Experimental Investigations and Microstructural Characterization of Construction Materials of Historic Multi-Leaf Stone-Masonry Walls

Point 1

A complete and complex article, well-drafted, on a topic of extreme importance and using the correct methodology.

Point 2

The title and abstract are appropriate; the bibliography is correct and updated.

Point 4

In our opinion, this paper should be published.

Response 1, 2, and 4

Thanks for the encouraging expressions about the importance and the usefulness of our manuscript. Your recognition of our work is much appreciated.

Point 3

It is recommended to review the placement of some commas.

Response 3

The entire paper was carefully reviewed and a complete spell check is done.

Point 1

The submitted manuscript is a multidisciplinary article concerning the physical, chemical, and mechanical properties of masonry walls. The article presents the framework and the results of an investigation campaign conducted on a vast number of historical sites in Egypt. The main focus of the research has been the multi-leaf-stone masonry construction typology which is a very popular construction technology due to its effectiveness and cost.

The research gathers a multidisciplinary investigation result on those walls, from physical, chemical and mechanical characterizations, such as; i) Petrographic investigation; ii) Mineralogical characterization; iii) Thermal analysis; iv) Microstructure; v) Physical characterization; vi) Thermal conductivity and resistivity; vii) Texture; viii) Mechanical characterization.

The article is well-conceived methodologically and represents an added value in the research community. It would represent one of the most comprehensive researching works, to my knowledge.

Response 1

The authors are very grateful for the encouraging expressions.

Point 2

The text is well written but with some slight modifications during the proofreading. No plagiarism is detected.

Response 2

The authors would like to thank the Reviewer for their comments. The entire paper was carefully reviewed and a complete spell check is done.

Point 3

The literature review could be enriched more with similar research works.

Response 3

Thank you for this suggestion. Additional citations have now been added to enriched the literature review with similar research works.

Point 1

Page 3, Line 74-75: The authors may just say five to be compatible with the numbering given after the statement.

Response 1

Thanks for your kind reminders. This has now been corrected as suggested.

Point 2

Page 7, Line 259: The first line of the sentence is not clear. Please, revise the statement.

Response 2

This has now been amended to read “Besides, the joint thickness was usually much lower than the thickness of stone-rubble units in the inner core layer”.

Point 3

Page 8, Line 263-264: The reviewer agrees with the authors; however, the statement can be improved by adding an extra sentence to mention the transversal bond element’s role in seismic behavior. This issue has been extensively studied in the literature from the computational modeling point of view. Please add the following references, which are directly related to the effect of transverse stones (or through stones):

-        Giuffré, A. (1989), “Mechanics of Historical Masonry and Strengthening Criteria”, XV Regional Seminar on Earthquake Engineering, Ravello, Italy

-        DOI: 10.12989/eas.2016.11.4.563, DOI: 10.1080/19648189.2020.1824823, etc.

Response 3

The text has now been amended to “These transversal bond elements were used to enhance the connectivity between wall’s leaves, see Figure 5. Moreover, adding a through stone to the cross section of the wall is greatly improve the deformation capacity, mechanical performance, and out-of-plane strength of wall section. The contribution of transversal bond elements in enhancing the seismic performance of masonry walls has been extensively studied in the literature from the computational modeling point of view [23, 24, 25]”. We have also added the suggested references. The authors would like to thank the reviewer for this suggestion.

Point 4

Page 11, Figure 7: Is there any way to increase the quality of these drawings. They are pretty blurred.

Response 4

The quality of Figure 7 has now been increased as suggested.

Point 5

Page 18, Section 3.2: This section is kind of superficial. How were these mechanical testing performed? Displacement or force-controlled. Softening brach of stress-strain curves were given. Did the authors attempt to compute related fracture energies? What were the boundary conditions set during the testing? For instance, frictional resistance was eliminated between the specimen and loading plate through compression testing, etc. Explanations are needed in this section. Because, in the future, when other researchers want to simulate or model the multi-layer unreinforced walls, they will take material properties from this kind of article; hence, the source and testing procedure of the data should be explained better.

Response 5

Thank you for this suggestion. The test setup and procedures were already described in section 2.7. We have also added the suggested content to the same section.

Point 6

In the conclusion section, the authors mention the modulus of rupture; however, it was not mentioned in the main text. If the results are not excellent and misleading, it is better not to include them in the article.

Response 6

Thanks for your kind reminders. This part is deleted as it is not included in the presented mechanical tested.

Point 7

The conclusion regarding the thermal conductivity is somehow expected. The authors should discuss the effects of voids on the temperature profile through wall cross-sections and how the morphology affects the thermal conductivity.

Response 7

Thank you for pointing this out. We agree with this comment. Therefore, we have provided to this point the necessary clarification of the effect of wall morphology on the thermal behavior of wall cross-sections.

Point 1

Line 393-394: The sentence may be revised as "...The contribution of the transversal bond element (also referred to as through stone) in enhancing the seismic performance and capacity of unreinforced masonry walls has been studied in the literature from the experimental and computational modeling point of view."

Response 1

Thanks for your kind reminders. This has now been revised as suggested.

Point 2

The resolution of the plots, given in Figure 12, can be improved.  

Response 2

The quality of Figure 12 has now been increased as suggested.

Point 3

Line 883-888: The added statements are too long and difficult to follow. Split the sentences and clearly explain the main interpretations. Moreover, is there any critical void ratio for this kind of wall-cross sections, where the voids may function as internal insulations up to a certain ratio? The authors should justify their comments by referring to some others studies.

Response 3

The text has now been amended to “The tests results proved that the thermal conductivity of multiple-leaf masonry walls depends mainly on the density of its components and the void ratio. Consequently, thermal resistivity of the wall can be improved by decreasing the void ratio in the in-fill layer, increasing the cohesion between the bedding mortar and rubble stone, and also by using stones with lower permeability. Moreover, it is possible to infer that the increase of block thickness of the external layers and, above all, the use of mortar coating attenuate the heat transfer to the inner skin of the wall.”

It would have been interesting to explore the effect of the void ratio on the thermal resistance of the historic masonry walls. However, in the case of our study, it seems slightly out of scope, as the research focused on characterizing the construction materials. This aspect would be very interesting in another detailed study that includes comprehensive experimental investigations on the thermal behavior of the historic multi-leaf masonry walls, where different mortar types and compositions are parametrically studied.