Use of Phosphoric Acid and Rice Hulk Ash as Lateritic Soil Stabilizers for Paving Applications
, Jaelson Budny 3 and Luciano Pivoto Specht 1Round 1
Reviewer 1 Report
Dear authors
Thanks for your efforts in conducting the analysis and experiments. This article aimed to evaluate the elastic behavior and simple compressive strength, at different ages of baking, using rice husk ash and phosphoric acid, in a simple and combined way, to stabilize lateritic soil. Laterite soil was mixed with different contents of RHA, H3PO4 and water and compacted at medium and modified Proctor energies. Broken soil samples were analyzed by scanning electron microscope and X-ray diffraction in mechanical compressive strength tests. The results show the stabilization potential of the discussed laterite soil in terms of elasticity and simple compressive strength through the addition of RHA and H3PO4 for different ages of curing.Here are some questions and comments:
- Is the soil used in this research alkaline or acidic? , Because phosphoric acid probably has an acidic base, it causes the soil to become too acidic. Add the explanation.
- Basically, in the stabilization and improvement of clay and sticky soils, we have positively charged atoms such as calcium carbonate, which reduces the polarity of clay and reduces water absorption. What is your explanation in this case when acid is used to improve the soil?
-How were the percentages chosen for rice husk ash and polyphosphoric acid? What is the basis of these percentages?
-Rice husk ash contains large amounts of silica with a high specific surface area, which is suitable for activating the reaction between lime and soil. But it is not clear in this research, what role do phosphoric acid and rice husk ash play in these reactions to stabilize clay.
-This article does not have a specific research method or diagram, it should be added.
-In this article, it is necessary to refer to the international standards, according to which national or international standards were the tests performed?
- The title of the article contains the word "Brazilian", while the area of soil preparation is not important in this research, the characteristics of this soil are more important. It is suggested to be removed.
-Laterite is often mistaken for Lateritic soil. Lateritic soils are fine-grained compared to laterite. An important physical difference between laterite soil and lateritic soil is that laterite has a gravel component while laterite soil does not. Please be careful, here in this article, this mistake does not exist.
-- Add pictures of the tested samples and some more important equipment.
Best Regards
Author Response
Dear Reviewer,
Thank you for your considerations. They have all been addressed and added to the text. Below are the individual responses to each questioning/comment made.
- Is the soil used in this research alkaline or acidic? Because phosphoric acid probably has an acidic base, it causes the soil to become too acidic. Add the explanation.
Answer: The soil under study is acidic (pH = 5,8), as can be seen in the chemical analyses presented in Table 1.
- Basically, in the stabilization and improvement of clay and sticky soils, we have positively charged atoms such as calcium carbonate, which reduces the polarity of clay and reduces water absorption. What is your explanation in this case when acid is used to improve the soil?
Answer: As shown in Table 1, the predominant composition of the soil is silicon dioxide (SiO2), iron oxide (Fe2O3), and aluminum oxide (Al2O3), so the acid could contribute to the solubilization of the chemical components, and consequently improve stability. This product formed was not visualized in the x-ray diffraction test, possibly because it was in the amorphous phase.
- How were the percentages chosen for rice husk ash and polyphosphoric acid? What is the basis of these percentages?
Answer: The percentages of RHA and H3PO4 were defined based on the main conclusions of other research conducted with the same materials and tropical soils. The studies of Budny (2018), Medina and Guida (1995), for example, were the basis for the definitions of the amounts of each material.
- Rice husk ash contains large amounts of silica with a high specific surface area, which is suitable for activating the reaction between lime and soil. But it is not clear in this research, what role do phosphoric acid and rice husk ash play in these reactions to stabilize clay.
Answer: Phosphoric acid is extremely reactive (intense exothermic reaction) with tropical soils that have free iron and aluminum oxides. Given the fact that stabilization takes place by chemical action of the additive on the soil minerals, thin soils are the most suitable for this stabilization. From the point of view of acidity, acid soils are favorable, in the sense that the action of phosphoric acid is not neutralized. The rice husk ash contributes in the gain in resistance properties together with the H3PO4 because it allowed a better homogenization of the mixture. The H3PO4 contributes with the formation of iron or aluminum phosphates, which show as hard and insoluble compounds.
- In this article, it is necessary to refer to the international standards, according to which national or international standards were the tests performed?
Answer: The standards that were taken into consideration for the development of the research are indicated throughout the text. Basically, national standards for performing resilient modulus tests were followed (Reference [44]). It is noteworthy that this standard was developed based on the AASHTO standard (Reference [48]). For the compressive strength test, another Brazilian standard was taken into consideration (Reference [56]). For X-ray diffraction a database was consulted American Mineralogist Crystal Structure Database.
