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<p>Dolomite is an important carbonate rock widely used as a construction aggregate, foundation material, and pavement resource; however, its engineering performance is strongly controlled by diagenetic processes such as dolomitization, recrystallization, cementation, pressure solution, stylolitization, dissolution, and fracture development. These processes modify mineralogy, pore structure, cementation, and microcrack networks, thereby influencing strength, water absorption, durability, and chemical reactivity. This study presents a comprehensive geomechanical and petrographic evaluation of dolomite from the Ambar Formation in the tectonically active Peshawar Basin, Pakistan, to assess its potential for structural and geotechnical applications. Representative bulk samples were subjected to laboratory testing, including unconfined compressive strength (UCS), unconfined tensile strength (UTS), specific gravity, porosity, and water absorption, along with thin-section petrography and SEM–EDS observations. The samples were classified as dolomitic packstone and exhibited fine- to medium-grained subhedral to anhedral dolomite textures with accessory micrite, spar calcite, quartz, and opaque minerals. Mechanical testing yielded UCS values of 45.7–139&#xa0;MPa and UTS values of 6.8–10.4&#xa0;MPa, indicating favorable strength potential for load-bearing applications. Physical/index properties showed high specific gravity (≥ 2.81&#xa0;g/cm³) and low porosity (&lt; 1%), supporting dense and low-absorption material characteristics. Petrographic observations revealed stylolites, microfractures, strained quartz, and reactive carbonate textures, indicating that strength variability is controlled by diagenetic fabric and microstructural heterogeneity. These features also suggest possible susceptibility to alkali–silica reaction (ASR) and alkali–carbonate reaction (ACR) if the material is used as concrete aggregate. However, because standardized ASTM expansion tests, such as ASTM C1260/C1293, were not conducted, the ASR/ACR risk is reported only as a screening-level indication requiring confirmation. Overall, the findings demonstrate that Ambar Formation dolomite has promising geomechanical properties, but its safe use in infrastructure applications requires integrated petrographic, mechanical, and durability-based verification.</p>

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Diagenetic controls on the petrographic, microstructural, and geomechanical properties of Ambar Formation dolomite for engineering and construction applications

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Hassan Ayaz,
  • Jiancong Xu,
  • Adnan Khan,
  • Sohail Ahmad,
  • Sohail Ahmed

摘要

Dolomite is an important carbonate rock widely used as a construction aggregate, foundation material, and pavement resource; however, its engineering performance is strongly controlled by diagenetic processes such as dolomitization, recrystallization, cementation, pressure solution, stylolitization, dissolution, and fracture development. These processes modify mineralogy, pore structure, cementation, and microcrack networks, thereby influencing strength, water absorption, durability, and chemical reactivity. This study presents a comprehensive geomechanical and petrographic evaluation of dolomite from the Ambar Formation in the tectonically active Peshawar Basin, Pakistan, to assess its potential for structural and geotechnical applications. Representative bulk samples were subjected to laboratory testing, including unconfined compressive strength (UCS), unconfined tensile strength (UTS), specific gravity, porosity, and water absorption, along with thin-section petrography and SEM–EDS observations. The samples were classified as dolomitic packstone and exhibited fine- to medium-grained subhedral to anhedral dolomite textures with accessory micrite, spar calcite, quartz, and opaque minerals. Mechanical testing yielded UCS values of 45.7–139 MPa and UTS values of 6.8–10.4 MPa, indicating favorable strength potential for load-bearing applications. Physical/index properties showed high specific gravity (≥ 2.81 g/cm³) and low porosity (< 1%), supporting dense and low-absorption material characteristics. Petrographic observations revealed stylolites, microfractures, strained quartz, and reactive carbonate textures, indicating that strength variability is controlled by diagenetic fabric and microstructural heterogeneity. These features also suggest possible susceptibility to alkali–silica reaction (ASR) and alkali–carbonate reaction (ACR) if the material is used as concrete aggregate. However, because standardized ASTM expansion tests, such as ASTM C1260/C1293, were not conducted, the ASR/ACR risk is reported only as a screening-level indication requiring confirmation. Overall, the findings demonstrate that Ambar Formation dolomite has promising geomechanical properties, but its safe use in infrastructure applications requires integrated petrographic, mechanical, and durability-based verification.