What is asphalt overlay?

Asphalt overlay is a mixture of aggregates, sand, asphalt, and additives that is applied as the final layer using asphalt paving machines on the surface of roads and streets. This overlay has a sticky nature and is used to improve asphalt and strengthen and protect the surface of roads against factors such as wear, cracking, and separation, as well as to prevent the accumulation and penetration of water into the underlying asphalt layers. In general, asphalt overlay improves the roads and streets for driving and the passage of various vehicles. With this common method, asphalt surfaces that have cracks and potholes can be repaired effectively and with the highest quality.

What is the importance of asphalt sealing?

Sealing or improving asphalt is one of the important and fundamental goals in the field of road and building engineering, significantly helping to maintain performance and extend the useful life of asphalt overlays on roads and streets. Its importance becomes evident when it prevents the destructive and negative effects of water on the surface of the asphalt overlay and its penetration into the structure.

Some of the most important goals of asphalt sealing include preventing water penetration and reducing material resistance, structural failures and cracks, protecting and preventing the degradation of the asphalt overlay against wear, rainwater, and vehicle passage, increasing the useful life of asphalt structures, enhancing driver safety, improving road security, and preventing road accidents. Interestingly, Germany and England were the first countries to produce geosynthetics, and France was the first country to use geosynthetic products to reinforce asphalt overlays in the late 1960s.

Advantages of using geogrid in asphalt improvement

One of the geosynthetic products that has significant applications in asphalt improvement and reinforcement of its overlay is geogrid. This product is made from polyester and polyethylene; in some cases, a combination of these two materials with similar materials such as polyvinyl chloride and polypropylene is used to produce geogrid.

Features of this product include tensile strength, resistance to ultraviolet rays, chemical resistance, and so on. Based on the production process, geogrids are divided into three groups: extruded, punched, and bonded, and in terms of tensile construction, they are divided into three groups: uniaxial, biaxial, and triaxial geogrids. To increase the load-bearing capacity of asphalt pavement, triaxial geogrids are used. The most important advantages of using geogrid in asphalt improvement include:

Increased stability of the road structure

Help reduce the risk of road fractures and cracking

Reduction of maintenance and periodic repair costs

Increased road resistance to erosion and damage

Improved useful life of the road and reinforcement of its structure

Stability of the road under adverse conditions and increased driving safety

Reduction of environmental impacts and increased recycling of materials used in road construction

Reduction of energy consumption

Reduction of environmental pollutants

Reduction of the need for road repairs and reconstruction

Possibility of quick and easy implementation

No need for specialized personnel for execution

Prevention of moisture and water penetration under the asphalt pavement

How to implement asphalt geogrid

In the implementation of asphalt improvement and increasing its lifespan through geogrid, several steps must be followed.

In the first step, the asphalt pavement surface of the desired road is prepared, and if necessary, the road surface must be geometrically corrected.

In the second step, cracks on the asphalt that have openings greater than 4 millimeters are sealed using the most suitable asphalt materials.

In the third step, after sealing the cracks, the asphalt surface must be cleaned of any soil materials. To increase the strength of the improvement, a suitable layer of asphalt must be poured on the asphalt. The asphalt used in this step is selected based on the conditions of the underlying layer or the asphalt pavement and the climatic conditions of the area.

Now it is time to remove the asphalt geogrid from the plastic cover. Placing the geogrid inside the plastic cover protects this product from external factors during transportation. The implementation of asphalt geogrid can be done in two ways: manually and mechanically. On a large scale, geogrid is implemented on the road surface using a roller connected to road construction machines.

In the final step, it is time to implement the final layer.

Advantages of asphalt geocomposite in reinforcing asphalt overlay

Asphalt geocomposite is another type of geosynthetic product that is used in the improvement of asphalt on roads and streets. This product consists of a non-woven geotextile layer made of polypropylene combined with geonet and geomembrane, reinforced with glass fibers. In fact, this product is made up of various layers.

