Behavior of Concrete in Rivers and Marine Dissertation

Excerpt from Dissertation :

Behavior of Concrete in Rivers and Marine Areas

The marine atmosphere and also the river atmosphere are infamously harsh on man-made structures; furthermore, the materials employed for construction are seriously examined through these elements and how they would impact each other. Strengthened concrete is among the materials frequently employed for near shoreline, as well as off the shore, structures. These structures, whether submerged in or suspended within the marine or river area are susceptible to high amounts of chlorides, sulphates and magnesium -- all of which are hazardous to the surrounding environment. Furthermore, they are also exposed to high velocity of waves, the potentially harmful results of that are well recorded. This paper will indicate whether another method of strengthened concrete design, inside the limits from the codes, for marine as well as river structures may be more beneficial in the perspectives of engineering, construction, sturdiness and financial aspects. This paper will also indicate and add to the avenues of future research about this subject material.

Literature Review


Degeneration and sturdiness of concrete has been a subject of considerable research effort through the years. Most of these studies, however, have measured and discovered the outcomes and means by codes and standards -- this is additionally a subject of monumental concern when talking about marine structures which is why the results of these studies have led to more questions as opposed to possible solution. This paper will not provide an in depth summary of such research, however, even though some references have been created; instead the paper will aim to mix the outcomes of these studies with other situation researches, measure and experiment thereafter and thus suggest a coherent approach for portnatial researches for the appearance of marine structures from the practical perspective. Some of the claims on design within this paper provide the authors' experience/findings in port and harbor structures during the last few decades (Castro et al., 2001).

Situation Encounters

You will find several recorded situational histories of archaic strengthened concrete structures in a variety of states of degeneration. What these cases make obvious may be the large difference in the performance and impact overall and in the long run, with both the levels of severe and limited degeneration experienced (Overbeek and Van Der Horst, 2006).

Several such good examples are listed in the study conducted by Costa and Appleton (2002). Their approach included searching in docks, wharves as well as bridge correspondingly and they found that the excessive presence of strengthened concrete, reduced covers as well as honeycombs were the primary reasons that led towards the degeneration and deterioration of the environment and the structures.

Choong (2003) asserted in his study that the performance of two jetties in Singapore was up to par even after half a century. This, he recorded, was in terms of their overall sturdiness except in certain places where the initial quality of concrete was below par overall in comparison to other nearby structures.

Among the recurring findings for this particular subject as well as other related cases seems to be that most of deterioration and degeneration of construction on river sites as opposed to marine sites is bases around bad workmanship or carelessness towards following specifications or following of prevailing codes in certain cases that had issues low performance even in the initial phases. These bits of information correspond using what 'common sense' normally indicates and structured guidelines present especially in documentations like the U.S. Military Corps of Engineers manual. All of the established guidelines put significant importance on how to rely on the predictions and adjustments presented by both the expertise of the authors and DMC. Generally, both find and confirm that damage is frequently started at places where excellence or quality of the concrete was lesser throughout the initial construction (Overbeek and Van Der Horst, 2006).

The areas where degeneration has been discovered to become worse than expected on structures in general are those areas that undergo greater occurrences of wetting and drying out, particularly with sea water. These occurrences are more frequent for the undersides of these concrete structures where the sloping structure of the revetments causes elevated waves to easily run up the slope and allows the waves to cause big splashes that result in sprays around the bottom of the concrete elements which then dry out. Furthermore, these slopes are not cleaned by rain water which means that the impact that the waves make sustains and causes damages in the construction sites. Similarly other areas like the front end of the mooring points can display greater situations of delamination or spalling. This is so because of the flow of the sea water from mooring lines has higher degrees and concentrations of chloride, sulphates and magnesium in them (Overbeek and Van Der Horst, 2006). All of these bits of information give relevant information for the importance and appearance of strengthened concrete structures.

Overview of Degeneration Causes

Concrete has different actions/reactions in various environment conditions, and certainly the most domain or industry which must consider various aspects to create concrete is marine area and rivers (Castro et al., 2001). You will find certain aspects that are common degeneration which are caused in both the marine areas and rivers which are discussed in detail below. Subsequently, the paper moves onto discussion of the specific reasons for degeneration in rivers and marine areas individually.

