SIFAT MEKANIK BETON GEOPOLIMER DENGAN AGREGAT TAILING
Rudi Setiadji Agustiningtyas, ST., Dr. Ing. Ir. Andreas Triwiyono
2011 | Tesis | S2 Mag.Teknologi Bahan BangnGeopolimer memungkinkan untuk penggantian seluruh semen dalam aplikasi konstruksi beton. Material tailing seperti pasir limbah dari P.T Freeport Indonesia terdapat di Timika, Kabupaten Mimika, Provinsi Papua, jumlah produksi 80.000 – 100.000 ton per hari. Penggunaan fly ash sebagai bahan pengikat geopolimer dengan tailing sebagai bahan agregat halus dalam beton berpotensi meningkatkan pemanfaatan kedua limbah tersebut. Tujuan penelitian ini adalah mengetahui kontribusi faktor pengaruh terhadap sifat mekanik, karakteristik jangka pendek beton geopolimer, dan komposisi campuran optimum yang menghasilkan sifat mekanik yang baik. Bahan pengikat dalam penelitian ini menggunakan fly ash tipe F dari PLTU Suralaya dengan aktivator NaOH dan Na2SiO3 sedangkan agregat halus menggunakan tailing PT. Freeport Indonesia. Kegiatan penelitian dilakukan melalui tiga tahap terdiri dari pembuatan mortar (5 x 5 x 5) cm 3 geopolimer dengan aktivator larutan NaOH, pembuatan mortar (5 x 5 x 5) cm 3 geopolimer dengan aktivator gabungan larutan NaOH dan Na2SiO3, dan pembuatan beton geopolimer dengan aktivator gabungan larutan NaOH dan Na2SiO3 bentuk silinder diameter 10 tinggi 20 cm dan balok (10 x 10 x 40) cm 3 . Tinjauan sifat mekanik meliputi kuat tekan, kuat lentur, modulus elastisitas, hubungan teganganregangan uji tekan, kerapatan, penyerapan, dan kadar rongga. Variasi konsentrasi NaOH 8, 10, dan 12 M, rasio Na2SiO3/NaOH sebesar 1, 2, dan 3, rasio aktivator/fly ash antara 0,3 – 0,5. Metode pemadatan dengan penusukan dan perawatan dengan suhu ruang tanpa perlakuan khusus. Kontribusi berbagai faktor pengaruh dalam rancang campur terhadap sifat mekanik beton geopolimer telah diketahui. Semakin banyak tailing, semakin kecil kuat tekan. Aktivator/fly ash beton geopolimer 0,4 hingga 0,5 menyebabkan kuat tekan berkurang. Konsentrasi NaOH 8 M hingga 12 M, tidak banyak mengurangi kuat tekan mortar. Nilai optimum waterglass/NaOH sebesar 2. Rasio Si/Al 3,402 hingga 3,618 berpengaruh negatif dan nilai 3,646 hingga 3,787 memiliki nilai optimum. Karakteristik jangka pendek sifat mekanik mortar dan beton geopolimer dengan agregat tailing sebagai berikut. Kuat tekan beton geopolimer minimal umur 7 hari sebesar 28,21 MPa dapat dicapai dengan metode perawatan suhu ruang. Nilai slump beton segar hingga 230 mm. Penyerapan air kurang dari 4,19%. Volume rongga permeabel 8,79 – 9,39 %. Modulus elastisitas beton geopolimer lebih rendah daripada perhitungan beton normal SNI 03-2847-2002. Kuat tarik lentur umur 28 hari lebih dari 5,90 MPa. Rancang campur optimal dengan sifat mekanik yang memenuhi syarat untuk beton adalah komposisi fly ash : agregat 1 : 3, rasio tailing : split 43 : 57, aktivator/fly ash 0,4, konsentrasi NaOH 10 M, Na2SiO3/NaOH sebesar 2 menghasilkan kuat tekan dan kuat tarik lentur 28 hari hingga 44,42 MPa dan 5,90 MPa
Geopolymer allows for replacement of the cement in concrete construction applications. Tailing is material such as sand-sized waste from PT Freeport Indonesia in Timika, Mimika District, Papua Province, with a total production of about 80,000 to 100,000 tons per day. The use of fly ash as a binder geopolymer with tailings as fine aggregate in concrete has the potency to increase the utilization of both the waste. The research goal is to find the influence of factors contributing to the mechanical properties, characteristics of short-term geopolymer concrete, and the optimum mixture composition that produces good mechanical properties. Binder of fly ash type F from Suralaya with activators NaOH and Na2SiO3 are used without the use of cement while the filler material is tailing of PT. Freeport Indonesia. Research activities was conducted through three stages, consisting of the manufacture of mortars (5 x 5 x 5) cm 3 geopolymer with NaOH activator, making mortars (5 x 5 x 5) cm 3 geopolymer with a combination of activators NaOH and Na2SiO3, and the manufacture of geopolymer concrete with a combination of activators NaOH and Na2SiO3 forming cylinder diameter 10 cm high 20 cm and beam (10 x 10 x 40) cm 3 . Review of mechanical properties include compressive strength, flexural strength, modululus elasticity, stress-strain relationship test press, density, absorption, and volume of permeable void. The variation of the concentration of NaOH is 8, 10, and 12 M, Na2SiO3/NaOH ratio of 1, 2, and 3, the ratio of activator/fly ash between 0.3 to 0.5. Compaction method with rodding and curing in room temperature without special treatment. The influence of factors contributing to the mechanical properties has been discovered. Increasing tailing reduced the compressive strength. Activator/fly ash 0.4 to 0.5 decreased the compressive strength. NaOH concentration 8M to 12 M reduced slightly the compressive strength. Optimum value of waterglass/NaOH is 2. Si/Al ratio 3.402 to 3.618 negatively influenced the compressive strength and between 3.646 to 3.787 has an optimum value. Characteristics of short-term geopolymer concrete are as follow. Minimum concrete compressive strength at 7 th days was 28.21 MPa in room temperature curing. Slump value was up to 230 mm. Absorption was less than 4.19%. Permeable void volume were 8.79 – 9.39 %. Modulus of elasticity were lower than calculation of normal concrete by SNI 03- 2847-2002. Flexural tensile strength 28th days were greater than 5.90 MPa. The optimum mixture composition that produces good mechanical properties was at fly ash : aggregate 1: 3, the ratio of tailings : split of 43: 57, the ratio of activator/fly ash by 0.4, NaOH concentration of 10 M, the ratio of Na2SiO3/NaOH as 2 produced 28th days compressive strength and flexural tensile strength up to 44.42 MPa and 5.90 MPa.
Kata Kunci : sifat mekanik, geopolimer, fly ash, tailing
