<p>This study aims to investigate the physical properties of indigenous shale found in the Balochistan Province of Pakistan for use as a coarse aggregate in structural concrete in comparison to natural coarse aggregates. The physical properties of the shale aggregate were evaluated. Subsequently, using the same aggregates, the mechanical properties of OPC and LC³- 50 based lightweight aggregate concrete were examined by replacing natural coarse aggregates with lightweight aggregates in increments of 20%, up to 100% by weight. In total twelve mixes were prepared, and specimens for compression, splitting tensile, and flexure tests were cast and tested as per ASTM standards. As OPC and LC³-50 are two different materials, the chemical composition of OPC and the raw materials of LC³-50 were also analyzed for a better understanding of the experimental results. The mechanical properties of OPC and LC³-50 concrete were analyzed through experimental results and Scanning Electron Microscope (SEM) imaging. LC³-50 exhibited enhanced performance in compressive, splitting tensile, and flexural tests compared to OPC, with higher strengths observed beyond 28 days. Despite the addition of lightweight aggregates resulting in reduced strengths for both concrete types, LC³-50 demonstrated a lesser decrease in compressive, tensile, and flexural strengths compared to OPC. Moreover, regression models were developed using multiple linear regression analysis based on the least squares method to predict various concrete properties as functions of process variables, i.e., compressive strength, LC³ content, lightweight aggregate (LWA) content, and curing age. All models showed satisfactory agreement with the experimental results.</p>