Rheological Properties and Flow Behaviour of Cement-Based Materials Modified by Carbon Nanotubes and Plasticising Admixtures
Round 1
Reviewer 1 Report
A well written paper on the effect of multiwalled carbon nanotubes on rheology of cement pastes inclusing the effect of different plasticizers.
I recommend to publish as it is.
As a minor comment I do not like smoothing of curves over the datapoints in plots as you can get artificial lows and highs between datapoints. I prefer straight lines connecting datapoints unless you can fit them to a function.
Author Response
First of all, we would like to thank you for the valuable reviewer’s comments which help to improve the quality of our paper in the future. We agree with you that the smoothing curves can cause some artificial lows and highs between datapoints. But in our research, we decided to use these types of curves, because our main aim was to established optimal MWCNT dosages. And, as we can observe from Figures in the manuscript, the degree of changes between nearby values of plastic viscosity and yield stress is not so high. Therefore, we considered that the smoothing type of curves can be suitable in this case.
Reviewer 2 Report
In this manuscript, Skripkiunas and his co-workers present a study of the rheological properties and flow behavior of cement-based materials modified by multi-walled carbon nanotubes and plasticizing admixtures, namely lignosulphonate (LS), sulfonated naphthalene formaldehyde condensate (NF) and polycarboxylate ether (PCE). This work is the continuation of their previous works: [28] G. Skripkiunas et al. 2019 IOP Conf. Ser.: Mater. Sci. Eng. 660 012032; [27] G. Skripkiunas et al. Advances in Materials Science and Engineering, Volume 2018, Article ID 8963542; [29] G. Skripkiunas et al. Journal of Silicate Based and Composite Materials, 2019/6, Vol. 71, No. 6, 184-189. Methods and materials in the current article are the same as in previous papers. These earlier articles, however, are very briefly mentioned in the introduction, as “Skripkiunas et al. [27-29] observed the increase in yield stress and plastic viscosity of nano modified cement paste as well”. I especially miss a critical comment on previous articles. Authors have to point out why are they studying the same system, and what is the aim of the current article in the context of previous studies. Some of the previous results are repeated in this article without citation. For example: the top curve in Figure 5 is exactly the same as the curve in Figure 1 of ref. [28]. References have to be provided when previously published results are quoted.
Additional comments:
--- Please explain the meaning of bwoc at its first appearance (by weight of cement)
--- line 15: not a MWCNT suspension, but a suspension containing both MWCNT and CMC was used. Please indicate correctly in the Abstract and the text.
--- line 22: insert respectively as “by 265 % and 107 %, respectively, in MWCNT”
--- keywords: it would be better to use “water bleeding” instead of simply “bleeding”
--- line 135: indicate correctly as “MWCNT/CMC” suspension with correct percentage.
--- line 440: the following sentence need explanation or correction: “the surface area of MWCNT is equal to 208.0 m2/g that is three orders more than for cement particles”. The three orders of magnitude means that the specific surface area of cement is smaller than 1 m2/g. Is this true? What is the surface area of cement particles?
--- The English of the manuscript should be improved.
Author Response
First of all, we would like to thank you for the valuable reviewer’s comments which help to improve the quality of our paper in the future.
Reviewers' comments
Reviewer: In this manuscript, Skripkiunas and his co-workers present a study of the rheological properties and flow behavior of cement-based materials modified by multi-walled carbon nanotubes and plasticizing admixtures, namely lignosulphonate (LS), sulfonated naphthalene formaldehyde condensate (NF) and polycarboxylate ether (PCE). This work is the continuation of their previous works: [28] G. Skripkiunas et al. 2019 IOP Conf. Ser.: Mater. Sci. Eng. 660 012032; [27] G. Skripkiunas et al. Advances in Materials Science and Engineering, Volume 2018, Article ID 8963542; [29] G. Skripkiunas et al. Journal of Silicate Based and Composite Materials, 2019/6, Vol. 71, No. 6, 184-189. Methods and materials in the current article are the same as in previous papers. These earlier articles, however, are very briefly mentioned in the introduction, as “Skripkiunas et al. [27-29] observed the increase in yield stress and plastic viscosity of nano modified cement paste as well”. I especially miss a critical comment on previous articles. Authors have to point out why are they studying the same system, and what is the aim of the current article in the context of previous studies. Some of the previous results are repeated in this article without citation. For example: the top curve in Figure 5 is exactly the same as the curve in Figure 1 of ref. [28]. References have to be provided when previously published results are quoted.
