Effect of Sample Type, Orientation and Coarse Aggregate Size on Compressive Strength of Normal Concrete: An Experimental Study

The effect of coarse aggregate size and sample orientation on the compressive strength, compressive fracture energy, and failure angle of concrete is not well understood, which affects structural performance. This study aims to investigate the impact of the maximum coarse aggregate size and sample orientation on these properties. Concrete mixtures with constant strength were prepared using rounded coarse aggregates of sizes of 4.75, 9.5, and 19 mm, with a specified water-to-cement ratio to ensure mix uniformity. Compressive strength was tested after 28 days to ensure sufficient concrete maturity and stable strength values. Two types of samples were tested: core samples extracted from concrete cubes and lintels and pipe samples cast in plastic pipes. The samples were analyzed at different orientations (0°, 22.5°, 45°, 67.5°, and 90°) to study the effect of orientation on mechanical behavior. The results showed that both sample types exhibited similar trends in compressive strength and compressive fracture energy. The compressive strength of the samples increased with the increase in aggregate size, with the 19 mm aggregate achieving the highest strength. The lowest compressive strength was observed at a 45° angle, while the highest was recorded at 0° for core samples and 90° for pipe samples. Core samples exhibited lower compressive strength but higher compressive fracture energy compared to pipe samples, due to damage occurring during core extraction. This study highlights the importance of coarse aggregate size and sample orientation in determining concrete strength, contributing to the optimization of mix designs and the selection of appropriate testing methods to enhance structural performance and meet long-term durability requirements.