The Effect of Recycled Sand on the Tensile Properties of Engineered Cementitious Composites

Round 1

Reviewer 1 Report

The paper may be accepted.

Author Response

Thank you very much for the comment.

Reviewer 2 Report

This paper presents systematic research on the feasibility of replacing natural sand with recycled sand to enhance the mechanical property of ECC. This innovative work relates the mechanical performance vs. mesoscale tests and microstructure. Such multi-scale research supplies an informative guideline for applying ECC in practice. The paper's content is within the journal's scope, and the findings and innovation of this study are interesting and worth publishing. The experimental procedure is correctly conducted and described with sufficient data. This paper is suggested to be accepted after minor revision. Some comments for the authors are as follows:

 

1- Abstract

Sufficient information is illustrated in the abstract, but a more concise version is highly recommended to improve the quality of the abstract. Further, scientific data are more appreciated than the simple literal description, supplying readers with a more visualized and precise impression.

 

2- Title

The title is suggested to be improved consistently by consistent with the research content.

 

3- Figures and tables

Figure 1 and 11, and Table 1 is warranted to improve.

Table 4 has added no further information in the text. It could be deleted.

Figure 17 -19 should add more information to explain the relationship between the rates of the fracture area vs. the fracture energy vs. crack propagation. This section is not clear

4- Conclusion

 

Please rewrite this section more logically, i.e., point out the main contributions one by one.

Author Response

This paper presents systematic research on the feasibility of replacing natural sand with recycled sand to enhance the mechanical property of ECC. This innovative work relates the mechanical performance vs. mesoscale tests and microstructure. Such multi-scale research supplies an informative guideline for applying ECC in practice. The paper's content is within the journal's scope, and the findings and innovation of this study are interesting and worth publishing. The experimental procedure is correctly conducted and described with sufficient data. This paper is suggested to be accepted after minor revision. Some comments for the authors are as follows:

1- Abstract

Sufficient information is illustrated in the abstract, but a more concise version is highly recommended to improve the quality of the abstract. Further, scientific data are more appreciated than the simple literal description, supplying readers with a more visualized and precise impression.

Thanks for your valuable comments，We have revised the abstract with more concise version and scientific data. The details are shown in following.

This research aims to investigate the feasibility of replacing natural sand (NS) with recycled sand (RS) to enhance the mechanical property of engineered cementitious composites (ECC). For comparative study, ECCs incorporating natural sands (NS) and recycled sands with different sieve sizes were taken as experimental subjects. The results demonstrated RS-ECC possessed better tensile properties featuring saturated cracks and superior strain-hardening behavior than that of NS-ECC. The highest tensile strain capacity of RS-ECC was up to 7%. Meanwhile, the compressive and flexural strengths of RS-ECC are over 50MPa and 20MPa. The pseudo-strain hardening(PSH) index of RS-ECC-20grid and RS-ECC-12grid are 141 and 201, which increase by 46% and 70% than that of NS-ECC. Furthermore, the thicker weak ITZ and comparatively aggregate/ITZ ratio were found in the RE-ECC by microstructure test, which revealed and explained the mechanism for the lower matrix fracture toughness of RS-ECC.

2- Title

The title is suggested to be improved consistently by consistent with the research content.

Thanks for the comment, we have changed the title to “The effect of recycled sand on the tensile properties of engineered cementitious composites”.

3- Figures and tables

Figure 1 and 11, and Table 1 is warranted to improve.

Thanks for the comment. The Figure 1 was remapped and the details were shown in Figure 1.

Table 4 has added no further information in the text. It could be deleted.

Thanks for the comment. To give a detail information of experiment, we would like to keep the Table 4. Thank you for understanding this.

Figure 17 -19 should add more information to explain the relationship between the rates of the fracture area vs. the fracture energy vs. crack propagation. This section is not clear

Thank you for the comments. In this section, the experiment result demonstrates most enhancement rates of the fracture area range from 3%-7%, which are considered of little influence on the fracture energy at such a large scale. The suppose about the RS-ECC with a fracture surface with a smaller area is excluded. Thus, the relationship between the above three in the question were not discussed in the paper.

4- Conclusion

Please rewrite this section more logically, i.e., point out the main contributions one by one

Thanks for the valuable comment. We rewrite the conclusion. The details are shown in following.

In the present research, the effect of recycled sand on the mechanical properties of engineered cementitious composites (ECC) was investigated. The strain-hardening mechanism of ECC with recycled sand was explored by the scanning electron microscope (SEM) and nano-indentation tests. The following conclusion could be obtained:

• The ECC with RS showed excellent tensile ductility with a tensile strain of 7%, which is greater than that of ECC with NS. Furthermore, incorporation of RS into ECC maintained the same tensile strength with that of NS-ECC.
• The compressive and flexural strength of ECC were over 50 MPa and 20MPa. The addition of RS did not cause a significantly loss of the compressive and flexural strength, compared with that of ECC with NS.
• The addition of RS decreased the matrix toughness and kept the fiber-bridging capacity constant. The pseudo-strain hardening(PSH) of RS-ECC showed a highest value, which would benefit tensile ductility. The main reason for this was the old residual mortar around the RS increased the gap of elastic modulus between sand and ITZ, which decreased the matrix toughness and improved the tensile ductility.

