《ACI-325.12R-2002.pdf》由会员分享，可在线阅读，更多相关《ACI-325.12R-2002.pdf（32页珍藏版）》请在三一文库上搜索。
1、ACI 325.12R-02 became effective January 11, 2002. Copyright 2002, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or or
2、al, or recording for sound or visual reproduc- tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. ACI Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in planning, designing
3、, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept re- sponsibility for the application of the material it contains. The American Concrete
4、 Institute disclaims any and all re- sponsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in con- tract documents. If items found in this document are de- sired by the Architect/Engineer to be
5、 a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer. 325.12R-1 Guide for Design of Jointed Concrete Pavements for Streets and Local Roads ACI 325.12R-02 This guide provides a perspective on a balanced combination of pavement thi
6、ckness, drainage, and subbase or subgrade materials to achieve an acceptable pavement system for streets and local roads. Such concrete pavements designed for low volumes of traffic (typically less than 100 trucks per day, one way) have historically provided satisfactory perfor- mance when proper su
7、pport and drainage conditions exist. Recommendations are presented for designing a concrete pavement system for a low volume of traffic and associated joint pattern based upon limiting the stresses in the concrete or, in the case of reinforced slabs, maintaining the cracks in a tightly closed condit
8、ion. Details for designing the distributed reinforcing steel and the load transfer devices are given, if required. The thickness design of low-volume concrete pavements is based on the principles developed by the Portland Cement Association and others for analyzing an elastic slab over a dense liqui
9、d subgrade, as modified by field observations and extended to include fatigue concepts. Keywords: dowel; flexural strength; joint; pavement; portland cement; quality control; reinforced concrete; slab-on-grade; slipform; subbase; tie bar; welded wire fabric. CONTENTS Chapter 1General, p. 325.12R-2 1
10、.1Introduction 1.2Scope 1.3Background 1.4Definitions Chapter 2Pavement material requirements, p. 325.12R-5 2.1Support conditions 2.1.1Subgrade support 2.1.2Subbase properties 2.2Properties of concrete paving mixtures 2.2.1Strength 2.2.2Durability 2.2.3Workability 2.2.4Economy 2.2.5Distributed and jo
11、int reinforcement Reported by ACI Committee 325 David J. AkersW. Charles GreerRobert W. Piggott Richard O. AlbrightJohn R. HessDavid W. Pittman William L. ArentMark K. KalerSteven A. Ragan Jamshid M. Armaghani Roger L. Larsen* Raymond S. Rollings Donald L. BrognaGary R. MassKieran G. Sharp Neeraj J.
12、 Buch* William W. MeinTerry W. Sherman Archie F. CarterJames C. MikulanecJames M. Shilstone, Sr. Lawrence W. Cole* Paul E. MuellerBernard J. Skar Russell W. CollinsJon I. MullarkyShiraz D. Tayabji Mohamed M. DarwishTheodore L. NeffSuneel N. Vanikar Al EzzyEmmanuel B. Owusu-AntwiDavid P. Whitney Luis
13、 A. GarciaDipak T. ParekhJames M. Willson Nader GhafooriThomas J. Pasko, Jr. Dan G. Zollinger* Ben GompersRonald L. Peltz Jack A. Scott Chairman Norbert J. Delatte Secretary *Significant contributors to the preparation of this document. The committee would also like to acknowledge the efforts of Rob
14、ert V. Lopez and Dennis Graber. 325.12R-2ACI COMMITTEE REPORT Chapter 3Pavement thickness design, p. 325.12R-10 3.1Basis of design 3.2Traffic 3.2.1Street classification and traffic 3.3Thickness determination 3.4Economic factors Chapter 4Pavement jointing, p. 325.12R-12 4.1Slab length and related des
15、ign factors 4.1.1Load transfer 4.1.1.1Aggregate interlock 4.1.1.2Doweled joints 4.1.1.3Stabilized subgrades or subbases 4.2Transverse joints 4.2.1Transverse contraction joints 4.2.2Transverse construction joints 4.3Longitudinal joints 4.4Isolation joints and expansion joints 4.4.1Isolation joints 4.
