An Investigation of Petrographic Characteristics and Physico mechanical Properties of Utch Khattak Formation Exposed in the Gudwalian Section, Gandghar ranges, Pakistan.

Abstract

A large exposure of Utch Khattak limestone in the Gudwalian section, Gandghar ranges, District Haripur was investigated petrographically, Physio mechanically and geochemically in order to evaluate the strength and durability as a source aggregate for construction projects. Utch Khattak limestone is quietly distinctive, thin to medium bedded, fine to medium grained and bluish grey to dark grey in color. Petrographically, the Utch Khattak limestone has classified on the basis of Dunham classification as a mudstone. According to the petrographic study, the fracture is filled with calcite and ferrous minerals, quartz and dolomite are found in very small amount in the form of fine grain, while other deleterious minerals were not observed during this investigation which can affect the strength, durability and suitability of an aggregate. Similarly, the geochemistry of the study rock has revealed that CaO ranging from 48.29% to 53.67% by weight, SiO2 1.21% to 2.56%, Al2 O3 0.49 to 0.95%, and other oxide such as K2O, P2O5, Fe2O3 present less than 1% by weight. The range of loss on ignition is from 40.15% to 42.14%, which indicate that these geochemical values for the concrete aggregate are in suitable range. Additionally, the average values of Los Angeles Abrasion test (25.53%) and impact value test (15.33%). Similarly, the average values of bulk saturated surface dry specific gravity 2.68%, water absorption 0.40%, bulk unit weight 1.68 gm/cc, Point Load test 7.28 KN, soundness test 4.09%, and unconfined compressive strength test 67.03MPa, are within ASTM limit. Furthermore, Mechanical characteristics such as UCS and PLT were compared statistically with petrographic characteristic through linear regression analysis. The amount of calcite has direct relationship with strength and durability of aggregate which means increase in concentration of calcite increase the value of UCS and PLT. On the other hand, greater the pore spaces and bioclasts within the carbonates lower will be the strength and durability of an aggregate. However, Utch Khattak Formation of Gudwalian section has a smaller number of pore spaces and bioclasts which depicts its suitability as an aggregate in heavy engineering projects. Hence, for the conformation of strength, durability and suitability of Utch Khattak Formation of Gudwalian section physico-mechanical properties were statistically compared through linear regression analysis. Thus, all the parameters i.e., petrographic, geochemical, and geotechnical investigations have revealed that Utch khattak limestone is an acceptable aggregate supply for construction industries.