Papers by Keyword: Marine Environment

Abstract: It is natural to define marine corrosion in terms of the different zones in which the corrosion occurs such as atmosphere splash, tidal and sea mud etc. However, this study focused on issues affecting the marine structures, different types of corrosion and their impact on the marine steel structures as well as the machinery/equipment. Furthermore, several control measures of corrosion necessary to avert corrosion in marine environments were discussed. However, it was established that prolonged contact of marine structures with seawater would lead to corrosion as well as ruing the safety elements present. Thus, the study provides potential information to material scientists on the need for using structural steels of adequate mechanical properties.

Abstract: Deterioration of concrete in marine environment and the durability of coastal constructions have raised great concern throughout the world. This work mainly focuses on the compressive strength of concrete in marine submerged environment. Data in previous researches has been collected in this work, which can be used in a particular environment and specific types of concrete for different background, while making it difficult to analysis the influencing factors as a whole. In order to find a relative systematical solution to summarize the data, Grey Relational Analysis method is applied to analysis the mass data collected from previous literates at home and aboard. The purpose of this study is to make a sensitivity analysis of factors influencing the concrete compressive strength in submerged marine environment and guide engineering practice. The results turn out that the initial strength plays the most important role in the final strength after long-term immersion. In addition, the immersing age and cationic ions also affect the final strength of marine concrete. In all, general deterioration exhibits the tendency that upgrading at the very beginning and then descending later.

Abstract: The offshore structure gradually will get damage. A number of offshore structure maintenance method require underwater working. Because of that, underwater welding become an importance thing. Through this research,will be assessed on changes in mechanical properties of steel weld joint in marine environmental. With same weld parameter, welding process also do in freshwater and on land for comparisonvariable. Welding process do in 0.2m depth with SMAW wet welding method on 1G position using AWS E6013 electrode coated with wax. After doing research, it is found that the tensile strength of welds in the marine environment is a little larger than the tensile strength in freshwater and on land, ie 49.44 kgf/mm²> 49.41 kgf/mm² > 48.99 kgf/mm². Hardness index value of welded steel in the marine environment is also higher than the value of the weld hardness results in freshwater and on land, in the amount of 195.37Hv10>181.13Hv10>153.6Hv10. The value of tensile strength and hardness values in the marine environment welds slightly larger than in freshwater due to the amount of grain mertensit phase. Ductility properties of the weld results in the marine environmentis smaller than the weld results in freshwater and land, it is characterized by a decline inelongation and reduction of area in underwater welding. From the observation of metallographic microstructure underwater welding it appears that phase grains coarser than the microstructure of welding on land. This can happen because the weld metal suffered liquefaction then freezes so quickly that opportunity grain experiencing severe grain growth during thawing did not get transformed into finer grains, so that the material is harder but brittle.

Abstract: In reinforced concrete structures constructed on the coastline of the hypersaline Arabian Gulf water, corrosion of reinforcing steel causes cracking, delamination and spalling of concrete, within a time span of a few years. The King Abdullah Civic Center (KACC), being constructed on a reclaimed land off the coastline in the Eastern region of Saudi Arabia, is a major complex with wharves, quay walls, and breakwater and commercial buildings. To ensure the durability of buildings in the harsh marine environment and to provide a minimum service life of 35 years, a concrete mix in which 70% of Portland cement is replaced by granulated ground blast furnace slag (GGBFS) was recommended based on durability modeling conducted using the software STADIUM^®. Concrete with 70% GGBFS provides for the dual objective of achieving a green concrete and an enhanced service life of the building. Based on durability modelling it was concluded that corrosion inhibitor should be used preferably in the concrete. A detailed experimental program was conducted to assess the durability and strength properties of the 70% GGBFS concrete, with and without corrosion inhibitor. This paper presents the results of experimental investigations and durability modeling conducted for the project. A 70% GGBFS concrete mix without corrosion inhibitor was adopted for the raft foundation and subsequently for the entire building to make it a green concrete building.

