ABSTRAK

Beton merupakan bahan bangunan yang sudah lama dikenal dan sangat banyak di gunakan. Beton terdiri dari bahan campuran semen, kerikil, pasir, air dan bahan tambah. Penggunaan bahan tambah berupa serat alam yakni serat sabut kelapa diharapkan dapat memperbaiki sifat mekanik beton terkhususnya beton normal. Penelitian ini dimaksudkan untuk mengetahui komposisi penambahan serat sabut kelapa yang meningkatkan nilai kuat tekan, kuat tarik belah dan kuat lentur pada beton. Pembuatan campuran beton mengacu SK SNI T-15-1990-003 tentang “Tata Cara Pembuatan Rencana Campuran Beton Normal”. Metode penelitian yang dilakukan adalah dengan merancang komposisi campuran beton untuk masing-masing tambahan serat serabut kelapa kemudian membuat sampel beton berbentuk silinder dan balok untuk kemudian dilakukan pengujian terhadap beton.

Penelitian ini menggunakan kuat tekan rencana f’c 24,90 N/mm². Benda uji berupa silinder beton berukuran 15x30 cm dan balok beton berukuran 15x15x60 cm. Setiap variasi adukan berjumlah 3 buah benda uji. Proses pengujian kuat tekan , kuat tarik belah, dan kuat lentur dilakukan pada umur beton 7 , 14, 21, dan 28 hari. Proporsi campuran beton serat sebanyak 3 variasi adukan. Serat serabut kelapa sebagai bahan tambahan berupa serat dengan ukuran panjang 25-40 mm dan dengan persentase 2%, 4%, dan 6%. Serat serabut kelapa diberi perlakuan dengan cara direndam dan direbus kurang lebih 1 jam dengan air kunyit, selanjutnya dijemur dan dikeringkan dengan tujuan menghilangkan sifat-sifat organik serat yang dapat melapukkan beton.

Hasil penelitian menunjukkan penambahan serat serabut kelapa 2% mempunyai pengaruh terhadap peningkatan kuat tarik belah dan kuat lentur, namun mengalami penurunan kuat tekan. Selanjutnya pada penambahan serat sebesar 4% dan 6% cenderung mengalami penurunan kuat tekan, kuat tarik belah dan kuat lentur dibandingkan beton dengan penambahan serat 2%.  Sehingga, kadar optimum penambahan serat serabut kelapa terhadap kuat lentur dan kuat tarik belah tertinggi terjadi pada penambahan sebesar 2% diperoleh rata-rata kuat tarik belah sebesar 2,38 MPa dan kuat lentur sebesar 5,705 MPa. Namun, kuat tekan tertinggi didapat pada beton normal yakni sebesar 25,75 MPa.

Kata Kunci: beton serat, serat serabut kelapa, kuat tekan, kuat tarik belah, kuat lentur.

ABSTRACT

Concrete is a building material that has long been known and is very widely used. Concrete consists of a mixture of cement, gravel, sand, water and added ingredients. The use of added ingredients in the form of natural fibers, namely coconut fiber, is expected to improve the mechanical properties of concrete, especially normal concrete. This study is intended to determine the composition of the addition of coconut fiber which increases the value of compressive strength, split tensile strength and flexural tensile strength in concrete. Making concrete mix refers to SK SNI T-15-1990-003 regarding "Procedures for Making a Normal Concrete Mixture Plan". The research method is to design the composition of the concrete mixture for each coconut fiber addition and then produce cylinder and beam concrete samples to then test the concrete.

This research using compressive strength plan f’c 24,90 N/mm². The test specimen is a 15x30 cm concrete cylinder and a 15x15x60 cm concrete beam. Each variation of the mixture amounted to 3 specimens. The testing process of compressive strength, split tensile strength, and flexural tensile strength was carried out at 7, 14, 21 and 28 days of concrete. The proportion of fiber concrete mixture is 3 variations of stir. Coconut fiber as an additional material in the form of fibers with a length of 25-40 mm and with a percentage of 2%, 4%, and 6%. Coconut fiber is treated by soaking and boiling it for about 1 hour with turmeric water, then dried with the aim to remove the organic properties of fiber which can decay the concrete.

The results showed that the addition of 2% coconut fiber had an effect on the increase in split tensile strength and flexural strength, but experienced a decrease in compressive strength. Furthermore, the addition of fiber by 4% and 6% tends to decrease compressive strength, split tensile strength and flexural strength compared to concrete with the addition of 2% fiber. Thus, the optimum level of coconut fiber addition to the highest flexural strength and split tensile strength occurred in an addition of 2% obtained by the average split tensile strength of 2.38 MPa and flexural strength of 5.705 MPa. However, the highest compressive strength was found in normal concrete which was 25.75 MPa.

Key words: fiber concrete, coconut fiber, compressive strength, splitting tensile strength, flexural tensile strength