Evaluation of Physico-Mechanical Properties of Crushed Rock Aggregates: A Case Study from the Sub-Himalaya, Pakistan

Abstract

Geological units of sub-Himalaya Pakistan lying in the core of Hazara Kashmir Syntaxial bend provide vast potential for concrete aggregates in the region. The selection of suiTab. aggregate within active tectonic, fragile lithologic and geotechnical environments is a challenging approach. The present study focused on evaluating the physico-mechanical properties of crushed rock aggregates (CRA) that are already being mined in Muzaffarabad and surrounding areas. For this purpose, integrated physico-mechanical with combined petrographic and mineralogical analysis was performed on dolomite and dolomitic limestone of the Cambrian Muzaffarabad Formation and Eocene Margalla Hill Limestone of Yadgar section. Therefore, samples of aggregates were collected from different quarries in accordance with ASTM standards and their mechanical and engineering properties were evaluated through ASTM and BS standards. The physico-mechanical properties of dolomite and dolomitic limestone conclude that the dolomite rocks have the average strength against abrasion (25.12%), impact (20.75%) and crushing (19.57%), higher specific gravity (2.76), lower water absorption (0.65%) and higher value of sulphate soundness (1.5%). On the contrary, the Margalla Hill Limestone which exhibits average values of abrasion (16.93%), impact (22.03%), crushing (19.95%) with lower specific gravity (2.63), high water absorption (0.68%), and low values sulphate soundness (0.77%). The petrographic investigations showed that chert 3 – 6 % and granular quartz 25 – 30 % on average are also found in dolomite and dolomitic limestone, which causes the alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR) when used in the concrete. The XRD analysis confirmed that both the formations dominantly contain the minerals dolomite, calcite and quartz. It was also found that Margalla Hill Limestone is more suiTab. to be utilised as coarse aggregate in concrete as compared to dolomite of the Muzaffarabad Formation. These exploitations allow recommending Eocene Margalla Hill Limestone of Yadgar section in the production of the coarse aggregate for concrete.