Issue 74

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

Element

Weight %

Atomic %

Error %

O

50.50

70.20

8.93

Na

0.52 8.81 0.43

0.50 6.98 0.27

17.42

Si

4.03

Cl

28.83

Ca 3.67 Table 11: Determination of chemical composition using the EDX technique of the sample PE1-3 (T1). 39.74 22.05

Figure 14: XRD and EDX analysis graph of the sample PE2-4 (T2).

Element

Weight %

Atomic %

Error %

O

53.28

72.10

8.74

Na

0.24

0.22 7.99 1.52

47.75

Si

10.37

3.99 9.99

Cl

2.49

Ca 3.82 Table 12: Determination of chemical composition using the EDX technique of the sample PE2-4 (T2). 33.63 18.17

SEM analysis SEM-EDX analyses of limestone samples identified a composition of oxygen (50.50 wt%), calcium (39.74 wt%), silicon (8.81 wt%), sodium (0.52 wt%), and chlorine (0.43 wt%) Fig. 13, Tab. 11. The presence of sodium (Na) and chlorine (Cl) confirms NaCl, indicative of salt crystallization, while silicon and calcium suggest silicates (SiO ₂ ) and carbonates (CaCO ₃ ), respectively. The high calcium content supports the classification of the stone as limestone, which is susceptible to salt induced deterioration. Salt crystallization tests on T1 limestone samples from Tamentfoust fort elucidated intricate chemical and mechanical degradation processes driven by saline interactions under varying environmental conditions. NaCl reactions produce highly soluble CaCl ₂ and NaHCO ₃ , which leach from the stone, compromising structural integrity, with the extent of deterioration modulated by humidity, temperature, and ion presence. Silicates (SiO ₂ ), while chemically resistant to direct NaCl interactions, undergo slow hydrolytic alteration in aqueous environments with additional ions, forming clay minerals or hydrated silicates, contributing to gradual long-term degradation. The mechanical impact of NaCl crystallization within pores exerts internal pressures of 2–5 MPa (lower than Na ₂ SO ₄ ’s 10–20 MPa), inducing microcracking and stone disintegration, amplified by repetitive dissolution-crystallization cycles, resulting in significant mechanical damage over time. SEM analysis at 200× (30 μ m) (Fig. 15a) reveals a calcite-dominated matrix (50%) with 30% elongated or irregular fossils (50–200 μ m) and angular quartz/feldspar grains (confirmed by XRD), characterized by a uniform, mildly porous cement texture (pores <5 μ m) from low-compaction sedimentary origins. Sparse sub-parallel microcracks (10–20 μ m) suggest preparation-induced or internal stresses, with minimal mass loss ( Δ M:

242