Abstrak. Penelitian ini menjelaskan perilaku flexural toughness dari reactive powder concrete berpenguat serat baja lokal dengan fraksi volume dan aspek rasio yang berbeda-beda. Contoh uji berbentuk prisma dengan ukuran 100 x 100 x 350 mm yang dibuat dengan serat baja dan tanpa serat baja. Serat baja yang digunakan 0% (kontrol), 1,0%, 1,5%, dan 2,0% terhadap volume dan aspek rasio 75, 100, 125. Contoh uji dikelurkan dari cetakan setelah 24 jam kemudian direndam dalam air selama 3 hari, setelah itu contoh uji dirawat dengan penguapan selama 8 jam pada temperatur 90°C. Pengujian Flexural toughness dilakukan ketika prisma telah berumur 28 hari. Hasil penelitian memperlihatkan, volume dan aspek rasio serat memiliki pengaruh yang signifikan terhadap flexural toughness reactive powder concrete.Abstract. This research present flexural toughness behavior of local steel fiber reinforced reactive powder concrete produced with different steel fibers volume fraction and aspect ratio. Prismatic concrete specimens of 100 x 100 x 350 mm were prepared with and without steel fiber. Steel fiber was used of 0% (control), 1,0%, 1,5%, and 2,0% by volume and 75, 100 and 125 as aspect ratio. Specimens were de-molded after 24 hours and cured in water until 3 days, after that the speciments were cure by steam curing for 8 hours at 90°C. Flexural toughness of the prisms has beendefined at 28 day old. The result show that the effects of fibre volume and aspec ratio on flexural toughness of reactive powder concrete are very significant.