Is excess cover good in insitu RC structures?

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Many times, during my site inspections, I have found fault with the Contractors for providing an inadequate cover for the reinforcements in R.C structures.  Obviously inadequate cover for the R.F has to be rectified immediately as less cover causes the larger crack widths in concrete and thereby it exposes the reinforcement to surrounding environment to get corroded. This is an important factor to consider in which bridge structures as it withstand severe environmental conditions.

 Furthermore, an inadequate cover leads to unsatisfactory fire resistant as well as the under developed bond strengths between concrete and R.F also.   Hence there should not be any argument whether inadequate cover is acceptable or not. The clear and loud answer is NO!!!!!

Then what about the other side of the story? In other words,  is provision of  an  extra cover than the specified limits  acceptable? Oki doki…take a little time and come up with an answer………………..

Many distinguished concrete specifications are very clear on this matter. The tolerance for the concrete cover is between +10 mm to -10 mm. However some inexperienced contractors, especially small scale subcontractors, do posses a misconception that increased concrete cover is acceptable and allowed to go unnoticed. This is wrong…….

What is the underlying theory behind the upper tolerance limit of the concrete cover? The upper limit of the concrete cover governs by its effect on Crack widths. Generally the Crack width of the concrete is governed by three factors namely 1.)  Tensile strain of the point  2.) Distance to the R.F bar from the concerned point &  3.) Depth of the tensile zone

In this case, the second factor is significant and it governs the upper limit of the concrete cover.  The increased concrete cover leads to longer distances of R.F bar from the cracking point.  Hence with an increased concrete cover, the crack width also becomes larger.

So cover for concrete should be in its specific limits whether it is plus or minus…keep checking for that….

Oki guys…that’s it for today…Looking forward to see your comments on this topic…. Cheers!!!!!

New way......

I have been very busy since last August,2010 owing to my academic work, job and family commitments. Although work loadings in every fronts are mounting up, I thought time is right for recommence this blog which I really enjoyed in past. It simply keeps alive my appetite to learn.

Unlike in previous writings, this time I am thinking of writing more on technical related civil engineering issues. Earlier I tried to address the non technical readers and attract them via linking simple every day examples to introduce civil engineering concepts to them. In this attempt, although I had many successes, I realised that it need high level of imagination skills other than the technical knowhow. My busy life style simply does not permit me to engage in such high level of imagination and sometimes I am not sure myself whether I do have such skills either.

One may be able to raise the issue that new approach will further diminish already limited number of readers or fans for this blog. But, instead of waiting without writing nothing and looking to provide a masterpiece one day, this approach makes me more comfortable and opens much wider range of topics. It only requires the focussing on technical matters and research skills on subject matter.

There were few loyal readers to this blog, who were not direct stakeholders of civil engineering field, but attracted owing to the simple everyday examples I drawn up previously. I really appreciate them and their comments encouraged me to continue in writing in past. But lack of time to engage in creative imagination compels me to keep distance away from such readers. I humbly regret for taking such a decision and leave apart non technical readers.

With this new platform I am expecting to write more regularly and effectively on civil engineering related issues. I invite you to stay with me and with this blog. Your valuable opinion or criticism always encourages me and strengthens my writing.

Artist = Engineer / 2

Last time I wrote that Civil Engineering is a half science plus half art. The artist feels something intangiable where he will convey that feeling to rest of us through his Art.

Then how could Engineer become a half artist?..confused??

Engineer feels the answer (which is an art) and then use his science to achive that answer ...that is an art..



see the picture below ....







Note: please note that author of the original document is unknown

The Wheel has been invented, Engineer you are supposed to use it..

During the time of my undergraduate, one of my professor took a great effort to teach us the difference between a mathematician and an engineer. To his credit, he almost did it in a 100%

Mathematics is paramount in engineering. But Engineering is not all about  the mathematics.


Engineer is always a practical,solution provider and most importantly see all the (most of) aspects of the problem in solving the issue.While doing so , he should not be restricted in specific theoretical framework but should be an out of box thinker.

