Fibre-Reinforced Concrete Is Sustainable and Cost-Effective for Water-Retaining Structures
Round 1
Reviewer 1 Report
The paper tries to synthesize several standards, norms and articles in the field of fiber reinforced concrete (FRC). FRC is already used in constructions such as pools, water tanks, water treatment basins, supply pipes, drains, marine constructions, etc., so the three water retention structures (WRS) proposed as design scenarios do not present a novelty in the field.
Polypropylene manufacturers recommend a quantity of concrete between 600-1200g / m3 (frequently 900g / m3) which represents Vf between 0.066-0.133% (often 0.11%), which is below the minimum limit of 0.15% mentioned in the article. Therefore, the lower limit for Vf should be dropped to 0.1%.
The article is limited to the use of only three types of fibers: Hooked-end steel (S), straight polypropylene (PP), and straight polyolefin (PO). There are other fibers that can be used in reinforced concrete such as glass, aramid or carbon. Because low carbon steel fibers are more expensive, steel wires can be used resulting in the so-called ferrocement.
On line 157 the abbreviation SCM should be explained to the readers.
All possible combinations of the different values in Table 1 lead to a total of 7128 FRC mixtures, which means a laborious experiment. However, in order to confirm the theoretical results, it is necessary to perform some real, eloquent, experimental tests. The article must contain the mathematical equations used and the theoretical results compared to the experimental ones. Readers should be shown and explained the mathematical relationships used, and not directed to the articles indicated as references for understanding and research.
The article is based on: "for each of these combinations fR1 and fR3 values were estimated by means of regression equations which were derived from the analysis of the database of FRC mixes and residual flexural strength results compiled as part of the ongoing project ‘Optimization of FRC mixes using data mining’ [32].", reference that is not yet published.
Readers should be explained more clearly the meaning of the values fR1 and fR3, respectively the mathematical equations in which they appear. Present the mentioned equations.
The citation [29] is not related to "the Oslo swimming pool complex".
The citations from articles [33] to [40] are not found chronologically in the paper.
Reference [38] does not give the unit costs of materials, so it is not possible to obtain such an accurate estimate of costs per linear meter of construction. However, a difference of only 2% is small and susceptible to error. If 1 linear meter is actually executed, then tests and experiments could be done and the cost differences could be verified. The same remark applies to embodied carbon. In the absence of some real values, the graphs from figures 5 and 6 seem too linear. The introduction of fibers can certainly be made uniformly ascending, but I don’t think the removal of conventional steel is as uniform.
The article does not bring a persuasive argument to justify the use of FRC instead of the classic reinforced concrete, at least in terms of sustainability. In addition to the economic factor and that of embodied carbon, which anyway have low values susceptible to error, there are many other factors that should be taken into account, such as gelivity, mechanical, wind and water erosion, chemical attacks, permeability, etc.
Figure 4 does not give the unit of measurement on the ordinate [mm].
Some of the conclusions were already known.
Author Response
Response to reviewer's comments in file attached.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This work is really relevant. Environmental legislation is becoming more stringent, and more attention is paid to environmental problems. Therefore, scientifically grounded design and materials science solutions in construction, aimed at improving the environmental situation, reducing the carbon footprint, are promising. Polymer fiber is a dispersed fibrous material capable of imparting new properties to concrete structures: lower average density, greater crack resistance, greater bending and shear strength. This is shown by the authors in relation to waterproof structures made of fiber-reinforced concrete. I believe that this article contains valuable scientific research that is interesting for specialists in the field of designing fiber-reinforced concrete compositions, as well as for designers of such structures.
Author Response
Reply to reviewer's comments in file attached.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Glass, carbon and aramid fibres have very good characteristics. The article is not convincing enough about why a potential user should choose only steel, polypropylene or polyolefin fibres.
The authors did not give a convincing answer to: “All possible combinations of the different values in Table 1 lead to a total of 7128 FRC mixtures, which means a laborious experiment. However, in order to confirm the theoretical results, it is necessary to perform some real, eloquent, experimental tests. The article must contain the mathematical equations used and the theoretical results compared to the experimental ones. Readers should be shown and explained the mathematical relationships used, and not directed to the articles indicated as references for understanding and research.” The authors say at line 133 "The central idea of this study was to generate alternative structural design solutions". What are these solutions? Designers must apply a calculation method, find out certain values from mathematical formulas, respect some minimum and maximum constructive conditions, etc. The paper does not provide this information, giving only a few references. The designer or reader must do the research themselves. So what is the calculation method? What relationships must be applied in these alternative solutions?
In the case of a new technology, experimental tests must be made on real elements, which confirm the theoretical calculations.
From the statement found in lines 400 and 401 "In average, fibres represented 8% of the cost when dosed at Vf = 0.15%, whilst they represented almost half of the cost when dosed at Vf = 1.5%" it is understood that the value of the fibres is 8% to 50% of the value of the reinforced concrete and not a cost reduction with the stipulated in Response 10 from the coverletter. The graphs in figure 3 confirm that the value of fibre concrete increases with Vf and does not decrease from 8% to 50%. Many readers would probably prefer the expression of prices in another currency (for example Euro), so, much more interesting for them would be a percentage approximation of the decrease in price following the use of fibres.
The authors did not give a convincing answer to: “The article does not bring a persuasive argument to justify the use of FRC instead of the classic reinforced concrete, at least in terms of sustainability. In addition to the economic factor and that of embodied carbon, there are many other factors that should be taken into account, such as gelivity, mechanical, wind and water erosion, chemical attacks, permeability, etc.”
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 3
Reviewer 1 Report
Glass, carbon and aramid fibres have very good characteristics. The article is not convincing enough about why a potential user should choose only steel, polypropylene or polyolefin fibres.
Readers must find in the article some values, mathematical formulas, some minimum and maximum constructive conditions, etc. The paper does not provide this information, giving only a few references. The reader must do the research themselves. The article must contain the mathematical equations used and the theoretical results compared to the experimental ones. Readers should be shown and explained the mathematical relationships used, and not directed to the articles indicated as references for understanding and research. In the case of a new technology, experimental tests must be made on real elements, which confirm the theoretical calculations.
Much more interesting for readers would be a percentage approximation of the decrease in price following the use of fibres.
The article does not bring a persuasive argument to justify the use of FRC instead of the classic reinforced concrete, at least in terms of sustainability. In addition to the economic factor and that of embodied carbon, there are many other factors that should be taken into account, such as gelivity, mechanical, wind and water erosion, chemical attacks, permeability, etc.
FRC is already used in constructions such as pools, water tanks, water treatment basins, supply pipes, drains, marine constructions, etc., so the three water retention structures (WRS) proposed by the authors as design scenarios do not present a novelty in the field.
Some of the conclusions were already known. Some manufacturers already recommend the range of doses that the authors find new in the first and last conclusion of the article.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
