Civil Engineering

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  • Topic: Concrete, Reinforced concrete, Water
  • Pages : 9 (2966 words )
  • Download(s) : 92
  • Published : April 23, 2013
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REPAIRS, REHABILITATION AND RETRO-FITTING|
Significance of Ferrocement repairs|
After, we in India, started manufacture of concrete in years 1930’s, the negative aspect of concrete started  showing after sometime as below:-| - Deterioration due to poor workmanship, particularly high water content and corrosion of reinforcement  and R.C.C. Technology being new.| - Leakages in concrete due to rain water as well as in water retaining structures| This menace become conspicuous after construction works which became old about 20 to 30 years. We started  realizing the importance of water cement ratio that only since about 40 years before and we have become very  much conscious and now most of our engineers try their best to have Water cement ratio to the extent of its  requirement. Even then, we did not stop production of concrete with water content comparatively more. It had  been accepted that concrete is heterogeneous material and theory of reinforced concrete design is on the basis  of cracked section below neutral axis. With this acceptance, scores of water proof additives and other admixtures  contributing to the increase in strength, durability, workability and waterproof quality of concrete have come into  market. Now it is a foregone conclusion that you cannot have best quality of concrete unless admixtures are used  in its manufacture. Also many instruments for diagnosis for defective concrete such as porosity, lamination of  cement matrix with course aggregate, corrosion of reinforcement, location of corroded reinforcement, strength of  concrete etc. have come in the market in a very big way. Systematic method of inspection observations with  measurements of the defects in concrete in a qualitative and also in quantitative manner have been developed  and schemes / system of management of diagnosis analysis to maintain / to restore water proof quality and  repairs to its original strength have been developed.| All the above methods / system of water proofing, repairs and rehabilitation of structure costs lakhs of crores  of  Rupees to the nation. In order to save such expenditure, in-convenience, loss of time and energy CAN  WE NOT  PRODUCE A CONCRETE FREE OF SUCH DEFECTS?| The quality of concrete can be improved to a large extent now. We are able to produce concrete of strength M100  or even sometimes M 200 with least reason for corrosion of reinforcement. Now a days corrosion of  reinforcement is prevented by epoxy coating and galvanizing of reinforcement. Because of theory of reinforced  concrete with provision of design of cracked section, the defects are bound to develop in due course of time  which may be delayed. Prestressed concrete is the solon to a large extent with pretension structures. However  there is possible corrosion in post tension structures due to errors in proper grouting of cables. In any case  structures now should be better than before.| Concrete is heterogeneous material. It has features to loose bond with aggregate and steel reinforcement at  early stages. It can be said it is not possible for concrete structure to last for hundred years.| Now it is the time when we should think of concrete which should not crack at all and there should be no extra  water more than required for reaction with cement. And concrete should not crack at all when put under design  loads. That means we must view or think about the theory of reinforced concrete that is a structural member is  designed as cracked section cracking accepted below neutral axis. Or crack formation can be thought to be  delayed. In other words crack width and minimum depths to stop entry of corroding forces upto reinforcement.  Also the crack width should be so minute and depth should be so shallow that water be trapped in stopping it to  travel below upto the bottom of the depth or reach reinforcement surface. The effect of atmospheric pollution or  carbonation can be minimized/eliminated by use of certain admixtures in...
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