Authors: The citation of the previous results was added in the text of the paper. The present paper is a continuation of the previous papers. In comparison with other papers, it described the changes in rheological properties not only for one plasticizing admixture (PCE) (as it is presented in the research [28] G. Skripkiunas et al. 2019 IOP Conf. Ser.: Mater. Sci. Eng. 660 012032), but for 3 types (LS, NF and PCE). In the course of our research presented in 3 previous papers, we used the same materials and methodology as it is in the current research. However, there are differences. As for [27] G. Skripkiunas et al. Advances in Materials Science and Engineering, Volume 2018, Article ID 8963542, it shows the research on rheological properties of cement pastes with MWCNT and PCE plasticizer. The difference between this research and the present one is that we used other dosages of MWCNT and PCE for homogenization of MWCNT suspension. Moreover, we applied the Bingham model for approximation of the rheological results. This model is suitable for cement pastes, but Hershel-Bulkley model (which we used in our further researches) is more accurate for plasticized cement systems. The third article [29] G. Skripkiunas et al. Journal of Silicate Based and Composite Materials, 2019/6, Vol. 71, No. 6, 184-189 is more focused on the possibility to use the Hershel-Bulkley model for cement pastes modified by plasticizer and MWCNT suspension. To sum it up, the current research includes part of the previous results and methods, but it is a summary result on the rheology of nanomodified cement pastes in the presence of different types of plasticizing admixtures with an application of Herschel-Bulkley model and establishment of MWCNT dosages, which affect the rheological parameters of cement pastes. The corresponding clarification on the previous researches was added in the text.
Reviewer: Please explain the meaning of bwoc at its first appearance (by weight of cement).
Authors: The explanation was added in the text of the manuscript.
Reviewer: line 15: not a MWCNT suspension, but a suspension containing both MWCNT and CMC was used. Please indicate correctly in the Abstract and the text.
Authors: The corresponding clarification was added in the manuscript.
Reviewer: line 22: insert respectively as “by 265 % and 107 %, respectively, in MWCNT”.
Authors: The line 22 was corrected.
Reviewer: keywords: it would be better to use “water bleeding” instead of simply “bleeding”
Authors: The keyword was refined.
Reviewer: line 135: indicate correctly as “MWCNT/CMC” suspension with correct percentage.
Authors: The line 135 was corrected and refined, the abbreviation MWCNT/CMC was added throughout the manuscript.
Reviewer: line 440: the following sentence need explanation or correction: “the surface area of MWCNT is equal to 208.0 m2/g that is three orders more than for cement particles”. The three orders of magnitude means that the specific surface area of cement is smaller than 1 m2/g. Is this true? What is the surface area of cement particles?
Authors: The surface area of cement particles is about 3500 cm2/g= 0.35 m2/g that is less than 1 m2/g and, as we can see, significantly smaller than it is for MWCNT.
Reviewer: The English of the manuscript should be improved.
Authors: The English was checked and improved.
Reviewer 3 Report
The work is dedicated to the study of rheological properties and flow behaviour of cement-based materials modified by carbon nanotubes and plasticizing admixtures. The work is interesting, is easy to comprehend, and is well structured.
I have some minor aspects to refer in order to improve the quality of the manuscript.
1- Check the mathematical expression (line 184)
2- The test results should be more discussed and cited (if need).More (in general) and newer (in particular) literature sources should be studied and used to discuss the findings.
3- Moreover, what is lacking in the study would be a scientific understanding in the results obtained in the study.
4- Why do you select cement I 42.5 R?) for the study?, I would be very useful it you justify it in the article.
5- The Conclusions should also be extended according to the above suggestions.
6- In my opinion, also it would be appropriate to include several correlations between properties, and some statistical analysis to assess the possibilities of using
This manuscript is interesting and one of high quality and i suggeste to be published in your journal after this minor revisions.
Author Response
First of all, we would like to thank you for the valuable reviewer’s comments which help to improve the quality of our paper in the future.
Reviewers' comments
The work is dedicated to the study of rheological properties and flow behaviour of cement-based materials modified by carbon nanotubes and plasticizing admixtures. The work is interesting, is easy to comprehend, and is well structured. I have some minor aspects to refer in order to improve the quality of the manuscript.
Reviewer: 1- Check the mathematical expression (line 184)
Author:
According to EN, there are not any regulations on how to measure water bleeding of cement pastes. As a result, we studied water bleeding according to own methodology described in the manuscript with the application of the presented formula to calculate the coefficient of water bleeding. The calculation of this coefficient by volume gives the possibility to judge how MWCNT dosage affects the degree of water bleeding in plasticized cement paste.
Reviewer: 2- The test results should be more discussed and cited (if need). More (in general) and newer (in particular) literature sources should be studied and used to discuss the findings. 3- Moreover, what is lacking in the study would be a scientific understanding in the results obtained in the study.
