In this study, one of the fairly known practical plate problems was investigated, a square plate laterally loaded with single concentrated load at mid-span under all edges clamped. Clamping was made continuously along the edges with a small quantity of rotation. This type of clamping could be called as partially fixed. The primal objective of the present study is to investigate the behavior of two slabs with different dimensions (660x660x40 mm and 1080x1080x40 mm), produced with high-strength and ordinary concrete. High-strength reinforced concrete plates containing 8 mm orthogonal reinforcement with 100 mm spacing were constructed and tested. Load-deflection relationships were investigated. Mechanical properties of high-strength and ordinary concrete were examined. Fracture patterns of plates were presented. Comparisions were made both for high strength and ordinary concrete slabs.