Study on the Corroded Hollow Section RC Columns Strengthened by ICCP-SS System

Round 1

Reviewer 1 Report

The paper deals with a new technique for existing concrete structures with cathodic protection and structural strengthening simultaneously.  It is well written, and tests results and discussions are clearly given.  However, the reviewer found some points to be improved and gives the following comments for the authors' consideration.

• Technical term: The cathodic protection has the principle that the potential of rebar in concrete is shifted more negative to avoid corrosion.  However, as mentioned in Chapter 4, change in chloride ion concentration is discussed as if the technique were used for chloride ion extraction.  These two techniques are categorized in the electro-chemical repair, but they have quite different objectives.  The authors are requested to describe how the technique is to be applied for real reinforced concrete structures. 
• Line 42: Please give whose research results are mentioned here.
• Line 62: Fragment, or delete comma between "system" and "and".
• Line 67: "diameter" is changed as "diameters"
• Line 68: Please give the reason why the diameter ratio was determined to be 0.53.  Also please give discussions how the diameter ratio is likely to affect the test results.
• Line 68: "length" is better to change "height".  Height is used in Line 76 with the same definition.
• Line 82: Please give the definition of the corrosion ratio.  Is it in terms of mass loss, diameter loss, or cross-sectional area loss?
• Line 91 (Table 1): Corrosion ratios of 5%, 10%, etc. are the target values.  Thus, real corrosion ratios achieved by the accelerated corrosion treatment and its longitudinal variations in a rebar should be given for discussion (preferably in lines 194-202).  
• About the rebar:  Please give the details of rebar, such as round bar or deformed bar, how to treat mill scale, rebars including stirrup are all electrically connected or not, etc.
• Figure 9 (b): Please give the specimen name shown in this photo.
• Line 114:  Insert "and" between the two sentences.
• Line 140 or another place:  Please add the experimental procedure about the accuracy of 3% NaCl solution.  Was it be kept constant during the ICPP treatment and how did the authors do it?
• Material properties: Please give the mix design of concrete.
• Line 161:  What does "calculated thickness" mean?  Please give explanations.
• Line 173: "stress" may be "strength".
• Figure 8(e):  The descent branch is not drawn in this figure.  What happened after the maximum load of I-20-S?
• Lines 206-208:  Almost the same ultimate loads can be found in I-20-S and I-20-5, which is not consistent with the discussion here.
• Equation (1):  The dimensions of left-hand and right-hand members are not consistent.
• Line 256:  Please give how to determine fcc.  Does it include the contribution of rebar?
• Line 275:  It is said that "the diameter of the coring machine was 90mm", but "the diameter of core" is not given.
• Figure 9(b):  This figure is not well understandable.  Please add some notes in the figure such as rebar, CFRP, outer side, inner side, etc.
• Chloride ion concentration:  Please specify the chloride ion concentration in this paper - either total chloride or acid-soluble chloride? 
• Figures 11-13:  In these figures, rebar is drawn by a straight line.  However, in the specimen, the rebar has 12mm thick, which should be drawn there.  As shown in Figure 10, chloride ion is contained at the depth of rebar (12mm part) and is distributed within this area.  Thus, the rebar should be drawn with its real size.
• Effect of cathodic protection: Electric current generally only passes between the anode and cathode; that is, only in the outer side.  In the inner side, there was no or very small corrosion protection current.  Please add discussion with taken into consideration the corrosion protection current.   

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Would you please check the symbols of all physical quantities to be written with italic letters (e.g. I and T in Table 1)

QUESTION:   You observed a kind of accumulation of chlorides at the inner side of the rebars while there was much depletion of chloride at its other side facing towatds the anode. Do you think that your ICCP-system will provide enough protection for the rebars with THAT SPECIFIC ARRANGEMENT of the electrodes? Please try to add a short discussion/explanation about it to your manuscript, if possible. 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The manuscript was well revised to meet the comments given by reviewers.  It would be acceptable for the journal, but still needs the following minor revision if the authors agree.

Lines 50-54:  Thank you for adding explanations from the practical point of view.  It is better to add comments on: is this technique applied for either new structures or existing structures for the purpose of strengthening, or both?

Equation (1):  Should the equation be 

f_y^*/ f_y0 = 1 - 1.1η, where f_y0 is the strength of non-corroded rebars, shouldn't it?

Line 291: "the cored concrete core" would be "the cored concrete"

Figs 11-13:  The reviewer's intention is that the inner side and the other side exist continuously even the rebar is embedded.  Thus, the horizontal axis of these figures is better to be continuously drawn from -40 to +40 mm with the 12 mm rebar part in between.  The 12 mm rebar part should be indicated with the real scale in the horizontal axis. 

Overall:  Please check the language (English) is yellow highlighted parts once again. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf