Enhancing Compressive Strength in Cementitious Composites through Effective Use of Wasted Oyster Shells and Admixtures

Wasted oyster shells generate environmental pollution and odor, thereby causing inconvenience to people. In addition, low-quality aggregates are generated owing to the lack of sand. To address these problems, cementitious composites that replaced sand with oyster shell powder were fabricated in this study, and a total 120 specimens were fabricated (specimen size: 50x50x50 mm3). The oyster shell substitution rate for sand, admixture type, and presence or absence of admixture were set as the experimental parameters. Herein, 0, 30, 70, and 100% of sand was replaced with oyster shell powder to examine the compressive strength of the cementitious composites according to the oyster shell powder content. The experiment results confirmed the decrease in the compressive strength of the cementitious composite with an increase in the oyster shell powder content. In the case of the cementitious composites mixed with oyster shell powder, silica fume, blast furnace slag, and an air-entraining water-reducing agent, the compressive strength increased by up to 30% with an increase in the oyster shell powder content. The results of cementitious composites containing oyster shell powder and admixture fabricated in this study indicate the potential of oyster shells as a new construction material that can replace sand.