The evaluation of Khyber limestone in Pakistan for using as road aggregate based on geotechnical properties

Khyber Formation of Paleozoic age, has been studied here to access its physiochemical and mechanical characteristics. There has been several studies on the sedimentology of the Khyber limestone, however, much more detailed study is required to understand it aggregate potential in desired resolution and precision. It is achieved by understanding the rock types, microscopic textures and physical/ mechanical properties. The Khyber Formation is widely exposed in eastern and central parts of district Khyber, Khyber Pakhtunkhwa (KP) Province, Pakistan. It is a thick bedded hard limestone unit. The carbonates in the Khyber Formation are dominated by calcite, with dolomite, and other accessory minerals as minor component. The mechanical and physical properties of aggregates like specific gravity (2.69), water absorption (0.80%), soundness (2.34%), Los Angeles abrasion value (23.60%), aggregate crushing value (12.18%), aggregate impact value (12.76%)  flaky index (10.15%), elongation index (13.02%),  California bearing ratio (90.35%), coating and stripping values (96.32%), Schmidt rebound attains (34.23) and compressive strength (38.58Mpa) are according to the available standards. The petrographic analyses of samples of Khyber Formation and energy dispersive X-Rays analysis (EDX) illustrate that it dominantly consists of calcite (88-92%) with small to trace assemblage of dolomite (2-8%), ungraded quartz (1-3%) and ores (1-2%). The chemical and petrographic examinations show that the limestone units of the Khyber Formation are inoffensive in terms of Alkali Silica Reaction (ASR) and Alkali Carbonate Reaction (ACR). These characteristics of the limestone units demonstrating that these deposits are potential aggregate for large-scale projects in the KP Province (Pakistan) and region.