Pengaruh Variasi Ukuran Butiran Tepung Kedelai pada Metode Calcite Precipitation untuk Peningkatan Kekuatan Tanah Pasir

Kedelai merupakan alternatif penggunaan enzim urease murni komersial dalam metode calcite precipitation. Ukuran butiran tepung kedelai merupakan salah satu faktor penting karena berpengaruh terhadap jumlah material yang tidak terlarut dan selanjutnya terhadap reaksi pembentukan kalsit. Tepung kedelai yang digunakan dalam penelitian ini telah diayak dengan saringan No. 300 (50 μm), No. 150 (100 μm), dan No. 75 (200 μm) dan bagian yang tertahan di setiap saringan digunakan dalam penelitian. Larutan tepung kedelai dengan konsentrasi sebanyak 20 g/L digunakan dan disaring melalui saringan No. 400 (40 μm), untuk mendapatkan ekstrak. Pasir Bangka digunakan sebagai sampel tanah pasir dan memiliki koefisien keseragaman sebesar 1.53. Evaluasi kemudian dilakukan dengan mengggunakan tiga parameter yaitu pengendapan kalsit, laju hidrolisis urea, dan evaluasi calcite content menggunakan asam klorida. Berdasarkan uji pengendapan kalsit dengan menggunakan tabung, semakin kecil ukuran biji kedelai, semakin banyak bahan tak terlarut yang dihasilkan. Rasio presipitasi kalsit dan massa kalsit yang diendapkan optimum tercapai pada ukuran butiran kedelai 100 μm. Laju hidrolisis tertinggi terjadi pada ukuran butiran kedelai 50 μm pada 752 U/g. Persentase kalsit tertinggi di dalam sampel terbentuk pada sampel dengan ukuran butiran kedelai 50 μm dengan persentase massa kalsit sebesar 0.60% atau setara dengan 43.81 kPa. Berdasarkan parameter yang dievaluasi, tepung kedelai dengan ukuran 50 μm memiliki hasil terbaik dan penurunan ukuran butiran tepung kedelai sejalan dengan peningkatan kekuatan tanah pasir. &nbsp

Pelatihan Pembelajaran Daring Berbasis Aplikasi Google Di Masa Pandemik Covid-19 Di SMAN 8 Kota Bengkulu

Pandemi Covid-19 telah menjadi darurat kesehatan global, banyak negara menerapkan social dan physical distancing. Hal tersebut berdampak langsung pada proses pembelajaran. Pandemi global ini telah berubah dari pembelajaran langsung menjadi pembelajaran online. Sebagian besar guru di sekolah belum menguasai pembelajaran online ini. Tujuan dari kegiatan sosialisasi ini adalah untuk melatih para guru menggunakan aplikasi berbasis Google untuk membuat, mengelola bahan ajar, dan menilai pembelajaran online. Pelatihan dilakukan dengan metode tatap muka dan pembelajaran mandiri. Sebagian besar peserta menyatakan bahwa materi pelatihan sangat puas dan bermanfaat untuk proses pembelajaran online. Kendala yang dihadapi peserta dalam melaksanakan pembelajaran online adalah: sinyal internet, pembelajaran karakter tidak terlihat. Kemampuan guru dalam memanfaatkan teknologi informasi di masa pandemi Covid-19 menjadi strategi yang sangat diperlukan, bahkan keahlian ini berguna dalam mempersiapkan era revolusi pendidikan 4.

Pengaruh Dissolved Organic Carbon (DOC) pada Efektivitas Perbaikan Tanah Gambut dengan Metode Calcite Precipitation

The problems that are generally found in land preparation for infrastructure developments are the characteristics of soils that have low bearing capacity, such as peat soils. Calcite precipitation is a soil improvement method that utilizes biochemical reactions with the final product being calcite. Peat soil has different characteristics from other soils, that it has high levels of Dissolved Organic Carbon (DOC). The amount of DOC present in peat soil significantly affects the specific gravity, liquid limit, density, and strength of the soil. Therefore, it is necessary to evaluate whether DOC in peat soil can affect the effectiveness of the calcite precipitation method. The research was conducted on soil with high organic content (95.35%) and soil with moderate organic content (73,51%). The research was carried out through five stages, namely soil properties, test-tube experiment, soil samples treatment, Unconfined Compressive Strength (UCS) test, and evaluating the soil pH. The results of this study obtained in the form of high organic content have an additional strength of 76.47%. Medium organic content soil has an additional strength of 137.50. Thus, DOC has an effect on increasing soil strength in the calcite precipitation method

Analisis Potensi Kelongsoran pada Ruas Jalan Raya Pangalengan menggunakan Sistem Informasi Geografis

