An Experimental Study on Electrical Properties of Self-Sensing Mortar

Round 1

Reviewer 1 Report

Although the research subject is of some interest and the experimental program is fair, the overall quality of the paper prevents its publication. The major criticism is the general lack of results discussion (the exception is XRD). Further, the introduction mainly consists of information from other studies, however presented separately, with no articulation between findings from different studies. The last paragraph of the introduction, besides being poorly organized, is a repetition of the penultimate paragraph.  

It is not clear that the authors understand the difference between concrete and mortar, as well as between resistance and resistivity. It is also not clear the research goal., as the goal disclaimed in the abstract does not match with the one presented in the introduction. 

The fibre content is not clear from the beginning, as the information that it concerns a volumetric ratio is only provided in 2.1.1. 

Another relevant issue is the ratio between the specimens and the wire meshes. 

It is not clear whether the strain was measured between two consecutive meshes or did the measuring fields encompass any mesh(es) 

Information on room temperature and relative humidity is lacking for air curing. 

2.2.2 consists of repeated information (from the last part of 2.2.1. 

Regular UTMs consist of several parts, among them load cells, whose purpose is to measure the sustained force. Then measuring load with a UTM may be not 100% wrong but surely is not precise. 

It is not clear the total volume of fibre blend considered in 2.4 

In 3.2.1 the results are not presented for all mixes and it is not clear why this happens. Furthermore, it is confusing the reference to a third-party work for figure 9 and 10. Why not authors’ results? Besides, consulting the cited reference, those results are not found. 

Reading carefully, nothing is mentioned about the content of CF SEM images. 

Anyone with a basic knowledge on carbon fibres does not need an EDS to know that the most abundant element in CF is carbon. 

The amount of silica found in carbon fibres at 600ºC must be thoroughly discussed. 

Editorial comments 

Ln 36 Finally instead of “Finely” 

Ln 61-64 Confusing sentence 

Ln 100 “percent” is redundant 

Ln 132-133 strengthen the strength is awkward 

Ln 151 a 10 m diameter fibre ? 

Ln 158 “x” are missing 

Ln 164-165 confusing sentence 

Ln 208 It is believed that this section mainly concerns the presentation of results 

Figure 7a) part of the legend is missing 

Ln 397 brass fibres? 

Ln 454 C2S and C3S stand for dicalcium silicate and tricalcium silicate, respectively 

All things considered, a new manuscript shall be prepared and submitted. 

Author Response

Responses to Reviewer comments

The authors sincerely thank the editor and the three reviewers for their constructive comments. All of their comments have been carefully considered and, wherever appropriate, revisions have been made to the manuscript. Responses to these comments and revisions implemented in the paper are detailed below. The Reviewers’ comments are in italic black fonts while our replies are in blue. Text changed in the manuscript is highlighted in green.

Reviewer 1

Although the research subject is of some interest and the experimental program is fair, the overall quality of the paper prevents its publication.

The suggestions for this manuscript are listed below:

(Q1) The major criticism is the general lack of results discussion (the exception is XRD).

(A1) We thank the reviewer for this valuable comment. As per the suggestion, changes have been made in the results and discussion.

The compressive strength of the mortar was higher when smart mortar was used. This is due to the presence of steel grids embedded into the mortar specimen. The fibres added to the mortar improved the compressive strength, and the additional increase was caused by the presence of steel grids.

Since the optimization of brass fibres was performed by electrical measurements, the optimised percentage was concluded as 0.25% volumetric ratio. Whereas the compressive strength was observed to be high for 0.30% volumetric ratio. Similarly, while comparing air-cured specimen results with water-cured specimen results, it was observed that the water-cured specimens conduct more electricity, which yields better electrical resistance values. Hence, in water curing, the self-sensing ability of the mortar is high due to the entrapped moisture inside the specimen. The compressive strengths was also higher when the specimens was subjected to water curing.

(Q2) The introduction mainly consists of information from other studies, however, presented separately, with no articulation between findings from different studies.

(A2) We thank the reviewer for this valuable comment. As per the suggestion, changes have been made in the introduction.

