Literature review
In the history of the construction of sea structures in oil exploration, load and corrosion together with how those structures will be maintained have always posed a scientific nightmare. Chamberlain, Adam and other authors in a scientific journal illustrate that for a good design of an onshore structure, there should be a right proportion of the ingredients in order for the structure to give maximum life service. They all agreed that in order to achieve this, keen interest should be paid to the permeability, strength, and durability of the mixture. Finally, they added that for effective control of corrosion, maintenance of the required concrete cover is also significant. Gonzalez, J. A., et al. in the “Cement and Concrete Research held that the mechanical weakness of a concrete structure is affected by the loss of metal bar in the section where there is intense corrosion. Therefore, the greatest penetration in the greatest depth will be a significant reference.
In 1995, Kaushik and Islam investigated the results of a mixture of sea water with a concrete based on bond power and tensile. They performed an experiment using six categories of mixtures of concrete. Four were mixed using fresh water and the remaining two using sea water. The key aim of the experiment was to find out the drop in strength with an upsurge in the time of exposure and also due to effects of crystallization. Alonso, C., et al. also focused on the investigation of the cracking concrete due to increasing products of corrosion such as the oxides. They found out that the oxides formed within the period of energetic corrosion of steel, in turn, created a force on the entire neighboring concrete resulting in covering cracking along the steel.
Introduction
Background
Concrete structures have been used successfully for more than three decades. They normally serve a similar purpose to their counterpart’s steel in the gas and oil production and storage. The first platform of concrete was fitted in Erkofisk field in the North Sea by Phillips Petroleum in 1973.From that time henceforth about fifty concrete structures which are onshore have been built, with nearly half of the concrete substructures designed by Dr. Olsen. The structures are mostly utilized in the petroleum industry as storage units for natural gas and oils in addition to drilling. They are classified into fixed and floating structures. They are highly durable, can carry heavy topsides, and offer storage capacities, suitable for a tough environment such as the seismic effects. However they face tear and deformation due to sea load, corrosion, and this hence leads to coming up with effective methods to maintain them.
Project approach
Guided by the essential questions on the effects of loads, the effects of corrosion on concrete structures and how this can be maintained will be done by simply doing a case study of the most affected areas. There are various types of deterioration of concrete features by sea waters depending on the parts of the structure. Secondly, there is concrete deterioration due to chemical processes, for an alkaline environment, there will be protection against corrosion with comparison with the acidic seawaters. Issues to be tackled will include: low water to cement ratio, the post tension to eventually cracking and permeability to sea water. The corrosion of steel reinforcement is also essential because steel is normally embedded in concrete and is prone to deterioration in case it is not protected. Checking of corrosion due to protesting tendons, the fatigue of the steel in concrete and finally checking on the accidental damages effects and causes.
Report structure
Introduction
Objective
Procedure and research methodologies
Analysis and Presentation of results
Conclusion
Methodology used for literature retrieval
1. Advance planning
1.1 Defining Goals and objectives
1.2Selecting literature reviews management
Review Coordinator
The searcher
Document delivery
1.3 equipment’s needed
2. Preliminary literature searching
2.1 volume searches
2.2 Applying search results
3. Comprehensive Literature Searching
3.1Limit Guideline Topic
3.2 Sources of Information.
3.3 Conduct searches
4. Literature management
5. Document retrieval
6 Final Bibliography
Academic papers
A Neville -Materials and structures, 1995
M Raupach-Material and Structures, 1996
Y Liu, RE Weyers –ACI Materials Journal, 1998
Stat fjord Gravity Base Structure
The Dunlin Alpha ANDOC platform
Lunskoye Platform
Summary
For various reasons sea water effect on concrete needs exclusive attention. First, the structures at the coast are exposed to various chemical and physical deterioration activities. This is exceptional in the comprehension of concrete durability.Secondly, the oceans cover up to 80 percent of the earth, meaning many structures are vulnerable to sea water damages.