Indonesian National Board for Disaster Management (BNPB) claimed the landslide incident on 5 May 2015 in Pangalengan District caused gas pipelines owned by PT. Geothermal Star Energy exploded, 9 people died, 154 displaced and 10 houses buried. Based on the facts, it is necessary to make an effort to reduce the risk of landslides by utilizing satellite imagery. The purpose of this study was to identify potential landslides on the Pangalengan highway and make recommendations mitigation actions for the local government. The method used was using 2 estimation system models made by the Directorate of Volcanology and Geological Disaster Mitigation in 2004 and 2005. The result of the DVMBG 2004 showed the very high classification had a percentage of 97.24% and the DVMBG 2005 result showed the high classification reached 53.26% and the very high classification reached 53.26%. The potential for landslides on the Pangalengan road is 98.37%. Recommended mitigation actions were cutting slopes or making soil retaining walls or drainage channel planning

The Utilization of Soybean as a Catalyst Material in Enzyme-Mediated Calcite Precipitation (EMCP) for Crack Healing Concrete

The effect of using soybean as a catalyst in the Enzyme-Mediated Calcite Precipitation (EMCP) method of crack healing concrete is discussed in this research. The existence of cracks in concrete reduces its quality, therefore, there is the need for repair efforts and one of these is through injection using the EMCP method. This technique employs the plant-derived urease enzyme to catalyze the reaction between calcium chloride (CaCl2) and urea (CH4N2O) towards precipitating calcium carbonate (CaCO3). Its effectiveness was, however, evaluated using a test tube experiment, and the optimum combination of urease, urea, and calcium chloride was selected and used as the preliminary data for the soybean added as a catalyst. Meanwhile, the concrete samples were prepared in the form of 5 cm x 10 cm cylindrical concrete and the crack was made through Universal Testing Machine (UTM) with a controlled area observed to be in the range of ± 0.2-0.3 mm. The injection solution was added to the concrete using the percolation method up to the period the height of the solution was 5 mm above the concrete surface and this was conducted several times with the effect on the concrete cracks evaluated through permeability tests which were used as one of the concrete quality parameters. Moreover, the permeability coefficient value was found to be inversely proportional to the quality and this means a smaller value of the coefficient produced better concrete quality and vice versa. The results showed the total calcite formed in the sample after the 4th injection was 18.3% of the total surface area of the concrete crack and was able to reduce the concrete permeability value by 95.43%. This, therefore, means the use of soybean in the EMCP method is considered feasible to repair concrete cracks

Distribution of grout material within 1-m sand column in insitu calcite precipitation technique

AbstractThis study evaluates the potential of improving an insitu calcite grouting technique. The grout is composed of an equimolar solution of urea–CaCl2 and an enzyme named urease. We examine the distribution of the grout materials and precipitated calcite within sand columns with a diameter of 5cm and a height of 100cm. In the first series of experiments, the concentration distributions of the individual grout materials (i.e., urea, CaCl2 and urease) within the sand specimen are evaluated. In the second series of experiments, an enzyme-reagent mixed solution (i.e., grout) is injected into the sand columns to evaluate the distribution of calcite. Sand samples are collected from various vertical locations within the treated columns and the amount of precipitated calcite is evaluated. Furthermore, attempts are made to achieve the uniform distribution of the injected grout and hence uniform calcite distribution throughout the specimen. The results show that a uniform distribution of the grout materials up to a distance of 1m from the inlet is achievable. It is also observed that a relatively uniform distribution of calcite is achievable as long as the rate of calcite precipitation is well controlled

Optimization of Enzyme-Mediated Calcite Precipitation as a Soil-Improvement Technique : The Effect of Aragonite and Gypsum on the Mechanical Properties of Treated Sand

The effectiveness of magnesium as a substitute material in enzyme-mediated calcite precipitation was evaluated. Magnesium sulfate was added to the injecting solution composed of urea, urease, and calcium chloride. The effect of the substitution on the amount of precipitated materials was evaluated through precipitation tests. X-ray powder diffraction and scanning electron microscopy analyses were conducted to examine the mineralogical morphology of the precipitated minerals and to determine the effect of magnesium on the composition of the precipitated materials. In addition to calcite, aragonite and gypsum were formed as the precipitated materials. The effect of the presence of aragonite and gypsum, in addition to calcite, as a soil-improvement technique was evaluated through unconfined compressive strength tests. Soil specimens were prepared in polyvinyl chloride cylinders and treated with concentration-controlled solutions, which produced calcite, aragonite, and gypsum. The mineralogical analysis revealed that the low and high concentrations of magnesium sulfate effectively promoted the formation of aragonite and gypsum, respectively. The injecting solutions which produced aragonite and calcite brought about a significant improvement in soil strength. The presence of the precipitated materials, comprising 10% of the soil mass within a treated sand, generated a strength of 0.6 MPa