Several types of conductive fillers have been used in past studies conducted by the researchers. One such conductive filler is intrinsic self-sensing concrete. From the extensive review made on intrinsic self-sensing concrete (ISSC), It is concluded that the ISSC has many advantages, like enhanced mechanical properties, high sensitivity, and easy installation [1]. Similarly, carbon fibres was used widely in the previous researches conducted. Carbon fibres added to the mortar by 0.7% weight of cement along with 2.5% graphite by the weight of cement produced an effective smart mortar with higher sensitivity to stress and strain [5]. A Piezoresistivity cement-based stress or strain sensor [PCSS] was produced with the addition of carbon fibre and carbon black. The relationship between stress or strain and the fractional change in electrical resistivity was determined as Δ =-0.022ε (Δ =-1.35σ) [6]. Carbon fibres and multiwall carbon nanotubes incorporated into reinforced cement concrete beams of length 1000 mm, width 100 mm, and depth 150 mm resulted in better behaviour with the addition of carbon fibres than carbon nanotubes. Results showed that the addition of carbon fibres improved the load-carrying capacity and ductility with a higher sensitivity to the electrical resistance of the beam [11]. Carbon fibres of 5mm length was added in cement mortar at a 0.2% to 0.5% volumetric ratio. A similar and linear relationship was found between stress vs strain and resistance vs strain graphs [15]. Carbon fibres with a length of 5mm-7mm at a dosage of 0.5% to 10% by mass of cement reinforced in cement mortar improved piezoresistive behaviour. The surface resistance is high at initial impact and then reduces drastically at 5–40 impacts due to the loss of connection between distributed fibres [24]. Hybrid micro steel and carbon fibres added to cement mortar improved the conductivity of the mortar since the hybrid fibres have better dispersion in the cement matrix when compared to monofibres [45].

The other type of conductive filler is brass fibre. Similarly, when brass fibres from the electrical discharge machining process was added to cement mortars, they improved the flexural strength with a reduction in compressive strength [13]. The addition of brass fibres of greater length and in larger amounts increases the thermal conductivity of the cement mortar [14]. Brass fibres added to the cement mortar with a fibre content of 0.25% volumetric ratio improved the piezoresistivity of the mortar [37]. Brass fibres was added to the concrete as conductive fillers along with crushed limestone aggregate as coarse aggregate. Crushed limestone 0-5 mm was used 60% time in the concrete mix, and 40% of crushed limestone of size 5-15 mm was used. The better piezoresistivity was observed in compressive and tensile loading conditions [47]. When brass fibres was added to the concrete, a linear relationship was observed between electrical resistivity and temperature, with the temperature ranging between 25 °C and 50 °C. Hence, after 150 °C, the electrical resistivity changes dramatically and hence can be used as a fire alarm sensor [50]. Another invention in conductive filler is carbon nanotube. Use of electrostatic self-assembled carbon nanotubes and carbon black to create self-sensing concrete resulted in reduced compressive strength with an increase in flexural strength and electrical conductivity of cement mortar [7]. Effective dispersion of multi-walled carbon nanotube (MWCNT) is achieved by the use of low-concentrated dispersive additives along with sonication [20]. Carbon nanotubes added to cement mortar subjected to repeated compressive and impulsive loading showed a linear relationship between loading and electrical resistance, which can be effectively used for traffic monitoring [21]. Similarly, Carbon nanofibres reinforced reactive powder concrete was formed with the addition of silica fume, and fine and coarse quartz sand along with conventional constituents. When compared to carbon nanofibres added to mortar, carbon nanofibres reinforced in reactive powder concrete are more conductive and sensitive [33]. Carbon nanofiber-added specimens tested at AC voltage was more stable than specimens tested at DC voltage with a fibre dosage greater than 2.5% volume of cement [34]. Also, the addition of carbon black to the cement mortar up to 4% of cement mass improved the mechanical properties, whereas the addition of carbon black by 7–10% of cement mass improved the piezoresistive properties [8]. Graphene nanoplatelets (GNP) and carbon black (CB) was used to make self-sensing cementitious composites. The use of these nanomaterials improved the electrical resistivity and durability of the materials [10].

