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  • Concrete Pavement Guide Part 2: New Construction Division of Maintenance Pavement Program CHAPTER 200 Continuously Reinforced Concrete Pavement (CRCP) January 2015

    200-1

    Disclaimer The contents of this guide reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the State of California or the Federal Highway Administration. This guide does not constitute a standard, specification, or regulation.

    CONCRETE PAVEMENT GUIDE PART 2 NEW CONSTRUCTION

    CHAPTER 200 CONTINUOUSLY REINFORCED CONCRETE PAVEMENT (CRCP)

    Chapter 200 provides specific information about designing continuously reinforced concrete pavement (CRCP). Refer to Chapter 120 for general information about concrete pavement structure design and HDM Chapters 600 670 for pavement design methodology and standards.

    200.1 PURPOSE AND DESCRIPTION Continuously reinforced concrete pavement (CRCP) is concrete pavement with steel reinforcing bars with no transverse joints. CRCP is reinforced in the longitudinal direction with additional transverse bars used to support the longitudinal bars (see Figure 200-1). The longitudinal bars are lap spliced (see Section 200.2.2) to maintain continuity, ensuring continuous reinforcement. CRCP develops transverse cracks that are spaced at random intervals due to:

    1. Internal forces caused by the shrinkage of concrete 2. Expansion and contraction due to temperature changes 3. Concrete volume change resulting from moisture variation

    Transverse cracks are restrained by continuous longitudinal bars that keep the transverse cracks tightly closed and minimize water penetration. Crack width can affect the corrosion rate of the reinforcing bars at the crack locations where water or deicing salts penetrate the cracks.

    Figure 2001: Epoxy coated CRCP reinforcement

    http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm

  • Concrete Pavement Guide Part 2: New Construction Division of Maintenance Pavement Program CHAPTER 200 Continuously Reinforced Concrete Pavement (CRCP) January 2015

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    The optimum amount of longitudinal bars, as detailed in the standard plans, is determined such that it satisfies all of the following three limiting criteria:

    Crack spacing: to minimize the potential of concrete punchouts and spalling, the spacing between consecutive cracks must be limited between 3 (to limit punchouts) and 7 (to limit spalling).

    Crack width: to minimize spalling, water infiltration, and load transfer the allowable crack width should not exceed 0.04.

    Steel stress: to prevent steel yielding and excessive permanent deformation, the tensile stress in steel is limited to < 75% of its ultimate tensile strength.

    200.1.1 Benefits CRCP has a number of benefits, including:

    Minimal maintenance is required, reducing future maintenance costs, traffic closures, and worker safety risks compared to other pavement types.

    Tighter transverse cracks and fewer joints result in smoother pavement and reduce water penetration and potential base damage.

    Lower life cycle costs despite higher initial cost. Ability to handle heavier truck loading and volumes.

    CRCP can provide a durable highway that can withstand high traffic and truck volumes for 40 years or more. Where cost effective, CRCP is the preferred type of concrete pavement. Life-cycle cost analysis (LCCA) is the most effective methodology to help make the determination. More information is available from the Division of Maintenance Pavement Program website at: http://www.dot.ca.gov/hq/maint/Pavement/Offices/Pavement_Engineering/LCCA_index.html.

    200.1.2 Limitations Situations where CRCP may not be desirable include:

    For conventional highways, local roads, and areas with underground utilities. Accessing utilities for maintenance can damage CRCP and result in costly repairs.

    For parking areas or where the traffic index (TI) < 11.5. CRCP is expensive to build for lightly trafficked locations.

    200.2 MATERIALS 200.2.1 Concrete Concrete consists of a combination of cementitious materials, coarse and fine-graded aggregate, water, and typically some property modifying admixtures. Concrete properties such as strength, durability, permeability, and abrasive wear resistance are materials dependent. Concrete properties such as strength, durability, permeability, and abrasive wear resistance are materials dependent. CRCP should be designed using the highest quality concrete materials to maximize long-term durability. Use of rapid strength concrete (RSC) is not recommended. Section 90 of the Standard Specifications defines the required chemical and physical concrete material properties for contractor developed mix designs, with some additional requirements for concrete pavement in Section 40. For more comprehensive information about concrete materials, refer to Chapter 120 and the Division of Engineering Services Concrete Technology Manual.

    http://www.dot.ca.gov/hq/maint/Pavement/Offices/Pavement_Engineering/LCCA_index.htmlhttp://dschq.dot.ca.gov/OSCHQDownloads/misc/CTM2013.pdf

