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Civil Engineering

Civil Engineering

posted 5 months 2 weeks ago
The steel reinforcement mostly is divided into two categories i.e.

Primary Reinforcement or Main Steel reinforcement
Secondary reinforcement or distribution reinforcement

Main steel reinforcement bars are employed in R.C.C structures to ensure resistance against the whole design loads coming over it.
The secondary reinforcement bars are mainly employed due to durability as well as for aesthetic reasons.

This reinforcement guarantee resistance for localized areas, like limited cracking. These also offer resistance against the stresses that are created due to temperature variations
The stirrups are reinforcements that are provided laterally, to keep the main bars of the structural elements like beams and columns, in position
The stirrups may be circular, square, rectangular, helical or diamond shape based on the cross-section of the structural element.
The reinforcement bars in the corners may be L – shaped.

The caging for the structural element under consideration must be properly tied, so that during concreting no bar is disturbed from its position

The rebars are mainly provided at the junctions where the formwork of the structural element is closed as well as at the point where a new structural element needs to be bond with the former one.

Bar bending schedule provides details of reinforcement cutting and bending length. Advantages of bar bending schedule when used along with reinforcement detailed drawing improves the quality of construction, cost and time saving for concrete construction works.

Repairs and rehabilitation of concrete structures, which of late has become an activity comparable to construction itself worldwide, is mostly because deterioration of concrete due to corrosion of embedded steel.

Nearly 40% of failure of concrete structures is due to corrosion of embedded steel reinforcement.

Ideally speaking, a good concrete is supposed to provide adequate protection to the embedded steel. This is due to the protective alkaline environment (pH value as high as 12.5) provided by fresh concrete resulting in formation of protective coating on the surface of the steel, which passivates it from further corrosion.

However, over the passage of time, due to carbonation or ingress of chloride ions, pH value starts declining slowly and alkaline surrounding of the reinforcement bar is lost, heralding the corrosion process, which in turn causes cracks and spalling of concrete. It would thus be realized that the crucial factor giving quality and durability of concrete appears to be its impermeability, which can be ensured by providing sufficient cement content, low w/c ratio, complete compaction and curing. The same can be further improved by using proper admixtures and providing increased concrete cover.

There can be many causes for corrosion of reinforcement, but mostly it is related to quality of concrete, environment and quality of construction practices. So, the first step in corrosion control of rebar is to provide good quality of concrete through good construction practices. The quality of concrete materials, mixing, placing and compaction techniques and good workmanship can help control the rebar corrosion.

Methods of Corrosion Control of Reinforcement in Concrete:

1. Cement-Polymer Composite Coated Rebars (CPCC)
2. Fusion Bonded Epoxy Coated Rebars (FBEC)
3. Corrosion Resistant Steel Deformed Rebars (CRSD)

The corrosion of steel reinforcement in concrete is complex, but basically it is an electrochemical reaction similar to that of a simple battery. The composition of mild steel varies along its length and potential anodic (more negatively charged) and cathodic (positively charged) sites can be set up at various points.
Thus, it becomes necessary to provide additional protection to reinforcement steel, especially because of chloride induced corrosion (worse than carbonation corrosion) which can develop even in good quality concrete.

Maintenance of passivation is conditional on an adequately high pH of the pore water in contact with the passivating layer. Thus, when the low pH front reaches the vicinity of the surface of the reinforcing steel, the protective oxide film is removed and corrosion can take place, provided oxygen and moisture necessary for the reactions of corrosion are present.

The differences in electrochemical potential can arise from differences in the environment of the concrete. Electrochemical cells form also due to a variation in salt concentration in the pore water or due to a non-uniform access to oxygen.
When there exists a difference in electrical potential along the steel in concrete, an electrochemical cell is set up: there form anodic and cathodic regions, connected by the electrolyte in the form of the pore water in the hardened cement paste.

It can be seen that oxygen is consumed and water is regenerated but it is needed for the process to continue. Thus, there is no corrosion in, dry concrete, probably below a relative humidity of 60 percent; nor is there corrosion in concrete fully immersed in water, except when water can entrain air, for example by wave action.

The transformation of metallic iron to rust is accompanied by an increase in volume, which depending on the state of oxidation, may be as large as 600 percent of the original metal. This volume increase is believed to be the principal cause of concrete expansion and cracking. It should be noted that the anodic reaction involving ionization of metallic iron will not progress far unless the electron flow to the cathode is maintained by consumption of the electrons at the cathode; for this the presence of both air and water at the surface of the cathode is absolutely necessary.