Author Response File: Author Response.docx

Reviewer 3 Report

This paper presents an experimental study on the influence of recycled sand on mortars with polymeric fibers, with relevance to the degree of sand fineness. The paper is relatively well exposed, although there are numerous studies on the replacement of natural sand by recycled sand in mortars, little has been clarified in the ECC. Therefore, the study enriches knowledge on the topic of recycling x ECC.

 

Major comments

 

There are several minor spelling errors that must be corrected. 

Some figures, such as 3 and 4, are not necessary, as they show tests and specimens that are described in various technical standards. It is enough to cite the test methods standards used.

There is a preciousness in the resistance values, in two decimal places of some results.

In the conclusion chapter, the RS characteristics that offered the most favorable results should also be highlighted.

 

Minor comments

On page 3, line 93, the term volume fracture is used. To avoid any misunderstandings, I think that it is just the volume of fibers incorporated into the mixtures. Fracture is a confusing term. Please explain what do you mean?

 

When the crack number are presented in table 5, the values 44.5, 37.1 and the others, seem bizarre and do not seem to have physical meaning. What do you mean by these crack count decimal numbers?

 

On page 3, line 93, the term volume fracture is used. To avoid any misunderstandings, I think that it is just the volume of fibers incorporated. Fracture is a confusing term. Please explain what do you mean?

 

When average results are presented and discussed, it is important that they are accompanied by their respective standard deviations. Thus, it is easier to see if the differences are significant.

Author Response

This paper presents an experimental study on the influence of recycled sand on mortars with polymeric fibers, with relevance to the degree of sand fineness. The paper is relatively well exposed, although there are numerous studies on the replacement of natural sand by recycled sand in mortars, little has been clarified in the ECC. Therefore, the study enriches knowledge on the topic of recycling x ECC.

 

There are several minor spelling errors that must be corrected.

Thank you for the comment. We have rechecked the paper and correct the spelling errors.

 

Some figures, such as 3 and 4, are not necessary, as they show tests and specimens that are described in various technical standards. It is enough to cite the test methods standards used.

Thanks for the comment. We have revised the question following with your comment. 

 

There is a preciousness in the resistance values, in two decimal places of some results.

Thanks for the comment. We have revised the question in the revised-manuscript.

 

In the conclusion chapter, the RS characteristics that offered the most favorable results should also be highlighted.

Thanks for the valuable comment. We have rewrite the conclusion and the details is as follows:

In the present research, the effect of recycled sand on the mechanical properties of engineered cementitious composites (ECC) was investigated. The strain-hardening mechanism of ECC with recycled sand was explored by the scanning electron microscope (SEM) and nano-indentation tests. The following conclusion could be obtained:

(1)   The ECC with RS showed excellent tensile ductility with a tensile strain of 7%, which is greater than that of ECC with NS. Furthermore, incorporation of RS into ECC maintained the same tensile strength with that of NS-ECC.

(2)   The compressive and flexural strength of ECC were over 50 MPa and 20MPa. The addition of RS did not cause a significantly loss of the compressive and flexural strength, compared with that of ECC with NS.

(3)   The addition of RS decreased the matrix toughness and kept the fiber-bridging capacity constant. The pseudo-strain hardening(PSH) of RS-ECC showed the highest value, which would benefit the tensile ductility. The main reason for this was the old residual mortar around the RS increased the gap of elastic modulus between sand and ITZ, which decreased the matrix toughness and improved the tensile ductility.

 

Minor comments

 

On page 3, line 93, the term volume fracture is used. To avoid any misunderstandings, I think that it is just the volume of fibers incorporated into the mixtures. Fracture is a confusing term. Please explain what do you mean?

Thanks for the valuable comment. That is a spelling mistake, which should be the volume fraction. The mistake has been corrected in the revised-manuscript.

 

 

When the crack number are presented in table 5, the values 44.5, 37.1 and the others, seem bizarre and do not seem to have physical meaning. What do you mean by these crack count decimal numbers?

Thanks for the comment. The crack number is the average value of 12 specimens, which really has no physical meaning. We have modified the crack number to be an integer.

 

On page 3, line 93, the term volume fracture is used. To avoid any misunderstandings, I think that it is just the volume of fibers incorporated. Fracture is a confusing term. Please explain what do you mean?

