Analisis Pengaruh Substitusi 25%, 50%, dan 75% Terak Nikel sebagai Agregat Halus pada Beton Padat Gilas terhadap Kuat Tarik Belah menurut ASTM C496 dan BS EN 12390-6 = Analysis of the Effect of Substitution of 25%, 50%, and 75% Nickel Slag as Fine Aggregate in Roller Compacted Concrete on Split Tensile Strength according to ASTM C496 and BS EN 12390-6