Aggregates are the biggest contributor to concrete volume and are a crucial parameter in dictating its mechanical properties.As such,a detailed experimental investigation was carried out to evaluate the effect of sand-to-aggregate volume ratio (s/a) on the mechanical properties of concrete utilizing both destructive and non-destructive testing (employing UPV (ultrasonic pulse velocity) measurements).For investigation,standard cylindrical concrete samples were made with different s/a (0.36,0.40,0.44,0.48,0.52,and 0.56),cement content (340 and 450 kg/m3),water-to-cement ratio (0.45 and 0.50),and maximum aggregate size (12 and 19 mm).The effect of these design parameters on the 7,14,and 28 d compressive strength,tensile strength,elastic modulus,and UPV of concrete were assessed.The careful analysis demonstrates that aggregate proportions and size need to be optimized for formulating mix designs;optimum ratios of s/a were found to be 0.40 and 0.44 for the maximum aggregate size of 12 and 19 mm,respectively,irrespective of the W/C (water-to-cement) and cement content.