Abstract:Concrete is the most widely used construction material in civil engineering. But plain concrete is a brittle material and has little resistance to cracking. The cracking in concrete promotes deterioration such as the corrosion of reinforcing rebar, therefore, repair in filling the crack is often carried out. Recently, repair methods using bio-based materials associated with microbial metabolic processes leading to precipitation of calcium carbonate have been intensively studied. In this study, influencing factors on the precipitation rate depending on the constituents of bio-based material comprising yeast, glucose and calcium acetate mixed in tris buffer solution was examined for improving the rate of initial reactions. In addition, effect of temperature change on the amount of calcium carbonate precipitation was also investigated. The precipitates were identified by X-ray diffraction. It was shown that the increase of temperature lead to a change on calcium carbonate precipitation and caused the pH decrease under 7.0.
This research examined differences in the concentration of Tris buffer solution on calcium carbonate precipitation in biobased repair materials. Four concentrations of Tris buffer solution were chosen based on previous research with initial pH 8.0 and 9.0. Initial experiments demonstrated that the concentration and pH of Tris buffer solution had an influence on the amount of precipitation of calcium carbonate. X-Ray Diffraction (XRD) analysis elucidated the morphological and structural differences of the calcium carbonate crystal, including calcite and vaterite. They are the prominent forms of CaCO 3 detected based on results obtained by according to FT-IR analysis. The result further explains the effectiveness of Tris buffer concentration.
The use of bio-based material for repairing concrete is a relatively new method. Therefore, more results from simulated real-condition experiments are needed before being applied on a practical scale. In the recent past, several studies have been conducted on the improvement of bio-based repair materials. In this study, the bio-based material involving yeast, glucose, and calcium acetate mixed in a Tris buffer solution showed the potential to develop a microbial process leading to the precipitation of calcium carbonate. We investigated the factors affecting the precipitation rate of the calcium carbonate of bio-based materials for repairing leakage in the concrete specimens. Based on a series of experiments involving temperature, the type of dry yeast, and the concentration of the Tris buffer solution, the composition of bio-based materials with the highest precipitation rate of calcium carbonate was selected. The selected mixture could be applied to repair leakage of concrete until the cracks are sealed entirely.
The applicability of bio-based materials for concrete repair has been studied. This technique employs yeast, glucose and calcium acetate mixed in Tris buffer solution. The microbial metabolic process leads to precipitation of calcium carbonate. First, this study investigated the applicability of bio-based repair materials to small-scale concrete specimens. On this research, water permeability test was carried out to evaluate the effectiveness of the selected mixtures for sealing cracks in the concrete specimens. As the result of permeability tests carried out using specimens with crack width of 0.6 mm, water leakage through crack was observed to be negligible after 216 hours by continuous pouring method using bio-based repair materials. Also, this study showed the initial flow rate for the specimens with the same crack width does not influence crack sealing time. Furthermore, the precipitation of the calcium carbonate from the bio-based materials was analyzed by Fourier-Transformed Infra-Red spectroscopy (FT-IR) and then examined by X-ray Diffraction (XRD) for mineral identification formed through the microbial metabolic process.
Kecamatan Sutera Kabupaten Pesisir Selatan adalah salah satu daerah yang berdampak terjadinya gempa bumi. Selain dari korban jiwa, gempa yang dialami memiliki resiko berupa kerusakan infrastruktur pada bangunan rumah sederhana yang dimiliki masyarakat. Grafik data demografi berdasarkan pekerjaan menyatakan bahwa 24,90% masyarakat termasuk dalam kategori tidak/belum bekerja, hal ini memiliki keterkaitan dengan pilihan masyarakat yang belum/tidak bekerja agar menjadi tukang lokal. Pembangunan rumah masyarakat sekitar dikerjakan oleh tukang lokal yang belum sepenuhnya memahami dan melaksanakan pengaplikasian pembangunan sesuai persyaratan pokok rumah aman gempa dan peraturan Standar Nasional Indonesia. Kegiatan dari Program Kemitraan Masyarakat, bertujuan untuk meningkatkan pemahaman masyarakat yang ingin maupun sudah berprofesi sebagai tukang lokal agar dapat memiliki pengetahuan mengenai rumah aman gempa. Kegiatan ini memberikan konstribusi untuk meminimalisir kerusakan bangunan jika terjadinya bencana gempa bumi dan menarik perhatian bagi masyarakat yang belum memiliki pekerjaan menjadi tukang yang berkompeten. Kegiatan dengan melakukan observasi lapangan, melaksanakan sosialisasi upgrading kemampuan tukang lokal, melaksanakan pelatihan dan evaluasi pada tukang lokal dengan memberikan soal pretest dan posttest. Hasil yang didapati dari perhitungan antara t-tabel dan t-hitung bahwa hipotesis H1 diterima yang artinya terdapat perbedaan rata-rata nilai sebelum dan sesudah pemberian materi mengenai struktur rumah sederhana aman gempa.
This study aims to design a cross-flow turbine in a micro hydro power plant as an alternative energy source for Indonesian remote areas that do not have electricity. The research location for the turbine design in this study is in the Ngalau Baribuik, located in Batu Gadang, Lubuk Kilangan district, Padang city. Based on the analysis of water flow characteristics, the type of turbine that is suitable for low water debit and head condition is cross flow turbine. The geometry of the cross-flow turbine is designed by considering the power electricity needs of the community and the electrical potential at the site. This experimental research was carried out in two stages; field investigations related to water flow characteristics and energy need analysis of local communities, the design and manufacture of the turbine. Based on theoretical calculation, the cross-flow turbine can produce up to 5 kW of electrical power which can meet 70% of the community's energy needs. Penelitian ini bertujuan untuk merancang sebuah turbin aliran silang pada Pembangkit Listrik Tenaga Mikro Hidro (PLTMH) sebagai alternatif sumber energi bagi daerah terisolir yang belum teraliri listrik. PLTMH dirancang untuk masyarakat kawasan Ngalau Baribuik yang berlokasi di Batu Gadang Lubuk Kilangan kota Padang. Berdasarkan analisis karakteristik aliran, untuk kondisi debit dan tinggi jatuh air yang kecil turbin yang paling sesuai digunakan adalah aliran silang. Disain dan geometri turbin disesuaikan dengan kebutuhan masyarakat dan potensi yang ada di lokasi. Penelitian eksperimen ini dilaksanakan dalam dua tahap; (a) investigasi lapangan terkait dengan karakteristik aliran air dan kebutuhan energi masyarakat, dan (b) proses perancangan dan pembuatan turbin. Secara teoritis, turbin aliran silang yang dirancang akan dapat memproduksi daya listrik hingga 5 kW yang akan memasok 25% kebutuhan energi masyarakat setempat.
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