Workability and Compressive Strength of Seawater-Mixed Concrete Containing Rice Husk Ash as Supplementary Cementitious Material

The world is grappling with the challenge of rapidly growing water crises. The increasing population demands increased infrastructure which at present leads to the consumption of trillion gallons of water every year in construction industry. This research aims to check the suitability of seawater as an alternate to freshwater for mixing and curing of concrete. Rice husk ash is used as supplementary cementing material in order to enhance the capacity of matrix to sustain higher stress. Specimens were prepared with rice husk ash using fresh water and seawater. Half of the specimens were cured in seawater and remaining half with freshwater. The water-cement ratio in this study was kept constant equal to 0.39. Workability of concrete was determined for both fresh water and sea water mixes. Density and strength parameters were determined at the end of curing periods. The workability of concrete was found to decrease in seawater compared to freshwater mixes. With the addition of RHA it was found to decrease in both freshwater as well as in seawater. The density showed a declining path with the use of seawater and increasing amount of RHA. The specimens for determining compressive strength were tested at 7 and 28 days. The compressive strength results concluded that initially rate of gaining strength of seawater specimen was higher than its freshwater counterpart. The seawater specimen showed higher strength at 10% replacement of cement with rice husk ash at the end curing period. It can be concluded that seawater added with RHA is suitable alternative to fresh water in concrete

SURVEI KAPASITAS TEKNIS STRUKTUR DERMAGA PELABUHAN LAMPIA

Pelabuhan Lampia direncanakan untuk digunakan oleh PT. Sinergi Perkebunan Nusantara melakukan pengapalan CPO (Crude Palm Oil) miliknya. Sebelum rencana tersebut direalisasikan, perlu dilakukan kajian untuk mengetahuikapasitas teknis struktur dermaga tersebut. Oleh sebab itu pada penelitian ini dilakukan survei kapasitas teknisdermaga untuk mengidentifikasi kondisi struktur dermaga eksisting. Survei yang dilakukan meliputi pengukuran layout dan dimensi struktur dermaga, hummer test dan uji karbonasi serta pengamatan visual. Berdasarkan hasil pengukuran layout dan dimensi dermaga diperoleh bahwa bentuk dermaga adalah tipe T yang terdiri dari trestle dengan panjang dan lebar masing-masing adalah 42.5 m dan 6.0 m serta dermaga dengan panjang dan lebar masingmasing adalah 80.0 m dan 10.0 m. Jumlah tiang pancang untuk trestle adalah 22 tiang sedangkan untuk dermaga adalah 64 tiang. Diameter tiang pancang untuk trestle dan dermaga adalah 508.3 mm. Hasil hammer test menunjukkan bahwa kuat tekan beton struktur dermaga berkisar antara K300-K400 dimana masih memenuhi persyaratan beton untuk lingkungan laut sebesar K300. Hasil uji karbonasi menunjukkan bahwa nilai karbonasi lebih besar dari 2.0 cm, sehingga perlu perbaikan pada permukaan beton minimal sedalam daerah yang terkarbonasi atau setebal selimut beton tulangan. Pengamatan visual menunjukkan bahwa struktur dermaga tidak mengalami pergeseran akan tetapi struktur balok dan pile cap telah mengalami korosi dan karbonasi

PERILAKU SAMBUNGAN BALOK-KOLOM PRACETAK SISI LUAR DENGAN METODE EKSPERIMENTAL DAN ANALISIS BEBAN DORONG

Precast system which begins popular is an alternative way to substitute the conventional system (case in place). An innovation has been done by PT.Holcim in creating a new precast system which probably conduce the more advantage to precast system. Precast beam in this system consist of a U shape (bataton-U) with 140 x 140 x 290 mm and column with 290 x 290 x 140 mm in size. The objective of this research is to know whether the precast joint could be applied for building in seismic area. There are two beam-column joint specimens of precast and monolith with the similar reinforcement. Beam-column joint placed between two loading frame and restraint at the lower end of K-2 column as a roll and K-1 as a hinge. Whereas B-1 beam is free (cantilever). Column K-2 subjected to axial force constant in 144.42 kN. After data collective, analysis to acquire a relation of load and displacement, stiffness, ductility, damping, curvature and performance level structure were done using SAP 2000 software. The result obtained from research show monolith joint has 20.40 kN of maximum lateral load capacity and precast joint has 19.00 kN. Avarage ductality of the monolith joint is 5.04 and precast joint is 4.86. Avarage elastic stiffnes (kc) of the monolith joint and precast joint 2.29 kN/mm and 1.93 kN/mm respectively. The first crack of monolith joint occurred at 5.85 kN of loading and precast joint at 5.95 kN. Failure criteria of all specimen categorized us flexural failure. The result from all joint specimens shows hysteteric loops shape were similar, with a wide loop. According to ACI T1.1, if the joint specimen is unappropiate for received criteria with drift ratio of 3.5% and 2.5%, continuation analisys will be done using pushover analisys method with the help of SAP 2000 software. It was obtained 6.69 of madification respon factor (R) and 4.17 of ductility (µ). There for, it can stated that performance level of precast structure in this research is life safety category (LS)

COMBINATION OF IMPRESSED CURRENT AND SACRIFICIAL ANODE CATHODIC PREVENTION TO IMPROVE CORROSION PREVENTION SYSTEM IN REINFORCED CONCRETE

In this study, effectiveness of impressed current cathodic prevention (ICCP) and sacrificial anode cathodic prevention (SACP) in corrosion prevention of rebar in reinforced concrete (RC) is compared. Firstly, SACP method is applied in chloride-contaminated specimens which are kept in air curing condition for 150 days, then changed to dry/wet cycle NaCl solution cycle condition. Result shows that extremely high initial protective current, then decreased drastically until being stabilized. The depolarization value increases in dry/wet cycle condition than air condition. Secondly, ICCP method is applied with different protective current density, where corrosion of the steel bars were accelerated beforehand. Result shows that higher current density provides higher depolarization value. However, even smaller current density still able to reach 100 mV criterion after 56 days of test period. Based on both results, ICCP and SACP were combined as “hybrid system” to extend the service life of SACP. Initial current consumption was controlled in ICCP stage before changing to SACP stage. Result shows that on potential value increases gradually in ICCP stage and stabilizes after changing to SACP stage, while depolarization value in SACP stage shows more stabilized value compared to the value in SACP only.The Conference was canceled because of COVID-19