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MDPIMDPI
by
  • Nathaniel Olukotun1,2,*,
  • Abdul Rahman Mohd Sam1,3 and
  • Olukotun Adebisi6
  • et al.

Reviewer 1: Anonymous Reviewer 2: Anonymous

Round 1

Reviewer 1 Report

The manuscript is well written and interesting to read. However, I would suggest that authors consider the comments below for improvements.

Abstract and conclusions

The analysis of "... environmental and ecological concerns" or “…minimize environmental problems” suggests that tin slag was viewed as a waste. However, it can be viewed as a by-product of other production with the respective environmental impacts. Consequently, the environmental assessment of replacing fine aggregate with tin slag in concrete can only be conducted using Life-cycle assessment. The environmental benefits of using tin slag can be considered an assumption, not a fact in this manuscript.

 

Author Response

Response to Reviewer 1 Comments

Point 1: The analysis of “ environmental and ecological concerns” or “minimize environmental problems” suggests that tin slag was viewed as a waste. However, it can be viewed as a by-product of other production with the respective environmental impacts. Consequently, the environmental assessment of replacing fine aggregate with tin slag in concrete can only be conducted using life-cycle assessment. The environmental benefit of using tin slag can be considered an assumption, not a fact in this manuscript.

Response 1. I have made the corrections and additions regarding your comment’s sir/ma.

Response to Reviewer 2 Comments

Point 1: Authors refer to the depletion of sand. However, one can use crushed sand. In fact, in many countries, the use of natural rolled sand and most of the sand used in concrete and mortar are crushed ones and come from quarries

Response 1. I have modified that part in line with your comment

Point 2. Ungraded tin slag sand was only used to measure workability properties? It will be very interesting to include the mechanical properties of ungraded TS mortars.

Response 2. Compressive strength results have been included, although the same trend as workability was observed.

 Point 3. Grading TS sand implies rejecting some quantity of ungraded TS sand. How many?

Response 3. Larger particles which was removed during grading was reused after crushing.

 Point 4. How many specimens were tested in each test?

Response 4. A total number of 135 cubes, 45 cylinders and 45 prisms were prepared for compressive, splitting tensile and flexural tests respectively. In addition, 45 mortar bars were prepared for ASR tests

Point5. Presented hardened tests were from graded TS sand mortars?

Response 5. Yes, graded tin slag. It has been clearly stated.

 

 

 

Reviewer 2 Report

The subject of the article fits perfectly in the topics covered by the Recycling MDPI Journal. The subject of the paper is a very interesting and up to dated one and is related to the incorporation of wastes, namely tin slag, in mortars and concretes. The paper is an experimental one, is well written but contains some lack of information and some results needs to be well analysed. However, the scientific contribution of the present paper can be considered relevant and I recommend its publication after being revised. It has potential if it will be well developed, namely:

  1. i) authors refers the depletion of natural sand. However, one can use crushed sand. In fact, in many countries the use of natural rolled sand is limited and most of the sand used in concrete and mortar are crushed ones and comes from quarries;
  2. ii) ungraded TS sand was only used to measure workability properties? It will be very interesting including mechanical properties of ungraded TS mortars.

iii) grading TS sand implies rejecting some quantity of ungraded TS sand. How many?

  1. iv) how many specimens were tested in each test? The text is not clear. And a measure of results’ dispersion is missing.
  2. v) presented hardened test results were from graded TS sand mortars, right? The text is not sufficiently clear about that.

Moreover:

1) abstract, line 2: replace “…of fine…” by “…of natural fine…”;

2) introduction, line 2 of 2nd §: replace “…of fine…” by “…of natural fine…”;

3) page 2, line 7 of last § of “1. Introduction”: setting time results were not presented neither analysed;

4) page 2, last line of “1. Introduction”: alkali silica reaction is not a mechanical property;

5) “2.1 Materials”: OPC density of 2.7 is an unusual value. It is almost around 3.1. What happens? Please review this result;

6) table 2: sum of TS compounds is only 78.45%. It is far from 100%. Please revise;

7) fig. 1 a): a scale is missing;

8) fig 1 b) is irrelevant. Please delete it;

