Hasil Pencarian  ::  Simpan CSV :: Kembali

Abstrak :
Latar Belakang: Tolok ukur baik tidaknya adaptasi tepi restorasi adalah tidak adanya kebocoran pada perbatasan restorasi dan gigi Restorasi resin komposit dapat menimbulkan kebocoran mikro akibat kontraksi saat polimerisasi sehingga terdapat celah antara dinding kavitas dengan resin komposit Penelitian ini bertujuan untuk menganalisis perbedaan tingkat kebocoran mikro dinding restorasi kelas I antara antara RK bulk fill dengan aktivasi sonik bulk fill tanpa aktivasi sonik dan inkremental Metode: Kavitas kelas I dipreparasi pada dua puluh tujuh gigi premolar rahang atas kemudian dibagi menjadi tiga kelompok Kelompok pertama ditumpat dengan RK bulk fill dengan aktivasi sonik kelompok kedua dengan RK bulk fill tanpa aktivasi sonik dan kelompok ketiga dengan RK yang diletakkan secara inkremental Selanjutnya spesimen direndam dalam air distilasi selama 24 jam dan kemudian dilakukan uji thermocycling yang diikuti perendaman dalam biru metilen 1 selama 24 jam Gigi selanjutnya dibelah longitudinal dan dilakukan pengamatan menggunakan mikroskop stereo pembesaran 12x dan dinilai dalam skala ordinal 0 4 Analisis statistik dilakukan dengan uji Kolmogorov Smirnov Hasil: Tidak terdapat perbedaan bermakna secara statistik di antara tiga kelompok Kesimpulan Tidak ada satupun dari kelompok RK bulk fill dengan aktivasi sonik bulk fill tanpa aktivasi sonik dan yang diletakkan secara inkremental yang dapat menghilangkan kebocoran mikro pada preparasi kavitas kelas I ......Background: A good marginal adaptation of a restoration can be measured by the absence of microleakage at the interface area Resin composite undergo contraction during polymerization which may result in gap formation between the wall cavity and composite and resulting microleakage The purpose of this study is to analyze the microleakage of class I cavity preparations that were filled with sonic activated bulk fill resin composite bulk fill resin composite without sonic activation and composite that were filled incrementally Methods: Standardized class I cavities were prepared on 27 extracted human upper premolars and randomly assigned to three groups The first group were filled with sonic activated bulk fill resin composite the second group were filled with bulk fill resin composite without sonic activation and the third group were filled incrementally The specimens were stored in distilled water for 24 hours and then subjected to thermocycling followed by immersion in 1 methylene blue dye for 24 hours The teeth were sectioned longitudinally and evaluated for microleakage under 12x magnification stereomicroscope and scored in ordinal scale 0 4 Statistical analysis was performed with the Kolmogorov Smirnov test Results: There was no statistically significant difference among the three groups Conclusion None of the the techniques was capable of eliminating the microleakage in class I cavity preparations

Abstrak :
Banyak penelitian yang telah menggunaka serat baja dalam campuran beton normal dan telah dilakukan dalam beberapa negara bagian di dunia. Namun, dikarenakan harga serat kawat baja itu sangat mahal di Indonesia, maka penggunaan serat kawat bendrat untuk menggantikan serat baja itu dan menggunakannya dalam campuran beton yang diteliti dalam penelitian ini. Serat kawat bendrat ini berdiameter 0,8mm dipotong dengan panjang 30 mm dan digunakan dalam campuran beton sebagai tulangan mikro beton yang diprediksi mampu meningkatkan kuat tekan beton dan mengurangi susut beton. Jumlah serat ini digunakan dari berat semen PCC dengan variasi 0%, 4%, 6%, 8%, 10% dan 12% dengan target kuat tekan fc? 25MPa. Untuk uji kuat tekan beton, benda uji akan dibuat dalam silinder kecil yang berdiameter 100mm dan tinggi 200 mm yang dites pada hari ke 3,7,14, dan 28 hari serta silinder besar dengan diameter 150 mm dan tinggi 300 mm yang akan di tes 28 hari agar diperoleh faktor konversi silinder kecil ke besar. Sedangkan untuk pengujian susut beton di uji pada balok berukuran 100mm x 100mm x 500mm (Standar UNI 6555) dan balok 75mm x 75mm x 254mm (Standar ASTM C49004) yang diuji selama 28 hari. Hasil penelitian menunjukkan bahwa penggunaan serat kawat bendrat dalam campuran beton meningkatkan kuat tekan beton sebesar 5,682% pada komposisi 6% serat kawat bendrat dan mengurangi susut sebesar 7,93% pada komposisi 10% serat kawat bendrat dan juga penggunaan serat kawat bendrat menurunkan kelecakan nilai slump beton. ......Many experiments on the use of steel fiber to strengthen the quality of normal concrete have been done in some regions of the world. As the price of this fiber in Indonesia is considerably expensive, the use of annealed wire is proposed to be a replacement of it and used as additives for concrete mixture is investigated in this research. This annealed wire of 0,8mm diameter is cut into pieces size of 30 mm length named as annealed-wire fiber (AW fiber) and added into normal concrete mixture as reinforcing fiber to increase the concrete compressive strength and reduce the shrinkage of concrete. The amount of this fiber measured in weight proportion to the content of Portland Composite Cement (PCC) is designed as 0%, 4%, 6%, 8%, 10%, and 12% based on the moderate concrete compressive strength fc? 25MPa. The concrete compressive strength is evaluated to numbers of cylinder type specimens size of 100 mm diameter by 200 mm height tested on 3 days, 7 days and 14 days and of 150 mm diameter by 300 mm height tested on 28 days of concrete age. And the shrinkage test is evaluated to numbers of beam type specimens size 100mm x 100mm x 500mm (UNI 6555 Standard) and 75mm x 75mm x 254mm (ASTM C490-04) The result from this experiment shows that the addition of AW fiber is increased the concrete compressive strength until 5,682% at 6% annealed-wire fiber composition and reduce 7,93% shrinkage at 10% annealed-wire fiber composition but decrease the workability by reducing the slump value.

