Petrography and geomechanical properties of some mine waste rocks from the Tarkwaian Group in Ghana: implications for their use as aggregates in general engineering works

This research investigated some mine waste rocks from the southwestern part of the Tarkwaian Group in Ghana to check their suitability for general engineering works using petrography and geomechanical characteristics of the rocks. The rocks were subjected to a total of ten (10) tests, including Aggregate impact value (AIV), Aggregate crushing value (ACV), Loss Angeles abrasion (LAA), Specific gravity (SG), and Water absorption (WA), as well as flakiness and elongation index, slake durability (SD), chloride test (CT), sulphate test (ST), and ten percent fines (TPF). The tests were carried out per the American Society for Testing and Materials guidelines (ASTM). The following average test results were obtained: AIV (7.12%), ACV (15.60%), LAA (23.16%), TPF (269.7 kN), sulphate (0.0215%), chloride (0.00123%), flakiness (39.5%) and elongation (39.4%). The mine waste rocks are dominated by quartz and sericite, according to the petrographic examination and thus, can be classified as quartzites. Except for the flakiness and elongation index tests, all the results were consistent with the ASTM standards. The analysis carried out on the selected mine waste rocks from the southwestern part of the Tarkwaian Group could be catastrophic for heavy engineering works such as roads, bridges, and heavy buildings but can be used for pavements, lightweight buildings, monuments, and decoratives due to the percentage of quartz present to compensate for the weakness posed by the sericite.