ANALISA AGREGAT KASAR SEBAGAI VARIABEL BAHAN CAMPURAN BETON MENGGUNAKAN METODE SNI DAN ACI (Studi Kasus Beton Mutu K-275)

Penelitian ini dilakukan dengan maksud dan tujuan adalah untuk menganalisa dan membandingkan kuat tekan beton yang dapat dicapai menggunakan agregat kasar sumber Padang Ratu, Tegineneng dan Tanjungan. Selain itu juga untuk mengetahui kualitas agregat kasar yang bersumber dari daerah Padang Ratu, Tegineneng dan Tanjungan sebagai bahan campuran beton dengan metode SNI dan ACI. Untuk membandingkan nilai kuat tekan beton yang dihasilkan menggunakan agregat kasar yang bersumber dari daerah Padang Ratu, Tegineneng dan Tanjungan korelasinya terhadap pencapaian mutu beton K-275 atau setara dengan 22,825 Mpa. Penelitian ini menggunakan sampel Uji Silinder diameter 15 cm dan tinggi 30 cm. Pengujian dilakukan saat umur 7, 14, 21 dan 28 dan setiap umur terdiri dari 3 benda uji. Sehingga dibutuhkan 72 benda uji. Dengan 3 variasi penggunaan agregat kasar dari 3 quarry yaitu Tanjungan, Padang Ratu dan Tegineneng menggunakan metode SNI dan ACI. Hasil penelitian menunjukkan bahwa kualitas agregat mempengaruhi mutu beton yang dihasilkan. Hubungan kuat tekan beton dengan umur beton menunjukkan bahwa semakin bertambahnya umur beton, kuat tekan beton meningkat juga. Dari hasil penelitian, beton yang mencapai kuat tekan rencana adalah pada campuran beton  menggunakan agregat kasar Tanjungan dengan umur 28 hari yaitu : 23,10 Mpa (Metode ACI) dan 277,42 Kg/cm2 (Metode SNI)

Adsorption and dissociation of H<inf>2</inf> on Pd doped graphene-like SiC sheet

© 2016 Hydrogen Energy Publications LLCDoped porous SiC nanostructures with metallic atoms, nanoclusters and nanoparticles have been recognized as promising materials for hydrogen storage. With this regards transition metal elements are interesting impurities for use as doping. In view of this prospect, a theoretical approach based on density functional theory (DFT) was applied to study of the interaction between hydrogen molecule and a graphene-like SiC sheet doped with palladium atom. We have selected a single graphene-like SiC layer, due to its more surface charge polarization in comparison with pure graphene which makes possible remarkable interactions with adsorbed hydrogen molecules. In our study we have included two different configurations of H2 adsorption: 1) at the first state, hydrogen atoms after adsorption stretched and distance between H[sbnd]H atoms has increased but their chemical bond doesn't break. In this situation a physical adsorption occurred and the binding energy restricts applicable interests where it is appropriate for reversible hydrogen storage; 2) at the second situation, atoms of hydrogen molecule discrete from each other and adsorption occurred in a chemical manner. As instance the when a H2 molecule interact simultaneously with Pd atom and SiC nanosheet, it can be dissociated as in this case a hydrogen atom makes bond with Pd atom and the other can be adsorbed chemically on the SiC nanosheet surface. More details about adsorption mechanism are discussed it the context

Neutron Diffraction and Magnetic Studies of Nd₂Fe₁₇₋ₓTₓ (T=Si, Mn) Alloys

We have carried out neutron and magnetic studies on Nd2Fe17-xTx (T=Si, Mn) alloys. the unit cell of the compounds contracts with both Si and Mn substitution. Si atoms avoid the 6c site, prefer the 18h site strongly, fill the 9d site steadily and fill the 18f site only at relatively high Si concentration. Mn atoms avoid the 9d sites but prefer the 6c site strongly, while the 18f site and 18h site fill slowly. the Si site occupancies appear to be dominated by the crystal environment while the Mn site occupancies are dominated by steric considerations. the Curie temperature of the compound Nd2Fe17-xTx increases significantly with Si substitution but is only affected slightly by the Mn substitution. Although the unit cell contracts with increasing Si concentration, the average length of bonds to the Fe(6c) and the Fe(18f) sites increase slightly at x\u3c4