This study compares the blast performance of reinforced concrete (RC) slabs with and without strengthening on the impact-facing side. The strengthening strategy employed the application of two thin layers of materials with a high mutual stiffness offset, i.e., high-contrast layers. The first is a low-strength, low-modulus damping layer made of infra-lightweight concrete, followed by a second layer of high-ductility fiber-reinforced concrete. The plain RC slabs under investigation vary in thickness of either 40 mm or 100 mm. The layered specimens consist of a 40 mm thick RC slab strengthened with a 40 mm damping layer and a 20 mm cover SHLC3 layer. This configuration enables a comparison of its behavior with the unstrengthened specimen (a plain 40 mm thick RC slab) and a specimen with a similar eigenfrequency (the plain 100 mm thick RC slab). The employed shock tube subjects the specimens to two rapidly rising areal pressures: a low-pressure wave reaching approximately 0.4 MPa and a high-pressure wave peaking at around 1.2 MPa. The study assesses the specimens’ response in terms of accelerations, velocities, and deformations. Additionally, it evaluates damage by analyzing crack patterns, Ultrasonic Pulse Velocity (UPV) measurements, and damping analysis. Overall, the layered specimens exhibited performance nearly equivalent to the 100 mm thick specimens, displaying similar deformations and velocities despite having lower mass and bending stiffness. The high-pressure shock wave hardly damaged the layered specimens, unlike the 40 mm thick slabs.