KAJIAN KARAKTERISTIK TANAH BAUKSIT SEBAGAI BAHAN KONSTRUKSI JALAN DI PULAU BINTAN PROPINSI KEPULAUAN RIAU

Zulkhairi, Dr. Ir. Hary Christady Hardiyatmo, M.Eng., DEA

2012 | Tesis | S2 Mag.Teknologi Bahan Bangn

Pulau Bintan dengan luas sekitar 110 ribu hektar mengandung hampir 70%- 80% tanah bauksit. Berkurangnya cadangan batu granit yang dapat diolah, memberikan keuntungan ekonomi tersendiri bagi tanah bauksit bila dimanfaatkan sebagai bahan lapis perkerasan dan jalan tak diperkeras. Pengujian awal dilakukan untuk mengetahui sifat-sifat fisik dan mekanis tanah bauksit. Nilai CBR rendaman tertinggi diperoleh dari 3 variasi campuran berdasarkan proporsi gradasi agregat kasar dan agregat halus, dan tanah bauksit asli. Campuran dengan nilai CBR tertinggi distabilisasi dengan kadar semen 6%, 8%, 10% atau kadar kapur padam 2,5%, 4,5%, 6,5% dan dilakukan pengujian CBR rendaman, kuat tekan bebas, durabilitas, serta beberapa pengujian sifat fisik. Menurut USCS, tanah bauksit merupakan tanah berbutir kasar terdiri dari campuran pasir berlanau-berlempung (SM-SC), sedangkan menurut AASHTO merupakan tanah granular kelompok A-2-4(0) dengan material pokok terdiri dari kerikil dan pasir berlanau-berlempung, serta bergradasi buruk. Campuran kode D bila distabilisasi dengan kadar semen 6%, 8% dan 10% dapat meningkatkan CBR rendaman (182,74%, 232,04%, 242,26%); UCS (23,19 kg/cm2, 28,65 kg/cm2, 30,17 kg/cm2); dan durabilitas. Stabilisasi dengan kadar kapur padam 2,5%. 4,5%. 6,5% menghasilkan CBR rendaman 55,21%, 75,22%, 58,53%; UCS umur 7 hari 2,09%, 1,65%, 1,19% dan umur 28 hari 4,61%, 7,01%, 6,58%; dan dapat meningkatkan durabilitas campuran. Tanah bauksit sebelum distabilisasi dapat digunakan sebagai subgrade dan subbase dengan beberapa ketentuan. Bila menggunakan lapis pondasi tanah bauksit-semen lebar jalan 4 meter dan panjang 1000 meter serta tebal 20 cm, maka diperoleh efisiensi nilai ekonomis sebesar Rp. 113.008.472,00 per km dibandingkan dengan lapis pondasi agregat klas A. Tanah bauksit masih memungkinkan digunakan sebagai bahan kelas C dan waterbound macadam pada lapis pondasi jalan tanpa penutup aspal, terlebih lagi bila dilakukan stabilisasi dengan semen.

Bintan Island covers approximately 110 thousand hectares and is composed of 70%-80% bauxite soil. The decreasing granite rock reserves may give special economic benefits when utilized as pavement material and unpaved road. The preliminary examination was carried out to identify the physical and mechanical characteristics of the bauxite soil. The highest value of soaked CBR was obtained from three mixture variations based on the coarse and fine aggregate and original bauxite soil proportions. The mixture with the highest CBR was stabilized within cement concentration of 6%, 8%, 10% or padam lime concentration of 2,5%, 4,5%, 6,5% and soaked CBR tests, such as the free compressive strength, durability and several tests of physical characteristics, were taken. According to USCS, the bauxite soil is soil in coarse granule and consisted of silt-cay sand (SM-SC). According to AASHTO, the granular soil in group A-2-4(0) with main material consisted of gravels and silt-clay sand and with unqualified gradation. The mixture code D was then stabilized with cement concretions of 6%, 8% and 10%, and might increase the soaked CBR (182,74%, 232,04%, 242,26%); UCS (23,19 kg/cm2, 28,65 kg/cm2, 30,17 kg/cm2); and durability. The stabilization by using 2,5%. 4,5%. 6,5% padam lime resulted in soaked CBR of 55,21%, 75,22%, 58,53%; UCS of 7 days was 2,09%, 1,65%, 1,19%; and 28 days was 4,61%, 7,01%, 6,58%; and increased the mixture durability. The bauxite soil before stabilization was able to be used as subgrade and subbase under several provisions. When base course of bauxite soil-cement was used for 4 meter width and 1000 meter length and 20 cm thickness, the economic efficiency obtained was Rp. 113.008.472,00 per km in compare to the Class A aggregate foundation. Bauxite soil was possible for class C and waterbound macadam on the asphaltic unpaved road base course, especially when cement stabilization was carried out.

Kata Kunci : tanah bauksit, CBR rendaman, UCS, durabilitas