Keywords

1 Introduction

The World Highways Organization set a target to have 70% of recycled materials used in the infrastructure industry by 2020. This occurred in Europe where around 1000 million tons of recycled materials are used in the pavement that are producing valuable sustainable scenarios at a lower rate of waste landfills. It should be noted that the number of materials that contribute to roadway pavement production such as stone, sand, gravel, and other aggregates of gravel is limited as a natural resource and vital in different other industries as well, such as building construction which means it shall be reserved and consumed with caution to ensure efficiency and sustainability (Balaguera et al., 2018). [1] Therefore, this research serves a significant role in addressing the sustainability approach in different categories all at once by exploring new potential techniques for the roadway pavement industry. Studying the current situation of the pilot project: Dibba -Masafi roadway in UAE. Roadway construction materials are an important economic factor for recycled asphalt over other content of the construction. Asphalt pavement comprises aggregates and bitumen products. The primary aggregates that are used during the development of roadways are either natural materials from the rocks or slag aggregates. Due to the large amount of material that is needed during roadway construction, there is a central section that is formed by the transport of aggregate resources. Studies have demonstrated that to reduce this impact, it is necessary to lower the distance that is covered during the transportation of roadway construction materials. (Zaumanis, Mallick, and Frank, 2015) [2].

2 Methodology

The author attempts to obtain research assessments and outcomes through mixed methods. as shown in Fig. 1.

Fig. 1.
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Data collection methods

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Besides that, the approaches of qualitative and quantitative are used to utilize the impact of the implementation of recycled pavement in terms of preventive maintenance. Further, the qualitative method is also taken into consideration for obtaining and analysing non-numerical data to understand viewpoints or experiences. It can be applied to gain a thorough understanding of a topic or to generate new research proposals. It is carried out to discover people's opinions on various topics. When analysing data, this kind of strategy is constantly concerned with keeping the rich meaning. (Bhandari, 2022) [3].

On the other hand, the quantitative method depends on creating numerical data that can be transformed into useful statistics. It formulates facts and uncovers patterns in the study using measured data. Because quantitative data is based on numbers, it requires some sort of mathematical analysis because it is based on numbers. The methods include elementary maths like calculating means and medians and more sophisticated statistical analysis like figuring out the statistical significance of your results. (Humphrey, 2022) [4].

The following is an explanation of each approach:

  1. A.

    Interviews

The interviews contribute with 10 experts with the scope of infrastructure. All the answers for the 10 interviewees were merged and summarised as follows:

  • How do you define RAP?

    RAP is a term that states a reclaimed or recycled asphalt pavement when utilizing the existing pavement material in new pavement construction. It essentially revolves around removed and reprocessed asphalt and aggregate pavement materials.

  • Why are most of the organization that deals with roadways in UAE oriented to recycled asphalt?

    The UAE adopted vision, policies, and strategies to be the world’s leading nation. On the other hand, most organizations carry out new tools and techniques to ensure happiness and welfare. The roadway organizations are concerned with having a better and smoother daily journey for drivers. Nowadays, infrastructure is considered one of the global trends which need attention and concern to be better.

  • How can recycled asphalt be a maintenance solution?

    Recycled highway materials are used in pavement construction to reduce waste, protect the environment, and create an affordable resource for building roadways. It is the most practical and cost-effective way to use millings from asphalt pavement.

  • What are the parameters that influence pavement quality?

    The most important parameter that influences the pavement quality is traffic volume which contains both heavy and light vehicles. Besides that, there are other factors that control pavement quality which are:

    • Materials selection and quality (materials characterization).

    • Structural and asphalt mix design in terms of:

    • Wheel load

    • Axle configuration

    • Type of Bitumen used

    • Contact pressure

    • Vehicle speed

    • Subgrade type

    • Roadway level of service.

  • How can you follow and monitor the traffic volume in the federal roadway network?

    The federal roadway network can be monitored by doing a traffic count study on weekdays at peak time and by integration and prediction of traffic volumes of ongoing and future development.

  • What is roadway maintenance? What are the maintenance types?

    Road maintenance is the process of preserving and keeping the road structure practicable and as normal as possible. The maintenance can be categorized from two perspectives. The first is from an actions perspective, the types include Asphalt overlay, Patching, Reshaping, slab replacement, smoothing, and reconstruction; while the second perspective is from the time of application, the types including Preventative/Routine maintenance which should be done periodically and Emergency maintenance which is special repairs when the damage happened in certain locations.

  • What is the difference between Conventional pavement and recycled pavement?

    Conventional pavement is pavement constructed using 100% new virgin asphalt mixture and can be used for any type of road from local roads to freeways, and any level of traffic from low traffic to heavy traffic.

    Recycled pavement is pavement where the RAP material is used partially with additional virgin aggregate and/or additional bitumen; in other terms, it utilizes a certain percentage of its material from recycled sources.

  • What is the limitation of implementing recycled asphalt?

