Impact of petrographic and physico-mechanical properties on aggregate suitability of the early Devonian Nowshera formation: a case study from the Peshawar Basin, Pakistan

The physico-mechanical properties of rocks play a crucial role in determining their suitability for construction applications, directly influencing the longevity, stability, and durability of structures. This study presents a novel evaluation of the Nowshera formation in the Peshawar Basin, Pakistan, to assess its potential as a construction material, integrating comprehensive petrographic, mineralogical, and engineering assessments. Unlike previous studies, this research provides a holistic approach by combining petrographic analysis with Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to precisely characterize the crystalline limestone composition, primarily composed of calcite and dolomite. Additionally, an extensive suite of standardized mechanical, physical, and durability tests was performed. The study uniquely investigates both Alkali-Carbonate Reaction (ACR) and Alkali-Silica Reaction (ASR), demonstrating that while the aggregates exhibit susceptibility to ACR due to the presence of reactive dolomite, they are not prone to ASR because of their low silica content. Furthermore, this research offers the first detailed correlation between petrographic features and engineering properties for the Nowshera formation, providing new insights into its performance under various construction conditions. The results confirm that the Nowshera formation aggregates meet the permissible limits set by ASTM and BS standards, verifying their suitability for infrastructure, pavement, and road construction. This study contributes novel findings by integrating advanced analytical techniques and a comprehensive geotechnical evaluation, establishing a new benchmark for assessing carbonate rock aggregates in construction applications.