The development of infrastructure in archipelago countries often faces difficulties and challenges due to the lack of fresh water. Hence, in some cases, the usage of seawater is favourable, in particular for concrete making. Little studies have been conducted on comparing the seawater, and freshwater concretes, especially on microstructure analysis. The objective of this study was to reveal the compressive strength, elasticity, and microstructure of concrete using seawater and freshwater as the mixing water. The methodology of this study was mix design, making test specimens, curing test specimens, and microstructure analysis. The tests of concretes were conducted for each sample with variations of 1, 3, 7, and 28 days and the mechanical behavior were tested using compressive strength and elasticity as parameters. At the same time, the microstructure was examined using an X-Ray Diffraction (XRD). The results showed an increase in compressive strength and elasticity of seawater and freshwater concretes at all variations with insignificant differences observed between the two types of concretes. It was also discovered that the formation of Friedel's salt (3CaO.Al2O3.CaCl2.10H2O) in the seawater concrete was not in the freshwater concrete. In conclusion, the differentiation of microstructure did not significantly affect the compressive strength and elasticity between seawater and freshwater in mixing concrete.
Split Material derived from Wekondo and Sand found in Poni-Poniki is an abundant material that has the potential to be used as a material for making concrete. The purpose of this research is to find out whether Wekondo split material and Poni-poniki sand can be used in making concrete both in terms of material characteristics and the quality of concrete achieved. This research is experimental by testing material characteristics as well as the making of 150 mm sized concrete cube test object on applicable SNI. The result of the test of the characteristic of Split material such as filter analysis at # 3/8 exceeds the specification of 6.25%, aggregate wear19,639%, pass filter sieve # 200 is 0.772%, specific gravity (SSD) 2,913 gr / cm3, 1.363%, 0.628% moisture content of 1.7kg / ltr solid content and 1.469kg / ltr of loose fill weight. While the examination of a sand material of Poni-poniki analyzed sieve all meet the standard specification, pass filter sieve # 200 is 1,680%, density of 2.661 gr / cm3, aggregate 1.647%, moisture content 0.580%, / ltr the loose weight of 1.531kg / ltr. While in concrete compressive strength test, the age of 7 days is 203,68 kg / cm2, and age 28 day is 257,55 kg / cm2. From the results of the study showed that the compressive strength at the age of 28 days can achieve K-250 quality.
This research discussed the effect of scouring on the stability of the slope on the Bujangga street STA 00+000 sd STA 00+075. A landslide had occurred in the development of a road located on the Bujangga riverside. The road is the result of widening which was previously only 2 lanes with a width of 8 m to 4 lanes with a width of 20 m. Landslides occured at STA 00+000 up to STA 00+075. At the STA the road experiences a landslide in the direction of the river to the elevation of the road surface down as deep as ± 2m. This research type is survey. Data was collected with documentation of post-landslide soil investigations, investigation of landslide conditions in the field, and sheet-pile slip simulation using the finite element method with helping the PLAXIS V.7.2 program. Data analysis with descriptive and back analysis to input soil parameters produces deformation and landslide mechanism that is relevant to actual conditions in the field. As a result of scouring of the river there is a reduction in passive pressure on the outside of the sheetpile which results in a decrease in the value of the safety factor of the road including other buildings such as settlements. This is indicated by the results of modeling and simulation above which gives the value of FS=1.2602 without scouring and FS=1.045 after scouring. The scouring of the river can be concluded that on a long-term scale the location is a landslide prone location.Keywords: Landslide Analysis, Finite Element, Road Development, Riverside Penelitian ini membahas pengaruh scouring terhadap stabilitas lereng pada kelongsoran Jalan Bujangga STA 00+000 sd STA 00+075. Pernah terjadi kelongsoran pada pengembangan jalan yang berlokasi di pinggiran sungai Bujangga. Jalan tersebut merupakan hasil pelebaran yang sebelumnya hanya 2 lajur dengan lebar 8 m menjadi 4 lajur dengan lebar 20 m. Kelongsoran terjadi pada STA 00+000 sampai dengan STA 00+075. Pada STA tersebut jalan mengalami kelongsoran ke arah sungai hingga elevasi permukaan jalan turun sedalam ± 2m. Penelitian ini berjenis survey. Data dikumpulkan dengan dokumentasi penyelidikan tanah pasca longsoran, investigasi kondisi longsoran di lapangan, dan simulasi kelongsoran sheetpile menggunakan metode elemen hingga dengan bantuan program PLAXIS V.7.2. Analisis data dengan deskriptif dan back analysis hingga parameter tanah input menghasilkan deformasi dan mekanisme kelongsoran yang relevan dengan kondisi actual di lapangan. Akibat dari scouring atau gerusan sungai terjadi pengurangan tekanan pasif pada sisi luar sheetpile yang berakibat penurunan nilai faktor keamanan dari jalan termasuk bangunan lain seperti pemukiman. Hal tersebut ditunjukkan oleh hasil pemodelan dan simulasi di atas yang memberikan nilai FS=1.2602 tanpa scouring dan FS=1.045 setelah adanya scouring. Adanya gerusan pada bibir sungai dapat disimpulkan bahwa dalam skala jangka panjang lokasi tersebut merupakan lokasi rawan bencana longsoran.Kata Kunci: Analisis Longsoran, Elemen Hingga, Pengembangan Jalan, Pinggiran Sungai
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