Performance Evaluation of Silane in Concrete Bridge Decks Using Transmission X-ray Microscopy

2.2 Depth of silane penetration/ Figure 1-not cited in text

Thanks for your comments. The authors reviewed the whole manuscript and doubled check to ensure all figures/tables have been cited in the text. Figure 1 was already cited in the text (Line 105 of the original submission)

2.3 Diffusion test/Figure 4-not cited in text

Thanks for your comments. The authors reviewed the whole manuscript and doubled check to ensure all figures/tables have been cited in the text. Figure 4 was already cited in the text (Line 191 of the original submission)

3 Results and discussion/ Figure nos. and citation- not in order

Thanks for your comment. The manuscript was reviewed one more time and all figures/tables are in the order of appearance in the manuscript.

Reviewer #2:

Comment

Response

In this submission to Applied Sciences, the authors use transmission X-ray microscopy (TXM) techniques and optical imaging to investigate mass transport properties and silane thickness of the field samples treated with silane. The authors carry out this study to give insight into the performance of silane coatings. The authors carry out quantitative measurements using optical staining techniques showing that on average the samples with silane coatings exhibited 8.5 times less penetration outside chemicals. The authors conclude that silanes are a useful and practical tool to significantly reduce the permeability of in-service concrete and resist corrosion.

I consider this manuscript to be of interest to materials science researchers as well as readers of this journal. As such, I am relatively supportive of publication with a few minor comments which should be addressed in the next revision. In particular, there has been much work using X-ray absorption spectroscopy to probe surface effects on concrete and other material surfaces, which should be noted

Waste Management 2006, 26, 699-705
Langmuir 2014, 30, 9, 2559–2565

In particular, these prior works showed that X-ray absorption spectroscopy (XAS) can be used to probe chemical speciation of trace elements in cementitious materials and other substrates, which should be noted in the next revision. With this minor revision, I would be receptive towards re-reviewing this manuscript for subsequent publication in Applied Sciences.

Thanks for your comment. The authors considered your comment and suggestion and cited the recommended papers in the introduction (Line 70).

Reviewer #3:

Comment

Response

1. please complete the content indicated as "Error!  Reference source not found" in the text.

Thanks for your comment. The authors reviewed the manuscript and realized that there is not such error in the original document. The issue has happened during submission and conversion. The authors will use another tool to convert and submit the revised manuscript to avoid such problem.

1. Provide the mixture proportion and compressive strength of concrete in the text.

Thanks for your comment. The authors tried it before submission but when they reviewed the manuscript, they found it distracting since no discussion was directly done on this table. For this reason, they moved it to appendix to make the manuscript more straight-forward.

There is no data provided on compressive strength in this manuscript. The samples were collected from field only for evaluation of silane not compressive strength test. Since the samples were collected from Oklahoma bridge decks, they have passed the criteria of acceptance provided by ODOT regulations. Therefore, there was no need for compressive strength evaluation.

Reviewer #4:

Comment

Response

The topic is interesting and at the same time a very important one for engineers and researchers. There are some minor issues to be addressed before the manuscript is fit for publication.

1. Literature review - Suggest the authors to include 1-2 more relevant references from the last 3-4 years. Also, some of the older works of Professors Davalos and Ray from West Virginia University such as the paper https://doi.org/10.1016/j.conbuildmat.2011.08.066 can be studied and cited to improve the literature review.

Thanks for your recommendation. The authors included the recommended paper in the introduction (Line 31)

1. Materials - There can be a separate sub-section for the materials. The sample acquisition part can be presented as the first sub-section of the methodology section. Along with the schematic image in Fig.1, a real-life photograph of the acquired sample will be better for the understanding of the readers.

Thanks for your valuable comment. The authors agree that it would be better to introduce the materials properties in a different sub-section, but unfortunately since this study is performed on the field samples, no more information rather than the information reported in Table A1 was provided for the authors. A picture of the acquisitioned sample was included in Fig.1 according to your suggestion.

1. What is the basis for the selection of the 9 spots? Were they selected randomly or were they spaced at equal distances?

The spots were selected randomly but it was tried to have spot all around the samples not only on one side of the samples. The manuscript was revised to make it clear for the readers. 

1. The digital image in Fig. 2 is having some light scattering at certain places due to the undulations in the sample. Is it possible to present a sharper image with fewer such striations?

Thanks for your comment. The authors replaced Fig 2 with another image.

1. For Fig. 3, please provide images of the real-life sample in addition to the present image.

Thanks for your comment. The authors added a real sample after applying a hydrophobic wax.

1. Line 159 - Why is the concentration of KI 0.6 mol/L? Please mention references to previous papers to justify.

Thanks for your valuable comment. We cited a paper which introduced this technique. In that paper it has been mentioned that 0.6 mol/L gives better contrast between sample and the tracer.

1. The use of ultrasonic pulse velocity methods might be able to validate the observations of cracking in silane-treated vs. non-silane-treated specimens in a better manner. This technique can be considered by the authors.

The authors appreciate your recommendation. The authors agree that UPV is a great technique to evaluate the samples but it was not the goal of this study. In this study we tried to investigate the reason of observing high concentration in the depth of some silane treated samples. Therefore, we used a tomography technique to prove the discussion where we claimed that silane loose its efficiency if concrete cracks. We wanted to use a technique to visualize the crack for the reader plus see the depth of crack. Due to the nature of crack, and due to the corner trap in UVP, the depth of crack couldn’t be evaluated precisely for our work.

1. A basic cost analysis of the silane treatment method is suggested. What is the expected life-span of the silane treatment method? That has to be clearly mentioned in the manuscript.

It is great recommendation but it is beyond the scope of the project that was defined and funded. In the literature some researchers have studied the service life of silane and its life cycle analysis. Examples can be found in the papers listed below:

1-      Moradllo, Mehdi Khanzadeh, Bryan Sudbrink, and M. Tyler Ley. "Determining the effective service life of silane treatments in concrete bridge decks." Construction and Building Materials 116 (2016): 121-127.

2-      Zeng, Yu, et al. "Determining the service life extension of silane treated concrete structures: A probabilistic approach." Construction and Building Materials 249 (2020): 118802.

3-      Liu, Min, and Dan M. Frangopol. "Multiobjective maintenance planning optimization for deteriorating bridges considering condition, safety, and life-cycle cost." Journal of Structural Engineering 131.5 (2005): 833-842.

4-      Frangopol, Dan M., and Min Liu. "Life-cycle cost analysis for highways bridges: Accomplishments and challenges." Structures 2004: Building on the Past, Securing the Future. 2004. 1-9.

1. Some of the linked references are showing errors [Ex. Line 104-105]. Please check and address such issues in other places too.

Thanks for your comment. The authors reviewed the manuscript and realized that there is no such error in the original document. The issue has happened during submission and conversion. The authors will use another tool to convert and submit the revised manuscript to avoid such problem.