Influence of Waste Tire Particles on Freeze–Thaw Resistance and Impermeability Performance of Waste Tires/Sand-Based Autoclaved Aerated Concrete Composites

Round 1

Reviewer 1 Report

The article shows an interesting issue. It is undoubtedly a valuable research material. However, there are some errors in the article that require improvement and some doubts that should be clarified for the work to be fully understood.

1. Please correct all references in the text according to the manuscript preparation instructions. Examples of incorrect filling: "(...) concerns[1,2].", "(...) concrete[1,5,6]."
2. Table 1 and Table 2
   It is necessary to correct the tables. They do not provide clear information on how many different types of samples were and what their compositions were. Table 2 states that waste tire content was 1% for all types of waste tires. However, in the text there is information about the addition "0.5–3.0 wt.% in 0.5 wt.% increments" 
3. "2.2. Preparation of the waste tires / sand-based autoclaved aerated concrete composites"
   Little data on sample preparation.
   How many samples were prepared of each type?
   What were the dimensions of the samples?
   The samples were prepared in a laboratory or in an industrial plant. 
4. "2.3. Materials characterization"
   The section name should be changed to better describe what the section contains. In addition, information should be added about the equipment used in individual tests and the standards according to which the tests were prepared. 
5. Please standardize the units used in the article. On line 76 the density is given in g/cm³ and on line 135 in kg/m³. Units should be corrected according to the International System of Units (SI). 
6. "Figure 5. Compressive strength and flexural strength of the SAAC samples with different content of waste tire particles."
   Test results suggest irregularities in sample preparation or testing. The samples should not have results which, as the amount of additive increases, first increases, then decreases, then increases and decreases again...
7. How many samples of each type have been tested and what were the standard deviations of the results? The results shown as it stands suggest a single study of each type of sample which is unacceptable. 
8. "3. Results and Discussion"
   There should be more references to the results of other scientists in this section. In the literature review, the authors provide many examples of the use of waste rubber ... References and comparisons in the discussion with the results of other researchers will raise the rank of the article and confirm the obtained results. 
9. "Figure 9. SEM images"
   The magnification of 2,000 is a bit too small to properly show the microstructure of the samples or their structure and arrangement of the tobermorite crystals. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

Indeed, it's a well-designed and written article, I had studied the content thoroughly and wish to provide some constructive comments for improvement, hope authors will take my suggestions and improve the content flow.

Before results section

1. In title it's given as Sand based concrete, please see abstract first two words its written as Waste Tire/ Sand based, this will end in confusion, please check
2. What is the connection between freeze-thaw resistance and permeability, this need to be justified clearly.
3. In title freeze–thaw resistance and  impermeability performance : I suggest : Freeze-thaw resistance and impact on permeability or on similar words
4. Line 14: microstructure of composite materials were examined, which composite material?
5. Line 15:750-μm-sized waste tire particles on the surface of the SAAC composite did not agglomerate, but the titles focus is on different aspects, why this aggregation is given weightage and written in abstract. Abstract and conclusion should point clearly what authors found from their work.
6. Introduction ends abruptly, give few connecting sentences connecting research gap with authors work, this will improve the transition

Section 2:

1. Section 2.1 may be read by readers of many countries and hence authors are advised to provide the code used in this experiments or on what norms this experiments were done. Ex: IS 2720: Part IV
2. Line 72: Lime was ground limestone: Change this sentence to " Lime used in this study was natural limestone which is ground to required fineness"
3. Line 74 Actually why Gypsum is added specially?
4. Line 76, density seems to be very low, gypsum has more than 2 g/cc density, how this much reduction occurs?
5. Author need to put a line or sentence on what and how this measurements in 2.1 is done: Ex: The quartz content of the tailings sand was >90%: How they found this is not clear, be precise.
6. Line 79: Three different waste tire: change to Three different sizes of waste tire is used in this study.
7. Line 70-90 please provide on what country norms/ procedure this analysis is done; this is mandatory. If this are done by instrumentation, please mention that, if its done based upon literature, please cite that
8. Line 102: The mass loss rate was measured by  weighing the samples under thawing conditions: Is mass lass occurring in thawing condition?
9. What authors target in freeze-thaw test, strength reduction or mass loss, if its mass loss, what is its significance on field?
10. Line 111: "The samples were collected and wiped with a damp cloth  before they were weighed". I beg to differ in science behind this, keeping it for some time in dry condition might have helped.
11. Line 112-114: Where are those values ? XRD values missing, if its not being used why this sentence here? In figure 8 the XRD with various values of tire is mentioned, but control sample data is not there. Also I wonder how adding rubber in concrete varies its phase and I beg to differ from authors opinion on using this study here. May be if they had used a chemical or admixture, using XRD has real meaning
12. Line 115:SEM was used to investigate the section morphology of samples.: How authors prepared the sample for this should be mentioned. If you check line 122: These particles were reported on the surface of the SAAC sample, authors will understand why I am asking this and what is the validity of this.

Results and discussion

1. Line 121: The 2 mm particles were unevenly dispersed in the samples: Is it a problem due to improper mixing?
2. Line 125-6 are very obvious results right?
3. Line 130,137,138: The slump flow values  of the slurry increased and then decreased with the increasing of the particle sizes of the  waste tires: I am unable to interpret, figure lags clarity, please note that entry level researchers may study this too, make figures interpretable please. In X axis you gave as Samples I,II,III, what are they? It may be three different samples too, please make this clear in image.
4. Line 139-141 seems to be prejudice to my understanding, please put some science behind this by writing clearly interpretable sentence.
5. Line 139, is it a good compressive strength, I do understand that the strength of aerated concrete varies from 1.9-6, I suggest authors to write few lines on the values.
6. What is the difference between figure 3 and 4, its not so clearly written, please substantiate, provide legends properly to make understanding easier please.
7. Line 151 by weight of what?
8. Why the  750-μm sized rubber tire is given importance in the results and discussion, on what basis?
9. Section 3.3 needs scientific validity or previous literature reference, many sentences are very obvious and no scientific rigor exists unless its validated properly. (es:188-189)
10. Line 192-195, how authors measured it? or understood it.
11. Figure 7: Water absorption property of autoclaved aerated concrete (AAC) was investigated by capillary suction method normally, how authors studied this? The water absorption values seem to be on higher side, if authors say the pores are locked by the particles, why this happens?
12. Section 3.5 validity is questionable unless authors substantiate, in particular table 3.
13. Is value mentioned in line 252 correct? 1 mm? Pore size?
14. Why this three points only were selected to be mentioned in conclusion, I suggest improvement here.

Hope my comments will give some inputs to authors, they are requested to perform the corrections and resubmit before finalising.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Dear Authors,

I had seen the revised version, I feel this is sufficient to be accepted, I recommend accepting article in its present form