Analysis of the axial and torsional free vibrations of cantilever and doubly clamped nanobeams serves to demonstrate the effectiveness of the stress-driven mixture [51]. The thermal characterization of Nylon 6 based nano-composite (NC) material was carried out, which resulted in effective dispersion of the fibres with high thermal resistivity [52]. Cement mortar specimens with photopolymers or titanium alloy fibres was prepared and short beam shear tests was carried out. The results showed that the surface roughness affects the energy absorption of the material [53].

(Q3) The last paragraph of the introduction, besides being poorly organized, is a repetition of the penultimate paragraph.

(A3) We thank the reviewer for this valuable comment. As per the suggestion, changes have been made in the last paragraph to avoid repetition.

(Q4) It is not clear that the authors understand the difference between concrete and mortar, as well as between resistance and resistivity.

(A4) We thank the reviewer for this valuable comment. The difference between concrete and mortar is understood whereas by mistake it was written as concrete instead of mortar in a few places which are being corrected now. Similarly, resistance is the physical property of a material to oppose the current whereas resistivity is in particular to an object with specific dimensions. Hence the word resistance, in general, is used throughout the paper and the changes are made wherever applicable.

(Q5) It is also not clear the research goal., as the goal disclaimed in the abstract does not match the one presented in the introduction.

(A5) We thank the reviewer for this valuable comment. As per the suggestion, changes have been made in the introduction that matches the abstract.

The objective of this research is to determine the self-sensing ability of mortars with the addition of two different types of fibres with varying fibre content. Smart mortar was made with the addition of brass fibres with the volumetric ratios of 0%, 0.10%, 0.15%, 0.20%, 0.25%, and 0.30%. These specimens was subjected to compression loading.

 (Q6) The fibre content is not clear from the beginning, as the information that it concerns a volumetric ratio is only provided in 2.1.1.

(A6) We thank the reviewer for this valuable comment. With the reviewer’s suggestion, fibre content has been mentioned clearly in section 2.1.1.

The brass fibres was added to the mortar mix with different fibre percentages of 0%, 0.10%, 0.15%, 0.20%, 0.25%, and 0.30% by volume.

(Q7) Another relevant issue is the ratio between the specimens and the wire meshes.

(A7) We thank the reviewer for this valuable comment. As per the suggestion information on wire, meshes is added in section 2.2

The four-probe method was used in this experimental study in which four steel meshes was inserted into each cubical specimen at an equal spacing between them.

 (Q8) It is not clear whether the strain was measured between two consecutive meshes or did the measuring fields encompass any mesh(es)

(A8) We thank the reviewer for this valuable comment. Strain measurements was taken with strain gauges mounted on either side of the cubical specimens. The grids placed are only for the electrical measurements. It is already mentioned in section 2.3.

(Q9) Information on room temperature and relative humidity is lacking for air curing.

(A9) We thank the reviewer for this valuable comment. As per the suggestion temperature and humidity details are added in the materials and methods section.

(temperature is 28℃ and the relative humidity is 50%)

(Q10) 2.2.2 consists of repeated information from the last part of 2.2.1.

(A10) We thank the reviewer for this valuable comment. Both these sections are the preparation of mortar with brass fibres and hybrid fibres added to the mortar. Few of the steps are similar in the preparation process and hence they are similar. With the permission of the reviewer, we would like to retain the sentences in both processes.

(Q11) Regular UTMs consist of several parts, among them load cells, whose purpose is to measure the sustained force. Then measuring load with a UTM may be not 100% wrong but surely is not precise.

(A11) We thank the reviewer for this valuable comment. The error of the UTM that was used in this study is 0.5%

(Q12) It is not clear the total volume of fibre blend considered in 2.4

(A12) We thank the reviewer for this valuable comment. The optimized brass fibre addition was obtained at a volumetric ratio of 0.25% and the optimized hybrid brass - carbon fibre addition was obtained at a volumetric ratio of 95% brass fibres and 5% carbon fibres. The 95% brass fibres added was of 0.25% volumetric ratio and the 5% carbon fibres added was of 0.24% volumetric ratio.

The volumetric ratio of brass fibres added was 0.25% to its volume and carbon fibres added was 0.24% to its volume.

(Q13) In 3.2.1 the results are not presented for all mixes and it is not clear why this happens.

(A13) We thank the reviewer for this valuable comment. Since the number of graphs was more, the results of all mixes was not presented in the paper. With the reviewer’s suggestion, the results for all the mixes are presented in the revised paper.

(Q14) It is confusing the reference to a third-party work for figure 9 and 10. Why not authors’ results?

(A14) We thank the reviewer for this valuable comment. As the reviewer mentioned, those are similar to the work carried out by the same author as in reference number 37 but the citation was mistakenly numbered wrong. It is now corrected in the revised manuscript.

(Q15) Nothing is mentioned about the content of CF SEM images.

(A15) We thank the reviewer for this valuable comment. As per the suggestion details about CF SEM images have been added to the revised manuscript.

The SEM images of carbon fibres at different temperatures showed that the surface texture of the carbon fibres changes as the temperature increases. At 600 °C, the fibres get burnt and the ash particles was seen on the fibre strands. At 800 °C, the fibres was burnt mostly, and hence only the ash particles was observed in the image.

(Q16) The amount of silica found in carbon fibres at 600ºC must be thoroughly discussed

(A16) We thank the reviewer for this valuable comment. Mistakenly the figures was titled wrongly which is changed in the new manuscript. The high silica is found in carbon fibres at 800℃.

The presence of silica, oxygen, calcium, and aluminium is due to the burning of carbon fibres into ash form since ash particles was found only at these two temperatures.

Author Response File: Author Response.docx

Reviewer 2 Report

In the Abstract section, it is recommended to justify the relevance of the research.

Line 99-120. A description of the course of the experiment and the materials used is given, which duplicates the information given in section 2. Materials and Methods. Repeat the description is recommended to be removed

In section 2, add data on the Scanning Electron Microscope

Line 151. Carbon fiber fiber diameter is incorrect.

 Line 176. In Fig.3 it can be seen that the metal grids are not inserted evenly into the samples. Please explain how the grids are fixed during the molding of the samples. The authors use woven metal meshes that do not have a smooth flat surface. How did the authors calculate the distance between the grids, taking into account the presence of protrusions and depressions on them?

Please explain what is the difference between the information presented in Figure 3 and Figure 4. Visually, this is the same thing only from different angles.

Line 188 Please indicate whether direct or alternating current was used in the experiments? If direct one, did the phenomenon of electrolysis of water in the cement samples occur, which could affect the accuracy of the measurements?

Line 218. Figure 7a does not show color code breakdowns for all of the studied brass fiber dosages. It is necessary to add a legend to all columns as in Figure 7b or make a general legend.

In Figure 7 b, a technical error is possible; and the outline of the fourth column from the left should be red (see image in Cover Letter)

Line 224. It is recommended to indicate how much hybrid fiber was added. The text provides the relationship between its components, only.

Line 246 Please explain the meaning of fcr.

Line 254. In Figures 10, 11, 15, 16, please indicate the unit of the “Strain” parameter. Why the actual values of this parameter do not exceed 0.0012, and the axis is labeled by the value 0.002? This reduces the visibility of the graphs.

Line 322. You should decipher the abbreviations CM, BF, BC on the diagram.

Line 395. 19b, c. Show on the microphotographs the particles of brass fibers.

Line 397. Probably erroneously listed as brass instead of carbon.

Line 413. In the text, it is necessary to explain for the solution of which problems the elemental analysis of the fibers used in the article was carried out? How do the authors explain the significant difference between the spectrograms obtained at temperatures of 400 and 600C (fig. 21 c, d; fig. 22 c, d) from other studied temperatures?

Line 453. In the text, it should be explained for the solution of which problems the analysis of the cement slurry by the X-ray powder diffraction (XRD) method was carried out in the article? How do the authors explain the effect of the fibers used on the results obtained?

In the text of the article, an assessment should be made of the uniformity of distribution over the volume of carbon fibers, since this largely affects the electrical conductivity of the material.

Comments for author File: Comments.pdf

Author Response

Responses to Reviewer comments

The authors sincerely thank the editor and the three reviewers for their constructive comments. All of their comments have been carefully considered and, wherever appropriate, revisions have been made to the manuscript. Responses to these comments and revisions implemented in the paper are detailed below. The Reviewers’ comments are in italic black fonts while our replies are in blue. Text changed in the manuscript is highlighted in green.

Reviewer 2

The suggestions for this manuscript are listed below:

(Q1) In the Abstract section, it is recommended to justify the relevance of the research.

(A1)     We thank the reviewer for this valuable suggestion. As the reviewer has mentioned the abstract is now being corrected.

Research has already been carried out with various types of conductive fillers incorporated into cement mortars to develop a self-sensing material. Carbon fibres are used as conductive fillers in the past which are uneconomical. In order to overcome this drawback, brass fibres are introduced.  

(Q2) A description of the course of the experiment and the materials used is given, which duplicates the information given in section 2. Materials and Methods. Repeat the description is recommended to be removed.

 (A2) We thank the reviewer for this valuable suggestion. As the reviewer mentioned, the repeated sentences are removed.

(Q3) In section 2, add data on the Scanning Electron Microscope

(A3) We thank the reviewer for this valuable suggestion. As the reviewer mentioned, the data on Scanning Electron Microscope was added in section 2.

Surface topography imaging of the specimens under high magnification was carried out using a Scanning Electron Microscope (SEM). Raw brass fibres and carbon fibres was subjected to elevated temperatures in a box furnace for a duration of four hours. These samples was magnified under SEM to visualise the surface topography. Similarly, these samples was subjected to Energy Dispersive Spectroscopy to perform element analysis. The fibres added to mortar samples was also observed under a SEM for understanding their bonding and dispersion of the mortar mix.

(Q4) Carbon fiber diameter is incorrect.

(A4) We thank the reviewer for this valuable suggestion. As the reviewer mentioned, the diameter of the carbon fibre is changed.

As shown in Figure 2, carbon fibers was 5 mm in length and 10 µm in diameter

(Q5) In Fig.3 it can be seen that the metal grids are not inserted evenly into the samples. Please explain how the grids are fixed during the moulding of the samples. The authors use woven metal meshes that do not have a smooth flat surface. How did the authors calculate the distance between the grids, taking into account the presence of protrusions and depressions on them?

(A5) We thank the reviewer for this valuable suggestion. During the casting process, the moulds was filled with mortar mix after which the grids are inserted into the moulds till it reaches the bottom of the mould. The grids are equally spaced i.e., 10mm in between the grids. The protrusions and depressions on the grids are due to the non-uniform cut of the metal grids. These protrusions are kept to connect the electrical connections to determine the resistance.

(Q6) Please explain what is the difference between the information presented in Figure 3 and Figure 4. Visually, this is the same thing only from different angles.

(A6)     We thank the reviewer for this valuable suggestion. Visually there are no changes in the images presented in Figure 3 and Figure 4. The difference is the fibres added to the mortar mix.

(Q7) Please indicate whether direct or alternating current was used in the experiments? If direct one, did the phenomenon of electrolysis of water in the cement samples occur, which could affect the accuracy of the measurements?

(A7) We thank the reviewer for this valuable suggestion. Direct current was used in this experimental study. This is the primary work carried out on this material. The effect of the electrolysis of water on the self-sensing ability of the mortar will be considered in future work.

(Q8) Figure 7a does not show color code breakdowns for all of the studied brass fiber dosages. It is necessary to add a legend to all columns as in Figure 7b or make a general legend.

(A8) We thank the reviewer for this valuable suggestion. As per the suggestion, the necessary changes have been made in the graph (Figure 7).

(Q9) In Figure 7 b, a technical error is possible; and the outline of the fourth column from the left should be red (see image in Cover Letter)

(A9) We thank the reviewer for this valuable suggestion. The necessary changes have been made in the new manuscript.

(Q10) It is recommended to indicate how much hybrid fiber was added. The text provides the relationship between its components, only.

(A10)   We thank the reviewer for this valuable suggestion. As the reviewer mentioned, the amount of fibres added in hybrid fibres are added in the materials section.

