PHYSIO-MECHANICAL PROPERTIES AND PETROGRAPHIC ANALYSIS OF THE SHAGAI FORMATION, SHAGAI AREA, KHYBER PAKHTUNKHWA, PAKISTAN

Abstract

The physical and mechanical properties of rocks have great importance in engineering geological applications such as selection of suitable materials for safe and economical construction activities. Pakistan has several varieties of limestone deposits, which are extensively used as an aggregate in concrete and in building construction. In the current study limestone of the Shagai Formation is evaluated in terms of its petrographic, and physiomechanical characteristics and, the interdependence of petrographic and mechanical properties and its suitability as a construction material. To determine the strength properties of Shagai Limestone different mechanical tests were performed like Point load test (ASTM D 5731-02), Uniaxial compressive strength (ASTM D-2938), and Schmidt rebound hammer test (ASTM D-5873) were conducted on cores that were taken from bulk samples. Physical properties tests were carried out including specific gravity and water absorption and the average values obtained are 2.77% and 0.58% respectively. The Shagai Limestone UCS test results range from 27.36 MPa to 83.44 MPa, with a mean value of 48.11 MPa. The range of the SRH results is 29 to 84.25, with a mean of 48.28. The PLT results are similar, with a range of 3.20 MPa to 9.50 MPa and a mean value of 6.13 MPa for the samples under study. Petrographic analysis of the Shagai limestone in the proposed areas, these limestones are mudstones and wackestone, the average calcite content is 77.28%, the average quartz content is 8.71%, the average Ooid content is 8.85%, and the average peloid content is 5.14%. Petrographic studies also indicate the presence of iron oxide veins, calcite filled veins and stylolite. Statistical correlation between mechanical and petrographic study indicates positive correlation between UCS/ PLT/SRH with calcite and quartz, while inverse relation with Ooid and peloid. The value of water absorption and specific gravity of limestone of Shagai formation meets the standard requirements (ASTM C127) for aggregate use in concrete and road construction. However, the UCS values are below the standard requirements and therefore limestone of Shagai limestone is not recommended for these applications.