<![CDATA[Agricultural waste such as crab shells has the potential to pollute the surrounding environment. Crab shells contain calcium carbonate (CaCO3) which will react with calcium hydroxide in cement, forming a solid compound called calcium silicate hydrate (CSH). This research examines the use of mud crab (Scylla Serrata) shell waste as a partial substitute for cement in making concrete, with the addition of a superplasticizer. The percentage of crab shells used is 0%, 10%, and 20%, as well as 2% superplasticizer. The research results showed a decrease in the compressive strength of concrete with crab shell substitution. At 10% substitution, the compressive strength decreased to 23.38 MPa, and at 20% substitution, it decreased to 16.14 MPa. The flexural strength of concrete also decreases, where 10% substitution produces a flexural strength of 3.53 MPa, and 20% substitution produces 1.60 MPa. With the addition of 2% superplasticizer, 10% crab shell substitution showed a compressive strength of 26.87 MPa, higher than normal concrete. However, at 20% substitution, the compressive strength decreased to 18.01 MPa. The flexural strength of concrete with 2% superplasticizer also decreased; 10% substitution shows a flexural strength of 3.87 MPa, higher than normal concrete, while 20% substitution decreases to 2.53 MPa.]]>
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