ABSTRACT
In this term paper, the many ways of asphalt pavement recycling, as well as the advantages of recycling, such as saving the cost, conserving aggregate and binder and preservation of existing pavement, geometries of the pavement, environmental conservation, and resource conservation, are discussed. In addition, less user delay and less energy are benefits of recycled asphalt following the initial introduction of asphalt pavement recycling. A guide on selecting a recycling process is offered and the applicability for a variety of recycling procedures. The structural design of these recycled asphalt pavements is also covered.
2. INTRODUCTION.
The concept of recycling or reusing pavement material is simple yet effective. Existing pavement materials can be recycled to create new materials, saving time, money, and energy (Krupa & Prof. Ashok, 2018). At the same time, recycling existing materials aids in the solution of disposal issues. Pavement geometrics and thickness can also be preserved during construction due to the reuse of existing material. Traffic description may be less in some circumstances than for other rehabilitation strategies. The following are some of the specific advantages of recycling:
- Lower construction costs, preservation of aggregate and binders
- Maintenance of current pavement geometrics
- Protection of the environment
3. PROBLEM STATEMENT.
The need for aggregate has risen in recent years due to infrastructure growth and improved facilities in roadway structures. Because aggregate is limited, asphalt pavement recycling is the best alternative for producing good results with benefits. While cost savings and environmental benefits are the most important, several variables drive the usage of recycled asphalt pavements. Aggregates make up the majority of the material used in bituminous concrete pavements. Because aggregate is a natural material, it is quickly consumed, resulting in a scarcity of resources needed for rapid infrastructure development.
On the other hand, new construction trends have resulted in the development of solid waste in demolished structures. Science and technology now should invent recent cost-effective and environmentally beneficial trends. Recycling helps to limit the quantity of building debris in landfills. Recycling asphalt conserves natural resources while also extending the life of the asphalt pavement. Recycled aggregate can be obtained from old
Demolished concrete constructions (RA). This can be utilized efficiently in conjunction with natural aggregates in various infrastructure needs in order to achieve a balance between demand and supply of construction materials, hence lowering environmental impact. This study will be aiming to recover aggregate and optimize natural resources, the demand for aggregate to construct pavement is increasing. To address the issue of dumped items, recycle them, and protect natural resources. To reduce negative environmental effects as much as possible.
4. OBJECTIVES
- To study various Asphalt Pavements Recycling Techniques.
- To study the benefits of recycling asphalt pavements.
- To study multiple structural designs of recycled asphalt pavements.
5. LITERATURE REVIEW.
5.1. Recycling as a Method of Rehabilitation
Asphalt pavements can be rehabilitated in various ways (E-L & Plescan, 2015). Recycling is just one of them. The severity of the pavement distress, laboratory and field evaluations of the existing material, and design characteristics influence the chosen rehabilitation strategy. The choice of rehabilitation method is also influenced by the preservation of geometrics and original pavement thickness, notably in under-passes. On the other hand, recycling provides some advantages that other forms of rehabilitation procedures don’t have. Recycling, for example, can save money, aid in natural resource conservation, and keep pavement geometry and thickness consistent. Many recycling technologies are now available to address specific pavement degradation and structural concerns. Many recycling processes are now available to solve particular pavement degradation and structural needs due to traffic and environmental conditions (Abdalrhman Milada & Nur, 2020). To keep the pavement in good shape, rehabilitation is required. Repair may be necessary if the ride quality is poor due to significant pavement distress. It may also be needed if the coefficient of friction between the tire and the pavement is reduced or if the structural capacity or capacity to carry expected traffic loads is insufficient.
5.2 Methods and Procedures for Recycling
It can be categorized as hot mix asphalt recycling, hot in-place recycling, cold in-place recycling, or full-depth recycling, depending on the procedure used to recycle the bituminous mix.
Hot mix asphalt recycling
Reclaimed asphalt pavement components are blended with fresh ingredients, sometimes coupled with a recycling agent, to make hot mix asphalt (HMA) mixtures in hot mix asphalt recycling. Batch and drum-type hot mix units are employed to make a recycled mix.
Milling, ripping and crushing operations can obtain recycled asphalt pavement material.
The tools and processes for placing the mix and compaction are the same as standard HMA.
Hot in-place recycling
This technique involves heating and softening the existing pavement before scarifying/milling it to a set depth.
Cold in-place recycling
The term “cold in-place recycling” refers to the reuse of existing pavement materials without the need for heat.
Except for any recycling agent, there is usually no need to carry materials, and aggregate can be added, so hauling costs are minimal.
As a recycling agent or binder, an asphalt emulsion is typically used.
Full-depth recycling
Full-depth recycling is described as a recycling procedure that involves treating the entire asphalt pavement section and a predefined portion of the underlying base material to generate a stabilized base course.
It’s essentially a cold mix recycling process in which various additives, such as asphalt emulsions and chemical agents like calcium chloride, Portland cement, fly ash, and lime, are added to obtain a better base. These recycling techniques provide a multitude of benefits, including the following (Administration, 1997):
Allow for the reuse of existing materials while eliminating disposal issues.
Changes to the aggregate or asphalt binder could improve the asphalt mix.
It is possible to improve the ride by correcting the pavement profile.
Cost savings over traditional rehabilitation approaches are possible.
5.3 Recycled Pavement Structural Design
The parts of the design that provide the proper strength or stiffness to the pavement structure are considered in pavement structural design. The design process has evolved from engineering judgment to primarily mechanistic or semi mechanistic techniques. Pavement materials can be classified based on their robust modulus and fatigue characteristics. “Structural numbers” can classify different types of pavement materials based on their strength and structure.
Pavements produced with recycled asphalt components can be as good as or better than those made with traditional hot mix asphalt.
The enormous variety of features of recycled mixtures coming from variances in material and building procedures must, however, be taken into account during the structural design of recycled pavements.
The coefficients for both recycled surface and recycled base courses were more significant than the coefficients for conventional mixtures in the AASHTO Road Test. According to the AASHTO handbook, there is no significant difference between hot recycled and virgin HMA material. The structural rehabilitation analysis approach (for conventional mix) is likewise suggested for the design of recycled pavements. However, because long-term performance data for recycled compounds is not accessible, engineering judgment should always be used when designing such blends. (AASHTO, 1986)
The AASHTO handbook presented an overlay design technique based on the structural number, underlying layer thickness, and drainage factors.
6. CONCLUSION
Recycling Asphalt is a new technology that allows for the construction of bituminous pavements at a lower cost by repurposing old bituminous pavement materials. It also ensures resource optimization and promotes long-term development. The optimal percentage of material relies on the bituminous material’s composition and the sort of layer to be applied. Numerous transportation agencies have recycled asphalt in unbound base and sub-base layers for many years. The Asphalt use specifications adopted by various transportation agencies have a general lack of uniformity.
7. REFERENCES
AASHTO. (1986). AASHTO Guide for Design of Pavement Structures,. Washington DC: American Association of State American Association of State.
Abdalrhman Milada, A. M., & Nur, I. M. (2020). A REVIEW OF THE USE OF RECLAIMED ASPHALT PAVEMENT FOR ROAD PAVING APPLICATIONS. Jurnal Teknologi, 35-44.
Administration, D. o. (1997). Pavement Recycling Guidelines forState and Local Governments, U.S.
E-L, P., & Plescan, C. (2015). ASPHALT PAVEMENT RECYCLING. Bulletin of the Transilvania University of Braşov, 265-270.
Krupa, S. S., & Prof. Ashok, P. (2018). Recycling of Asphalt Pavements. International Research Journal of Engineering and Technology (IRJET), 1242-1244.
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