Factors Influencing Corrosion of Steel Reinforcement

Chlorides,Ambient temperature and relative humidity,Severity of exposure, Quality of construction materials,
Quality of concrete,Cover to the reinforcement,Initial curing conditions, andFormation of cracks.

Damages to Concrete Due to Corrosion of Steel Reinforcement
Stage 1: Formation of white patches
Stage 2: Brown patches along reinforcement
Stage 3: Occurrence of cracks
Stage 4: Formation of multiple cracks
Stage 5: Spalling of cover concrete
Stage 6: Snapping of bars
Stage 7: Buckling of bars and bulging of concrete

Minimizing the Risk of Steel Reinforcement Corrosion
*Quality of Concrete
*Depth of Reinforcement Steel Cover
*Materials of Concrete Construction
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Civil Engineering

posted 6 months 2 days ago
Development parameters of a country are defined by the level of infrastructure it maintains. It may be termed as the length of Highways, Railways,Buildings and the ecosystems provided within a nation .Like most of the developed countries fulfill all these parameters and provide there citizens the basic as well as comfort infrastructure.
                  While developing these huge infrastructure the nation spends lots of its GDP in it but as the the matter always fixes at quality is important than quantity ,the term Infrastructure asset
Management comes into play. The quality of asset we maintain will finally decide the health of the nation. For an example if a person is travelling on a road full of potholes he will face psychological as well as physical problem in passing through the path it will deter his health on long run,while the creation of these roads takes a long time and heavy investment there is always a need to maintain these ways whether its road or rail keeping in mind the depreciation of every object in this world. Infrastructure asset management is all about maintaining these capacity developed on a long run with huge investment .
                            Maintenance is a term important in these respect as all the things in this universe carries certain depreciation value. As per a government report 50% of government expenditure are incurred on the asset maintenance. While most of the government projects run on newer concepts of BOOT,PPP,OPMRC etc where the agency constructing these are made responsible for maintaining them for a certain period which helps in maintaining a healthy infrastructure with minimal cost.
                        The importance of Infrastructure asset management is important in many ways which can be illustrated through following points :-
1.   It helps in improving the health of nation like a better and efficient connectivity will enhance the life standard and business operation. For an example China is working on a project OBOR ( One belt One road ) which aims to connect major Asian countries will finally helps in improving the economy with such a huge infrastructure.
2.    As per a study most of the floods are caused due to breaches of embankments which are a result of poor maintenance so putting emphasis on the maintenance of these embankments considering it as an infrastructure can save many lives.
3.    Maintaining a schedule of establishment like periodical repairs, alterations etc all comes under the Infrastructure asset management.
                              The role of government is important as the basic infrastructure is developed by them with huge investment and putting a mechanism for the management of these assets will finally helps in  improving the quality of life .The implementation of IAM can be done in following ways. :-
1.    Implementing a maintenance policy for the assets to be created.
2.    Providing cost of the maintenance in the project for a specified period .
3.    Working on quality plan rather than quantity to improve the conditions of infrastructure created.
4.     Use of updated technology to enhance the quality of infrastructure and increasing the life span .
                        So in my view Infrastructure asset management is an important term in todays context as to optimize the cost and life span of created infrastructure and enhance the quality of living .
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Civil Engineering

posted 6 months 1 week ago
With the advent of computers many of our day to day activities made simpler. As the customized approach towards a definite work can be done using computers by feeding the desired data. So our  civil engineering stream is also influenced by this phenomenon as in every stage whether its planning,controlling, organizing etc their is utility of computers in every field. The first and the foremost thing that a computer can do is to simplify tedious job.Through this blog I am going to discuss about the E- quality control where "E" stands for electronic.
                Scarcity of skilled manpower and other factors which influences a construction project are primarily responsible for the technological inclusion. When we plan something its in the office but the execution part is played at the site and also its the most important aspect so we need better skilled manpower and tools to carry this part..But in the absence of these or with inclusion of computers we can achieve better results. Various benefits includes:-
1. Less time consuming.
2. More efficient system.
3. Real time quality control.
4. Requires less manpower.
5. Reduce project cost.
                         E-quality control can be done by done using various forms  like installing web camera at site ,tools for on-site check like the production of ready mix concrete,data analyzer at site etc.Now a day with the increase in volume of project and change in process E- quality control is an upgraded option and need of the hour.
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