9) fig 2 and fig 3: please maintain the colors in the two graphics. For instance, sand is yellow in fig. 2 and blue in fig. 3;

10) page 4, line 2 of “2.3 Mix proportioning and sample preparation”: replace “…aggregate ratio…” by “…aggregate volume ratio…”;

11) page 4, line 1 of 2nd § of “2.3 Mix proportioning and sample preparation”: why “…about 20%..”. Why not using the correct value which is 3.00/2.62 = 1.145 = 14.5%???;

12) authors must refer that ungraded TS sand mortars were produced and its workability will be analyzed. And must justify why hardened properties of ungraded TS sand mortars were not included in this study;

13) table 4: please explain in detail how the multiplier factors were determined. Please take into account 11);

14) table 5: mix proportions for 1 m3 of mortar, right? Please mention in table caption;

15) table 5: value 397.5 of TS25 mixes seems to be wrong once not affected by the multiplier factor 1.06 (which I think it is wrong according to 11) and 13)) of table 4;

16) page 5, line 4 of 2nd §: replace “…mm…” by “…mm3…”;

17) page 5, line 6 of 2nd §: replace “…are…” by “…were…”;

18) page 5, line 2 of 3th §: replace “…are…” by “…were…”;

19) page 5, line 3 of 3th §: replace “…mm…” by “…mm3…”;

20) page 5, line 8 of 3th §: replace “…mm…” by “…mm3…”;

21) page 6, line 4 of 2nd §: replace “…workability of increased…” by “…workability increased…”;

22) page 9, line 15 of “3.4 Compressive strength”: replace “…0.55, Moreover…” by “…0.55. Moreover …”;

23) page 9, line 16 of “3.4 Compressive strength”: replace “…was…” by “…were…”;

24) page 9 last 4 lines of “3.4 Compressive strength”: please rephrase…;

25) page 10, line 4: it seems that elongated shape particles are better than cubic ones. Please discuss/correct;

26) page 12, line 9 of “3.6 Flexural strength”: replace “…12 MPa…” by “…12.00 MPa…”;

27) page 13, replace “4.0 Conclusions” by “4. Conclusions”;

28) page 13, “4.0 Conclusions”: a general conclusion about feasibility of using TS sand in mortars is missing.

Author Response

Response to Reviewer 2 Comments

 

 

Point 1: Authors refer to the depletion of sand . However, one can use crushed sand. In fact, in many countries, the use of natural rolled sand and most of the sand used in concrete and mortar are crushed ones and come from quarries

Response 1. I have modified that part in line with your comment

Point 2. Ungraded tin slag sand was only used to measure workability properties? It will be very interesting to include the mechanical properties of ungraded TS mortars.

Response 2. Compressive strength results have been included, although the same trend as workability was observed.

 

Point 3. Grading TS sand implies rejecting some quantity of ungraded TS sand. How many?

Response 3. Larger particles that were removed during grading were reused after crushing.

 Point 4. How many specimens were tested in each test?

Response 4. A total number of 135 cubes, 45 cylinders, and 45 prisms were prepared for compressive, splitting tensile and flexural tests respectively. In addition, 45 mortar bars were prepared for ASR tests

Point5. Presented hardened tests were from graded TS sand mortars?

Response 5. Yes, graded tin slag. It has been clearly stated.

 

 

 

Round 2

Reviewer 2 Report

The authors reviewed and improved the overall quality of the paper, satisfying almost all, but not all, of the reviewer's comments. There are still some improvements to be made:

1) grading TS sand implies rejecting some quantity of ungraded TS sand. How many?

2) how many specimens were tested in each test? The text is not clear. And a measure of results’ dispersion is missing.

3) table 2: sum of TS compounds is 84.19% still far from 100%. Please revise;

4) table 4: explanation of how the multiplier factors were determined is still missing. Multiplier factor for TS100 shouldn’t be equal to 1.145? Please detail;

5) table 5: replace “Kg” by “kg”;

6) 1st line after Fig. 12: replace “Fig. 12…” by “Fig. 13…”;

7) Fig. 12: W/C ratio of tested mixtures are missing;

8) Fig. 12: age of tested mixtures are missing.

Author Response

 

Comments uploaded

Author Response File: Author Response.pdf