ABSTRAK
Berat jenis beton adalah salah satu unsur yang sangat diperhitungkan saat merencanakan struktur bangunan karena berpengaruh pada perhitungan pembebanan. Sehingga, muncul berbagai penelitian mengenai beton ringan. Satu diantaranya adalah pembuatan beton ringan dengan teknologi gas. Beton ringan gas dibuat dengan menambahkan Alumuium pasta yang terdiri dari serbuk alumunium dan air kedalam campuran mortar. Dewasa ini, pemakaian beton ringan masih ditujukan pada beton non struktural saja karena pada umumnya beton ringan mempunyai kekuatan dibawah beton  struktural yang mempuyai kuat tekan minimal 17,5 MPa. Solusi untuk meningkatkan kekuatan beton ringan gasini adalah dengan menambahkan serat kedalam adukan berupa serat polypropylene. Tujuan penelitian ini adalah untuk mengetahui pengaruh penambahan serat polypropylene terhadap sifat-sifat mekanik beton berupa kuat tekan, kuat tarik belah, dan modulus elastisitas.
Metode yang digunakan adalah metode eksperimen yang dilaksanakan di Laboratorium Bahan UNS. Benda uji berbentuk silinder dengan diameter 10 cm dan tinggi 20 cm untuk pengujian modulus elastisitas, kuat tekan, dan kuat tarik belah. Benda uji masing-masing berjumlah 3 buah untuk 1 variasi kadar penambahan serat. Persentase serat yang digunakan adalah 0%; 0,25%; 0,5%; 0,75%; dan 1%. Pengujian menggunakan alat UTM (UltimateTesting Machine). Perhitungan yang digunakan adalah analisis statistik dengan regresi linear pada batas elastis beton menggunakan program Microsoft Excel.
Hasil dari penelitian ini adalah peningkatan nilai kuat tekan, kuat tarik belah, dan modulus elastisitas beton ringan gas setelah ditambah serat polypropylene. Peningkatan paling maksimum terdapat pada kadar penambahan serat sebesar 0,75% dari berat volume beton. Berat jenis benda uji paling tinggi adalah 1892,30 kg/m3, sehingga masih termasuk beton ringan karena mempunyai berat jenis dibawah 1900 kg/m3. Penambahan kadar serat sebesar 0,75% menghasilkan peningkatan kuat tekan, kuat tarik belah, dan modulus elastisitas berturut-turut sebesar 48,18%; 48,44%; dan 59,47% , dibandingkan dengan beton ringan gas tanpa serat. Berdasarkan analisis regresi polynomial diperoleh kadar optimal penambahan serat polypropylene untuk kuat tekan, kuat tarik belah, dan modulus elastisitas beton dengan nilai optimal berturut-turut sebesar 13,91MPa, 2,96 MPa, dan 6659,12 MPa.
Kata kunci : beton ringan, serat polypropylene, kuat tekan, kuat tarik belah, modulus elatisitas
ABSTRACT
The density of concrete is one of aspect which is calculated when designing a building framework because it has influence the loading calculation. For that reason, so is rises many researchs on the lightweight concrete and one of them is making a lightweight concrete using gas technology. gas lightweight concrete is made by adding  Aluminium Paste which consist of Aluminium Powder, and water into a mortar mix. Recently, the utilization of lightweight concrete is still purposed to a non-structural concrete only, because generally a lightweight concrete has less strength than the structural concrete which has minimum compressive strength at 17.5 MPa. The solution to improve this foam lightweight concrete’s strength is by adding fiber to the mixing in form of polypropylene fiber. The purpose of this research is to determine the effect of polypropylene fiber addition to the concrete’s mechanical properties, such as compressive strength, split tensile strength, and modulus of elasticity.
The method that is used is experimental method that have been conducted in the Material Laboratory of UNS. The specimen is in form of cylinder with diameter of 10 cm and height of 20 cm for testing the modulus of elacity, compressive strength, and the split tensile strength. Each specimen consist of 3 pieces for 1 variation of fiber additional rate. The fiber precentage that is used are 0%; 0.25%; 0.5%; 0.75%; and 1%. This experiment using UTM (Ultimate Testing Machine) tool. The calculation that is used is statictic analysis with linear regression on the elasticity limit of the concrete using Microsoft Excel.
The result of this research is increase in the compressive strength, split tensile strength, and modulus of elasticity of gas lightweight concrete after have been added by some polypropylene fibers. Maximum increase is in fiber addition of 0.75% from concrete’s volume weight. The highest specimen’s density is 1892,30 kg/m3 so it is categorized as lightweight concrete because it has density below 1900 kg/m3. The fiber addition of 0.75% makes an increasing in compressive strength, split tensile strength, and modulus of elasticity 48,18%; 48,44%; and 59,47%  continously, compared with gas lightweight concrete which without fiber. Based on the polynomial regression analysis, it is obtained that polypropylene fiber addition optimum rate for compressive strength, split tensile strength, and modulus of elasticity weight with optimum value of 13,91 MPa, 2,96 MPa, and 6659,12 MPa.
Keywords: lightweight concrete, polypropylene fiber, compressive strength, split tensile strength, modulus of elasticity