Tanah mempunyai peranan yang sangat penting dalam suatu bidang pekerjaan konstruksi. tanah yang dijumpai dilapangan sangat bervariasi dan kualitasnya tidak selalu memenuhi persyaratan yang ditentukan untuk suatu konstruksi bangunan diatasnya. penelitian ini mencoba menganalisis besarnya kuat tekan bebas dan nilai cbr laboratorium tanah asli yang dicampur semen yang dilakukan dengan pengujian unconfined compression test dan california bearing ratio laboratorium. pengujian dilakukan di laboratorium mekanika tanah, fakultas teknik, jurusan teknik sipil, universitas borneo tarakan. sampel tanah asli diambil 2 titik pada proyek pembangunan outer ring road (binalatung-juata laut), tarakan, yaitu pada sta 0+400 dan sta 25+650. pengambilan sampel dilakukan secara terganggu (disturbed soil). nilai dari pengujian analisis saringan dan batas konsistensi didapat jenis tanah menurut aastho dan unified. sampel tanah i merupakan jenis tanah yang bercampur pasir lanau sedangkan jenis tanah sampel ii adalah kerikil berpasir yang berlempung yang berwarna coklat muda. berdasarkan jenis tanah didapat variasi kadar semen, yaitu 10%, 12% dan 14% dengan masa peram 2, 7, dan 14 hari. dengan menggunakan kadar air optimum dan kepadatan kering maksimum dari percobaan pemadatan, maka didapat uji kuat tekan bebas sampel i dengan masa pemeraman 2, 7, 14 hari yaitu kadar semen 10% sebesar 3.13 kg/cm 2 , 6.59 kg/cm 2 , 7.60 kg/cm 2 , kadar semen 12% sebesar 3.30 kg/cm , 6.79 kg/cm 2 , 8.40 kg/cm 2 , dan kadar semen 14% sebesar 3.51 kg/cm , 7.78 kg/cm 2 , 9.60 kg/cm 2 , untuk sampel ii dengan kadar semen 10% sebesar 8.99 kg/cm 2 , 11.95 kg/cm 2 , 14.60 kg/cm 2 , kadar semen 12% sebesar 17.90 kg/cm , 19.90 kg/cm 2 , 19.92 kg/cm 2 , dan kadar semen 14% sebesar 20.30 kg/cm , 21.88 kg/cm 2 , 23.30 kg/cm 2 . demikian pula yang didapat cbr laboratorium semakin banyak penambahan semen, maka semakin meningkat nilai kekuatan yang didapat. meningkatnya nilai cbr dan kuat tekan bebas disebabkan semakin rapatnya tanah karena diikatnya butiran-butiran tanah oleh semen sehingga tanah semakin padat dan keras, dan juga penambahan semen ini dapat mengisi ruang-ruang kosong diantara partikel-partikel padat tersebut. 2 2 2 2

Soil have very important role in construction working area. soil which were found in field is very variation and its quality is not always fill requirement, that defineted to building construction its above. this research tries to analyze large of unconfined compression strength and cbr laboratory of original soil that mixed cement with conducted with examination unconfined compression test and california bearing ratio laboratory. the research was conducted in mechanic laboratory of soil, technique faculty, majors of technique civil, borneo university tarakan. sample of original soil were taken two dots on the development project outer ring road (binalatung-juata laut), tarakan, those are on sta 0+400 dan sta 25+650. intake of sample conducted in disturbed soil. value of filter analysis and boundary of consistency were found soil type acording to aastho dan unified. sample of soil i are mixed with silt soil, while sample of soil ii are sandy gravel which have young tan clay. based on type above had found variation of rate cement, those are 10%, 12%, and 14% with periode 2, 7, and 14 days. with using optimum water rate and dry density maximum of attempt of condensation, therefore found unconfined compression strength of sample i with a periode 2, 7, 14 days cement rate 10% are 3.13 kg/cm 2 , 6.59 kg/cm , 7.60 kg/cm 2 , 12% are 3.30 kg/cm 2 , 6.79 kg/cm 2 , 8.40 kg/cm 2 , and 14% are 3.51 kg/cm 2 , 7.78 kg/cm 2 , 9.60 kg/cm 2 , to sample ii with rate cement 10% are 8.99 kg/cm 2 , 11.95 kg/cm 2 , 14.60 kg/cm 2 , 12% are 17.90 kg/cm 2 2 , 19.90 kg/cm , 19.92 kg/cm 2 , and 14% are 20.30 kg/cm 2 , 21.88 kg/cm 2 , 23.30 kg/cm . that way also which are found laboratory cbr if more in addition of cement, so progressively mount strength value were got. the increasing of value cbr an unconfined compression strength are caused density of soil items by cement. so that, soil progressively hard and solid this addition it too cal fill empty rooms among solid particles. 2 2