Abstrak :
internal curing is promoted as a way tpo mitigate autogenous shrinkage in high-performance concrete having a low water binder ratio (w/b). Different methods of internal curing have been proposed. In this study, the effect of substituting 20% of normalweight sand by an equal mass of lightweight sand on the development of shrinkage was investigated on a 0.35 w/b high performance concrete . Shrinkage was monitored using vibrating wire gauges cast at the center of 100x100x400 mm (4x4x16 in.) concrete samples. Two samples were sealed with self-adhesive aluminum foil to present a closed curing system without any exchanged of humidity between the concrete and its environment, After demolding at the age if 23 to 25 hours. two other samples were cured under water for 6 days . Thereafter these two samples were removed from water and maintained at 23 C (73 F ) and a 50% relative humidity (RH) Environment . Experimental results clearly demonstrate the effeciency of a 20% substitution of normalweight by a lightweight sand to reduce autogenous and drying shrinkage . The Incorporation of 20% lightweight sand did not significantly affect the 28-day compressive strength. The cementitious matrix presented low chloride ion permeability. Internal curing through the use of partial replacement of normalweight sang by lightweight sand definitely represent and efficient method to diminish autogenous and drying shrinkage in low w/b concretes where external water curing does not allow in-depth curing of concrete

Abstrak :
Self-Consolidating Concrete (SCC) mixtures for use in Prestressed Concrete applications are evaluated in this paper . Twenty one SCC mixtures were made under laboratory conditions with varying water to cementitious materials ratios, sand to total aggregate rations, and cementitious materials combinations (type III cement , class C fly ash, ground-granular blast-furnance slag, and silica fume). The SCC mixtures archived prestress transfer compressive strengths between 5470 and 9530 psi (38 and 66 MPa). The moduli of elasticity of the SCC Mixtures were in reasonable agreement with the elastic stiffness assumed during the design of conventional slump concrete structures. The long term drying shrinkage strain for all the SCC mixtures were approximately the same or less than those measured for the control mixtures. A change in sand to total aggregate ratio had no significant effect on the long term drying shrinkage. At later ages of 56 and 112 days, the measured drying shrinkage corresponded reasonable well to those predicated by the ACI 209 procedure.

Abstrak :
The columns of a building must be stronger than the beams. The aim of this study is to obtain the cause of the long-term deformation difference by shrinkage between the beams and columns of high performance concrete with compressive strength of 60 MPa. This research was done experimentally in Indonesia during 410 days. Specimens measuring 150 mm × 150 mm × 600 mm were used, 3 pieces for the beams and 2 pieces for the columns. Deformation was obtained by using an embedded vibrating wire strain gauge for each specimen. The difference of long-term deformation in columns and beams is in their autogenous deformation behavior. This is because during the autogenous phase, swelling abnormally occurs in the column before shrinkage occurs. The abnormal swelling is caused by the press of its own weight. This phenomenon does not occur in beams. In the age range of 1 to 200 days, the behavior of the beam deformation has a similar pattern to the deformation behavior of the column with a high deformation rate. After that, at 200–410 days, column deformation changes to a very slow deformation rate. Long-term deformation in columns is lower (64%) than in the beams at 410 days age.

Abstrak :
Pada bangunan bertingkat tinggi, perubahan bentuk inelastis komponen struktur akibat rangkak dan susut beton dapat memicu timbulnya redistribusi gaya internal. Penelitian ini mempelajari pengaruh perbedaan metode pembebanan, umur awal pembebanan, dan rasio penulangan kolom terhadap gaya-gaya internal struktur, perbedaan pemendekan aksial komponen vertikal, dan redistribusi momen yang terjadi. Hasil penelitian menunjukkan bahwa metode pembebanan langsung secara dominan memberikan respon struktur yang lebih besar. Perbedaan pemendekan negatif maksimum mencapai -74.87 mm dan positif maksimum sebesar 73.20 mm. Umur awal pembebanan yang lebih awal dan rasio penulangan kolom yang lebih kecil memberikan respon struktur yang lebih besar. ...... In high-rise building, inelastic deformation due to concrete creep and shrinkage can cause internal forces redistribution. This study investigates the influence of the differential of loading method, age at loading, and column reinforcement ratio to the internal forces, differential shortening of vertical structural component, and beam-column bending moment redistribution. The results of the study indicate that direct loading method has greater structural responses than sequential one. The maximum negative differential shortening reach -74.87 mm and the maximum positive differential shortening reach 73.20 mm. Early age at loading and low column reinforcement ratio give higher structural responses.

Abstrak :
The directional solidification which is not toward to riser causes the shrinkage defect. This defect can be predicted by investigating the temperature distribution in riser or casting products. The goal of this research is to examine the temperature distribution using Finite Element Software (ANSYS) and then an ad hoc experiment has been performed to verify the result of the simulation, especially the existences cf shrinkage The simulation is carried out by sand casting process using pure aluminum. This research uses enthalpy method to examine the distribution of temperature. The properties of melted metal that being used for the simulation are enthalpy H(T) and thermal conductivity k(T). For experiment, the sand casting process uses pure aluminum and eutectic aluminum. The eutectic aluminum castings is used to support the pure aluminum castings. The result of the simulation hypothesis against shrinkage defect is appropriate with the experiment result.