Phase Analysis of Alkali-Activated Slag Hybridized with Low-Calcium and High-Calcium Fly Ash
Round 1
Reviewer 1 Report
- Minor language spell check is required - line 41, 'of' is missing in 'amount incorporation'
- explain and differentiate 'sole slag' - (Line No.:35) and 'raw slag' (Line No.:43)
- For Fig. 2, 5, 6, 7 there is no unit in the Y axis.
- The activator used in this study was a 6M NaOH solution with a pH of 14.7-- is it 14.7? (Line No.:104)
- Temperature has to be specified for the '...ambient condition' - (Line No.:109) with typo error/Minor grammar error - 'stored in ambient conditions'
- In Table 1- hkl was in one of the headings where in the note section it is mentioned that 'hk refers to...'.
- Magnesium content was not mentioned in the materials section for FA-C fly ash, but effect is discussed here (Line No.:172)
- Fig. 5 - is it '80%FA+20%SL' or '50% FA-F or FA-C with 50% slag'?
- Figure 9 - various parts/ composition should be specified in the Fig. 9.
- FA-C with 19.2% CaO is used (Line No.:88) which exhibits cementitious properties (Line No.: 33); but in the conclusion, The low cementitious capability of alkali-activated FA-C may be attributed to the unstable N-C-A-S-H gel structure with concurrent high Na and Ca contents. The contradicting reason between the above has to be clearly given.
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Reviewer 2 Report
The research concerns the investigates the hydrated phase assemblage, microstructure, and gel composition of sodium hydroxide (NaOH)-activated fly ash-slag blends with either low-calcium or high-calcium fly ash. The results show that the nature of precipitated calcium-aluminosilicate-hydrate (C-A-S-H) and alkali aluminosilicate-hydrate (N-A-S-H) depends on the fly ash composition and slag-to-fly ash ratio.
The article is well written, I have no objections.
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Reviewer 3 Report
The work presented in this paper is technically sound and well organized. Please address the following comments.
1) Figure 1: Please specify the equipment and parameters used to perform laser diffraction to arrive at figure 1. Describe any sample prep or other relevant procedure in a succinct fashion.
2) Lines 110-117: This is the first instance when i have seen mixture design for AAMs defined in volumetric fashion. Generally they are presented as Na2O/solids. Could you please include a table that shows the mix designs by weight for each ingredient so that other research could replicate these mixtures for repeat or further studies.
3) The phrase "At such" is used instead of "As such" multiple times in the manuscript. Please correct thsoe errors.
4) Please justify the reason for choosing to evaluate mixtures after 1 and 28 days. Why not do another measurement at 7 or 14 days also so clearly define a trend. why pick just 1 and 28d....why not 1 and 14d or 1 and 7d.
5) Line 194 - the word should be "wider" or "larger" not "border".
6) Line 216: Explain what is basal spacing. This is a very technical term that certain readers might not be aware of. Please introduce the term in the manuscript to help a relatively novice reader in XRD.
7) Lines 229 - 240: There is lots of conjecture in this paragraph. Please site other studies that justify the postulations that are made. Otherwise, clearly specify that more research needs to be done to confirm these hypotheses.
8) Figure 9: Please mark a,b, c, and d on the figures. I am not sure which is b or c.
Good luck with all other reviews and I hope you get this published soon after making the appropriate changes.
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Reviewer 4 Report
In this paper, the phase assemblages of alkali-activated slag-high Ca fly ash and slag-low calcium Ca fly ash are systematically studied. The conversion of C-A-S-H and N-A-S-H is well discussed. Overall speaking, this is a very interesting paper.
- The literature review is not enough. This paper deals with the mix design of AAMs and the relationship with reaction products. A recently published paper has shown that thermodynamic simulation could determine the phase assemblages of AAMs, which could assist the material selection and mix design of AAMs. ("Analytical investigation of phase assemblages of alkali-activated materials in CaO-SiO2-Al2O3 systems: The management of reaction products and designing of precursors. Materials & Design, 194, p.108975.")
- The innovation of this study is not clear. The authors should explain the knowledge gap and how this study can help gain new insights into the problem.
- # Line 156. The statement may be wrong. C-A-S-H is poorly crystalline. N-A-S-H is a highly disordered phase. Zeolite is the crystalline form of N-A-S-H. However, based on most literatures, the alkali-activation cannot form the crystalline N-A-S-H.
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Round 2
Reviewer 4 Report
This paper has been revised based on the comments and should be ready for publication.
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