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Perhaps the most important step in designing a pavement is the estimation of the design traffic. Overestimation of the design traffic results in a thicker pavement than necessary with associated higher costs. Underestimation of traffic results in a thin pavement that will fail prematurely, resulting in higher maintenance and user costs. If the proposed pavement […]

The AASHTO pavement design equations have some variables that are common to both rigid and flexible pavements, including serviceability, traffic loading, reliability, overall standard deviation, and roadbed soil resilient modulus. These parameters are discussed in the following articles. Subsequently, the design procedure is presented for rigid pavements in Art. 3.6 and for flexible pavements in […]

AASHTO has given interim approval for a new approach to pavement design as described in the AASHTO Interim Mechanistic-Empirical Pavement Design Guide Manual of Practice. Several years in development, this M-E pavement design guide and the accompanying software should provide a significant advancement in pavement performance prediction. As its title implies, mechanistic-empirical models are used […]

Perhaps the most widely used pavement design method in the United States and throughout the world is that presented in the AASHTO Guide for Design of Pavement Structures. A long history of pavement studies has led to the current (1993 with 1998 supplement) edition. FIGURE 3.8 Joint in composite pavement that has been sawed and […]

Rigid pavement constructed with an asphalt overlay is referred to as composite pavement. The advantage of constructing an asphalt overlay on a rigid pavement is solely in the areas of ridability and noise. Rigid pavements are considered by most to create more road noise inside a vehicle than flexible pavements. This phenomenon is largely due […]

Asphalt concrete pavement, also referred to as flexible pavement, is a mixture of sand, aggregate, a filler material, and asphalt cement combined in a controlled process, placed, and compacted. The filler material can range from quarry crushing dust and asphalt-plant baghouse fines to wood fibers (cellulose). There are many additives that can be used in […]

As the name implies, continuously reinforced concrete (CRC) pavement is a rigid pave­ment constructed with continuous longitudinal reinforcement. No transverse joints are installed. Instead, the pavement is allowed to develop random transverse cracks, and the steel reinforcement holds the cracked sections together. The size and spacing of the cracks are influenced by the percentage of […]

Joint sealing prohibits the infiltration of water into the pavement base and prevents incompressibles from lodging within the joint cavity. The advantages of keeping water out from under a pavement are documented extensively in the AASHTO Pavement FIGURE 3.4 Layout of joints in rigid pavement at skewed intersection. Conversions: 1 in = 25.4 mm, 1 […]

The following basic principles must be observed in developing a correct jointing detail: 1. Never taper concrete down to less than 2 ft (610 mm) in width. 2. Depending upon the amount of transverse reinforcing steel, be careful of the number of lanes that are tied together. In JPCP, tying more than three 12-ft (3.7-m) […]

Jointed rigid pavements tend to crack at 13 to 25 ft (4 to 8 m) lengths because of (1) initial shrinkage after placement as excess water evaporates, (2) temperature-induced expansion and contraction resisted by friction with the subgrade, (3) curling and warping caused by temperature and moisture differences between the top and bottom of the […]