Rock Aggregate Potential of Cretaceous and Paleocene Carbonates Exposed in the Darsamand Anticline, District Hangu, Khyber Pakhtunkhwa, Pakistan

Abstract

Limestone is widely used in mega-construction projects and chemical companies all over the world. Pakistan is endowed with vast resources of carbonates, which are widely used in major engineering projects and infrastructure construction. Therefore, vast deposits of carbonates of Cretaceous Kawagarh Formation and Paleocene Lockhart Limestone are exposed in the vicinity of Darsamand Anticline, District Hangu are evaluated petrographically, geochemically, and physico-mechanically for assessing their suitability as an aggregate source in asphalt and concrete works. These carbonates are vastly exposed in the western parts of the Kohat Plateau, Khyber Pakhtunkhwa. The limestone from the Kawagarh Formation is comprised of micrite, bioclasts and planktonic foraminifera while that of the Lockhart Limestone is composed of bioclast, algae and micrite. The limestone from Kawagarh has a mudstone depositional fabric while that of the Lockhart Limestone has a wackestone texture. Diagenetic calcite veins and stylolites occur in both the studied rock units. No deleterious minerals were encountered in both these carbonate units. The physical properties of the Kawagarh Formation The physical properties of the Kawagarh Formation limestone units and Lockhart Limestone as aggregate materials (i.e., soundness, water absorption, Los Angles abrasion, specific gravity, and coating and striping) are in accordance with ASTM standards and can thus be used as aggregate sources in construction projects and Lockhart Limestone as aggregate materials (i.e., soundness, water absorption, Los Angles abrasion, specific gravity, and coating and striping) are in accordance with ASTM standards and can thus be used as aggregate sources in construction projects. Moreover, the geotechnical parameters of these two carbonate units i.e Lockhart Limestone and Kawagarh Formation were correlated theoretically with the petrographic characteristic. If the carbonates having more CaO, less pore spaces, and less amount of bioclasts the more will be the strength, durability, and suitability of the limestone and vice versa. Similarly, if limestone having more SiO2, Fe2O3, and K2O can negatively influence the physical parameters of aggregate, and can cause failure of the structure. The amount of clay minerals within carbonates can negatively effects the strength of carbonates. However, from the petrographic, geochemical and geotechnical analysis show that the Lockhart Limestone and Kawagarh Formation of Darsamand Anticline is having no effects of oxides, cryptocrystalline and other deleterious on the geotechanical parameters of aggregate. Hence, Lockhart Limestone and Kawagarh Formation have the potential aggregate source to be used in large and small construction projects.