The volumetric ratio of brass fibres added was 0.25% to its volume and for carbon fibres added the ratio was 0.24% to its volume.

(Q11) Please explain the meaning of fcr.

(A11)   We thank the reviewer for this valuable suggestion. As per the suggestion, the meaning of f_cr is provided.

The definition of f_cr is mentioned in the abstract as “Fractional change in electrical resistivity (f_cr) is defined as the change in its electrical resistivity with respect to its initial resistance (ΔR/R)”.

(Q12) In Figures 10, 11, 15, 16, please indicate the unit of the “Strain” parameter. Why the actual values of this parameter do not exceed 0.0012, and the axis is labeled by the value 0.002? This reduces the visibility of the graphs.

(A12)   We thank the reviewer for this valuable suggestion. For better comparison of the graphs, all the graphs in the manuscript are marked with similar limits.

(Q13) You should decipher the abbreviations CM, BF, BC on the diagram.

(A13)   We thank the reviewer for this valuable suggestion. As the reviewer has mentioned the abbreviations CM, BF, BC on the diagram is changed.

(Q14) 19b, c. Show on the microphotographs the particles of brass fibers.

(A14)   We thank the reviewer for this valuable suggestion. As the reviewer mentioned, the particles of brass fibers and carbon fibres was shown on the microphotographs as in Figure 19 b and c.

(Q16) In the text, it is necessary to explain for the solution of which problems the elemental analysis of the fibers used in the article was carried out? How do the authors explain the significant difference between the spectrograms obtained at temperatures of 400 and 600C (fig. 21 c, d; fig. 22 c, d) from other studied temperatures?

(A16)   We thank the reviewer for this valuable suggestion. As the reviewer mentioned, the explanation for elemental analysis is added in the text.

Element analysis was performed to determine the changes occurring in the specimen’s elements when subjected to elevated temperatures. At elevated temperatures of 400℃, 600℃ and 800℃, the presence of carbon, oxygen and nitrogen was seen. These particles was the result of the burning of brass fibres.

(Q17) In the text, it should be explained for the solution of which problems the analysis of the cement slurry by the X-ray powder diffraction (XRD) method was carried out in the article? How do the authors explain the effect of the fibers used on the results obtained?

(A17)   We thank the reviewer for this valuable suggestion. As the reviewer mentioned, the required explanation is provided in the manuscript.

Since materials like silica fume, methylcellulose, superplasticizer and fibres was added in addition to the conventional mortar, XRD was carried out to determine the changes in the crystalline forms created in the mortar matrix. Materials such as silica fume and methyl cellulose have the ability to react with cement components and hence can form new crystalline forms that can affect the strength of the resulting mortar.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear Authors,

Self-sensing cementitious composites is a combination of conventional materials used in the construction industry along with any type of electrically conductive filler material. This study concentrates on the behaviour of self-sensing mortar under two different curing conditions including air and water curing. The main aim of this paper is to determine the self-sensing ability of various types of smart mortars.

The paper describes the proposed research activity well.

I suggest the following insights:

1. Better specify the characteristics of the added fibres;

2. Characterise the test compound;

For further information I suggest the following bibliography:

a.          A. Apuzzo, R. Barretta, F. Fabbrocino, S. Ali Faghidian, R. Luciano, F. Marotti de Sciarra, Axial and Torsional Free Vibrations of Elastic Nano-Beams by Stress-Driven Two-Phase Elasticity, J. Appl. Comput. Mech., 5(2) (2019) 402-413, DOI: 10.22055/jacm.2018.26552.1338.

b.  Boparai K.S., Singh R., Fabbrocino F., Fraternali F., Thermal characterization of recycled polymer for additive manufacturing applications, COMPOSITES. PART B, ENGINEERING (IF: 6.864), 2016, Vol. 106, Pag. 42-47, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2016.09.009.

c.       Fabbrocino, F., Farina, I., Amendola, A., Feo, L. Fraternali, F. Optimal design and additive manufacturing of novel reinforcing elements for composite materials, ECCOMAS Congress 2016 – European Congress on Computational Methods in Applied Sciences and Engineering, 5- 10 JUNE 2016 Crete Island, Greece, Proceedings of ECCOMAS Congress 2016 Crete Island ECCOMAS Vol. No. 4544, Pag.1-16, ISBN:978-618828440-1, (DOI): 10.7712/100016.1928.4544.