 As an engineer one does not need to immersed in rigorous theories always, how it invented, but he should be able to use the theory creatively  in  day to day problems....

What they need is creativity  blended with a sound technical background.......and essentially unframed imagination skills......

See this

who ever wrote this answer, I see a different person behind this, ..for sure he has seen a different aspect of the question that conventional thinker, a framed mind will never find .. He should be given full marks...



again the above answer shows the creativity which is handy in an engineering (or civil engineering?)

Answer may be wrong in an eyes of a mathematician. But answer gives an indirect indication of a creative thinker......

the following is a good lesson for the teachers. Picture says thousand words

Before you drink....

Nothing is softer or more flexible than water, yet nothing can resist it. - Lao Tzu

Water is an important entity in our life.

Still most of you may not aware that Civil engineers play a significant role when it comes to providing the potable water to your tap.

Water treatment is a highly developed area where so many civil engineers have contributed to the development of the subject.

Recently I had an opportunity to visit a Water Treatment Plant in Australia.
Inorder to provide you a general idead about the water purification process, I will go through a small description with a relevant photo.

Non technical readers , please skip what i have written under brakets



Pump House, the place where water is pumped from the river.



Water is pumped, 34m below from the tratment plant level. Can you guess why plant has been bult on a such a higer level....?


Then chemicals are been mixed to the raw water ( Alum and NaOH). it happens in the following chamber (its called Rapid Mixer: can any one remember 'hydrulic jump' we lerned at UOM?? that is the theory based here))



Chemical mixed water been allowed to flow through the 'flocculation tank' ( I'm sorry to use a technical term..but in this tank chemical particles get adhear to the tiny particals in the raw water and form a much bigger particles..which will easilly get settled than tiny particles)




particales in the water allow to settle in the larger tanks (Sedimentation tank)



Then water is been flitrated using filtration tanks.



(abouve picutre is a back wash of the flteration)

Filtered water collected through the pumpms and send them to the purified water well, to be distributed to the consumers.




These are the stroage tanks which store the varoius chemicals for the tratment processes.




Particles taht have been removed from the water (Sludge: after thickning)




So many efforts, time and money have been spent to provide you a good drinkable water to your tap. So it is your duty to optimise your water usage...


"Nothing is softer or more flexible than water, yet nothing can resist it......"

The Tallest Bridge

There are so many Guinness records for the tallest entities  such as tallest man,tallest woman,tallest building etc.

when it comes to bridges which one will line up with the tallest tag? 

The world tallest  Bridge is 'Millau Viaduct' which is a part of the A75 road that links the Paris with Barcelona, France.




The bridge is 343 meters high and its highest point is more higher than the Eiffel Tower as well.



The total Cost of the project was AUD $ 525 million.





This project has the most highest bridge piers in the world. Above picture shows the constriction of such a pier.

This cable stay bridge has a total length of 2.5km and it crosses the Tarn River.




At a time, when I was having  my doubts of my choice of undergraduate studies in the uni, my lost interest triggered back with double power, after seen a presentation of a bridge construction similar to above. Still I can still feel the same and runs it in my veins when I am going through above pictures...........

what's happening in UOM?

This year (2010),the field selections of University of Moratuwa (UOM), SL, have depicted a different trend from its past consistent behavioral pattern. Even though, when considering the whole picture, it cannot be catogorised as a radical change, still it is a very significant change in view of Civil Engineering aspects. It shows that, the modern demand pattern in engineering professional market is slowly but steadily, influencing to more and more bottom levels of the engineering professional’s hierarchy. i.e engineering students.
According to the graph more than 40 students who may have qualified to study Electrical engineering had preferred to study Civil engineering as their choice. Among them nearly 12 students have a better GPA than the lowest GPA student in the Electronic Engineering. Further almost all 40 students have a better GPA than the lowest GPA student in computer science.

This trend is highly welcome to the field of civil engineering where present turbulent market is demanding more and more highly skilled, innovative thinkers to address modern civil engineering dilemmas in environmental, structural and project management issues.

note:purple line: electronic
Green line : computer science
Brown line : civil
Red line : electrical