The Federal Highway Administration (FHWA) released the 8-page tech brief “Optimized Design Details for Continuously Reinforced Concrete Pavements” (FHWA-HIF-19-066), which covers the design optimization for continuously reinforced concrete pavements (CRCP). Authored by Dr. Shiraz Tayabji, Ph.D., P.E., Advanced Concrete Pavement Consultancy LLC and ISCP Honorary Member (2007), and Mike Plei, P.E., Pavement Engineering Consultant and ISCP Member, the publication begins with an overview of CRCP technology, including benefits including the potential to provide long-term “zero-maintenance” service life under heavy traffic loadings and challenging environmental conditions,provided that proper design and quality construction practicesare utilized. CRCP is widely used by several highway agencies in the United States, typicallyfor heavily trafficked roadways.
CRCPs have a long history of good performance in the United States and other countries when designed and constructed well. Many U.S. highway agencies consider CRCP their pavement of choice for implementing long-life pavement strategies that have lower life-cycle costs and require fewer lane closures for routine maintenance and repair/rehabilitation. Since the 1950s, CRCP design and construction practices have advanced considerably, resulting in a truly low-maintenance concrete pavement.
CRCP differs from other concrete pavements as follows:
1. CRCP has no active transverse joints, except at ends
2. CRCP provides continuous longitudinal reinforcement, which results in tight cracks in the concrete at about 2–6 feet (0.6–1.8 m) spacing. Sufficient reinforcement is necessary to keep the cracks tight, <0.02 inches (<0.5 mm). In the United States, the longitudinal reinforcement, typically No. 6 bars, is placed over transverse bars to ensure proper placement with respect to depth and transverse spacing.
3. CRCP can extend, joint-free, for many miles with breaks provided only at structures (e.g., bridges). Joints, designed as expansion joints, are provided at structures or at a terminus of the CRCP.
CRCP design focuses on managing the cracking that develops so as to reduce the structural distresses that may develop as aresult of traffic and environmental loadings. These distresses include punchouts, steel rupture, and crack spalling. CRCP design involves determining the proper combination of slab thickness, concrete mixture constituents and properties, and steel reinforcement content and location; providing for sufficient slab-edge support; strengthening or treating the existing soils; and providing non-erodible bases that also provide friction, which leads to desirable transverse cracking patterns.
The publication provides guidance on optimizing several key design features including:
• Introduction
• Optimizing Longitudinal Steel Content
• Simplified Details for Terminal Ends
• Improved Transverse Construction Joint Detail
• Shoulder Type with CRCP
• Concrete slab/base interface
• Summary
The publication is based on information included in the previously cited references and recent refinements implemented in the field. To download a copy, please go to: https://www.fhwa.dot.gov/pavement/concrete/pubs/hif19066.pdf