Maintenance and Rehabilitation
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Flexible Pavement Rehabilitation

The combined effects of traffic loading and the environment will cause pavements to deteriorate over time. Although maintenance can slow the rate of deterioration, it cannot stop it.

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Cold In-Place Recycling

Cold in-place recycling (CIR) is the processing and treatment with bituminous and/or chemical additives of existing HMA pavements without heating to produce a restored pavement layer (AASHTO, 1998[1]). It involves the same process of cold plant mix recycling except that it is done in-place by a train of equipment. Procedure The typical CIR process involves … Read more »

Figure 1. Heater Scarification Train Showing 2 Preheaters, the Heater/Scarifier, the Paver and Rollers.

Hot In-Place Recycling

Hot in-place recycling (HIR) is a less common form of hot asphalt recycling. There are three basic HIR construction processes in use, all of which involve a specialized plant in a continuous train operation (FHWA, 2001c[1]): Heater scarification (Figure 1). This method uses a plant that heats the pavement surface (typically using propane radiant heaters), … Read more »

Figure 2. 3.7 x 3.7 m (12 x 12 ft.) UTW slabs at the [[http://mnroad.dot.state.mn.us/research/mnresearch.asp Mn/ROAD test facility.

Structural PCC Overlays for HMA Pavement

A PCC overlay of an existing flexible pavement, called “whitetopping”, is a newer, viable rehabilitation alternative for flexible pavements. The overlayed rigid layer offers a reasonably thin, highly durable wearing course with a significant structural capacity. Although there are risks, whitetopping can be effective for almost all applications. They have been successfully used on interstate … Read more »

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Structural HMA Overlays for HMA Pavement

Structural overlays are used to increase pavement structural capacity. Therefore, they are considered rehabilitation, although they typically have some maintenance-type benefits as well. Asphalt concrete structural overlay design can be broadly categorized into the following (modified after Monismith and Finn, 1984[1]): Engineering judgment Component analysis Non-destructive testing with limiting deflection criteria Mechanistic-empirical analysis Each of … Read more »

Figure 2: Sketch of HMA Overlay Thickness Required to Reduce Pavement Deflection  from a Measured to a Design Deflection Value (Asphalt Institute, 1983)

Limiting Deflection – Asphalt Institute

The basic approach of the overlay design procedure is to identify continuous pavement sections of uniform performance, obtain “static” pavement surface deflections with the Benkelman Beam or other device and determine the expected traffic by use of ESALs. This section summarizes the approach described in the Asphalt Institute’s Asphalt Overlays for Highway and Street Rehabilitation … Read more »

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Component Analysis – Asphalt Institute

The Asphalt Institute’s component analysis design approach (termed “effective thickness” by the Asphalt Institute) uses relationships between subgrade strength, pavement structure, and traffic (Asphalt Institute, 1983). The existing structural integrity of the pavement is converted to an equivalent thickness of HMA, which is then compared to that required for a new design. The structural evaluation … Read more »

Figure 1. Whitetopping

Thin Whitetopping

Thin Whitetopping (TWT) is a 4 to 7 in. thick concrete overlay bonded to an existing ACP to create a composite section. TWT is typically constructed at intersections where rutting and shoving in asphalt pavement continue to cause problems. TWT may also be used at access or exit ramps to interstate highways, entire sections of … Read more »

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Flexible Base Overlay

Flexible Base Overlay The flexible base overlay has been used as an intermediate layer of a rehabilitated pavement structure, placed directly on top of an existing highway surface. The primary purpose, in addition to adding additional structure, has been to resist the propagation of reflective cracks from the old structure. The existing structure still offers … Read more »

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Flexible Base Thickening

Flexible Base Thickening Flexible base thickening can be used to improve the structural capacity of low to moderate volume highways. This technique can be used where there are low levels of existing structural damage, the existing base is uniform and the subgrade offers good (>15ksi) support. The new base material should be of equal or … Read more »

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