Thanks for the valuable comment. That is a spelling mistake, which should be the volume fraction. The mistake has been corrected in the revised-manuscript.

 

When average results are presented and discussed, it is important that they are accompanied by their respective standard deviations. Thus, it is easier to see if the differences are significant.

Thanks for the valuable comment. In fact, we have added the variance to the important experimental data, as shown in Figure 11 and Table 8. Although some data have no variance, the data of all specimens are given in table, such as Table 9. We have added variance or listed the data of all specimens in the important data. We do not think it is necessary to list the variance of all data.

Author Response File: Author Response.docx

Reviewer 4 Report

The article is interesting and shows important solution of used recycled sand.

I recommend expanding conclusions. Much research has been carried out and the conclusions do not reflect this. Please quote the current literature, currently the latest one is from 2018.

Author Response

The article is interesting and shows important solution of used recycled sand.

 

I recommend expanding conclusions. Much research has been carried out and the conclusions do not reflect this. Please quote the current literature, currently the latest one is from 2018.

Thanks for the valuable comments. We have rewrite the conclusion and the details of conclusion is as follows. We have supplied some recent papers in the revised-manuscript.

In the present research, the effect of recycled sand on the mechanical properties of engineered cementitious composites (ECC) was investigated. The strain-hardening mechanism of ECC with recycled sand was explored by the scanning electron microscope (SEM) and nano-indentation tests. The following conclusion could be obtained:

• The ECC with RS showed an excellent tensile ductility with a tensile strain of 7%, which is greater than that of ECC with NS. Furthermore, incorporation of RS into ECC maintained the same tensile strength with that of NS-ECC.
• The compressive and flexural strength of ECC were over 50 MPa and 20MPa. The addition of RS did not cause a significantly loss of the compressive and flexural strength, compared with that of ECC with NS.
• The addition of RS decreased the matrix toughness and kept the fiber-bridging capacity constant. The pseudo-strain hardening(PSH) of RS-ECC showed a highest value, which would benefit the tensile ductility. The main reason for this was the old residual mortar around the RS increased the gap of elastic modulus between sand and ITZ, which decreased the matrix toughness and improved the tensile ductility.

Author Response File: Author Response.docx

Reviewer 5 Report

The manuscript represents a valuable contribution in terms of experimental results and thus it can be published if the authors wish to consider some minor revisions

- better explanation of the research significance and novelty of the work is needed in the introduction

- can the authors provide further details of the fresh state properties and specimens preparation methods?

- deeper analysis in section 3 is recommended

- conclusions should be re-written, better highlighing the relevant conclusions driven from the research work rather than just summarizing it

- review english

Author Response

The manuscript represents a valuable contribution in terms of experimental results and thus it can be published if the authors wish to consider some minor revisions

 

- better explanation of the research significance and novelty of the work is needed in the introduction

Thanks for the valuable comment. We have supplied the significance of recycled sand in the introduction.

 

- can the authors provide further details of the fresh state properties and specimens preparation methods?

Thanks for the comment, the fresh state properties of specimens were not tested. We will test the fresh state properties in the future research. As for the specimen preparation methods, the specimens preparation methods and mix proportion are shown in section 2.2 and Table 1.

- deeper analysis in section 3 is recommended

Thank you for the comments. The section 3 contains many content, which can be time-consuming to revise. Moreover, we have analyzed the effect of RS on the ECC from the aspects of mechanical properties, mesoscopic tests and microscopic tests. We think that the current analysis can reasonably explain the effect of RS on the ECC. We hope you understand this. Thank you.

 

- conclusions should be re-written, better highlighing the relevant conclusions driven from the research work rather than just summarizing it

Thank you for the valuable comment, we have re-written the conclusion following your comments. The detail are as following:

In the present research, the effect of recycled sand on the mechanical properties of engineered cementitious composites (ECC) was investigated. The strain-hardening mechanism of ECC with recycled sand was explored by the scanning electron microscope (SEM) and nano-indentation tests. The following conclusion could be obtained:

(1)   The ECC with RS showed an excellent tensile ductility with a tensile strain of 7%, which is greater than that of ECC with NS. Furthermore, incorporation of RS into ECC maintained the same tensile strength with that of NS-ECC.

(2)   The compressive and flexural strength of ECC were over 50 MPa and 20MPa. The addition of RS did not cause a significantly loss of the compressive and flexural strength, compared with that of ECC with NS.

(3)   The addition of RS decreased the matrix toughness and kept the fiber-bridging capacity constant. The pseudo-strain hardening(PSH) of RS-ECC showed a highest value, which would benefit the tensile ductility. The main reason for this was the old residual mortar around the RS increased the gap of elastic modulus between sand and ITZ, which decreased the matrix toughness and improved the tensile ductility.

- review english

Thank you, we have rechecked the paper and revised some spelling mistake.

Author Response File: Author Response.docx