Research on the Properties of a New Type of Polyurethane Concrete for Steel Bridge Deck in Seasonally Frozen Areas
Round 1
Reviewer 1 Report
The paper's topic is an interesting and up-to-date problem of searching for new materials for pavements on steel bridge decks. The field of the Authors' interest are pavements exploited at very low temperature in seasonally frozen areas. The offered solution is polyurethane-cement concrete containing both cement and polymer binders.
The paper presents the results of the investigation of specific properties of the material, including mainly the mechanical performance – compressive strength, tensile strength, elasticity modulus and bond strength to the steel substrate. The influence of temperature on these features was also studied.
Generally, the material concept and verification research is well established. The use of similar materials (epoxy-cement concrete and latex-cement concrete) for making road pavements has a long tradition, particularly in the USA. However, the introduction of such kind of material – polyurethane-cement concrete – for pavement in steel bridges is relatively new and not obvious. The paper brings some new and valuable findings. However, it still needs improvement before publishing. The main concerns are as follows:
- terminology: the Authors use the term "polymer concrete" for their material, which is confusing as it contains both polymer and cement as a binder. Therefore, this is polymer-cement concrete (PCC);
- the statement on page 4 that "the mix ratio was designed through the test" needs explanation. What exactly does it mean? Trial and error method? How was the concrete designed?
- if the concrete is to be exploited at a very low temperature, freeze-thaw resistance testing is expected. And if it is assumed that the freezing is long-lasting (seasonal), not cyclical, testing material immediately after reaching the assumed temperature in the climatic chamber is not enough. The tests should also be performed after long-term storage at low temperature to exclude the possibility of damages caused by ageing in such conditions;
- on page 7 in subchapter 3.3, the range of experimental temperature is given as from -40°C to -60°C, which is not true since the results are presented for the range from -40°C to +60°C;
- some pictures should be removed, namely Figs. 2, 3, 7 and 8; there is no need to show the images of the specimens or their preparation;
- the edition of the text needs amendment. There are a lot of grammatical and logical language errors; the lack of verbs in some sentences makes some paragraphs hard to understand – for instance, on pages 2, 16, and 18, particularly in Conclusions. Some terms used by the Authors are not clear, too; for example, there is no such property as “flexural tensile tensile strength”;
Concluding, I suggest improving the paper according to the above remarks before considering its publication.
Author Response
Our reply is submitted as an attachment，Please see the attachment，thank you!
Author Response File: 
Author Response.docx
Reviewer 2 Report
Manuscript ID: coatings-2005189
Title: Research on the Properties of a New Type of Polyurethane Concrete for Steel Bridge Deck in Seasonally Frozen Areas
Journal: Coatings
Comments to authors:
In the present study, a new type of polyurethane concrete material for steel bridge deck pavement in seasonally frozen areas was developed, and it was applied to the deck pavement engineering of steel bridges with orthotropic slabs. Through mechanical tests, such as compressive strength and flexural tensile strength tests at different temperatures, the mechanical properties, failure modes and constitutive relations of polyurethane concrete materials under the influence of different temperatures were studied and the compressive elastic modulus was calculated. Through the scanning electron microscope test of the damaged sample, the microstructure of the polyurethane concrete after damage was observed, and the mechanism of its strength formation was analyzed. An extensive work has been performed but the novelty can be questioned. However, before it can be considered for publication, please address the following comments for a major revision:
1) The Abstract should be enriched with the brief details of the experimental methodology. The problem to be addressed in this study should also be highlighted in the Abstract.
2) Please highlight the novelty in the Abstract also.
3) The authors should also present some quantitative results in the Abstract.
4) English proofreading is required for grammatical mistakes and typos such as there should be a space between numeric values and units.
5) The novelty and significance of the present work should be highlighted in the last paragraph of the Introduction section.
6) The authors are recommended to add latest relevant literature review on such works.
7) What is the need for this work? Is this work helpful for practical applications? Which applications?
8) The literature review should be improved by adding latest references and discussion.
9) Work methodologies need more discussion.
10) Results section should be defended using technical reasons and relevant references.
11) SEM images need to be clearly discussed and labelled.
12) More instrumental analysis of the fabricated samples is also recommended such as TGA, XRD, etc. to study the compositions.
13) More technical discussion to the presented experimental results should be added.
14) There are no critical review/discussions before the Conclusions. Authors should add it.
15) Conclusions should be refined and briefly presented. More numerical results should be added.
16) What are the limitations of the present study? Please mention them in the manuscript.
17) The authors can add the future recommendations based on the present study.
Author Response
Our reply is submitted as an attachment，Please see the attachment，thank you!
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
I found the revised version of the paper improved sufficiently for publishing, except to the terminology concern. According to all sources known to me (European Standards, documents of American Concrete Institute ACI, etc.), the building composite containing both polymer and cement is called polymer-cement concrete (PCC). The "polyurethane concrete" means the material in which polyurethane is the only binder. However, I am not going to dispute this question further and leave the decision to the Editor. If the Editor will decide that the present terminology may be consider appropriate, I will not oppose.
Reviewer 2 Report
The authors worked hard to address the comments. This work can be accepted now.
