Using Existing Pavement in Place and Achieving Long Life (2014) / Chapter Skim
Currently Skimming:
Pages 41-64
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 41... ...
41 A p p e n d i x A The R23 team conducted a thorough literature search for information on highway renewal using existing pavements. The resources utilized for this task include the following: • The Transportation Research Information Service (TRIS)
|
From page 42... ...
42 Asphalt Concrete (AC) Renewal Approaches AC over AC Methods The team sought information on the following potential flexible pavement renewal methods: • AC over existing AC, • AC over crushed and shaped AC, and • AC over reclaimed AC.
|
From page 43... ...
43 layers or hot mix for the upper base layer. The categories of pavement recycling options are shown in Figure A.3 (National Highway Institute 2003)
|
From page 44... ...
44 Hot In-Place RecyclIng (HIPR) ARRA defines three types of HIPR operations: heater scarification, repaving, and remixing.
|
From page 45... ...
45 for future traffic, minus Deff, the effective thickness of the existing concrete slab) by an adjustment factor, A, that converts the thickness deficiency from inches of concrete to inches of asphalt.
|
From page 46... ...
46 the crack and seat technique can perform well when the subgrade support is uniform and the subgrade modulus is more than 15,000 psi after cracking. Nondestructive testing (NDT)
|
From page 47... ...
47 Rubblizing involves breaking the existing concrete pavement into pieces, and thereby destroying any slab action, and overlaying with HMA. The sizes of the broken pieces usually range from 2 to 6 in.
|
From page 48... ...
48 strike the pavement at an angle of 30° from the transverse direction. The hammers in the second row strike the pavement parallel to the transverse direction.
|
From page 49... ...
49 thickness for rubblized concrete pavements (Thompson 1999)
|
From page 50... ...
50 layer, as illustrated in Figure A.11 (Newcomb, Buncher, and Huddleston 2001)
|
From page 51... ...
51 or PCC) , although experience shows that reflective cracking can be more predominant when the existing pavement is a PCC pavement.
|
From page 52... ...
52 Because the pavement foundation is critical to the construction and performance of a long-life HMA pavement, the question of whether an existing pavement can be used in place largely depends on the quality of the existing foundation. A careful consideration of the existing condition of the pavement foundation must therefore be made.
|
From page 53... ...
53 predicted using mechanistic-empirical distress models. The distresses considered should include at least fatigue cracking, and ideally rutting and thermal cracking as well.
|
From page 54... ...
54 A mechanistic procedure for design of AC overlays of cracked and seated concrete pavements was developed by Thompson at the University of Illinois as part of the FHWA/ Illinois DOT study Mechanistic Evaluation of Illinois Flexible Pavement Design Procedures. For a given overlay thickness, the required inputs are the design AC elastic modulus, the subgrade resilient modulus, and the "equivalent modulus" of the cracked and seated concrete.
|
From page 55... ...
55 Source: Washington State Department of Transportation 2005. Figure A.18.
|
From page 56... ...
56 are being overlaid with PCC (J.
|
From page 57... ...
57 pavements, including those with existing asphalt overlays. Unbonded concrete pavements are appropriate for pavements with little or no remaining structural life and/or extensive and severe durability distress.
|
From page 58... ...
58 Field observations do not support the implication that un- bonded overlay performance is as sensitive to existing pavement thickness as the structural deficiency concept suggests. One alternative to the Corps of Engineers equation for design of an unbonded overlay is to design the overlay as if it were a new pavement, with the existing pavement structure characterized as a foundation for the new slab.
|
From page 59... ...
59 can potentially reflect through the new overlay and compromise its performance. Typically, a fine-graded asphalt surface mixture is used for the separator layer.
|
From page 60... ...
60 Bonded PCC over PCC Bonded PCC overlays of PCC are generally not considered very long-life pavement rehabilitation techniques because of their sensitivity to the condition of the underlying pavement and the difficulty of achieving the long-lasting bond necessary for composite bending action. Bonded concrete overlays are not often used, because they perform best on pavements in good to fair condition, that is, pavements that are not in urgent need of rehabilitation.
|
From page 61... ...
61 pavement, the design considerations that must be taken into account to ensure good long-term performance include the adequacy of the foundation, the required thickness and any constraints on it, the method of connection to the adjacent lane, the design of transitions, and, in the case of widening, geometric considerations such as the availability of horizontal and vertical space for relocating shoulders, slopes, ditches, and/or drainage systems, interchanges, and bridges. Lane Replacement The evident viability of this technique as a long-life in-place renewal method seems at odds with the relatively little use that it has seen to date in the United States.
|
From page 62... ...
62 Concrete Overlay Materials Needed for Long Life Much of the emphasis in defining the characteristics of inplace pavement renewal options with the potential for service lives in the range of 50 years is necessarily on the structural design of the new material. Decisions regarding PCC mix materials are affected by the type of mixture -- conventional or fast track (accelerated)
|
From page 63... ...
63 reducers, and supplementary cementitious materials (SCMs) such as fly ash and ground granulated blast furnace slag (GGBFS)
|
From page 64... ...
64 of Pavement Evaluation and Repair (SAPER)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.