Full-Depth Reclamation - (Page 13) new specified grade elevation after placement of the 2-inch asphalt surface. Portland cement was incorporated across the area for the next four days with a total of 300 tons being utilized. Proper density and moisture levels were ensured through a QC testing and inspection program by PSI with no problems reported. With the expectation of needed parking for the weekend, Thompson Arthur Paving began surfacing operations on Friday, September 21, after successful proof-rolling was performed the day before on approximately one-half of the reclaimed area. Even though the area had only a two- to three-day cure, no sign of movement was reported under the fully loaded tandem axle water truck used for proofrolling. Further adding to the observed stability of the FDR, no observed damage to the FDR section occurred when a 50-ton crane sat on jacks for several hours while repairing a malfunctioning high-mast light. Paving was completed the following Monday after successful proof-rolling operations of the remaining unpaved reclaimed section. With a lower cost and timely construction schedule, FDR provided JCPenney an alternative rehabilitation technique for a deteriorated parking area. Shoppers for years to come will now have the support of a strong and durable base created through FDR with portland cement. Long-Term Performance of Full-Depth Reclamation with Portland Cement Introduction This article summarizes the findings of an extensive investigation into the design, construction, testing, and long-term performance of failed flexible pavements rehabilitated through full-depth reclamation (FDR) using portland cement. Objectives of this investigation included: • Evaluating the in-service long-term performance of roads rehabilitated using FDR with cement • Evaluating the design protocol for field and laboratory investigation for FDR with cement pavements •Determining what problems agencies encounter by implementing this rehabilitation technique • Developing guidelines for successful implementation The complete research report is available as Full-Depth Reclamation with Portland Cement: A Study of Long-Term Performance, by Imran M. Syed, Ph.D., Portland Cement Association (PCA) publication SR016. Axle loads on streets and highways have increased significantly over the years, while funds for road maintenance have shrunk. Most public agencies have existing road networks comprised primarily of flexible pavements. Progressive public officials looking to save time, materials and money needed to provide a safe and efficient road network are making it their top priority to salvage these existing flexible pavements at the end of their service lives. The FDR with cement process has been used on pavement projects for more than 20 years and rebuilds worn out asphalt pavements by recycling the existing roadway. This cost-effective technique is popular with state, county, and city highway agencies attempting to correct their deteriorating pavements and increase the pavements' structural capacity. UCS measurements State and Local Agencies The actual field performance of more than 75 projects in eight states scattered across the country were evaluated. Agency personnel involved with the FDR process were contacted and interviewed about the methodology used to select candidate projects, and about the design and construction of their FDR projects. Performance-related data such as pavement inventory, functional and structural information, traffic data, material composition, amount of cement added, and construction details were collected. Performance Evaluation The performance evaluation process consisted of interviewing the agency/owner of the facility, performing visual pavement surveys, taking cores at select pavement locations, and performing strength measurements on the cores. This provided a qualitative assessment of the long-term strength and stiffness of the reclaimed bases. Pavements rehabilitated using the FDR process underwent a visual inspection, which focused on finding evidence of pavement distress at the selected project sites - particularly distresses that may have been due to the condition of the base (such as block cracking, roughness, and deep potholes). The pavement distresses were systematically recorded to identify their type, extent and severity. From this data, a numerical composite distress index, termed the Pavement Condition Index (PCI), was calculated. The PCI values range from zero for a failed pavement to 100 for a pavement in perfect condition. Table 1 summarizes the results of the pave- ment condition surveys in the study and shows that almost all of the roads rehabilitated using the FDR process are performing well. The average PCI for each agency type ranged from 88% to 97%, indicating an excellent rating. Most of the distresses noted during visual inspection of the pavement sections were in the asphalt layer. Any distresses caused by the base (such as minor reflective cracking) did not affect the roughness or overall road performance. Long-Term Strength Representative core samples of the reclaimed base from some of the pavement sections were obtained and subjected to laboratory Unconfined Compressive Strength (UCS) measurements to determine the inplace strength of the reclaimed base after many years of performance. UCS of these samples ranged from 260 to 2,110 psi (1.8 to 14.5 MPa), as shown in the figure above with the average of all samples being 914 psi (6.3 MPa). Typically, these FDR sections were originally designed for a 7-day UCS of between 400 and 600 psi (2.8 and 4.1 MPa). The majority of cores were tested for UCS Special advertising supplement to the McGraw-Hill Construction Regional Publications 13 http://www.cement.org/fdr
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.