16、4.2Expansion joints 4.5Slab reinforcement 4.6Irregular panels 4.7Contraction joint sealants 4.7.1Low-modulus silicone sealants 4.7.2Polymer sealants 4.7.3Compression sealants 4.7.4Hot-applied, field-molded sealants 4.7.5Cold-applied, field-molded sealants Chapter 5Summary, p. 325.12R-21 Chapter 6Ref
17、erences, p. 325.12R-21 6.1Referenced standards and reports 6.2Cited references Appendix APavement thickness design concepts, p. 325.12R-24 A.1Load stresses and fatigue calculations Appendix BSubgrade, p. 325.12R-28 B.1Introduction B.2Soil classification B.3Subgrade soils B.4Expansive soils B.5Frost
18、action B.6Pumping Appendix CJointing details for pavements and appurtenances, p. 325.12R-31 CHAPTER 1GENERAL 1.1Introduction The design of a concrete pavement system for a low traffic volume extends beyond the process of pavement thickness selection; it entails an understanding of the processes and
19、the factors that affect pavement performance. It also encompasses appropriate slab jointing and construction practices that are consistent with local climatic and soil conditions. Concrete pavements for city streets and local roads are often used in residential areas and business districts, and in r
20、ural areas to provide farm-to-market access for the move- ment of agricultural products. The term “low volume” refers to pavements subject to either heavy loads but few vehicles, or light loads and many vehicles. City streets and local roads also serve an aesthetic function because they are integrat
21、ed into the landscape and architecture of a neighborhood or business district. Concrete pavement performs well for city street and local road applications because of its durability while being contin- uously subjected to traffic and, in some cases, severe climatic conditions. Because of its relative
22、ly high stiffness, concrete pavements spread the imposed loads over large areas of the subgrade and are capable of resisting deformation caused by passing vehicles. Concrete pavements exhibit high wear resistance and can be easily cleaned if necessary. Traffic lane markings can be incorporated into
23、the jointing pattern where the concretes light-reflective surface improves visibility. Concrete pavement surfaces drain well on relatively flat slopes. The major variables likely to affect the performance of a well-designed concrete pavement system for city streets and local roads are traffic, drain
24、age, environment, construction, and maintenance. Each of these factors may act separately or interact with others to cause deterioration of the pavement. Due to the nature of traffic on city streets and local roads, the effects of environment, construction, and maintenance can play more significant
25、roles in the performance than traffic. Nonetheless, complete information may not be available regarding certain load categories that make up the mixture of traffic carried on a given city street or local road. 1.2Scope This guide covers the design of jointed plain concrete pavements (JPCP) for use o
26、n city streets and local roads (driveways, alleyways, and residential roads) that carry low volumes of traffic. This document is intended to be used in conjunction with ACI 325.9R. References are provided on design procedures and computer programs that consider design in greater detail. This guide e
27、mphasizes the aspects of concrete pavement technology that are different from procedures used for design of other facilities such as highways or airports. 1.3Background The thickness of concrete pavement is generally designed to limit tensile stresses produced within the slab by vehicle loading, and
28、 temperature and moisture changes within the slab. Model studies and full-scale, accelerated traffic tests have shown that maximum tensile stresses in concrete pave- ments occur when vehicle wheel loads are close to a free or unsupported edge in the midpanel area of the pavement. Stresses resulting
29、from wheel loadings applied near interior longitudinal or transverse joints are lower, even when good load transfer is provided by the joints. Therefore, the critical stress condition occurs when a wheel load is applied near the pavements midslab edge. At this location, integral curbs or thickened e
30、dge sections can be used to decrease the design DESIGN OF JOINTED CONCRETE PAVEMENTS FOR STREETS AND LOCAL ROADS325.12R-3 stress. Thermal expansion and contraction, and warping and curling caused by moisture and temperature differentials within the pavement can cause a stress increase that may not h
31、ave been accounted for in the thickness design procedure. The point of crack initiation often indicates whether unexpected pavement cracking is fatigue-induced or environmentally induced due to curling and warping behavior. Proper jointing practice, discussed in Chapter 4, reduces these stresses to
32、acceptable levels. Concrete pavement design focuses on limiting tensile stresses by properly selecting the characteristics of the concrete slab. The rigidity of concrete enables it to distribute loads over relatively large areas of support. For adequately designed pavements, the deflections under lo