Important features of asphalt geocomposite include very high tensile strength, resistance to ultraviolet rays, very high melting point and heat resistance, low weight, resistance to chemicals, environmental compatibility, wear resistance, high durability and longevity, effective drainage, high cost, and so on. The advantages of asphalt geocomposite in reinforcing and improving the asphalt overlay include:

Delaying the growth of reflective cracks in the new asphalt overlay layer

Creating adhesion between the old overlay layer and the new asphalt overlay layer

No need for specialized personnel for the installation of this geosynthetic product in asphalt improvement

Installation of asphalt geocomposite can be done in the shortest possible time and easily

It significantly helps reduce long-term maintenance costs of the asphalt overlay

This product can be used on excavation strips

It increases the strength and resistance of the asphalt overlay against heavy loads and vehicle passage

It prevents the penetration of water and moisture into the underlying layers of asphalt

It prevents undesirable deformation of asphalt and increases its cracks

It increases the useful life of asphalt structures on roads and streets

It reduces construction costs by decreasing the need for heavy materials

It has high flexibility and adapts to structural changes

How to implement asphalt geocomposite

The implementation of asphalt geocomposite for reinforcing the asphalt overlay consists of four stages, which are:

Initial preparation stage of the asphalt surface, strengthening stage, installation stage of asphalt geocomposite, and compression and stabilization stage of asphalt geocomposite. In the first stage, the asphalt overlay surface is thoroughly cleaned, and damaged layers are removed and cleaned.

In the second stage, a material such as geotextile primer is applied to increase strength and durability and enhance bonding on the asphalt overlay.

In the third stage, it is time to install the asphalt geocomposite on the overlay and geotextile primer.

In the fourth stage, using road construction machines and tools such as rollers, the asphalt geocomposite is compressed to the overlay surface and stabilized in place.

Advantages of using geotextile in asphalt improvement

Geotextile is another type of geosynthetic product that has significant applications in asphalt improvement. This product is produced as a flat fabric-like material using polymer materials such as polyester and polypropylene. By placing a geotextile layer between the old asphalt overlay and the new overlay, problems such as potholes and cracks can be prevented. The most important advantages of using geotextile in reinforcing asphalt overlay include:

Sealing the subgrade and asphalt pavement by creating a hydraulic barrier

Increasing the movement time of reflective cracks in the old asphalt pavement

Increasing tensile capacity and preventing settlement of the asphalt surface

Reducing the thickness of the asphalt layer by placing a geotextile layer between the new and old pavements

Shock absorption and stress adjustment between the layers of the asphalt overlay

Increasing durability and longevity and reducing maintenance costs

Eliminating the asphalt milling and replacement asphalt stage

Factors affecting the cost of asphalt improvement implementation

Various factors influence the cost of asphalt improvement implementation. Some of the most important and fundamental factors include:

Calculating the area of the road or street based on square meters or linear meters

The type of asphalt and the type of geosynthetic product as the polymer base

The thickness of the asphalt overlay layer

The number of laborers

The number of equipment needed for the improvement and reinforcement of asphalt

The condition of the asphalt infrastructure

The level of access to the location of the road or street

The proximity or distance of the location for transporting or transferring materials needed for asphalt overlay improvement

The public or private nature of the employer and the terms of the contract

The weather conditions and their impact on the progress and speed of work

Conclusion

In this article, we discussed asphalt overlay, the importance of asphalt sealing, the advantages of using geosynthetic products including geogrid, geocomposite, and geotextile in asphalt improvement, and how to use these products to increase the resistance of asphalt overlay. We explained that by using these products, it is possible to prevent the formation of cracks and potholes on the asphalt surface of roads and streets and significantly increase the useful life of asphalt. At the end of the article, we also introduced the factors affecting the cost of asphalt overlay improvement implementation. We hope you have made the most of the explanations provided in this article.

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