We proposed our idea on the action mechanism of complex admixture based on MWCNT and plasticizer in the Discussion section of the paper, where highlighted the steric effect, surface area, distribution density effect and chemical interactions. As for new similar sources, unfortunately, there are not so much research work on the rheological properties of nanomodified cement systems in combination with plasticizing admixture. Among new similar sources can be mentioned the following publications (which have been cited in the manuscript): Ma, S.; Qian, Y.; Kawashima, S. Performance-based study on the rheological and hardened properties of blended cement mortars incorporating palygorskite clays and carbon nanotubes. Constr. Build. Mater. 2018, 171, 663-671. https://doi.org/10.1016/j.conbuildmat.2018.03.121; Souza, T.C.; Pinto, G.; Cruz, V.S.; Moura, M.; Ladeira, L.O.; Calixto, J.M. Evaluation of the rheological behavior, hydration process, and mechanical strength of Portland cement pastes produced with carbon nanotubes synthesized directly on clinker. Constr Build Mater. 2020, 248, 118686. https://doi.org/10.1016/j.conbuildmat.2020.118686; Paula, J.N.; Calixto, J.M.; Ladeira, L.O.; Ludvig, P.; Souza, T.C.C.; Rocha, J.M.; Melo, A.A.V. Mechanical and rheological behavior of oil-well cement slurries produced with clinker containing carbon nanotubes. J. Petrol. Sci. Eng. 2014, 122, 274–279. https://doi.org/10.1016/j.petrol.2014.07.020; Reales, O.A.M.; Jaramillo, Y.P.A.; Botero, J.C.O.; Delgado, C.A.; Quintero, J.H.; Filho, R.D.T. Influence of MWCNT/surfactant dispersions on the rheology of Portland cement pastes. Cem. Concr. Res. 2018, 107: 101–109. https://doi.org/10.1016/j.cemconres.2018.02.020 30 are more related to our research and they have been cited in the manuscript.
Some additional discussion and citation were added in the text of the manuscript.
4- Why do you select cement I 42.5 R for the study? It would be very useful if you justify it in the article.
Firstly, this type of cement was chosen due to the fact that it is more widely used cement in construction practice. Secondly, other types of cement with mineral additives is possible to use too, but it will give additional difficulties in interpretation of actions mechanisms of complex admixtures based on MWCNT, CMC and Pl in the cement paste. Rheological parameters of cement pastes are very sensitive to the type of additives and admixtures, particles sizes etc., they depend on a lot of factors, which is sometimes difficult to keep under control even for ordinary Portland cement without additives and admixtures. In other words, any modification of ordinary Portland cement by mineral additives creates additional difficulties in interpretation of the obtained rheological results.
5- The Conclusions should also be extended according to the above suggestions.
The conclusions were extended.
6- In my opinion, also it would be appropriate to include several correlations between properties, and some statistical analysis to assess the possibilities of using. This manuscript is interesting and one of high quality and I suggest to be published in your journal after this minor revisions.
As for rheological properties (yield stress, plastic viscosity), the definite MWCNT dosage which affects the yield stress and plastic viscosity were identified in the present research. Yield stress and plastic viscosity are changed not remarkably with increase of MWCNT up to definite dosage. The dependence between yield stress and shear rate (flow curves) were approximated by Hershel-Bulkley rheological model, the obtained equations for cement pastes with each MWCNT dosage in 5, 60 and 120 min after cement paste mixing can be sent as supplementary material. The statistical analysis was added for dependence between water bleeding and MWCNT dosage.
Reviewer 4 Report
This paper investigated the rheological properties of cement modified by MWCNT with different plasticizing admixtures. Experiments are well designed and results are discussed in details. In the discussion section, more related references which show similar work to validate the results are suggested.
Author Response
Thank you for your valuable comments. Unfortunately, there are not so much researches on the rheological properties of cement pastes modified by nanotubes and plasticizing admixtures. The similar research performed by
Ma, S.; Qian, Y.; Kawashima, S. Performance-based study on the rheological and hardened properties of blended cement mortars incorporating palygorskite clays and carbon nanotubes. Constr. Build. Mater. 2018, 171, 663-671. https://doi.org/10.1016/j.conbuildmat.2018.03.121;
Souza, T.C.; Pinto, G.; Cruz, V.S.; Moura, M.; Ladeira, L.O.; Calixto, J.M. Evaluation of the rheological behavior, hydration process, and mechanical strength of Portland cement pastes produced with carbon nanotubes synthesized directly on clinker. Constr Build Mater. 2020, 248, 118686. https://doi.org/10.1016/j.conbuildmat.2020.118686;
Paula, J.N.; Calixto, J.M.; Ladeira, L.O.; Ludvig, P.; Souza, T.C.C.; Rocha, J.M.; Melo, A.A.V. Mechanical and rheological behavior of oil-well cement slurries produced with clinker containing carbon nanotubes. J. Petrol. Sci. Eng. 2014, 122, 274–279. https://doi.org/10.1016/j.petrol.2014.07.020;
Reales, O.A.M.; Jaramillo, Y.P.A.; Botero, J.C.O.; Delgado, C.A.; Quintero, J.H.; Filho, R.D.T. Influence of MWCNT/surfactant dispersions on the rheology of Portland cement pastes. Cem. Concr. Res. 2018, 107: 101–109. https://doi.org/10.1016/j.cemconres.2018.02.020 30
are more related to our research and they have been cited in the manuscript.