Best regards

Author Response

Responses to Reviewer comments

The authors sincerely thank the editor and the three reviewers for their constructive comments. All of their comments have been carefully considered and, wherever appropriate, revisions have been made to the manuscript. Responses to these comments and revisions implemented in the paper are detailed below. The Reviewers’ comments are in italic black fonts while our replies are in blue. Text changed in the manuscript is highlighted in green.

Reviewer 3

Self-sensing cementitious composites is a combination of conventional materials used in the construction industry along with any type of electrically conductive filler material. This study concentrates on the behaviour of self-sensing mortar under two different curing conditions including air and water curing. The main aim of this paper is to determine the self-sensing ability of various types of smart mortars.

The paper describes the proposed research activity well

The suggestions for this manuscript are listed below:

 (Q1) Better specify the characteristics of the added fibres

(A1) We thank the reviewer for this valuable suggestion. As the reviewer mentioned, the explanation is added in the revised manuscript.

The tensile strength of the carbon fibre was 690 MPa. The tension modulus of the carbon fibre was 48 GPa. The electrical resistivity of carbon fibre is 3.0 × 10-3 Ωcm. The tensile strength of the brass fibre is 280 MPa. The shear modulus of the brass fibre is 40 GPa. The tensile modulus of the brass fibre is 125 GPa. The electrical resistivity of carbon fibre is 6.5 × 10-6 Ωcm.

(Q2) Characterise the test compound

(A2) We thank the reviewer for this valuable suggestion. As the reviewer mentioned, the explanation is added in the revised manuscript.

The specific gravity of cement used was 3.12 g/cm³. The bulk density of cement is 1440 kg/m³ with fineness modulus of 285 m² /kg. The specific gravity of silica fume used was 2.2 g/cm³.  The bulk density of silica fume is 1350 kg/m³ with fineness modulus of 22000 m² /kg.

(Q3) For further information I suggest the following bibliography

(A3) We thank the reviewer for this valuable comment. As per the suggestion the bibliography was added to the reference.

51. Apuzzo, R. Barretta, F. Fabbrocino, S. Ali Faghidian, R. Luciano, F. Marotti de Sciarra, Axial and Torsional Free Vibrations of Elastic Nano-Beams by Stress-Driven Two- Phase Elasticity, J. Appl. Comput. Mech., 5(2) (2019) 402-413, DOI: 10.22055/jacm.2018.26552.1338.
52. Boparai K.S., Singh R., Fabbrocino F., Fraternali F., Thermal characterization of recycled polymer for additive manufacturing applications, COMPOSITES. PART B, ENGINEERING (IF: 6.864), 2016, Vol. 106, Pag. 42-47, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2016.09.009.
53. Fabbrocino, F., Farina, I., Amendola, A., Feo, L. Fraternali, F. Optimal design and additive manufacturing of novel reinforcing elements for composite materials, ECCOMAS Congress 2016 – European Congress on Computational Methods in Applied Sciences and Engineering, 5- 10 JUNE 2016 Crete Island, Greece, Proceedings of ECCOMAS Congress 2016 Crete Island ECCOMAS Vol. No. 4544, Pag.1-16, ISBN:978- 618828440-1, (DOI): 10.7712/100016.1928.4544.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Despite some improvements done by authors, which raised the paper’s quality, it still cannot meet the requirements of a ready-to-publish paper in my opinion. Actually, authors failed to address some major queries. Furthermore, it is reminded that the design of the experimental plan  has relevant flaws that prevent the approach to the results adopted by the authors. That is why the initial recommendation was to prepare a new manuscript. 

Reference 37 is not complete and publication year is wrong. 
 
I regret to still decline this paper.

Reviewer 2 Report

I am satisfied with the changes

Reviewer 3 Report

Dear Authors 

the paper is accepted in present form.

Best regards