What Is an Asphalt Overlay?

Asphalt pavement refers to the pavement paved with stone and sand as aggregate, ore powder as filling material, asphalt as gelling material, heating pouring or mixing. The asphalt pavement layer includes an asphalt bottom layer and an asphalt surface layer. Asphalt bottom layer, also known as asphalt base layer, is placed under the surface layer, and together with the surface layer, transmits the repeated effects of wheel load to the base layer, cushion layer and soil foundation, which plays the main bearing role.

The bottom layer of asphalt refers to bearing the wheel load transmitted by the surface layer and spreading it to the lower layers, so it can play a role in reducing the thickness of the surface layer, but the base layer is basically not affected by wheel horizontal forces and adsorption. At the same time, it is not directly affected by the atmosphere. Therefore, the base layer requires lower shear and abrasion strength of the material, but requires sufficient compressive strength. Generally, gravel, gravel, lime soil, or various industrial waste residues are used. Materials to build. In order to meet the needs of the overall performance of the pavement structure, an additional layer is needed between the surface layer and the base layer, the purpose is to strengthen the connection between the surface layer and the base layer, to prevent the surface layer from sliding along the surface of the base layer, and to eliminate cracks caused by the base layer. And reflected to the surface layer. Base layer When the base layer is paved into two layers, the layer below it is called the base layer. The purpose of setting the base layer is to share the load-bearing effect of the base layer to reduce the thickness.

The function and role of asphalt pavement is self-evident to meet the purpose of safe and comfortable traffic behavior of traffic vehicles. As the highway is a geotechnical structure exposed to natural environmental conditions, the asphalt pavement must also meet and adapt to natural environmental conditions. . As time passes, the composition of traffic vehicles on the highway is constantly changing, and the requirements for the functions and functions of asphalt pavements are constantly changing, so the connotations contained in the functions and functions of pavements are also constantly changing. China's current design specifications for highway asphalt pavements make clear requirements for the design of asphalt pavement structures, that is, "the pavement is within the design life and meets the corresponding bearing capacity of highways at all levels,

Asphalt pavement cushion requirements

The most widely used material for pavement is gravel. Due to the large difference in the quality of the gravel itself, it will have a certain impact on the quality of the entire pavement. Therefore, the project supervision staff must control the quality of the gravel and strictly follow the technical requirements. To carry out the work, the specific requirements are: first control the gravel, its crushing value must not exceed 30%. Gravel with a size of 0.5 to 5 cm must not be less than half. Given that the strength of the graded gravel cushion is mainly related to particle grading and compaction, the grade of the graded gravel should be required.

Asphalt graded gravel cushion construction requirements

The gravel used in the project is a relatively loose material. In order to avoid damage to the pavement caused by the passage of vehicles, the supervisors of the project must always ask the construction staff to take half of the traffic and half of the construction when carrying out the construction. The unfavorable impact of the chaos at the opening site on the gravel cushion caused the vehicle surface to be tight, uneven, or lead to a longer construction period.

Asphalt cement stabilized gravel base

According to the construction measures, it can be divided into two methods, one is the road mixing method, and the other is the plant mixing method. Road mixing methods are mostly used in sub-base construction. The plant mixing method is generally used in the construction of the upper base. Cement stabilized gravel, as the base layer of high-grade highway pavement, is an important part of the pavement structure, which is related to the overall strength of the pavement and the key part of protecting the normal use of the pavement during the design cycle ^[2] .

Construction requirements for gravel base

There are two types of common gravel base construction methods, which are usually performed according to road mixing methods. The specific steps are as follows: first level the material, then spray water, place the cement, spread it flat, use mechanical stirring, and finally level it. Then it can be rolled and formed. However, the plant mixing method has unique features. First, prepare the materials, prepare the amount of cement, sprinkle the water to stir the materials, transport them by vehicle, and finally spread and then roll compact.