Concrete is an important part of making a building. Concrete can be constructed
using several materials, one of which is fine aggregate. Material development is
currently being a very important part. For instance, it is common these days to
use trass as an ingredient to substitute fine aggregate. The purpose of this study
was to determine the effect of using trass in the concrete mixture on the
compressive strength of the concrete. Replacement of iron sand in concrete
mixed from 0%, 25%, 50%, and 75% of the weight of fine aggregate. The test
sample was used on a concrete cylinder with a diameter of 15 cm and a height of
30 cm with a test life of 3 days. The results showed that the use of trass as a
substitute of fine aggregate tended to decrease the compressive strength of the
concrete, in order, the average compressive strength of the concrete conversion
for 28 days starting from normal concrete, 25%, 50%, and 75% trass was 25.55
Mpa. ; 21.77 Mpa; 18,40 Mpa; 16,04 Mpa. The decrease in the compressive
strength of concrete is due to the calculation of air absorption which is greater
than ordinary sand, namely 11% for trass and 3% for ordinary sand.