High-performance Continuously Reinforced Concrete Pavements in Richmond and Lynchburg, Virginia

About the report:

This study evaluated the properties of two high performance concrete (HPC) paving projects in Virginia. These continuously reinforced concrete pavements were placed on State Route 288 near Richmond and on the U.S. 29 Madison Heights Bypass in Lynchburg; a minimum flexural strength of 650 psi at 28 days was required for each. In an attempt to control cracking, reduced shrinkage was sought through the use of large maximum size well-graded aggregates and proper curing. The results showed that satisfactory strengths can be obtained at 28 days. Concretes with the lowest water content had the lowest shrinkage, as expected. For desired performance, good construction practices including a level base, correct steel placement, proper consolidation, timely texturing, and effective curing are required. Although pavement designs are based on flexural strength, compressive strength tests are more convenient and less variable than are flexural strength tests. Therefore, a correlation was established between flexural and compressive strength, and acceptance of the pavements was based on compressive strength. The findings of the study led to the following recommendations with regard to the concrete used in HPC paving projects: Consider specifying strength at ages above 28 days to encourage the use of a higher percentage of pozzolanic material; specify the use of large maximum size aggregate in combination with well-graded aggregate to reduce water content and minimize segregation; use trial batches to determine the minimum cementitious materials content that provides acceptable strength and workability; use actual elastic modulus values to check and adjust the design of the pavement; use a test section before the start of the paving operation to determine if any changes to the equipment and placement procedures are needed; use compressive strength for the acceptance of a project after a correlation with flexural strength is established; permit maturity testing to estimate the strength of concrete in the pavement for opening to traffic based on concrete curing time and temperature. If as little as a 10 percent increase in service life were achieved by using HPC, the savings would be in the millions of dollars over the life of the pavement. With proper selection of the aggregates, a reduction in the cementitious material content of 50 lb./yd3 is possible and would translate to a savings of about $400,000 dollars for the two projects investigated in this study. The reduction in time for opening to traffic of new or reconstructed pavements through strength estimation by the maturity method and the use of appropriate earlier strength mixtures can lead to road user cost savings close to $0.5 million per year.

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