Influences of Silica Fume on Compressive Strength and Chemical Resistances of High Calcium Fly Ash-Based Alkali-Activated Mortar

Round 1

Reviewer 1 Report

Congratulations to the authors of a very interesting work.
The work is experimental and I am curious if the authors had the opportunity to test the results of their experiences in industry or in a single application. Such a supplement to the work would be an added value. Please, explain or supplement the exact description of how the samples were prepared and cared for. I miss information about the number of samples in each experiment and the maximum and minimum results in each study. The results presented are mean and the standard deviation is quite large.
Please also complete the information on the origin / producer of the materials used.
After completing the additions and information, the work will be more complete.

Author Response

AUTHOR’S RESPONSE LETTER

 REVIEWER #1

Congratulations to the authors of a very interesting work. The work is experimental and I am curious if the authors had the opportunity to test the results of their experiences in industry or in a single application. Such a supplement to the work would be an added value. Please, explain or supplement the exact description of how the samples were prepared and cared for. I miss information about the number of samples in each experiment and the maximum and minimum results in each study. The results presented are mean and the standard deviation is quite large. Please also complete the information on the origin / producer of the materials used. After completing the additions and information, the work will be more complete.

Thank you very much for your great effort to review our paper and give the valued comments. The authors had added the information about the number of samples and the standard deviation in each experiment as follows:

 2.3.1. Compressive strength

The averaged results of three samples are reported for each tested age with maximum permissible range of 8.7%. The total samples for investigating compressive strength were 72 samples.

 2.3.2. Sulfuric acid resistance

In accordance with …. mortar specimens. The total of 72 mortar specimens were immersed in 3% sulfuric acid solution (pH = 0.5) for 28 days after being cured in air.

 2.3.3. Sulfate resistance

The loss of compressive strength of …. of 180 days according to the ASTM C109 standard [46]. The reported result was obtained from the average of three samples with maximum permissible range of 8.7%. The total samples were 18 samples.

The expansions of the mortar bars after the immersions of 1 - 98 days were recorded to determine the expansion percentages. Three samples for each mortar type were determined and the total samples were 18 samples.

 For the quite large standard deviation in results.

The authors had checked and revised the error bar shown in Figure 4, please see more details in the revised manuscript. For Figure 6, the large standard deviation bar shown in figure was due to the very low value of expansion of mortar (all expansion values were lower than 0.09%). However, the result was clearly seen that the increase in curing temperature could reduce the expansion of alkali-activated mortars and the use of silica fume gave higher value of expansion of alkali-activated mortars when immersing in 5% by weight sodium sulfate solution.  

 Additionally, the authors had added origin/producer of the materials used in this study in the revised manuscript as follows:

This study used fly ash (FA) from the Mae Moh power plant in northern Thailand as the primary precursor in alkali-activated mortar. The effects of using silica fume (SF) to partially replace the fly ash to promote the strength of the mortar were also studied. Silica fume used in this study was commercial products and obtained from company in Thailand.  

Author Response File: Author Response.pdf

Reviewer 2 Report

The methods are adequately described and are reinforced by the literature background. The results are properly presented, although it is suggested that in Figures 1 and 2 the same line type is used to identify the same mortar, for ease of interpretation. The durability performance of the designed mortars is adequate, and it has been assessed through proper testing methods. However, the quality of the graphs is appropriate for a research paper.

The conclusions included in bullet points are adequate. It is suggested that the paragraph preceding the bullet points is revised so as to integrate the compressive strength instead of jumping directly to durability issues. 

Author Response

AUTHOR’S RESPONSE LETTER

 REVIEWER #2

The methods are adequately described and are reinforced by the literature background. The results are properly presented, although it is suggested that in Figures 1 and 2 the same line type is used to identify the same mortar, for ease of interpretation. The durability performance of the designed mortars is adequate, and it has been assessed through proper testing methods. However, the quality of the graphs is appropriate for a research paper.

Thank you very much for your great effort in reviewing our paper.

 The conclusions included in bullet points are adequate. It is suggested that the paragraph preceding the bullet points is revised so as to integrate the compressive strength instead of jumping directly to durability issues.

The authors agreed with this comment and the conclusion had been revised as follows:

This paper presents the properties of alkali-activated mortars with silica fume and curing at ambient temperature. The effects of using silica fume to enhance properties of alkali-activated mortars was investigated and the results was compared with alkali-activated mortars curing at elevated temperature.  These measurements included compressive strength, mass loss due to attack from 3% by weight sulfuric acid resistance, compressive strength loss due to 5% by weight magnesium sulfate attack, and expansion due to 5% by weight sodium sulfate attack. Based on these results presented in this paper, we draw the following conclusions:

 Author Response File: Author Response.pdf