Advantages And Disadvantages Of Asphalt

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4 Base and sub-base Layers
The materials used in these layers are graded with sufficient fines and moisture content to enhance their compatibility (Mukabi & Nganga 183). The compaction test is undertaken for each layer to determine if the required density has been achieved. Each pavement should be shaped, compacted, and approved before placement of subsequent materials. The aggregate base acts as the main load-spreading layer and consists of crushed pieces of rock or gravel, and sand fillers. The materials must be free from clay, and the coarse aggregate should not have elongated shapes. Proper grading of the materials is critical to facilitating adequate rolling for optimum compaction.
The concrete mix is placed and spread uniformly. Each layer is compacted
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It can be constructed in stages.
3.4 Disadvantages:
i. It requires high maintenance costs. ii. Its life-span is considerably reduced when subjected to heavy loads
4. The Differences between Airport and Highway Pavements
4.1 Texture:
The airport pavement is quite smooth in texture and is devoid of any loose materials. In contrast, the highway pavement is slightly rough, but the presence of loose materials poses no danger to movement along the tracks
4.2 Design Tolerances:
The allowable tolerances are higher in airport pavements compared to highway pavements. For example, from the Federal Aviation Authority (FAA) specifications, the percentage of aggregate wear for airport pavements as evaluated by abrasion test, be ≤ 40 percent, except where the desired quality of aggregate cannot be reasonably obtained. In such cases, special provisions may allow for a higher percentage of wear. On the contrary, the percentage of aggregate wear for highway pavements as evaluated by abrasion tests, should be strictly ≤ 40.
4.3 Surface Bonding:
The surface of the airport pavement is well-bonded than that of the highway pavement. This enables it to resist the shear stresses exerted by the wheels of a plane.
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