Previous studies have shown that flat slabs constructed from reactive powder concrete (RPC) exhibit greater punching shear strength compared to those made from normal concrete (NC). However, constructing a complete slab using RPC may not be economically viable. This study aimed to determine the optimal use of RPC in the critical punching shear area, while the rest of the slab remains composed of NC. Four flat slab specimens with dimensions (940×940×60 mm) and drop panels (500×500×30 mm) were tested, with two column sizes (75×75 mm, 125×125 mm) and two types of concrete within the drop panel area (normal concrete and RPC). The slabs were examined under concentric loading to investigate the influence of RPC and column size on punching shear capacity. Results showed that RPC in the drop panel increased punching shear capacity by 109%, with column dimensions significantly affecting shear resistance.