33、ad are small and the pressures transmitted to the subgrade are not excessive. Although not a common practice, high-strength concrete can be used as an acceptable option to increase performance. Because the load on the pavement is carried primarily by the concrete slab, the strength of the underlying
34、 material (subbase) has a relatively small effect on the slab thickness needed to adequately carry the design traffic. Subbase layers do not contribute significantly to the load-carrying capacity of the pavement. A subbase, besides providing uniform support, provides other important functions, such
35、as pumping and faulting prevention, subsurface drainage, and a stable con- struction platform under adverse conditions. Thickness design of a concrete pavement focuses on concrete strength, formation support, load transfer conditions, and design traffic. Design traffic is referred to within the cont
36、ext of the traffic categories listed in Chapter 3. Traffic distribu- tions that include a significant proportion of axle loads greater than 80 kN (18 kip) single-axle loads and 150 kN (34 kip) tandem-axle loads may require special consideration with respect to overloaded pavement conditions. Like hi
37、ghway pavements, city streets and local roads have higher deflections and stresses from loads applied near the edges than from loads imposed at the interior of the slab. Lower-traffic-volume pavements are usually not subjected to the load stresses or the pumping action associated with heavily loaded
38、 pavements. In most city street applications, concrete pavements have the advantage of curbs and gutters tied to the pavement edge or placed integrally with the pavements. Curb sections act to carry part of the load, thereby reducing the critical stresses and deflections that often occur at the edge
39、s of the slab. Widened lanes can also be used to reduce edge stresses in a similar manner. Dowel bars on the transverse joints are typically not required for low-volume road applications except, in some cases, at transverse construction joints; however, they may be considered in high truck-traffic s
40、ituations where pavement design thicknesses of 200 mm (8 in.) or greater are required. Roadway right-of-way should accommodate more than just the pavement section, especially in urban areas. The presence of utilities, sewers, manholes, drainage inlets, traffic islands, and lighting standards need to
41、 be considered in the general design of the roadway. Provisions for these appurtenances should be considered in the design of the jointing system and layout. Proper backfilling techniques over buried utilities also need to be followed to provide uniform and adequate support to the pavement.1 Interse
42、ctions are a distinguishing feature contributing to the major difference between highways and local pavements. Intersection geometries need to be considered in the design of the jointing system and layout. Slabs at intersections may develop more than a single critical fatigue location due to traffic
43、 moving across the slab in more than one direction. 1.4Definitions The following terms are used throughout this document. A typical cross section in Fig. 1.1 is provided to facilitate the design terminology. Average daily truck trafficself-explanatory; traffic, in two directions. Aggregate interlock
44、portions of aggregate particles from one side of a concrete joint or crack protruding into recesses in the other side so as to transfer shear loads and maintain alignment. California bearing ratio (CBR)the ratio of the force per unit area required to penetrate a soil mass with a 1900 mm2 (3 in.2) ci
45、rcular piston at the rate of 1.27 mm (0.05 in.) per min to the force required for corresponding penetration of a standard crushed-rock base material; the ratio is typically determined at 2.5 mm (0.1 in.) penetration. Concrete pavementthis term is used synonymously with “rigid pavement.” Cracka perma
46、nent fissure or line of separation within a concrete pavement formed where the tensile stress in the concrete has equaled or exceeded the tensile strength of the concrete. Deformed bara reinforcing bar with a manufactured pattern of surface ridges that provide a locking anchorage with the surroundin
47、g concrete. Dowel(1) a steel pin, commonly a plain round steel bar, that extends into two adjoining portions of a concrete construction, as at a joint in a pavement slab, so as to transfer shear loads; and (2) a deformed reinforcing bar intended to transmit tension, compression, or shear through a c
48、onstruction joint. Fig. 1.1Typical section for rigid pavement structure. 325.12R-4ACI COMMITTEE REPORT Drainagethe interception and removal of water from, on, or under an area or roadway. Equivalent single-axle loads (ESAL)number of equivalent 80 kN (18 kip) single-axle loads used to combine mixed t
49、raffic into a single design traffic parameter for thickness design according to the methodology described in the AASHTO design guide.2 Expansive soilsswelling soil. Faultingdifferential vertical displacement of rigid slabs at a joint or crack due to erosion or similar action of the materials at the slab/subbase or subgrade interface due to pumping action under load. Frost heavethe surface distortion caused by volume expansion within the soil (or pavement structure) when water freezes and ice lenses form within the zo