Review Reports - Labeling Strategy for Evaluating the Performance of Thin Asphalt Wearing Courses

Round 1

Reviewer 1 Report

The paper "Labelling strategy for evaluating the performance of thin wearing courses" is interesting and within the scope of Applied Sciences. I think the content is innovative and never published. The manuscript contributes to a real and interesting advance in knowledge. The work has enough relevant information to develop eco-labelling criteria from a stategic sustainability perspective in the road sector. It uses Spanish and International standards which validate the analysis. Strategies to evaluate sustainability of transport infrastructures are nowadays a hot topic whose impact in financial, social and environmental terms is really remarkable. Several groups around the world are currently working to balance technical features, environmental protection and economic development.

I have some questions for the authors:

the last sentence of the abstract is not correct and it should be rewritten. The same (uncorrect) sentence is at lines 406-408. Please avoid these repetitions;

line 27: "its design" is not correct: the authors refer to "its use";

the sentence at line 32-34 is not always true: if the pavement is porous, these problems are avoided;

line 39: the cited methods should be referenced;

line 50-52: this sentence should be referenced. A recent research analyses this problem: Moretti, L., Mandrone, V., D'Andrea, A., & Caro, S. (2018). Evaluation of the environmental and human health impact of road construction activities. Journal of Cleaner Production, 172, 1004-1013. Lines 53-61 should be referenced

In table 1, all the cited standards should be referenced;

Figure 5 is not readable. The same for Figure 9 and Figure 10. In general, the quality of figures is poor;

The authors cite the research project Labelling road surfaces in the Netherlands, which considers four categories: skid resistance, noise (reduction), rolling resistance and lifespan. How is the present research related to the cited project?

Author Response

Ms. Ref. No.: applsci-473563

Title: Labelling strategy for evaluating the performance of thin wearing courses (revised)

Applied Sciences

Dear Reviewer,

We, the authors of the manuscript with reference APPLSCI-473563, have considered all your comments and have written a revised version of this article (please find corrections highlighted in yellow). We strongly appreciate your suggestions and share knowledge to make this study more valuable and of interest for the scientific community.

We hope that the new manuscript will achieve the requirements of Applied Sciences Journal (MDPI)

Yours sincerely,

Lívia Garcia-Gil

Universitat Politècnica de Catalunya-BarcelonaTech

Jordi Girona 1-3, Módulo B-1, 08034, Barcelona, Spain

Phone 0034932254800

livia.garcia@upc.edu

Point 1:

the last sentence of the abstract is not correct and it should be rewritten. The same (uncorrect) sentence is at lines 406-408. Please avoid these repetitions;

Response 1: Following the suggestion of the reviewer a native English translator has revised the manuscr

ipt and this sentence has been rewritten. Changes can be found highlighted in yellow.

Point 2:

line 27: "its design" is not correct: the authors refer to "its use";

Response 2: This suggestion has been implemented.

Point 3:

the sentence at line 32-34 is not always true: if the pavement is porous, these problems are avoided;

Response 3: Completely agree. Porous asphalt pavements have been successfully used to improve storm water drainage, increase wet-weather driving safety and reduce tyre-pavement noise. What these lines attempted to express is that in situations where water accumulates on the pavement surface the “splash&spray” and hydroplaning risk increases. These undesirable situations can be avoided through the design of the asphalt mixture (i.e. open graded mixtures) and the subsequent maintenance tasks to reduce clogging.

Point 4:

line 39: the cited methods should be referenced;

Response 4: As suggested, more bibliographical references have been given.

Point 5:

In table 1, all the cited standards should be referenced;

Response 5: References of all the standards have been included.

Point 6:

Figure 5 is not readable. The same for Figure 9 and Figure 10. In general, the quality of figures is poor;

Response 6: The mentioned figures have been modified in order to avoid reading difficulties. Moreover the size of all figures has been increased.

Point 7:

Response 7: The mentioned research project is an earlier project and it opened up the Industry to apply the labelling concept to road surface and compare performance among different types of pavements. Both projects were based on the energy label concept and aimed to increase safety, environmental and economic efficiency of road transport.

Eco-labels were introduced in late 1970s in Germany, and have been steadily rising since then, from a dozen worldwide in the 1990s to more than 435 labels to date. However, the development of labels for the road industry is not extended because it considers multiple factors that are often hard to measure.

