Several laboratory tests including compressive strength testes were performed to investigate the characteristics of soil mortar blended with crushed oyster shell, which is treated as waste material and disposed illegally at coastal oyster farm site. The soil mortar specimens were prepared for the experiments in terms of varying blending ratio of cement, water, sand, and oyster shell. Experimental results show that up to 60% of dosages of oyster shell instead of sand do not reduce the compressive strength of soil mortar much compared to that of normal cement mortar. Also, it was found that blending of an oyster shell caused not to reduce the 28-day compressive strength of soil mortar. Based on laboratory test results, the waste crushed oyster shells were judged as promising reusable construction materials.