Experimental Investigation of Recycled Fine Aggregate from Demolition Waste in Concrete
Round 1
Reviewer 1 Report
This manuscript deals with utilization of recycled fine aggregate in the development of concrete, strength properties are evaluated, I have given my comments it should be addressed before the acceptance.
The authors have denoted “In all cases, 17 the average of two tested samples at the age of 28 days was considered” in the ABSTRACT section. Why two specimen any justification?
The authors say, “Recycled fine aggregate has some cementitious properties”, but conclude at least 75% of strength gain obtained as compared to control specimen. This is conflicting. With the cementitious properties and better compaction it is possible to achieve the target strength?
What is the contribution of the author in line with meeting sustainability; need more discussion with strong background. It is generally highlighted, more insights needed based on any one of the factors such as cost/energy/CO2 emission/life cycle etc.,
Figure 2 seems to be like conventional sand, considering the colour of concrete, dis you mean it as the crushed concrete?
As per figure 8 addition of RFA does not have any significant reduction in Compressive strength, but it was mentioned in ABSTRACT only 75% strength obtained? Check
Tensile strength results does not follow any pattern of compressive strength, there are ups and downs in the results why?
The limitations and scope for future work to be added
Figure 10 and Figure 11 seems to be same, I understand both are different test. The first one is tensile strength of concrete measured by cylinder specimen and the second one is flexural strength/modulus of rupture measured by prism specimen, check
Correlate compressive strength with modulus of rupture also.,
Microstructure of concrete to be added (SEM analysis) to show the contribution of RFA as a filler/cementitious materials
Refer the following manuscripts to improve the discussion
Mathews, M. E., Kiran, T., Naidu, V. C. H., Jeyakumar, G., & Anand, N. (2021). Effect of high-temperature on the mechanical and durability behaviour of concrete. Materials Today: Proceedings, 42, 718-725.
Murali, G., Vardhan, C. V., Rajan, G., Janani, G. J., Jajan, N. S., & Sri, R. R. (2012). Experimental study on recycled aggregate concrete. International Journal of Engineering Research and Applications (IJERA), 2(2), 407-410.
Puthussery, J. V., Kumar, R., & Garg, A. (2017). Evaluation of recycled concrete aggregates for their suitability in construction activities: An experimental study. Waste management, 60, 270-276.
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Author Response
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Reviewer 2 Report
The authors conducted valuable research on recycled fine aggregate from demolition waste in concrete.
The tests were carried out for various proportions of the weight of recycled material.
Tests for the waste material included visual examination, chemical composition, grain size distribution, specific gravity, and fineness modulus. Tests on the incorporated recycled fine aggregate in new concrete mixes involved tests of the hardened plain concrete product. In total, eight concrete mixes were considered.
Results of the study showed that the recycled fine aggregate has some cementitious properties, which is capable of hardening when mixed with water and left to dry, even without adding cement from exterior sources.
The most important conclusion is that the recycled aggregate contains traces of cement and has some binding properties.
The research also proved that concrete made with partial replacement equal to 25% or 100% of natural sand with recycled fine aggregate has comparable mechanical properties to concrete made with natural sand if the concrete has a cement content that can yield concrete compressive strength around 30 MPa.
The work has practical ecological values ​​and should be published.
Remarks:
Please enlarge the fonts for figures 9, 10 and 11.
The value of the work would be higher if more physical properties of recycled concrete were tested (E-modulus, density, porosity, etc.)
Author Response
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Round 2
Reviewer 1 Report
The authors have addressed some of the comments, before the acceptance the following comments to be addressed to enhance the readership of the academic community
Considering two samples for research with new proposed material is very less, at least for compressive strength the no of samples should be more. So that, the proposed results can meet the acceptable probability and standard deviation. The authors should discuss this for their justification in the manuscript
The sustainability role of recycled fine aggregate is not convincing, any one specific component such as cost, energy, and emission should be discussed in detail with appropriate reference. Introduce the subsection, as the journal objective is focusing on sustainability it is essential
In the case of compressive strength of cubes, the different levels of replacement between 25% and 100% do not have any major impact on strength, showing marginal variation ???
Considering two samples only for cube compressive strength, how it is possible to get an average strength reduction of 75%? I can see the attainment of compressive strength is nearly 42MPa, strength reduction is not observed for cube strength in other cases
Please provide a table (or modify the Table 3) for compressive strength denoting sample no, strength for all the replacement percentages, and variation in strength concerning the original control specimen of both low and high cement content for a better understanding
Variation in strength for different replacement percentages is higher for cylinder specimen (for higher cement content), but for the cube, it is almost NIL. Need more relevant discussion
Author Response
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