United States Department of Transportation
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Performance of I-57 recycled concrete pavements.
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2009-01-01
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Edition:Final report, Jan. 2008-Dec. 2008
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Abstract:In 1986-1987 the Illinois Department of Transportation (IDOT) constructed a demonstration project on I-57 near Effingham, Illinois to evaluate the viability
of recycling an existing jointed reinforced concrete pavement for use as its primary aggregates in the surface mixture of a 10-in continuously reinforced
concrete pavement (CRCP). This CRCP test section on northbound and southbound I-57 contained a 7-in cement-stabilized subbase and a 13.5-ft
extended lane width. Longitudinal reinforcement bars were placed using the tube feeding method. Functional and structural data, including falling weight
deflectometer testing (FWD), distress surveys, friction testing, surface profile testing, and conditions rating surveys were collected periodically throughout
the life of the pavement. Structural test data demonstrates a pavement section that has exhibited excellent load carrying capacity (less than 0.006-in
deflection under 9-kip load), and load transfer efficiency across the transverse cracks. Furthermore, the cement-treated subbase and subgrade have
performed well over the CRCP’s service life. There also was no structural response or cracking difference between the sections with the stabilized base
extended under the shoulder versus the base that is only a standard lane width.
Few structural distresses are observed except for the prominent amount of longitudinal cracking that appears over the reinforcement bars in all lanes. This
abnormal cracking pattern has been noted for many years and has been attributed to settlement cracking associated with the original tube feeding
process, the bar size selected, the bulk density of the concrete with recycled concrete aggregate (RCA), and the higher drying shrinkage of RCA concrete.
The section has developed a significant amount of localized distresses and patches over the past 5 years as a result of the further deterioration of this
longitudinal cracking distress. A petrographic examination has concluded that there is no deleterious alkali-silica reaction occurring in the RCA test section,
and that the air void system is normal. The mean transverse crack spacing is approximately 1.5 ft, which is significantly shorter than normal CRCP and
can be attributed to the greater drying shrinkage potential, slightly lower tensile strength, and reduced fracture properties of RCA. Functionally, the
pavement shows good skid resistance and fair-to-good ride quality. Overall, the performance of this CRCP pavement with RCA has exceeded roughly 50
percent of the 10-in CRCP within Illinois in terms of age and 25 percent in terms of traffic.
Based on the 20 years of performance on the I-57 CRCP section, the future use of RCA on concrete pavement in Illinois can be approached with
confidence and optimism. IDOT’s original material assessment has avoided any material-related distress such as freeze–thaw damage (D-cracking), ASR,
and corrosion of the steel from excess chloride content. Future application of RCA in concrete pavements should consider its higher drying shrinkage
potential and lower tensile strength and fracture energy. Future implementation of moist curing on concrete pavements with RCA or use of two-lift
construction technique would minimize risk of the extremely close crack spacing due to excessive drying shrinkage noted on the I-57 CRCP test section.
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