuation, while GB2 had the highest compressive strength. The authors describe the stone’s shielding as moderate, not equivalent to lead or heavyweight concrete, and say that site-specific investigation and durability testing are needed before construction use.
What the study tested
Azer et al. examined eight cubic specimens, each measuring 5 × 5 × 5 cm, from the El-Bakriya ring complex in eastern Egypt. The reported results describe those specimens and the study’s laboratory conditions; they are not universal specifications for granodiorite or a qualification of a full-scale wall or facility.
For gamma-ray measurements, the researchers used Cs-137 at 0.662 MeV and Co-60 at 1.173 and 1.332 MeV. They report background subtraction, three repeated measurements and 1,800-second measurement intervals. The study’s reported photon-energy coverage is limited to those three energies.
Physical and mechanical results
Across the eight El-Bakriya specimens, the reported ranges show both low water absorption and meaningful variation in mechanical properties. These are ranges observed in this sample set, not acceptance limits for construction stone.
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| Property | Reported result for the eight specimens | What it indicates |
|---|---|---|
| Bulk density | 2.71–2.91 g/cm³ | Mass per unit bulk volume; relevant to handling, dead load and, alongside composition, radiation attenuation. |
| Water absorption | 0.21–0.51% | The measured absorption range. It does not by itself establish long-term weathering or moisture durability. |
| Uniaxial compressive strength | 112.10–242.58 MPa | Resistance to compression under the reported test; GB2 had the highest reported value. |
| Flexural strength | 7.41–10.90 MPa | Resistance to bending under the reported test. |
| Modulus of elasticity | 52.9–77.9 GPa | Stiffness: a higher modulus means less elastic strain for a given stress within the measured elastic range. |
For these El-Bakriya specimens, the authors associate between-sample differences with mineralogy, alteration, porosity, microfractures and texture. The ranges therefore matter more to selection than the label “granodiorite” alone: a result for one specimen should not be assumed to describe stone from another part of the complex or another source.
Gamma-ray attenuation and the specimen trade-off
The study reports linear attenuation coefficients (LAC) that fall as photon energy rises. LAC describes attenuation per unit path length in the tested setup; it is not by itself a wall-design result.
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| Photon energy and source | Reported LAC across the eight specimens |
|---|---|
| 0.662 MeV, Cs-137 | 0.209–0.223 cm⁻¹ |
| 1.173 MeV, Co-60 | About 0.159–0.170 cm⁻¹ |
| 1.332 MeV, Co-60 | 0.149–0.159 cm⁻¹ |
At the measured energies, GB4 was the best-performing specimen for attenuation. The paper reports its density at about 2.91 g/cm³, its maximum LAC at 0.223 cm⁻¹, and its lowest half-value layer (HVL) at 3.11 cm. HVL is the thickness associated with reducing the measured beam intensity by half under the stated measurement conditions; it should not be treated as a complete shielding design thickness.
The authors report radiation protection efficiency of 65.5–68.0% at 0.662 MeV and 53.1–55.5% at 1.332 MeV across the tested specimens. These figures belong to the laboratory measurements and specified energies; they are not a guarantee of protection in a building or installation.
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The performance ranking changes with the property being considered: GB2 led in compressive strength at 242.58 MPa, whereas GB4 led in attenuation. The strongest specimen in compression was not the study’s top shielding performer.
What the shielding results do—and do not—establish
The authors characterize the granodiorite’s gamma attenuation as moderate and state that it is less effective than conventional high-density shielding materials such as lead or heavyweight concrete. They say significantly greater granodiorite thickness would be required to reach comparable protective capability. Thus, the study does not establish granodiorite as a substitute for conventional shielding or as approved for a medical or nuclear installation.
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The measurements were made on small laboratory specimens, not a complete wall or facility. The reported evidence covers three photon energies and does not provide full-scale qualification. A building application would need a design based on its radiation source, required protection, geometry and applicable regulations; the reported specimen values alone cannot determine wall thickness or demonstrate regulatory compliance.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Construction uses considered by the authors
The paper discusses flooring, wall cladding, decorative panels, dimension stone and structural aggregate as possible uses for suitable granodiorite. These are applications considered by the study, not blanket engineering approvals. The spread in compressive strength and stiffness also means that high-load applications require testing and design based on the actual supplied material, rather than an assumed value for the rock type.
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The authors identify weathering, moisture exposure, temperature fluctuation and chemical interaction as durability considerations. Low measured water absorption in these specimens does not resolve those longer-term questions.
How to assess granodiorite for a project
- Identify the actual source. Do not assume stone from another quarry or deposit matches the El-Bakriya specimens.
- Obtain independent, project-relevant testing. Match tests to the intended use, including mechanical properties for load-bearing or bending demands and durability exposures relevant to the site.
- For shielding, commission a radiation-specific design. Use the actual source energies and required protection criteria, and have the proposed assembly evaluated for its geometry and regulatory requirements.
- Review the results with the project’s qualified professionals. Treat published specimen values as context, not as design values or approval for a particular structure.
For sourcing, seek locally available stone and independent testing; the tested samples do not establish that other commercially available granodiorite matches them.
Study citation
Azer et al., Scientific Reports (2026), reporting physical, mechanical and gamma-ray shielding measurements on granodiorite from the El-Bakriya ring complex in eastern Egypt.
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