Compressive Strength Enhancement in Early Age Acid Activated Mortars: Mechanical Properties and Analysis

Round 1

Reviewer 1 Report

The authors conducted an interesting material research on the use of various amounts of hydrochloric acid to increase the hydration rate of mortars based on Portland cement 42.5. Interesting work and the research was carried out correctly. It is only surprising that the parameters of the mortar were not tested additionally after 7, 14 and 21 days just after 1, 3 and 28 days. This would provide a more complete picture of how mechanical parameters change over time.

At work, you should replace all descriptions in Chinese with descriptions in English. Detailed comments are provided below.

1. Page 2. Line # 82. Tap water was used. It would be good to give the chemical composition of this water, because it could be useful in the analysis of the behavior of the material during the tests described later.
2. Page 4. Lines # 133-136. Compressive strength was tested after 1.3 and 28 days. To get a more complete picture of changes in endurance over time, it is usually also tested after 7, 14 and 21 days. Obviously, this requires more samples, but it is much better in line with the nature of the strength build-up process over time. The authors' commentary on this point could be useful.
3. Page 5. Fig.1. It is unacceptable to mark the axes in the charts with Chinese characters. It is completely unreadable for people outside of China. Axis descriptions must be in English.
4. Page 8. Fig.2. Note as above.
5. Page 10. Fig.3. The same note regarding the description of the axle.
6. Page 11. Fig.4. Note as above.
7. Page 13. Line # 534-535. Error in formatting references.

Author Response

 Response to the Reviewers

The authors would like to thank all the reviewers for their great comments on the manuscript. Their comments have been taken into consideration seriously while revising the manuscript. The revisions are underlined in the revised manuscript for easier tracking. Their comments/concerns are addressed as follows. Note that the line numbers referred to by the reviewers may change due to the revision of the manuscript.

Reviewers' comments:

Reviewer #1:

1. The authors conducted an interesting material research on the use of various amounts of hydrochloric acid to increase the hydration rate of mortars based on Portland cement 42.5. Interesting work and the research was carried out correctly. It is only surprising that the parameters of the mortar were not tested additionally after 7, 14 and 21 days just after 1, 3 and 28 days. This would provide a more complete picture of how mechanical parameters change over time.

Generally speaking, the compressive strength of mortar cured for 1d and 3d is the early age strength, while cured for 28 d is the standard age compressive strength. In this experiment, the compressive strength of mortar cured for 1d and 3d was tested to analyze the effect of acid excitation on the early age, and the compressive strength of mortar cured for 28d was tested to analyze the effect of acid excitation on the standard age. Of course, testing the compressive strength for 7d, 14d and 21d can make the data more accurate, but the data for 1d, 3d and 28d can show the basic development law of the compressive strength.

2. Page 2. Line # 82. Tap water was used. It would be good to give the chemical composition of this water, because it could be useful in the analysis of the behavior of the material during the tests described later.

It has been revised according to the reviewer's comments.

3. Page 4. Lines # 133-136. Compressive strength was tested after 1.3 and 28 days. To get a more complete picture of changes in endurance over time, it is usually also tested after 7, 14 and 21 days. Obviously, this requires more samples, but it is much better in line with the nature of the strength build-up process over time. The authors' commentary on this point could be useful.

 Of course, testing the compressive strength for 7d, 14d and 21d can make the data more accurate, but the data for 1d, 3d and 28d can show the basic development law of the compressive strength.

4. Page 5. Fig.1. It is unacceptable to mark the axes in the charts with Chinese characters. It is completely unreadable for people outside of China. Axis descriptions must be in English.
5. Page 8. Fig.2. Note as above.
6. Page 10. Fig.3. The same note regarding the description of the axle.
7. Page 11. Fig.4. Note as above.

I am very sorry for this mistake, It has been revised according to the reviewer's comments.

8. Page 13. Line # 534-535. Error in formatting references.

Thank you very much for your careful review. But that's what it means in the system. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear author, please consider the following remarks.

1. The review part of the INTRODUCTION section is not like a search for a ready-made solution to the problem facing the author. The absence of such a solution in publications has not been formulated. The list of References is not too short. Unfortunately, only eight sources are used in the overview in the Introduction section. Consequently, the author's research is not properly motivated.

2. Line 183, 187, 195, 222, 229, 247` 249, 260, 266, 289, 291, 312, 317, 319,322, 342, 350, 356, 367, 376, 389, 393, 407, 410, 412, 429, 434, 43,6 474, 492, 500. It is not clear what the word "this" means. It is recommended to add a noun connecting the previous and the current sentence after the word "this".

Author Response

Reviewer #2:

1. The review part of the INTRODUCTION section is not like a search for a ready-made solution to the problem facing the author. The absence of such a solution in publications has not been formulated. The list of References is not too short. Unfortunately, only eight sources are used in the overview in the Introduction section. Consequently, the author's research is not properly motivated.

It is generally believed that the hydration of cement must be carried out under strong alkaline conditions, and that strong acids will cause serious corrosion to cement-based materials. Therefore, few scholars use acid to stimulate the activity of cement, and it is difficult to find papers on acid stimulated cement in SCI system. However, in the experiment, the author found that when mixing cement-based materials, adding an appropriate amount of acid did promote the hydration reaction and improve the compressive strength. Therefore, since no relevant research papers can be found, the author can only list some papers on the mechanism of cement hydration reaction. The research motivation of this article is to further enhance the hydration reaction rate and the amount of hydration products and early strength of cement-based materials, which has been stated in the first sentence of the abstract. At the same time, lines 40-45 on the first page of the introduction also put forward the research purpose. “However, the development of early age strength of cement-based materials is often insufficient and the requirement of a long curing period run counter to the modernization goal [5]. Therefore, it has become a hot issue in the field of cement-based materials to improve early age mechanical properties, accelerate the hydration reaction rate, and shorten the curing cycle.”

I searched SCI journals and found only one patent for Cement-based Materials excited by lactic acid. SG Rajeshkuma, LACTATE ACTIVATED CEMENT AND ACTIVATOR COMPOSITIONS, November 24, 2011

2. Line 183, 187, 195, 222, 229, 247` 249, 260, 266, 289, 291, 312, 317, 319,322, 342, 350, 356, 367, 376, 389, 393, 407, 410, 412, 429,434,43,6 474, 492, 500. It is not clear what the word "this" means. It is recommended to add a noun connecting the previous and the current sentence after the word "this".

This issue has been carefully revised by the translation agency.

Author Response File: Author Response.pdf