The Effect of Shell as a Substitution of Coard Aggregate with Superplasticizer Additional on the Compression Strength of Concrete

Concrete is a type of building structure material, both buildings, bridges, and roads. Concrete is a construction material obtained from mixing sand, gravel, or crushed stone, cement, and water. To improve the properties of concrete, several kinds of additives that have certain functions are added to the concrete mixture, to improve or improve the properties of concrete, namely increasing the workability, durability, and hardening time of the concrete. Shells with excellent quality and shape are used as craft materials, while bad shapes can cause waste which results in a series of other problems, especially the cleanliness of the surrounding environment. This study aims to determine the effect of shells as a substitution of coarse aggregate with superplasticizer added material on the compressive strength of concrete. The specimens used were cylindrical with a diameter of 15 cm and a height of 30 cm. The composition of the shells determined in this study was 0%, 5%, 10%, 15%, 20% and 0.5% superplasticizer added. The planned concrete quality is Fc = 25MPa. The value of the compressive strength of concrete increased with the addition of shells by 5% and decreased in the addition of shells above 5% with 0.5% superplasticizer added. The compressive strength of normal concrete and 0.5% superplasticizer concrete is 28.26 MPa and 29.15 MPa at the age of 28 days and the compressive strength of shell concrete with a composition of 5%, 10%, 15%, and 20% added with superplasticizer 0,5% produces a compressive strength of 30.78MPa; 26.78MPa; 24.71 MPa, and 22.93 MPa at the age of 28 days.