Concrete is the main material factor in a construction project field that is often used, because concrete has a high compressive strength value so it is very useful for structural buildings to withstand axial forces or compressive forces on the building itself where the structure can be used. for the long term. However, along with the increase in construction development in Indonesia, it has a negative impact on the environment around the construction site because with the rampant construction of this building it will trigger environmental pollution due to the remaining concrete waste from the construction project. On this basis, it encourages the author to conduct research by utilizing waste concrete as a substitute for coarse aggregate for the compressive strength of concrete, by reusing the concrete waste will increase the life of the material from the waste itself. In this study, the materials used were tested first, such as; cement density, silt content, water content, specific gravity absorption, wear testing and sieve analysis on aggregates. Then for the concrete mixture using concrete waste with variations of 0%, 25%, 50%, 75% and 100% of the total weight of coarse aggregate. In this study, the compressive strength at the age of 21 days with a mixture of 0%, 25%, 50%, 75%, and 100% concrete had a compressive strength of 200.92 kg/cm2, 188.83 kg/cm2, 206, respectively. 96 kg/cm2, 177.50 kg/cm2, and 179.01 kg/cm2. Then experienced an average shrinkage of 9.53 kg/cm2 at the age of 28 days. The optimum compressive strength is at 50% mixed variation, with a value of 206.96 kg/cm2 because it has an increase of 3% higher than normal concrete compressive strength with a mixing ratio of 1:2.5:3.5 and a slump value of ±13.25 cm and the dry weight of the concrete is 7.69 kg.

This study uses silica sand, which has a high SiO2 content and micron size as a substitute for normal sand with control specimens with compressive strength of fc ′ 45 MPa. Two types of silica sand gradations were used, namely 80-100 mesh(0.177 mm – 0.149 mm) in size and 325 mesh (0.044 mm) in size from Bangka as the fine aggregate. There were 45 cylindrical specimens sized 15 cm in diameter, 30 cm in height, and age of7, 14, and 28 days. The tests carried out were absorption test and compressive strength test based on SNI 1974: 2011, which explained the testing method of the compressive strength of concrete with cylindrical specimens. Based on the test results, the optimum compressive strength was 53.07 MPa in the specimen with a composition of 50% sized 80-100 mesh (0.177 mm – 0.149 mm) (+) 50% sized 325 mesh (0.044 mm) silica sand, which can increase 4.12% of the compressive strength from normal concrete. On the other hand, the lowest compressive strength was obtained in a specimen with a composition of 25% sized 80-100 mesh (0.177 mm – 0.149 mm) (+) 25% size325 mesh (0.044 mm) silica sand, which was 48.43 MPa at 28 days.