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An investigation was performed to assess the state-of-the-art of recycling Portland cement concrete (PCC) airport pavements. Previous laboratory studies have shown that recycling of PCC pavements is technically and economically feasible. This has been demonstrated in airport reconstruction projects at Jacksonville International Airport (Florida), Love Field (Texas), and Coffeyville Municipal Airport (Kansas), where PCC was recycled into econocrete base and aggregate subbase, cement stabilized base, and part of the aggregate base course, respectively. Recycling of PCC for surface courses in airport pavement construction has not yet been performed, but this should also prove to be beneficial as has been experienced by the Iowa DOT and other state highway agencies who have recycled PCC for surface courses. Equipment for recycling PCC pavements is currently available in the construction industry; however, these, along with the technology of PCC recycling, could be improved substantially. Recommendations for specific improvements are therefore made. (Author).
The objective of this study was to develop criteria and guidelines for recycling portland cement concrete (PCC) airport aprons. Included in this study are all aspects of the recycling process including breakup and removal, steel reinforcement removal, crushing, screening, stockpiling, mix design, testing, placing, finishing, and performance. Recycling of PCC requires some specialized equipment such as pavement breakers and electromagnets for steel removal; however, all of the other equipment and procedures are those commonly used in the construction industry. Based on the regression experimental design procedure and laboratory tests conducted on pavement samples from six airports of widely varying age and conditions, it has been conclusively shown that aged PCC pavements can be recycled into new surface courses that meet strength requirements and have the same cyclic load carrying (fatigue) characteristics as those constructed with virgin sand content - 42 percent.
This synthesis will be of interest to pavement designers, construction engineers, and others interested in economical methods for recontstructing portland cement concrete (PCC) pavements. Information is provided on the processes and procedures used by a number of states in using PCC pavement as aggregate in reconstructed concrete pavement. Since 1975 a number of state highway agencies have reconstructed concrete pavements using the old PCC as aggregate in the new pavement. This report of the Transportation Research Board describes the processes used on various projects in several states, giving details of construction procedures, as well as test results on various properties of the recycled aggregates and the resultant concrete.
The review of current technology pertaining to the recycling of existing portland cement concrete pavements was conducted. The purpose was to assess the applicability of recycling to U.S. Air Force pavement rehabilitation work. Costs of alternatives were reduced to simple models for use in evaluating sensitivity to cost factors. A study of projects on which this technology was used identified aggregate cost and haul distance as key factors.
The recycling of portland cement concrete pavements (PCCP) can help alleviate any material disposal problems during construction, especially in urban areas and reduce the consumption or importation of virgin aggregate into aggregate poor areas. Two test sections using the coarser fraction from the original crushed PCCP were placed on K-7 in 1985. One section incorporated a recycled base and standard PCCP construction; another section was designed as a recycled base and recycled PCCP. Two other sections were control sections constructed with regular aggregate.
This report constitutes a review of the literature concerning recycling of portland cement concrete pavements by crushing the old pavement and reusing the crushed material as aggregate in a number of applications. A summary of the major projects conducted by state transportation departments is included. Crushed portland cement concrete is shown to have been successfully used in the following applications. 1. Graded-aggregate bases 2. Cement-treated bases 3. Asphalt base courses and pavements 4. Portland cement concrete bases (econocrete) and pavements 5. Source of supply for independent commercial operations selling aggregate for a variety of applications. In any given circumstances the cost and availability of new aggregate and the cost of disposing of the old concrete play important roles in establishing whether or not recycling is a desirable alternative. Consequently, each project or the general situation for a given area must be examined separately and the decision made on the basis of local conditions.