- The title of the article contains the word "Brazilian", while the area of soil preparation is not important in this research, the characteristics of this soil are more important. It is suggested to be removed.
Answer: The word “Brazilian” was removed from the title of the article.
- Laterite is often mistaken for Lateritic soil. Lateritic soils are fine-grained compared to laterite. An important physical difference between laterite soil and lateritic soil is that laterite has a gravel component while laterite soil does not. Please be careful, here in this article, this mistake does not exist.
Answer: Thank you for comment.
- Add pictures of the tested samples and some more important equipment.
Answer: In figure 1 an image of a compacted sample and the repeated load triaxial equipment used for resilient modulus testing has been added.
Reviewer 2 Report
1. The scanning electron microscopy method used is described in detail in Section 2.2.2. It would be better if this method could be described in more detail
2. In Figure 2, the average resilient modulus of the composite model and UCS at 7 and 91 days are comprehensively expressed, but the description is not clear enough
3. In the discussion section, it would be better if this study could be compared with the past research and compare its advantages and disadvantages
4. In Figure 3, the resilient modulus of the composite model is intuitively expressed, but the figure is less described in the paper. It would be better to give a specific description for Figure 3
Author Response
Dear Reviewer,
Thank you for your considerations. They have all been addressed and added to the text. Below are the individual responses to each questioning/comment made.
- The scanning electron microscopy method used is described in detail in Section 2.2.2. It would be better if this method could be described in more detail.
Answer: The authors thank you for your consideration. Therefore, more details of the scanning electron microscopy test have been added in Section 2.2.2.
- In Figure 2, the average resilient modulus of the composite model and UCS at 7 and 91 days are comprehensively expressed, but the description is not clear enough
Answer: The description of Figure 2, as well as the explanation related to the results and conclusions of the MRI and UCS tests, have been added throughout the text in the article.
- In the discussion section, it would be better if this study could be compared with the past research and compare its advantages and disadvantages
Answer: We thank you for your considerations. The advantages and disadvantages of using the mixtures and comparison to previous research are presented in the results section.
- In Figure 3, the resilient modulus of the composite model is intuitively expressed, but the figure is less described in the paper. It would be better to give a specific description for Figure 3.
Answer: We thank you for your considerations. The comment was answered, and the results presented in Figure 3 were discussed in more detail.
Reviewer 3 Report
From my point of view, some data on the characterization of RHA is missing. There is some data about soil (XRF, chemical characterization,…) but the RHA characterization is missing. What is the RHA composition, particle size distribution, … All these parameters can affect the experiments.
Figure 7 The lines on diffractogram are not fluent, there are some “curls” (e.g. peak of quartz – 50° has some curls) . Please process the figure to the correct shape.
Presented manuscript is very interesting and data are clearly interpreted. Grammar improvement and is needed throughout the manuscript.
Author Response
Dear Reviewer,
Thank you for your considerations. They have all been addressed and added to the text.
More information about rice husk ash has been added. We know the importance of the characterization and the parameters in the scope of the mechanical behavior.
A grammar review has been performed throughout the article. In addition, the considerations of the other reviewers were taken into account.
Reviewer 4 Report
Good morning,
The reviewed work contains information about the research to evaluate the resilient behaviour and the simple compressive strength, at different curing ages, of the use of rice husk ash and phosphoric acid for the stabilization of lateritic soil, comes from the city of Cruz Alta, located in the state of Rio Grande do Sul in Brazil. The researches are is potentially valuable because it meets the needs of the modern world in terms of environmental protection and proper management of technological waste. Properly designed mixtures of soil with additives, in the form of compacted samples with energy appropriate to obtain the desired (ideal) compaction parameters, were tested. The mechanical tests, scanning electron microscopy and X-ray diffraction were used to assess the results of the research.
The critical remarks:
1. In my opinion, the theoretical introduction to the subject of the presented research, and what is very important, the reference to source materials on the subject is very poor.
2. The conclusions should be more precise and practical.
3. There were no important, from the point of view of work, comments on the possibility of practical use of the benefits presented in the conclusions.
Regards,
Author Response
Dear Reviewer,
Thank you for your considerations. They have all been addressed and added to the text.
The introduction has been improved. Also, more information about the materials used in this research has been added. An attempt was made to demonstrate more objectively the relevance of the study to the practical environment.
Round 2
Reviewer 1 Report
Thanks to the dear authors
Reviewer 4 Report
The adjustments made are sufficient.
