The paper describes shell-limestone treatment with stone strengthener Oxal NK 100. Aging impairs the mechanical characteristics of the stone and reduces its bearing capacity. The purpose of the study was to investigate the efficiency of the stone-strengthening composition Oxal NK 100. The composition is supposed to reduce water absorption and strengthen the stone. Cube samples of the Crimean shell-limestone were used. Several testing operations were made to reveal such specifications as absorption of water, compression capacity, freeze-thaw resistance, and porosity of the material. Tests were done on two kinds of samples: treated and non-treated. The results of the study indicated an improvement of mechanical properties of treated stone, compared to non-treated rock samples. The study proved the efficiency of the use of stone-strengthening materials for construction and restoration with shell-limestone.