TESTS DONE:

 Corrosion of reinforcing steel is an electro chemical process and the behavior of the steel can be characterized by measuring its half cell potential. The greater the potential the higher the risk that corrosion its takes place. Contour lines may be plotted between points of equal potential to indicate those areas that have the greatest risk of corrosion.
 

HALF CELL POTENTIAL

 As per ASTM C876 for Half cell potential Values between 150-200 indicates - Good 200-300 indicated - Initial Corrosion 300 above Corroded -ve values are obtained from Multimeter. Copper Sulphate is used as an Half Cell which is placed over the surface the concrete with one end connected to voltmeter The concrete surface or an overlaying material, or both, must be cleaned and pre-wetted before test . Place the half cell on the concrete surface and do not move Another wire from Voltmeter is connected to exposed rod . Observe the voltmeter for the readings.

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REBOUND HAMMER TEST
METHOD OF TESTING : Rebound Hammer Method. Piers at different locations are selected.  Rebound Hammer (IS 13311( Part 2 ) : 1992) The rebound hammer method could be used for: i) Assessing the likely compressive strength of concrete with the help of suitable correlations between rebound index and compressive strength, ii) Assessing the uniformity of concrete, iii) Assessing the quality of the concrete in relation to standard requirements iv) Assessing the quality of one element of concrete in relation to another.When the rebound hammer is pressed against the surface of the concrete, the spring controlled mass rebounds and the extent of such rebounds depends upon the surface hardness of concrete.The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete. The rebound is read off along a graduated scale and is designated as the rebound number or rebound index.

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DETERMINING CHLORIDE  & PH IN CONCRETE
This method is used to determine the concentration of water soluble chloride ions in concrete. Then the obtained samples are sent to lab test in order to determine the chloride content in the collected sample.

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TEST ON LAB Chloride Test
Sieve the powdered Sample in 150 micron sieve .10gm is taken in 500ml Beaker .Then, Add 50ml of Nitric acid (6N) .Place it on Hot plate for half an hour .Then, add 30ml distilled water in it .Take 250ml standard flask and filter using 40watman paper . Take the filtered solution and add 250ml distilled water.Ammonia thiocyanate (0.02N) in Burette and take 20ml Silver nitrate + 5ml nitric acid + 5ml Nitro Benzene + 5ml ferric alum (indicator) in pipette . After titration the sample changes from white to reddish brown . Calculation can be done from the obtained value . If the value is greater than 0.6 (concrete is attacked by chloride) Chloride Value - 7.25.

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PH Test
The sample is added with Ph9 solution .Then from the obtained result we can compare the values
pH value - 11.3.

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COMPRESSION TEST BY CORE CUTTING METHOD : Core sample of 69mm dia is collected by core cutter .The place in which the core to be collected is marked based on the concrete cover .The collected sample of 89mm is only collected due to interface of reinforcement .But the sample should be 2x Diameter of the core .So the correction factor should be applied as per IS 516.

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CARBONATION TEST
The core sample is then added by copper sulphate in order to find out the carbonation attack in concrete.