In this study, I conducted an experimental investigation to understand the behaviour of high-strength, selfcompacted reinforced concrete beams under static loading. Simply supported, slender concrete beams with different parameters were tested. The investigated beams were 100 × 750 mm in size and 4000 mm long and were tested under 4-point loading. The main parameters investigated were the web reinforcement ratio, the concrete strength and the span to depth ratio (a/d). The effects of these parameters were investigated on mid-span deflection, lateral torsion, concrete strains, steel strains, failure modes and crack patterns. It was found that the main reinforcement ratio and the ratio of shear span to shear depth have a remarkable influence on the mid-span deflection of slender beams. As the main reinforcement ratio increases, the midspan deflection of slender beams generally decreases. It was found that an increase in concrete strength leads to a 20% reduction in mid-span deflection for B6 at =55 MPa compared to B2 at =30 MPa. The effect of principal reinforcement ratio on the cracking pattern of slender beams is significant and increasing the principal reinforcement ratio leads to a more controlled and tighter cracking pattern. Higher concrete strength is better able to resist tensile stresses, resulting in smaller crack widths and fewer cracks overall. A higher ratio between shear span and shear depth results in a more distributed and wider crack pattern.