A Comprehensive Review of the Improvement of the Thermal and Mechanical Properties of Unfired Clay Bricks by Incorporating Waste Materials

Round 1

Reviewer 1 Report

Comments and recommendations are listed below:

-    ’’fired clay bricks and hollow clay bricks’’ may be replaced by ’’solid and hollow clay bricks’’ (line 137).

-   The statement that the bricks are dry pressed and dried in sunlight (lines 133-134), is valid in the case of handmade bricks. The most of commercial fired clay bricks are extruded and dried in oven at a standard temperature.

-   Did you mean by “the blocks are extruded from the molds” that “the blocks were removed from the molds” (line 161)?

-    Industrial wastes are not construction material (line 280), they can be considered as raw materials to produce new ones.

-     In the tables from pages 10-13, are you referring to the year of publication or the year when the material was produced?

-        In the section 4, references should be made to the properties of the unfired brick. The data presented in figs. 1 and 2 should also contain values related to unfired bricks.

-      Can you specify in the section 4.2 which are the minimum value for compressive, tensile, and flexural strengths or water absorption required by standard for unfired bricks?

-     Please rename the figs. 1-4 from section 4.1.  Consequently, the fig. 1 become fig. 4; fig 2 become fig. 5; fig.3 become fig. 6 and fig. 4 become fig.7.

-    Also, the Table 1 and 2 from sections 3.1.2 and 5.2 must be renamed. Table 1 from page 11 become table 4 and table 2 from page 23 will become table 5.

-    In the table 6 you should mention which is the optimum fiber content for each recipe, otherwise it will be understood that it is the same for all.

-     The water absorption or other thermal parameters of unfired bricks having waste materials can also be useful data to correlate the information’s presented in the last section with the parameters discussed in the section 4.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This review paper deals with the state of the art of recent research advances on adding agricultural and industrial wastes to the manufacturing of unfired earth bricks and the effect of adopted additives on the performance of obtained brick products. The topic is of interest, but the presented status of this manuscript is not quite satisfactory. For example, the effect of additives on the physical properties of unfired bricks has been ignored, making this review incomprehensible and undeveloped. The reviewer would suggest a major revision prior to its publication in Buildings.  For the detail, please see below.

Line 30 Weird blank between “that” and “the”. Please correct.

Lines 32-33 Why use italics? Same issue is in line 40. Please check through the manuscript to avoid this mistake.

Line 52 Remove one comma after “materials”. The authors must check through the manuscript to avoid typos and grammar mistakes.

Lines 60-61 “In contrast to industrial construction materials like concrete, earth-based material requires approximately 99% less energy during the manufacturing process”

The reviewer may have a different opinion. Fired clay brick is also an earth-based building material that consumes extensive energy during production.

Line 125 “Clay is the most abundant natural mineral material on earth, a cost-effective material that is easy to work with when compared to other building materials.”

Clay is not a mineral but a mixed material consisting of clay minerals and other phases. Regarding the definition of clay and its application to brickmaking, the paper https://doi.org/10.1016/j.jobe.2022.105802 is recommended to be cited.

Line 125 Reference [29] mainly talks about concrete. Better to replace it with some brick-related publications, like https://doi.org/10.1016/S1572-4352(05)01016-0.

Line 128 “for decades”

Please note that bricks made of air-dried clays are reported to be used as early as the Neolithic period, and fired clay bricks were made around 4500 BCE. For the origin of clay bricks, it is better to cite the following paper as a reference: https://doi.org/10.1016/j.conbuildmat.2021.125828.

Line 134 “in sunlight” In ancient times this may be true, but nowadays bricks are mainly dried in kiln. Also the definition of fired clay brick is described in the mentioned references.

Line 143 No need to keep Figure 3. The morphology of fired clay brick has already been shown in Figure 2.

Line 113 The title of section 2 may be inappropriate. Section 2 introduces the types of earth bricks, and the benefits and drawbacks of unfired earth bricks. Both of them seem irrelevant to “Earth Construction Methods”. The reviewer thus invites a more accurate title to be used here.

Also, the title of section 2.2 tends to be inaccurate. The authors only demonstrated the characteristics of unfired earth bricks in this section but used a title covering both unfired and fired earth bricks. Please correct or argue.

From the reviewer’s point of view, section 2.2 doesn’t really contribute to the gist of this review. Firstly, Tables 1 and 2 in section 2.2 are from published literature instead of being summarized by the authors. Secondly, the content of this section is unrelated to the addition of waste materials to unfired brickmaking. Thus, the reviewer would suggest deleting section 2.2 from the current version.

Lines 223-226 Please check to use a consistent alignment format throughout the manuscript.

Line 276 The title of section 3.1.1. should be “Incorporation of industrial waste” considering the context and consistency with section 3.1.2.

Durability and water absorption are not mechanical properties. Please delete them from section 4.2. Also, the reviewer believes section 4 should be removed or at least compressed to a large extent, as this section only briefly lists definitions of a few thermal and mechanical properties of unfired bricks. Most of them are common sense and do not contribute to the current literature. For example, an undergraduate can tell what thermal conductivity and specific Heat capacity are as these contents can be easily found in any civil material-related textbook or a single Google search. The reviewer does not see any necessity to put these definitions here.

Lines 328 The authors mentioned physical properties in section 4 but did not present any summary or analysis of this aspect in the text. The reviewer believes that the research advance on the effect of waste addition on physical properties, for example colour, bulk density, porosity, water absorption, drying shrinkage, etc., of obtained brick products should also be supplied.

Line 650 Again, water absorption is not a mechanical property.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thank you for the given responses and for the improvements provided to the article. Few other recommendations are listed below:

-        “Environmentally Sustainable” appears twice in table 1 ((iv) and (vi) are the same). Can you please correct this?

-        In the fig. 3 some values of the thermal conductivity of unfired bricks and a brief discussion on their values in relation to other materials would be important in supporting the statements presented in Table 1.

-        In the line 960 please delete the “higher elastic modulus (3.5 GPa)” because the density of the brick is not influenced by elastic modulus value.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The reviewer appreciates the careful revision by the authors. Most issues have been properly addressed, while others remain: 1) Wrong ordering of section titles in Section 3 - Section 3.2 should not be before Section 3.1.1. 2) The first letter of some section titles is capitalized, while others are not. Please use a consistent title format throughout the manuscript.

Author Response

Please see the attachment.

Author Response File: Author Response.docx