ABSTRACT
Beach sands are one of the natural wealth sources in Indonesia. The beach sand are formed by the blasht of waves and ocean flow on the corals, then it will produce a smooth and round teksture that very good for concrete material. The reasearch uses beach sands and shells from Madura island as concrete materials. This reasearch also uses river sands as control. For material validation test the results to density of the sand beach of a 2,64, while in the river sand to density of 2,69. After a testing material of concrete, the next stage of the mix design with the quality of concrete plans K-225. The results from both of the materials are very satrsfying. From the mixed beach sand materials show compressive strength 227,41 kg/cm2, while in the river sands in compressive strength all the concrete at 260,00 kg/cm2. The use of shells as divided into three variations 3%, 5% and 7% from the needs of cement to show positive results in the proportion of the 3% and 5% compressive strenght all the concrete had increased to 237,78 kg/cm2, and 231,11 kg/cm2. While for the 7% proportion, the compressive strenght it decreases to 220,00 kg/cm2. So beach sand can be used as a mixture of concrete, and the proportion of seashells said he was 3% of the total demand for cement.