The cited project focused on attributes related to tyre-road interaction (traffic noise reduction, skid resistance and rolling resistance) and lifespan, while the present research addresses the structural, functional and environmental performance. Therefore, the proposal made by the present authors intends to address all the issues related to the performance of wearing courses, so it can be considered as a more complete approach. For instance, structural properties and other relevant environmental factors such as production temperature, the use of by-products or the reuse of recycled materials were not studied in the cited project.

On the other side, given the growing concern of Infrastructure Managers on safety and ride comfort, thin overlays are a preservation technique that is gaining popularity. For this reason the present research has focused on establishing a labeling strategy for thin wearing courses and facilitating the assessment of their performance.

Reviewer 2 Report

The manuscript by Livia Garcia-Gil and Rodrigo Miro is a statistical analysis and classification study on wearing courses of Spanish roads. The papers describes the authors attempt to define a labeling strategy for designed pavements in Spain based on mechanical, functional and environmental properties to improve decision making of infrastructural mangers (IMs). After data collection and analysis, the authors used the data and minimum available standards to define 4 grades of A, B, C and D for each category of mechanical performance, functional properties and environmental performance.

The paper is well written and shows a great effort by authors to collect, analyze and define labels. As authors mentioned correctly, many criteria, standards and data are selected specifically for Spain and in some cases, even the methods of analysis is based on some criteria from specific University in Spain. Although the mythology can be used for different counties and can be adjusted based on different mechanical, functional and environmental criteria; all these choices make labelling less globally acceptable. Therefore, I don't find the labeling strategy very scientific as it doesn’t show what criteria have been used.

Author Response

Ms. Ref. No.: applsci-473563

Title: Labelling strategy for evaluating the performance of thin wearing courses (revised)

Applied Sciences

Dear Reviewer,

We hope that the new manuscript will achieve the requirements of Applied Sciences Journal (MDPI)

Yours sincerely,

Lívia Garcia-Gil

Universitat Politècnica de Catalunya-BarcelonaTech

Jordi Girona 1-3, Módulo B-1, 08034, Barcelona, Spain

Phone 0034932254800

livia.garcia@upc.edu

Comments:

Response:

Following the suggestion of the reviewer a native English translator has revised the manuscript and more relevant references have been included. Changes can be found highlighted in yellow.

The purpose of the present research project was to establish a methodology to create a tool that evaluates the structural, functional and environmental attributes of any thin wearing course. This methodology can be summarized in four main steps:

(1) Data collection,

(2) Statistical treatment of each property to detect outliers, establish the working range and determine their statistical distribution,

(3) Class limits definition,

(4) Global labeling

The criteria to stablish the limits of the labels (step 3) are shown in section 2.2 of the paper. Once the statistical distribution of the considered property is determined, the limit that indicates label D is firstly defined. This first boundary is given by the technical requirements or tests of each Road Administration, in this case by the Spanish technical standards. For instance, in the case of the Sideway Force Coefficient (Table 2), the Spanish technical standard establishes a minimum value for gap-graded mixtures that is 65, so any obtained value less than 65 will obtain a D label. The boundaries of A, B and C labels were defined according to the percentiles of its statistical distribution mentioned in section 2.2. The proposed methodology ensures that based on all the available data, some of them represents an excellence performance; others represent a current good practice and the rest and acceptable condition.

Therefore, when applying the proposed methodology in one country or another, the boundaries of each label class not only may change from one country to another, but they must be adjusted because there are different factors that vary considerably from one country to another: technical standards, specifications, type of mixture, construction techniques, used materials, traffic, weather conditions, age of the pavement, preservation techniques, etc.

This is the reason why the methodology is described in detail in the paper but the used data to obtain the label limits for each property are not shown, since the obtained boundaries will change based on the database but the methodology remains the same. The authors want to emphasize that the methodology and the statistical criteria adopted are more important than the values obtained for the limits that separate one label from another. The established boundaries for label classes are proposals of the authors to make the subject more tangible, since these values represent a particular case.

Wearing courses are not a replicable product such as electrical appliances, and their attributes strongly depend on their local conditions. For this reason, road conditions may differ from a one country to another and what may represent an excellent performance in one country may be an acceptable performance to another.

The uniqueness of any country should not be a drawback but a technical fact to bear in mind when developing this tool, so the methodology should be flexible enough to be tailored to suit countries’ specific requirements to ensure its use, the ultimate goal of any developed product.

