Construction Methods and Lessons Learned for a Non-Proprietary Ultra-High Performance Concrete Overlay
Johan Silfwerbrand
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsTechnical comments
1. Please, define the word ”non-proprietary” in the term ”non-proprietary UHPC” the very first time this term appears in the text. (page 2, line 51?).
2. The bond strength is not solely dependent on the characteristics of the overlay (here: the UHPC overlay). In the literature you may find more than 20 factors. The most important ones (beside the overlay strength) are substrate strength, absence of microcracks, cleanliness of the interface prior to casting, compaction of the overlay and curing of the overlay. (2, 76).
3. Which type of cement did the authors use? Which was the maximum size of the aggregate (sand)? (Table 1).
4. Cracks differ in size, shape and depth from crack to crack and along the very same crack. The crack width is also dependent on the temperature when it is measured. Providing a figure with two decimals (1.59 mm) and state that the value is “approximately” is somewhat ridiculous. Please, provide a range of crack width measures (from smallest to widest) and state the temperature when making the measurements. (3, 109).
5. Which technology was used to remove concrete? Some methods (e.g., milling, pneumatic hammers) leads to microcracking whereas others (e.g., water-jetting or hydro-demolition) result in a very good surface promoting good bond. (4, 120).
6. How did the authors clean the substrate surface prior to the overlay casting? (6, 159).
7. The laboratory environment seems to have been extremely dry (RH = 30%). That may lead to a reduced hydration and possible surface cracking. Why did the authors use such a tough climate? It is likely that the climate on the bridge itself is much more beneficial for the concrete hardening process. (8, 235).
8. The values with +/- sign in Tables 3 and 4, are they the standard deviation values?
9. I understand that it is not that easy to explain the low strength increase between 7 and 56 days. But water control does not seem to be the best explanation. It could lead to both more and less water and in only the first case it would lead to poorer results. And too much water would have influenced also the 7 day compressive strength. Strength development is mainly dependent on the cement type (finer cement grains hydrate faster) and the temperature. Did the authors use very fine cement and was it cold in the room? The addition of fly ash may also have resulted in a slower strength gain. (14, 355).
10. How large part of the total bridge area was identified as delamination areas? (15, 389).
11. Which material was the UHPC applied on? NSC (according to page 16) or HDP (Abstract and page 6)? (16, 407 and Table 4).
12. It seams that the authors have done the very same misinterpretation of bond strength data in identifying the surface texture as the most important factor promoting bond. But it is just a secondary factor. The important ones are listed in point number 2 above. (17, 452).
13. You cannot compare hydro-demolition with sandblasting and shotblasting. By using hydro-demolition, it is possible to efficiently remove several inches of concrete and do it selectively (by removing poor and damaged concrete while leaving sound concrete almost intact). The other two methods can only remove a couple of millimeters. However, they have one advantage in common, none of them introduces micro-cracking in the substrate. (17, 451).
14. The recommended surface preparation is saturated surface dry (SSD) a condition that is neither too wet nor too dry. You may obtain it by pouring water on the surface during one day and let it dry the following night. Next morning, the surface will be SSD.
15. The list of recommendations is good. Please, add an item on the importance of prolonging the curing time. Usually, 5-7 days are much better than just 24-48 hours. (19, 528).
Editorial comments
a. It is not clear what ”This method” aims at in on page 1, line 34. It is possible to guess but the reader should not deed to guess.
b. It is not clear what ”These overlays” aim at in on page 1, line 36. An overlay that has been provided with a protective system or am UHPC overlay?
c. It is not clear what ”it” aims at in on page 2, line 49. If aiming at UHPC overlays, it would be better to write the entire word.
d. It is not clear what ”its” aims at in on page 2, line 51. If aiming at the UHPC overlay, it would be better to write the entire word.
e. Summarize the results in Table 2 in a couple of sentences or a very short table and move the entire table to a new Appendix.
f. For Figure 10, read Figure 11, (14, 374).
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThis paper details the rehabilitation of a concrete bridge deck in Socorro, New Mexico, using a non-proprietary ultra-high performance concrete (UHPC) overlay, incorporating lessons learned and best practices from the process. It covers the entire rehabilitation process, including the removal of deteriorated concrete, installation of a high-performance deck, placement of UHPC overlay, and long-term monitoring, culminating in a comprehensive set of recommendations for similar future projects.
Due to the highly practical aspect of the issues addressed, it seems that the article should be placed in the "technical note" category. If the article is to remain in the article section rather than being classified as a technical note, it seems necessary to supplement it with some discussion and explanation of the obtained research results. This would enhance the depth and academic value of the paper, providing a more comprehensive understanding of the study's implications.
The introduction and methods sections appear to be accurately described, yet the authors could decide whether to illustrate all the employed research methods in photographs or none at all, as exemplified by the inclusion of the four-point bending test but the exclusion of the compression test.
The reviewer opines that the results presented seem more pertinent to High-Performance Concrete (HPC) rather than to Ultra-High Performance Concrete (UHPC). It would be beneficial to clarify the rationale behind this classification.
However, the authors should work on improving the results presentation section. For instance, Table 2 is too lengthy for inclusion in the text. If the authors deem a tabular presentation necessary, it should be moved to an Appendix. The reviewer suggests that these data could be more effectively presented in the form of charts, such as box-and-whisker plots.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe corrections introduced to the manuscript have enhanced its quality and scientific clarity. The article, in its current form as a "technical note," is suitable for publication.
