Issue 74

N. Meddour et alii, Fracture and Structural Integrity, 74 (2025) 227-261; DOI: 10.3221/IGF-ESIS.74.16

compressive strength ( σ c : 27.57 MPa), density ( ρ b : 2.22 g/cm³), and porosity ( po : 8.59%), consistent with a partially consolidated calcite matrix tempered by fossils and pores. These properties (V p : 3.5–4.0 km/s; σ c : 25–40 MPa) indicate medium strength and compactness but fall below optimal limestone standards (4–6 km/s) per ASTM D2845, suggesting limited suitability for deep foundation applications [26].  The Schmidt hammer rebound test (SHR), a non-destructive method, was used to estimate uniaxial compressive strength ( σ c ) by measuring rebound hardness (R), reflecting energy restitution post-impact on stone surfaces. The rebound values were converted to σ c using rock-specific calibration curves per NF EN 12372, though the method is sensitive to surface roughness, heterogeneity, and moisture. For the T2 limestone sample (PE2-6), a mean R value of 24.28 (minimum 18) was recorded from ten perpendicular rebounds across multiple surface points, ensuring measurement precision per ISRM (1978). Testing of T1 samples was not conducted, as their low uniaxial compressive strength ( σ c : 4.26 MPa) fell outside the recommended 20–150 MPa range per ASTM D5873 and ISRM (1978). Porous or rough surfaces absorb impact energy, reducing the method’s reliability for low-cohesion stones like T1, highlighting the influence of intrinsic stone properties on mechanical behaviour. T2’s R value corresponds to low-to-moderate compressive strength (20–40 MPa) per ISRM (1981), slightly underestimating the laboratory-measured uniaxial compressive strength ( σ c: 27.57 MPa) due to sclerometer limitations related to surface conditions and microstructure. This moderate strength reflects T2’s porous limestone composition, with calcite (40%, Mohs hardness 3) and fossils (35%) limiting durability, while quartz (15%), silica (5.85%), and alumina (1.99%) provide minimal cohesion. Fossil inclusions and variable grain sizes (0.05–3 mm) of quartz and feldspars promote crack propagation under load, despite minor interlocking benefits. Clay minerals (chlorite, muscovite) and iron oxides (0.805%) contribute negligibly to cementation. Porosity ( po ) correlates negatively with SHR and σ c , while atmospheric water absorption (A b : 3.31%) and capillary absorption ( C : 1.93%) indicate moderate pore connectivity, further reducing mechanical integrity. These properties collectively limit T2’s suitability for high strength applications.

(a)

(b )

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(d) (f) Figure 15: Scanning electron microscopy analysis (SEM) of the T1 stone type, before (a,b,c) and after (d,e,f) salt crystallization test. (a) x200,(b) x2.51k,(c)x514,(d)x197,(e) x58 ,(f)x2.20k. (e)

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