Utilisation of Recycled Silt from Water Treatment and Palm Oil Fuel Ash as Geopolymer Artificial Lightweight Aggregate

Round 1

Reviewer 1 Report

The authors present an interesting research topic that can be published after the authors take the following comments into account.

- shortening the content of the descriptions in this work (introduction, description of tests and the results)

- considering removing information which is not essential for the topic and discussion;

- checking the description of samples (Table 3 and Fig. 4-8)

- improvement/rewriting of conclusions

- correction of language errors

Author Response

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Reviewer 2 Report

The article presents an interesting method to reuse two types of wastes as raw materials in obtaining lightweight aggregates. Although the results are promising, some other tests might be at least proposed in the article (for example: Los Angeles test). Also, the Conclusions chapter can provide future directions, as for example obtaining and testing cement samples. Moreover, the past tense used throughout the article makes everything peculiar and hard to follow. Also, some small observations are presented as follows:

- line 59: ”Malaysia is the largest” instead of ”Malaysia is a largest”;

- line 75: please rephrase;

- line 116: the phrase should end with a punctuation;

- line 133: ”compared to” instead of ”compared with”;

- lines 148-155: the subchapter title and the paragraph is the same as those from lines 138-145;

- Table 2: how come NaOH contains more SiO2 than Na2O?

- More details could be presented, about the used instruments: at least for SEM, XRD, XRF;

- line 223: ”a round” instead of ”around”;

- line 229: preheating temperature is 450 oC while Table 4 presents this temperature to be 400 oC;

- line 230: sintering time is 1 hour while Table 4 presents this time to be 30 minutes long;

- line 250: please rephrase;

- line 269: please rephrase;

- line 275: please rephrase;

- line 300: ”the share of activated POFA increased” instead of ”the activated POFA increased”;

- line 301: please rephrase;

- lines 364-365: please rephrase;

- lines 370-371: please rephrase;

- line 377: ”compressive strength” instead of ”crushing strength”;

- please rephrase this expression throughout the article: ”This result was due to that the”;

- Chapter 4 might be named ”Conclusions” since more than one conclusion is presented;

- lines 501-504: please se subscript in chemical formulas;

- line 504: please separate the last two words;

- line 509: please separate the last few words;

- line 528: coat?

Author Response

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Reviewer 3 Report

-We live now in a climate emergency so its most strange that the authors have not start the paper by mentioning exactly that. It seems that they are not aware about the words of a Professor of Physics at the University of Oxford authored a paper where one can read the following:

 “Let’s get this on the table right away, without mincing words. With regard to the climate crisis, yes, it’s time to panic”

Pierrehumbert, R., 2019. There is no Plan B for dealing with the climate crisis. Bulletin of the Atomic Scientists, pp.1-7.

So please start the introduction by draw a connection between environmental degradation,  resource efficiency, and waste recycling

 

- remove the word sustainable in the title. The article has no life cycle analysis or at least a carbon footprint study

 

-Add the word geopolymer to the title

 

- In the introduction the authors cite references 15 and 19 in what concerns previous geopolymer mixtures but fail to cite some of the many works already produced on geopolymer mixtures with  palm oil fuel ash (POFA). That way is not possible to assess the originality of the current investigation

 

- Authors wrote that the sodium hydroxide molarity has chosen due to recommendations on references 20 and 21. But the fact is that those references do not concern geopolymer mixtures with  palm oil fuel ash (POFA). So why have authors not use as recommendation molarity the one already studied in similar mixtures ?

Author Response

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Round 2

Reviewer 1 Report

I would like to thank the authors for editing the content of the paper, which in my opinion contributes to better understanding of it by a reader.

Unfortunately, the work still contains mistakes/errors (grammar, speeling). Especially in the following parts: abstract, introduction and point 2, although there are also minor errors in the rest of the work.

Other comments for improvement

• point 3.1. the density of materials in the content of the work is expressed in g/cm3, while in Fig. 4, as well as in Fig. 5, it is expressed in kg/m3; are these data correct?
• in table 4 the time “1 day” is given; could the autors put the number of hours, as below in this table it is done for sintering.
• the authors very often use the expression "due to that .." which is not always correct.
• point 3.3, line 473/474 - is this sentence the result of SEM research?
• line 541 "Kyanite was detected ... more than 30%"?
•  in conclusions: line 556-557, point iii, line 573-575, line 600

 

Author Response

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Round 3

Reviewer 1 Report

in Fig. 9:  there is Mpa, should be MPa

line 149: NaOH molecular weight is not 30 g/mol, but 40 g/mol

line 170: potassium oxide (K₂O),

lines 198-199: This particle showed..... filler  particles.?

lines 226/227: The fresh granular particle?  .. it was not a sample?

Author Response

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