Some of these explanations have been included in the article in order to clarify the applicability of the proposed methodology.

Reviewer 3 Report

The aim of the paper is to develop a multi-labelling scheme for asphalt mixtures used in thin wearing courses construction. These materials’ properties, in fact, have to be expressed in a more complete way, having regard on their mechanical, functional and environmental performances.

To do this, some properties of the asphalt mixtures were classified into their categories and referred to European standards and practises, if existing. In the cases where no harmonised European methods were available, Spanish technical standard was used. Afterwards, four label classes (A-D) have been proposed, considering these label classes as variable from A to D: A when the performances are excellent, B when they represent current good practice, C in the case of acceptable performance and D when the material does not meet the standards. In order to define the limits of each label class, statistical treatments have been performed to establish the reference statistical distributions. The approach has been used for both mechanical, functional, environmental and global properties of the materials.

Due to the origin of the collected data, the study was specifically oriented to the Spanish case, but the proposed methodology can be easily adapted to other requirements or countries.

In general, the paper is clear and methodologically correct; the review of literature is quite wide but it can be further improved. The title and abstract are appropriate; the subject rather fits with the journal’s aims and scope.

The novelty of research is fair and, in my opinion, it could be interesting for readers. However the need to set up such a kind of labelling for asphalt mixtures and/or thin wearing courses should be better demonstrated, for example by means of requirements or specifications issued by public or private road Agencies or Ministries. At the best of my knowledge, at the moment the main clients of road works in Europe are not demanding such a product qualifications, and it is not clear if this condition is due to the lack of a shared methodology or to the suitability of other data that allow to indirectly obtain the same information.

With regard to the properties and data considered in the study, a discussion about the effectiveness of these ones respect to the performances characterization will be useful to better evaluate if the proposed methodology is adequate also for other countries or it should be opportunely customized.

More general, the paper can be considered as an interesting suggestion for a new approach to the bituminous mixes labelling, as well as a proposal for the development of new classification methods and standards.

Author Response

Ms. Ref. No.: applsci-473563

Title: Labelling strategy for evaluating the performance of thin wearing courses (revised)

Applied Sciences

Dear Reviewer,

We hope that the new manuscript will achieve the requirements of Applied Sciences Journal (MDPI)

Yours sincerely,

Lívia Garcia-Gil

Universitat Politècnica de Catalunya-BarcelonaTech

Jordi Girona 1-3, Módulo B-1, 08034, Barcelona, Spain

Phone 0034932254800

livia.garcia@upc.edu

Comments:

Due to the origin of the collected data, the study was specifically oriented to the Spanish case, but the proposed methodology can be easily adapted to other requirements or countries.

Response:

A comprehensive review of the article has been conducted and numerous references have been added to the paper.

As the reviewer comments, currently most Road Administrations, including the Spanish Administration, only establish compliance specifications for certain properties: if the requirement is met, the product is accepted (in this case the bituminous mixture) otherwise, it is rejected and it must be manufactured/constructed again. But a product qualification in terms of acceptable or excellence performance is not required. However, there is a real need for more information about the performance of the used materials. Proof of this is this research project that has been co-funded by the Spanish Government.

The purpose of the present project was to establish a methodology to create a tool that evaluates the structural, functional and environmental attributes of any wearing course for thin layers. This methodology and the criteria for setting the boundaries of the label classes are clearly defined and represent a suitable solution for any country. However, the boundaries of each label class not only may change from one country to another, but they must be adjusted because there are different factors that vary considerably from one country to another: technical standards, specifications, type of mixture, construction techniques, used materials, traffic, weather conditions, age of the pavement, preservation techniques, etc. The attributes of wearing courses strongly depend on the local conditions, so road conditions may differ from a one country to another and what may represent an excellent performance in one country may be an acceptable performance to another.

To ensure the use of any tool, the methodology should be flexible enough to be tailored to suit countries’ specific requirements because the uniqueness of any country should not be a drawback but a technical fact to bear in mind when developing this tool.

In order to clarify the applicability of the proposed methodology some of these remarks have been included in the article.

Round 2

Reviewer 2 Report

I believe the quality of the paper has been improved. Although I believe labeling a complex material design is not a good idea, but I believe the work is novel and could be interesting for infrastructural mangers.

Reviewer 3 Report

The Authors have correctly addressed the most of suggestions proposed, and the paper has been improved if compared to the previous version.