  • Concrete Pavement Guide Part 2: New Construction Division of Maintenance Pavement Program CHAPTER 200 Continuously Reinforced Concrete Pavement (CRCP) January 2015

    200-3

    200.2.2 Bar Reinforcement CRCP contains both longitudinal and transverse reinforcement bars. Steel reinforcing bar requirements are in Section 52 of the 2010 Standard Specifications. Because bar reinforcement is deformed, slippage is minimized and bonding with the concrete is increased. As a result, contraction and expansion movements are minimized. Epoxy coated bar reinforcement is required within half a mile of a salt water body and in high desert and all mountain climate regions to mitigate corrosion (see Figure 200-1). The climate map is available on the Headquarters Division of Maintenance Pavement Program website at: http://www.dot.ca.gov/hq/maint/Pavement/Offices/Pavement_Engineering/Climate.html.

    Longitudinal Bars Longitudinal bars strengthen the pavement, provide the desired transverse crack spacing, and keep transverse cracks tightly closed. Narrow cracks maintain aggregate interlock, providing a high level of load transfer between the fractured concrete surfaces and reducing pavement flexural stress due to traffic loading. Tight cracks also reduce water infiltration and intrusion of incompressible material. The cross-sectional area ratio of steel to concrete should between 0.55 to 0.70% for longitudinal bars. Longitudinal reinforcement used for CRCP consists of Grade 60, No. 6 steel bars spaced from 5.5 to 8.0 center-on-center. The first bar is placed 3 to 4 from the joint or edge of pavement. The longitudinal bar depth is 4 minimum clearance from the concrete surface to the top of the bars. For CRCP thicknesses > 0.95, 5 minimum cover is required so the transverse bars clear the sawcut at longitudinal joints (see Revised Standard Plan RSP P4). Maintaining steel continuity by overlap splicing each steel bar in the longitudinal direction ensures good CRCP performance. The staggered splice pattern shown schematically in Figure 200-2 is recommended for lap splicing longitudinal bars. Requirements for reinforcement splicing are in Standard Specification Section 52-6.03B. Additional longitudinal bars are placed at transverse construction joints to ensure sufficient reinforcement at points of discontinuity (see Section 200.3 and Revised Standard Plan RSP P31A for other types of CRCP joints).

    Figure 2002: Staggered lap splices

    Transverse Bars Transverse bars are used across the entire width of CRCP lanes primarily to support the longitudinal bars during construction and to hold random longitudinal cracks tightly closed to mitigate the potential risk of punch outs. Longitudinal cracks occur approximately parallel to the roadway centerline. Since transverse bars are used across the entire width of CRCP, intermediate transverse bars are also used to tie adjacent lanes together across longitudinal contraction joints (see below and Section 200.3.3).

    http://www.dot.ca.gov/hq/maint/Pavement/Offices/Pavement_Engineering/Climate.htmlhttp://www.dot.ca.gov/hq/esc/oe/project_plans/highway_plans/stdplans_US-customary-units_10/viewable_pdf/rspp31a.pdfhttp://www.dot.ca.gov/hq/esc/oe/project_plans/highway_plans/stdplans_US-customary-units_10/viewable_pdf/rspp31a.pdf

  • Concrete Pavement Guide Part 2: New Construction Division of Maintenance Pavement Program CHAPTER 200 Continuously Reinforced Concrete Pavement (CRCP) January 2015

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    Transverse bars are usually Grade 60, No. 6, deformed steel bars spaced at 48 center-on-center and placed on either steel or plastic support chairs (see Figure 200-3).

    a) Steel chairs b) Plastic chairs

    Figure 2003: Reinforcement support chairs

    Tie Bars and Intermediate Transverse Bars Tie bars and intermediate transverse bars hold the faces of abutting concrete in contact and maintain adequate load transfer efficiency. Tie bars are deformed, 50 long, epoxy-coated, Grade 60, No. 6, steel bars placed in the same plane as transverse reinforcement, perpendicular to the longitudinal construction joint or between a lane and shoulder. Tie bar spacing is 24 where placed midway between or on adjacent transverse bars. Tie bars are commonly placed with a mechanical splice coupler shown in Revised Standard Plan RSP P16 because bending and straightening tie bars after concrete placement is not allowed because of potential damage to the epoxy coating and the surrounding concrete. Intermediate transverse bars tie the adjacent slabs together. They are deformed, 50 long, epoxy-coated, Grade

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