Findings
Technical findings
Load effects: Load has an effect on the concrete in a marine environment in that, the sand from the wave action brings about the load to the structure, subjecting them to extra weight which might be unbearable. Similarly, the crystallization of salts within the concrete subjects it to wetting and this results in the increase of permeability for further erosion action due to the load on the concrete.
Corrosion effects: Most seawaters have a relatively uniform chemical composition, with a percentage of 3.5 soluble salts. The Ionic concentrations of sodium ions and Chlorine ions being the highest. Ranging from 11000 to 20000 mg/.This makes seawater aggressive to cement concrete (Gonzalez et al 260).
Maintenance: Permeability is the main factor to the durability of a concrete structure. When seawater is allowed to penetrate through the concretes’ interior, the wetness causes inadequate water tightness which poorly proportions the mixtures of the concrete.
Gaps emerged from retrieval findings
Nature and rigorousness may be ununiformed within the concrete structure. For example, a cylinder-shaped concrete, the portion which is always above the high tide will be more vulnerable to corrosion of steel and frost action. The portion that is between the low and high tide will be susceptible to cracking and spalling not only from corrosion but also from dry-wet cycles.
Synthesis of Findings
Impact of the findings
The introduction of new materials which are added to the steel to reduce the rate of its corrosion. Choosing of the appropriate mixture design, where the cement o water ratio are wisely chosen according to the Building Code Requirements, this makes the concrete protected from the effects of corrosion.
Conclusion
Some concrete structures such as bridges and pillars have lasted for less than a decade simply because of the corrosion and effects of load, in addition to the fact that they are quite expensive to repair. Understanding of the nature of seawater deterioration and critically selecting the mix design will go a long way ensuring maximum concrete life. This will be enhanced by investigating on the marine environment from which you will understand the deterioration processes such sulfate attack, erosion, and abrasion, freezing and thawing. The mix design should also be chosen wisely to make sure the cement compositional type are the appropriate ones. From the implementation of the above procedures, the concrete structure will show an exemplary performance.
References
Andrade, Carmen. "Calculation of chloride diffusion coefficients in concrete from ionic migration measurements." Cement and concrete research 23.3 (1993): 724-742.
ACI Committee, American Concrete Institute, and International Organization for Standardization. "Building code requirements for structural concrete (ACI 318-08) and commentary." American Concrete Institute, 2008.
Chamberlain, Adam L., et al. "High‐Strength Zirconium Diboride‐Based Ceramics." Journal of the American Ceramic Society 87.6 (2004): 1170-1172.
Recommendation, RILEM Draft, and PROJETS DE RECOMMANDATION DE LA RILEM. "Creep and shrinkage prediction model for analysis and design of concrete structures-model B3." Ed. ZP Bazant, S. Baweja, Materials and Structures 28 (1995): 357-365.
Bazant, Zdenek P. "Physical model for steel corrosion in concrete sea structures—theory." Journal of the Structural Division 105.6 (1979): 1137-1153.
Ahmad, Shamsad. "Reinforcement corrosion in concrete structures, its monitoring and service life prediction––a review." Cement and Concrete Composites 25.4 (2003): 459-471.
Gonzalez, J. A., et al. "Comparison of rates of general corrosion and maximum pitting penetration on concrete embedded steel reinforcement. “Cement and Concrete Research 25.2 (1995): 257-264.
Kaushik, S. K., and S. Islam. "Suitability of sea water for mixing structural concrete exposed to a marine environment." Cement and Concrete Composites 17.3 (1995): 177-185.
Fajardo, G., G. Escadeillas, and G. Arliguie. "Electrochemical chloride extraction (ECE) from steel-reinforced concrete specimens contaminated by “artificial” sea-water." Corrosion Science 48.1 (2006): 110-125.
Alonso, C., et al. "Factors controlling cracking of concrete affected by reinforcement corrosion." Materials and structures 31.7 (1998): 435-441.
