Integrated petrographic, geochemical and mechanical evaluation of diorite rocks for sustainable aggregate usege: A case study from Zardali Banda Area, northern Pakistan

The well-exposed outcrop of ZardAli Banda Diorite has been studied for its petrography, geochemistry, and physico-mechanical properties. The field investigations and petrographic observations indicate the primary composition of dark grey coarse-grained diorite is plagioclase, quartz, alkali feldspar (orthoclase), hornblende, clinopyroxene, orthopyroxene, and biotite, with a sufficient amount of sericite and traces of olivine. The geochemical signatures show the intermediate nature with SiO2 percentages ranging from 56.63 % to 59.03 %, followed by Al2O3 composition ranges from 21.76 % to 24.01 %, CaO 8.2 % to 9.2 %, Fe2O3 6.04 % to 6.86 %, Na2O 2.15 % to 3.67 %, TiO2 0.37 % to 0.77 %, K2O 0.61 % to 0.77 % and P2O5 0 %, respectively. The physico-mechanical tests, conducted according to ASTM standards, yielded average results of 2.832 gm/cm3 for specific gravity, 0.627 % for absorption, 4.497 % for flakiness index, 6.527 % for elongation index, 12.58 % for Los Angeles Abrasion value, 3.357 % for soundness, 36.914 Mpa and 6.151 Mpa for UCS and UTS, respectively. These analyses are within the potential limit of ASTM to use as a successful aggregate. The UCS and UTS values fall in the medium-strong category. The impact of geochemical trends on physico-mechanical analyses reveals that variation in major oxides influences mineral crystallization, affecting strength, durability, and aggregate suitability, with an inverse relationship between SiO2 and Fe2O3 enhancing compressive strength while CaO contributes to higher density and reduced absorption. The overall ASTM results of the ZardAli Banda Diorite suggest that these rocks can be used as an aggregate for heavy construction works (CPEC developmental scheme), road materials (Dir-Chitral Expressway), dams, and other construction projects.