The Tsunami disaster in Aceh is a natural disaster of such a large scale that it is considered an international disaster. One of the measures taken for the reconstruction of damaged buildings is the use of lime taken from shells to partially replace the use of cement. In general, it can reduce global warming by reducing the use of cement in the manufacture of concrete. The research was conducted to determine the effect of the use of shellfish shells on the compressive strength of concrete. The maximum diameter of the aggregate used is 19 mm, the cement used is Portland cement type I. The concrete mix design used the American Concrete Institute (ACI) method with a slump design of 75–100 mm. The test object used was a cylinder with a diameter of 15 cm and a height of 30 cm. The variations in the use of shellfish shells powder were 0%, 2%, 4%, 6%, and 8%, and 0% shellfish shells powder is a comparison test object. For each variation of shell powder, 3 (three) cylindrical specimens were made with test times of 7 and 28 days. The test results show that for the split tensile strength of concrete at 28 days of concrete age with a variable of 2% and compressive strength of a variation of 4%. The addition of 2% clamshell powder can increase the split tensile strength of normal concrete by 10.48%, and an increase in concrete compressive strength of 21.98% in the substitution of 6% shell powder. The novelty obtained from this research is the use of shell powder with 6% substitution to replace cement, which produces a significant concrete compressive strength, namely 0% shellfish powder has a compressive strength of 26.610 MPa compared to 6% substitution, which has a strength of 32.460 MPa.