Concrete type

The kind of concrete accustomed to safeguard reinforcement includes a major reliance on the sturdiness and quality of concrete because the material controls the speed of deterioration where aggressive agents take on and attack the coverage of concrete. Current codes of practice allow for an enhanced chloride resistance of greater grade concrete but largely disregard the influence of binder type. This method sees that physical qualities of concrete control transport qualities from the material, while largely disregarding the negative chemical effects. The access of chloride into the concrete mix isn't just based on the permeability from the pore structure but additionally by interactions between the material and also the diffusant that dissipates the overall level of concentration and as a consequence also restricts the pore structure. Concrete that contains fly ash and slag have been proven to possess exceptional chloride binding qualities and high quality/performing material of high chloride resistance (Mackechnie, 2001).

Cover to reinforcement

The possible sturdiness of strengthened concrete is greatly enhanced if sufficient cover to reinforcement is specified and accomplished on-site. For the appropriate level of protection needed for reinforcement when dealing with constructions on marine sites, the covers ought to be around 75 mm and 50 mm for the construction sites on the rivers. The reduced level of cover is dangerous even if using top quality concrete since defects for example cracks and voids may give a low resistance road to the deterioration that follows. Growing the overall degree of cover given to depths i.e. more than 75 mm may however lead to excessive surface crack sizes and it is frequently not practically possible (Mackechnie, 2001).

Site practice

Poor site practice, particularly regarding placing, compaction and treating of concrete may negate the advantages of good design and material selection. Studies have established the need for good site practice for example active moisture treatment in enhancing the near-surface qualities of concrete. Specifications have always been customized and thus suggested to manage these site activities, but regrettably sufficient supervision and appropriate techniques to watch compliance haven't been implemented on-site. The lack of ability to make sure consistent quality of concrete on-site is in fact one of the primary reasons for the ongoing prevalence of concrete sturdiness problems in construction sites in both marines and rivers (Mackechnie, 2001).

Harshness of exposure

The seriousness of marine exposure varies substantially based on different factors for example climate and/or location in accordance with the ocean and structural factors. Current codes of practice provide a somewhat restricted level of guidelines when dealing with the conditions of marine or river exposure. There are, however, more guidelines available on marine exposure and the established guidelines usually define only two marine groups: 1) extreme exposure for concrete exposed to full abrasive action from the ocean, and 2) incredibly severe exposure for concrete exposed to spray or placid abrasive wave activities. The more expansive versions of exposure within the marine spray zone aren't adequately based on these groups. Many of the problematic occurrences in marine constrictions surface because most marine concrete structures are situated within the spray zone. Because of the attention on marine conditions and exposure thud far, there is a need for a through and logical approach needed to determine the seriousness of exposure that constructions site undergo on river sites as well (Mackechnie, 2001).

In River Atmosphere

Degeneration of strengthened concrete structures in river conditions is usually connected with exterior agents for example chlorides that penetrate into concrete leading to damage. While using this premise, the potential sturdiness of strengthened concrete is dependent upon the security supplied by the coverage concrete; numerous factors affecting sturdiness might be…

Sources Used in Document:


Castro P., Rincon O.T. de and Pazini E.J., (2001), Interpretation of chloride profiles from concrete exposed to tropical marine environments, Cement and Concrete Research, 31, 529 -- 537. Taken from: Overbeek, J and Van Der Horst. (2006). Revaluation of Concrete Design in Marine Engineering. Delta Marine Consultants.

Choong K.Y. (2003), Durability performance of fifties years old concrete jetties in tropical marine environment, International Conference on Port and Maritime R&D and Technology, 97 -- 103, Singapore. Taken from: Overbeek, J and Van Der Horst. (2006). Revaluation of Concrete Design in Marine Engineering. Delta Marine Consultants

Costa A. And Appleton J. (2002), Case studies of concrete deterioration in marine environment in Portugal, Cement & Concrete Composites, 24, 169 -- 179.

Dehwah, H.A.F., Maslehuddin, M., and Austin, S.A. (2002). Effect of Cement Alkalinity on Pore Solution Chemistry and Chloride-Induced Reinforcement Corrosion, ACI Materials Journal, V.99, No.3, pp. 227-233. Taken from: Islam, M., Islam, S., Mondal, B.C. And Islam, M.R. (2010). Strength behavior of concrete using slag with cement in sea water environment. Journal of Civil Engineering (IEB), 38 (2): 129-140.

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