Pemanfaatan beton Styrofoam ringan untuk fondasi sumuran

RAMADHANI, Sriyati, Prof.Dr.Ir. Kabul Basah Suryolelono, Dip.He.,DEA

2006 | Tesis | S2 Teknik Sipil

Akhir-akhir ini harga material bangunan semakin melambung terutama harga semen sebagai bahan pokok suatu konstruksi bangunan (konstruksi fondasi). Di daerah tanah lunak dengan letak muka air tinggi diperlukan ukuran luasan fondasi cukup besar (fondasi telapak, pelat) atau digunakan fondasi tiang. Apabila jenis fondasi tiang, fondasi langsung (telapak) atau fondasi pelat digunakan pada bangunan ringan berakibat mahalnya biaya konstruksi. Untuk itu, dicari alternatif lain yaitu fondasi beton ringan guna mengurangi volume pemanfaatan material semen, dan menekan biaya konstruksi fondasi. Dalam penelitian ini, pemanfaatan beton ringan merupakan salah satu alternatif untuk menyelesaikan masalah tersebut dengan memanfaatkan styrofoam. Penelitian ini menitikberatkan pada pengaruh pemanfaatan beton styrofoam ringan untuk fondasi sumuran pada tanah lempung lunak dengan dua kondisi muka air tanah yaitu di atas dasar fondasi dan di bawah dasar fondasi. Beton styrofoam ringan dimodelkan dalam kotak uji di laboratorium, bahan yang digunakan berupa semen Portland tipe I, styrofoam dengan diameter 2-3 mm, pasir dan air, di mana komposisi air proporsional dengan campurannya. Perbandingan volume bahan dengan 6 variasi campuran berupa campuran styrofoam 100 % dan pasir 0 %, styrofoam 80 % dan pasir 20 %, styrofoam 60 % dan pasir 40 %, styrofoam 40 % dan pasir 60 %, styrofoam 20 % dan pasir 80 % serta styrofoam 0 % dan pasir 100 %. Model fondasi dengan ukuran diameter 44 cm dan panjang 50 cm dan tertanam 45 cm. Uji beban dilakukan dengan cara memberi secara bertahap dan dicatat penurunannya. Dari hasil uji beban statis dapat dilihat bahwa dengan memanfaatkan beton styrofoam ringan untuk fondasi sumuran diperoleh nilai penurunan yang terkecil pada persentase styrofoam 100 % untuk muka air tanah di atas dasar fondasi dan pada persentase styrofoam 0 % untuk muka air tanah di bawah dasar fondasi. Kapasitas dukung ultimit yang terbesar terjadi pada kandungan styrofoam 0 % baik untuk muka air tanah di atas dasar fondasi maupun muka air tanah di bawah dasar fondasi.

Recently, due to economical condition, material price for construction especially for cement tended to rise up. Some foundation types that could be used in soft clay with high ground water level were footplate with large contact area or pile foundation. The usage of pile foundation, spread footing and footplate in lightweight construction were very expensive. Alternative solution suggested was lightweight concrete, it was chosen to reduce cement volume in foundation construction and to reduce foundation construction cost. In this research, the usage of styrofoam in lightweight concrete was presented as an alternative solution. This research emphasized in the effect of lightweight-styrofoam concrete usage as caisson foundation constructed on soft clay with two ground water level conditions which were the condition of ground water level that higher than the depth of foundation base and lower than the depth of foundation base. Styrofoam concrete was modeled in test box in laboratory. The materials used were Portland cement type I, styrofoam with 2 – 3 mm for grain diameter, sand and water, where the composition of water was proportional. There were 6 variations of volume composition between styrofoam and sand. They were 100 % styrofoam and 0 % sand, 80 % styrofoam and 20 % sand, 60 % styrofoam and 40 % sand, 40 % styrofoam and 60 % sand, 20 % styrofoam and 80 % sand, 0 % styrofoam and 100 % sand. The sizes of foundation model were 44 cm for diameter size, 50 cm length and embedded in 45 cm depth. Load test was carried in stage condition and settlement was measured for each stage. Load test on lightweight-styrofoam concrete usage as caisson foundation showed that the smallest settlement of foundation obtained in 100 % styrofoam composition with ground water level was higher than foundation base and in 0 % styrofoam composition for ground water level that was lower than foundation base. The highest bearing capacity for either higher or lower level of ground water toward foundation base obtained in 0 % styrofoam composition.

Kata Kunci : Fondasi Sumuran,Beton Styrofoam, lightweight-styrofoam concrete, soft clay, ground water level