1.Functions and Techniques of the Three Asphalt Pavement Layers
When discussing asphalt pavement construction, we often encounter the key terms: permeate coat, tack coat, and seal coat. Each plays an indispensable role, and together they comprise the three-layer structure of an asphalt pavement. So, what are the unique functions of these three layers, and what techniques are there for applying them? Let's delve into the world of asphalt pavement and explore the mysteries of these three layers.
In studying municipal road engineering, we encounter not only important concepts such as surface course, base course, sub-base, and roadbed, but also the permeate coat, tack coat, and seal coat. However, the location and function of these layers often confuse students. Therefore, this article aims to provide a clear summary to help you better understand the mysteries of these three layers.
2.Overview and Function of Permeate Coat
The permeate coat plays a vital role in municipal road engineering. Located between the roadbed and the base layer, the percolator strengthens the pavement structure by spraying it. Especially when applied to lime-stabilized or cement-stabilized soil base layers, it effectively promotes the bonding between the asphalt mixture surface layer and the base layer. The percolator's primary function is to promote a good bond between the asphalt mixture surface layer and the non-asphalt base layer.
The percolator effectively enhances the integrity and durability of the pavement structure. To achieve this, the percolator should be sprayed on the base layer surface before the asphalt mixture surface layer is laid. Specifically, for lime-stabilized or cement-stabilized soil base layers, the percolator should be sprayed immediately after the base layer is compacted and formed, when the surface is slightly dry but not yet hardened. After spraying, traffic should be closed to ensure that the percolator fully penetrates and works effectively. Liquid asphalt or emulsified asphalt with excellent permeability is preferred.

3.The Function and Construction Techniques of the Tack Coat
The tack coat, another critical step in pavement construction, primarily serves to strengthen the bond between the surface layer and the pavement. To achieve this, tack coat oil must be sprayed after the penetration oil has penetrated and solidified. Use liquid or emulsified asphalt with good permeability, and ensure traffic is closed to allow for full penetration.
Tack coat oil is typically sprayed after the penetration oil has penetrated and solidified, allowing it to fully enhance adhesion. Furthermore, to ensure even coverage and penetration of the tack coat into the pavement structure, traffic must be closed for a period of time after spraying. Highly permeable liquid or emulsified asphalt is also preferred when selecting materials.
To enhance the adhesion between asphalt layers and the bond between the asphalt layer and the cement concrete pavement, tack coat oil should be applied on the same day as the surface layer is laid. This oil should be sprayed at the interface between existing structures, curbs, manholes, and other structures, and the asphalt mixture layer. When choosing materials, prioritize fast-cracking or medium-cracking emulsified asphalt, modified emulsified asphalt, and fast-setting or medium-setting liquid petroleum asphalt. Sealcoat Application and Precautions
The sealcoat, using asphalt concrete or asphalt sand, further enhances the pavement's waterproofness and smoothness, thereby ensuring its structural stability and durability. During application, the upper or lower sealcoat must be selected based on the location, and the material should possess excellent waterproof properties.
The sealcoat application follows immediately after the tack coat application. The purpose of the sealcoat is to further enhance the pavement's waterproofness and ensure the long-term smoothness of the pavement. Commonly used materials include asphalt concrete or asphalt sand. Using specialized construction machinery and methods, the materials are evenly applied to the pavement, forming a protective sealcoat.
The functions of the sealcoat include sealing and protection, transition and connection, reinforcement, and temporary protection. Commonly used sealcoat materials include modified asphalt or modified emulsified asphalt, which offer excellent waterproofness and durability. It is important to note that the temperature and wind speed requirements during application are stringent. When spraying the penetration coat, tack coat, or sealcoat, the temperature should be at least 10°C and the wind speed should not exceed force 5. If the temperature is too low or the wind is too strong, it will affect the adhesion of the oil and the construction effect