<![CDATA[Concrete is one of the most widely used construction materials due to its high compressive strength, good durability, and the availability of its constituent materials. However, the increasing demand for natural fine aggregate has led to excessive exploitation of natural resources, creating environmental concerns. Therefore, alternative materials are needed to partially replace fine aggregate. This study aimed to analyze the effect of partially substituting fine aggregate with Malang Sand and Stone Dust on the compressive strength of concrete with a design strength of 20 MPa and to determine the optimum mixture proportion. The research employed an experimental method conducted at the Civil Engineering Laboratory of Universitas Islam Lamongan UNISLA. Cylindrical concrete specimens measuring 15 cm × 30 cm were prepared using the mix design method based on SNI 03-2834-2000. The substitution levels of fine aggregate were 5% (2.5% Malang Sand + 2.5% Stone Dust), 10% (5% Malang Sand + 5% Stone Dust), and 15% (7.5% Malang Sand + 7.5% Stone Dust), with normal concrete used as the control mixture. The results showed that the average compressive strength of normal concrete was 20.52 MPa, while the 5%, 10%, and 15% substitution mixtures achieved compressive strengths of 19.85 MPa, 18.47 MPa, and 17.50 MPa, respectively. Increasing the substitution percentage of Malang Sand and Stone Dust tended to reduce the compressive strength of concrete. The 5% substitution mixture produced the best performance because its compressive strength was the closest to both the normal concrete and the target design strength of 20 MPa.]]>