    The limitations of implementation due to recycling are mentioned below:

    • Particle shape, size, and density of Mixture performance

    • Volume stability

    • Quality of products

    • \({\text{Climate}}\,{\text{change}}\)

  1. B.

    Case Studies Approach

Case studies are considered a roadmap that guides the author in aligning and integrating the objectives and finding answers to the research questions, as shown in Table 1.

Table 1. Case studies summary
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  1. C.

    Site Visits Approach

All of the site visits were performed according to the health and safety regulations with the provision of an expert engineer in the project. The first visit was to identify the failures within Dibba -Masafi roadway, as shown in Fig. 2.

Fig. 2.
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Identifying and exploring the failures with E89 roadway

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The noticed failures within the roadway were addressed through a field survey sheet. Since they are repeated failures, the author identified them through random segments. The first segment was between (519–521), (528–530) and (531–533) poles with a distance of 60 ms. The most apparent failures were identified as shown in Table 2 which recognizes cracks as the most common failure parameters that influence the roadway level of service.

Table 2. Failures appearance in the research case study
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  1. D.

    Road Analysis Management System (RAMS)

The author evaluates the current pavement of the research case study in three random segments to diagnose the damages. Also, inspection and observation of the roadway surface state demonstrate the need for maintenance to increase the quality and comfort of the driving environment as it applies to the condition of the pavement. This can be done by assessing the degradation stage of each section that needs to be repaired on the federal highway. The following Table 3 is a group of pavement conditions extracted from the RAMS.

Table 3. Dibba-Masafi failure parameters, source: MoEI, RAMS,2021
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3 Results and Discussion

The main three evaluation parameters are the life cycle assessment, waste sent to the land field, and life cycle cost assessment. This will be able to show the effectivity of using recycled asphalt rather than the use of conventional asphalt where a comparison between both of them will be held in this chapter to show how effective and sustainable using these materials is in the road maintenance industry.

  1. A.

    Life Cycle Analysis

The time needed to execute any project including roadway maintenance will have a high impact on financial and social aspects as it impacts users and traffic flow in the selected area. Therefore, it is important to consider the time needed to complete the project as a major factor in selecting the best maintenance procedure for the roadway, in addition to the manpower needed and logistic facilities required during the project duration. All these factors contribute to the decision-making of the most sustainable roadway maintenance procedure, as these factors influence social and economic sustainability. Any project activity needs to be implemented according to the work order which has been modified through the contract. In this section, the author compares conventional asphalt and recycled asphalt in terms of implementation duration time. The following activities are for implementing conventional asphalt within this project that complies with 12 activities. The maximum duration is for the second activity which is traffic diversion & NoC, this is because the rest of the activity is a compulsory need for traffic diversion and organizing the traffic volume movement, which is approved by the local authorities, as shown in Fig. 3.On the other hand, the following activities are for implementing recycled asphalt within the research study that complies with 9 activities as shown in Fig. 4.

Fig. 3.
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Conventional pavement life cycle, source: MoEI, 2022

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Fig. 4.
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Recycled pavement life cycle, source: MoEI, 202

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  1. B.

    Life Cycle Cost Analysis

Using recycled asphalt as a preventive maintenance process from an economical perspective supports the idea of saving in cost. The following Table 4 illustrates the impact of using recycled asphalt as a solution in improving the roadway level of service and performance which is less costly and more sustainable in terms of cost and time. As a result, the saving percentage of using recycled pavement in the execution stage is 70% as saving with 12,147,500 Dhs.

Table 4. Activities and cost comparison between conventional and recycled asphalt, source: MoEI, 2022
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  1. C.

    Waste Land Fill

Asphalt waste makes up most of the waste produced by the construction industry, and occupies precious public space by being dumped in landfills. By using recycled asphalt to replace conventional asphalt that has already been utilized in roads, these high amounts of asphalt waste may be decreased.

The conventional asphalt waste volume is calculated through width, length, and depth in meters and total waste volume in meters cubic with 23,104 m3, as shown in Table 5.

Table 5. Conventional asphalt waste volume, source, MoEI, 2022
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On the other hand, recycled asphalt structure contains two layers the 8 cm base course and 25 cm granular base to be recycled, whereas the 5 cm wearing course of asphalt is to be replaced as shown in figure (66) with a total waste volume of 3,040 m3, as shown in Table 6.

Table 6. Recycled asphalt rehabilitation solution waste, source: MoEI,2022
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Shifting to recycled asphalt saves landfill by 87%. This is by comparing the total waste volume of conventional asphalt and recycled asphalt.

4 Conclusions

This paper has conducted the importance of the new approach using recycled asphalt in roadways. This approach supports sustainability, and in this study two pillars: economics and environment were highlighted and achieved. The recycled asphalt showed evidence of a reduction in cost and duration. On the other hand, from economic perspective this approach sequence with green phenomena by saving land fill and reuse the construction waste as landscape in neighborhoods or in new construction roadways.