Abstract: Concrete structures in the Eastern region of Saudi Arabia are exposed to the harsh Arabian Gulf environment, and they suffer from deterioration due to accelerated corrosion of the reinforcing steel resulting in reduced service life. The service life of reinforced concrete structures in this environment is strongly affected by the quality of concrete. The resistances of concrete to chloride penetration, the chloride threshold for corrosion initiation and corrosion rate of the reinforcing steel are critical in ensuring long-term durability of concrete structures. In order to ensure that the concrete functions in the harsh environment for which it is expected to meet the service life requirement, the concrete must be designed for durability performance. A prescriptive concrete specification emphasizing on limits on mix parameters is generally ineffective for durability issues. A performance based specification based on concrete quality represented by durability indices and compliance criteria measured on cast-in-place concrete provides a framework for the contractor and ready-mix concrete supplier to produce a structure meeting the stipulated service life by the client. This paper presents the results of experimental investigations conducted for mass-concrete blocks used in the quay walls off the coastline on a reclaimed land. For long-term durability, a concrete mix in which 50% and 70% of cement was replaced by ground blast furnace slag was used to cater for the durability performance requirements.

Abstract: This paper focuses on reinforced concrete columns load carrying capacity degradation over time due to chloride induced steel pitting corrosion. The structural element is exposed to marine environment and the effects of corrosion are described by the time degradation of the axial-bending interaction diagram. Because chlorides ingress and consequent pitting corrosion propagation are both time-dependent mechanisms, the study adopts a time-variant predictive approach to evaluate residual strength of corroded reinforced concrete columns at different lifetimes. Corrosion initiation and propagation process is modelled by taking into account all the parameters, such as external environmental conditions, concrete mix proportion, concrete cover and so on, which influence the time evolution of the corrosion phenomenon and its effects on the residual strength of RC columns.

Abstract: Slow strain rate test (SSRT) applied with different potential was adopted to investigate the stress corrosion cracking (SCC) sensibility of stainless steel under marine environment. The fracture morphology of 321 stainless steel SCC specimens were analyzed with the aid of SEM. The strain-stress results showed that 321 stainless steel exhibited less SCC sensitivity when anodic potential or cathodic potential were applied on the specimen, both fracture elongation and fracture time ascended compared with that of corrosion potential. The fractography analysis results also proved this susceptibility clearly.

Abstract: Corrosion inhibition of concrete steel-reinforcement in 3.5% NaCl, simulating saline/marine environment, by the leaf extract of Rhizophora mangle L. was studied in this paper. For this, duplicated specimens of steel-reinforced concrete slabs, admixed with different concentrations of the leaf extract, were immersed in the corrosive test-medium. Analyses, as per ASTM G16-95 R04, of the electrochemical test-results identified 0.0833% Rhizophora mangle L., per weight of cement, with optimal inhibition efficiency η = 95.73±0.15%. The study established a decrease in inhibition effectiveness as concentration of Rhizophora mangle L. increases.

Abstract: Offshore wind turbine supporting structure long term works in the harsh marine environment, suffering from a variety of negative factors such as the seawater corrosion, marine growths, water scour, collision of sea ice and ship, etc.. Through numerical analysis software SACS and ANSYS, the marine environment impacts on the supporting structure and protective measures were put forward. The study found that such adverse environmental factors might easily result in a whole or partial component damage of the foundation support structure, and eventually lead to the reduction of security and durability. Reasonable preventive measures to ensure the security of the offshore wind turbine supporting structure were proposed and theoretical guidance for the design of future offshore foundation was provided.

Abstract: Abstract: A form of static coupon following the boat was developed to carry the natural aging test for CF3011/BA9916-II composite in marine environment, and the weather resistance of composite in marine climate was studied. The changes of the morphology of the composite were observed, the changes of the quality ,tensile strength and interlaminar shear strength for specimen were analyzed, and the aging regulation was studied combining with the mechanism of hygrothermal aging for carbon fiber epoxy composite. The test results showed that with the aging time increasing, the moisture absorption of the composite increased, the mechanical strength decreased , and the plastic behavior of the material was showed.