Design Manual for CRCP
PDF courtesy of the American Concrete Pavement Association’s (ACPA’s) technical resources archives.
Continuously reinforced concrete pavement (CRCP) may be defined as a concrete pavement in which the longitudinal reinforcing steel is continuous for its length and no transverse joints other than construction joints are installed. In actual practice. the continuity is interrupted by expansion joints at structures. Except for these, there is technically no limit as to the length of CRCP.
CRCP is considered a relatively new pavement type by many engineers, although it has been in use since 1938. State highway departments for Indiana, Illinois, Texas. California. Mississippi. New Jersey, Michigan. Maryland, and Pennsylvania have pavements of this type that have provided good service for a number of years. The older of these pavements range in age from 17 to 30 years. Seventeen other state highway departments and the Chicago Airport Authorities have also used CRCP. As of January 1, 1969. approximately 5700 miles of two-lane-equivalent CRCP had been constructed or let to contract in the United States.
Concrete pavement is used on highways because of its structural strength, durability, adaptability to exacting construction control. low maintenance. and high visibility. The highway user wants and expects good riding quality and a minimum of delay due to maintenance. By applying the design principles of this manual, the designer will retain all the benefits of concrete pavement and also give more satisfaction to the highway user through the following added features of CRCP:
- a smoother ride by elimination of joint thumping,
- reduced maintenance cost and traffic delay,
- longer pavement life, and
- lower annual cost of operation.
Transverse contraction joints were long considered essential to preventing pavement damage from volume-change stresses. CRCP takes care of these stresses in another way: it allows the pavement to develop a filagree of very fine cracks. seemingly uncontrolled and random, mostly transverse. The principle of design for this pavement type is to provide sufficient reinforcement to keep the cracks tightly closed and to provide adequate pavement thickness for the wheel loads.
Two basic types of pavement designs are covered in this manual: design for new pavement and design for concrete overlays of existing concrete pavements. The manual is divided into six sections. Section 1 provides guidance as to the specifications and test procedures for the materials used in continuous pavement. Sections 2 and 3 provide nomographs and charts for designing the various component parts of new pavements and overlay pavements. respectively. Section 4 covers pertinent items and potential problem areas that must be carefully monitored during construction. Sections 5 and 6 are example problems covering the step-by-step procedure used in a typical design analysis for a new CRCP and a CRCP overlay. respectively. Although the manual is intended to be as complete as possible. some reference to other manuals and specifications is relied on. The following three sources may be especially useful in supplementing the information herein, as indicated :
- “Study of Continuously Reinforced Concrete Pavements” by J.E. Funnell and D. K. Curtice for background information. engineering data. design details. and suggested specifications
- “Design of Subbases for Concrete Pavement” by B. F. McCullough and W. R. Hudson for more specific information on design of subbases.
- “Use of Linear Elastic Layered Analysis for the Design of Concrete Pavements. Concrete Overlays and Subbases” by B. F. McCullough and K. J. Boedecker, Jr .. for technical development of the design curves.
The engineer is encouraged to design each pavement for the soil conditions, traffic, materials, etc., present at the site and to be wary of stereotyped minimums and practices. In this age of rapid equipment and material development, the engineer must be progressive and use experience as a guideline for the future. Such an approach will insure the highway user the most economical product for his investment.
Author: B. Frank McCullough, PhD