Trass is a pozzolan whose utilization has not been maximized, which is often found in the highlands because trass is a volcanic rock that has experienced changes in chemical composition caused by weathering and the influence of underground water conditions. The use of trass as a material for making concrete is part of an effort to solve the problem of dependence on sand. This study aims to determine the ideal proportion of trass that can be added to the concrete mix fc '21.7 MPa, compared to concrete without the use of added material (normal concrete) with variations in the use of trass 0%, 10%, 20%, 30% and 40%. This study uses an experimental method, with partial replacement of sand with trass. Making samples using concrete cylinders 15 cm in diameter and 30 cm high. concrete mix design planning refers to SNI Concrete Planning 03-2834-2000. The results of this study indicate that the average compressive strength of normal concrete is 21.84 MPa, while for variations of trass 10% = 22.58 MPa, 20% = 22.21 MPa, 30% = 20.17 MPa, 40% = 18 , 87 MPa, so that the percentage variation of 10% and 20% obtained a good compressive strength in the concrete mixture.