Pemanfaatan pasir pantai sebagai bagian agregat halus pada beton kedap air :: Suatu studi Pasir Pantai Congot, Kulonprogo, Yogyakarta

OKTAWIDYANTO, B. Adi, Ir. Kardiyono Tjokrodimuljo, ME

2005 | Tesis | S2 Teknik Sipil

Ketersediaan sumber daya alam yang melimpah di Indonesia belum dimanfaatkan secara optimal. Salah satu contohnya adalah pasir pantai yang ketersediaannya sangat melimpah di pantai Congot, Kulonprogo, Yogyakarta. Pasir pantai Congot dengan modulus halus butir 1,4 sebenarnya cukup potensial dimanfaatkan sebagai bahan susun beton kedap air. Sehingga perlu dilakukan penelitian untuk mengetahui karakteristik beton kedap yang meliputi berat jenis, kuat tekan, modulus elastisitas dan serapan air. Dalam penelitian ini digunakan semen Portland Pozzolan, pasir Pantai Congot, pasir Sungai Progo dan batu pecah asal Clereng. Proporsi agregat campuran untuk beton kedap air dengan pasir pantai (DPP) adalah 10% pasir pantai : 30% pasir sungai : 15% batu pecah 5 - 10 mm : 45% batu pecah 10 - 20 mm, sedangkan untuk tanpa pasir pantai (TPP) adalah 40% pasir sungai : 15% batu pecah 5-10 mm : 45% batu pecah 10-20 mm, dengan mhb masing-masing sebesar 5,05 dan 5,18. Faktor air-semen ditetapkan sebesar 0,45; 0,50 dan 0,55. Untuk setiap nilai fas ditetapkan berat semen per meter kubik beton sebesar 380 kg, 410 kg dan 440 kg. Karakteristik pasir Pantai Congot meliputi berat jenis sebesar 2,926; kandungan lumpur 0,36%; kandungan garam 0,0819% dan kadar ion khlorida 218,158 ppm. Nilai slam adukan beton DPP lebih rendah daripada TPP. Berat jenis kedua macam beton (DPP dan TPP) tergolong beton normal. Kandungan butir halus beton DPP lebih besar daripada TPP, dan semua beton yang diteliti memenuhi syarat kandungan butir halus minimal. Berdasarkan jumlah ion khloridanya, beton DPP lebih berpotensi menimbulkan korosi daripada TPP. Kuat tekan beton DPP sedikit lebih tinggi daripada TPP. Modulus elastisitas beton DPP dan TPP sedikit dibawah rumus SNI untuk beton normal, sedangkan perbedaan antara modulus elastisitas kedua macam beton tersebut tidak begitu nyata. Semua beton yang diteliti memenuhi syarat beton kedap air agresif normal. Beton kedap air agresif sedang yang terbaik tercapai pada beton DPP fas 0,50 dengan jumlah pasta antara 570 kg/m3 – 670 kg/m3, sedangkan beton kedap air agresif kuat pada beton DPP fas 0,45 dengan jumlah pasta antara 550 kg/m3 - 650 kg/m3. Hasil penelitian ini menunjukkan bahwa beton DPP lebih kedap air daripada TPP.

In Indonesia the abundance of natural resources deposits has not been optimally explored yet. One of the examples is the seashore sand deposits in Congot beach, Kulonprogo, Yogyakarta. Congot seashore sand which consists of fineness modulus of 1.4 (mhb) is potential materials to make watertight concrete. Hence, a research is needed to investigate the characteristic of watertight concrete which made of seashore sand. The characteristics are specific gravity, compressive strength, modulus of elasticity and water absorption. This research used Portland Pozzolan cement, sand from Congot seashore, sand from Progo river and crushed stone from Clereng. Concrete of type I was made with ratio of seashore sand : river sand : crushed stone of 5-10 mm diameter : crushed stone of 10-20 mm diameter = 10% : 30% : 15% : 35% (DPP) and the type II was made of river sand : crushed stone of 5-10 mm diameter : crushed stone of 10-20 mm diameter = 40% : 15% : 35% (TPP). Water/cement ratio (w/c) viz. 0.45; 0.50 and 0.55 and cement content viz. 380 kg/m3, 410 kg/m3 and 440 kg/m3, with mhb are 5.05 and 5.18 respectively. Seashore sand indicates 2.926 of specific gravity; 0.36% of mud content; 0.0819 % of salt content and 218.158 ppm of chloride ion content. The slump value of DPP (with seashore sand) concrete mix is lower than TPP. Specific gravity of both kinds of concrete (DPP and TPP) is regarded as a normal concrete. Fine particle content of DPP concrete is bigger than TPP, and all concrete have been checked up to the standard of minimum fine particle content. Pursuant to the amount of chloride ion, DPP concrete is more potential than TPP in generating corrosion. The compressive strength of DPP concrete is a little higher than TPP. Modulus of elasticity of both DPP and TPP concrete is below Indonesian National Standard (SNI) formula for the normal concrete, while the difference in modulus of elasticity for both kinds of concrete is not real. All concrete have been checked up to the standard of normal aggressive watertight concrete. Medium aggressive watertight concrete is best reached by DPP concrete w/c 0.50 with paste content is between 570 kg/m3 – 670 kg/m3, while strong aggressive watertight concrete is best reached by DPP concrete w/c 0.45 with paste content is between 550 kg/m3 – 650 kg/m3. The result showed the DPP concrete is more permeable than TPP.

Kata Kunci : Beton Kedap Air,Pasir Pantai,Kuat Tekan,Serapan Air,seashore sand, watertight concrete, compressive strength, water absorption