<![CDATA[Concrete is a construction material used so that alternative components are needed, in coastal areas. This study aims to determine the effect of Suppa Beach sand and Ujung Tape Beach sand as a substitute for fine aggregate with the addition of Modacon Concrete Additive on workability and compressive strength. The study used an experimental method with a design compressive strength of 25 MPa. Cylindrical test specimens 15 × 30 cm with normal variations and beach sand substitution of 50%, 75%, and 100%. Modacon was added 2% of the cement weight. Testing included slump tests and compressive strength at the age of 7 and 28 days. The slump results showed normal 82.50 mm, the highest in 100% Suppa Beach sand at 92.50 mm, and the lowest in 100% Ujung Tape Beach sand at 75.00 mm. At the age of 28 days, the normal compressive strength was 25.19 MPa, while the highest was in 50% Suppa Beach sand at 26.89 MPa. Both 75% and 100% substitutions reduced the compressive strength. A 50% substitution was the optimum variation, with Suppa Beach sand performing better.Keywords: Concrete, Beach Sand, Suppa Beach Sand, Ujung Tape Beach Sand, Compressive Strength]]>
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