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https://www.nationalacademies.org/trb/events

Performance of Cement-Treated Aggregate (CTA) and Full-Depth Reclamation (FDR) Bases for Semi-Rigid Pavement Design

Cement-treated aggregate (CTA) and cement-stabilized full-depth reclamation (CS-FDR) are both used to increase pavement foundation stiffness, distribute wheel loads, reduce stresses transmitted to underlying layers, and support asphalt-surfaced pavement systems. Although both are cementitiously stabilized base materials, they are produced and constructed in fundamentally different ways. CTA is generally plant-produced from virgin materials while CS-FDR is produced in place by pulverizing existing bound and unbound pavement materials and stabilizing the reclaimed blend with cement. Consequently, CS-FDR may contain variable quantities of existing materials depending on original construction uniformity. CTA is expected to be more uniform, but Virginia experience has also shown that transport, placement, moisture loss, grading, and compaction can produce substantial field variability. This is important as Virginia Department of Transportation (VDOT) begins the use of semi-rigid pavement analysis in AASHTOWare Pavement ME Design. Cement stabilized layers require material properties that represent their strength and stiffness rather than treating them as conventional unbound aggregate. Laboratory characterization and stiffness testing of field placed materials is necessary to describe properties of these materials for design, but laboratory testing alone is not sufficient. Repeated loading can produce progressive stiffness loss and damage even when a stabilized layer does not reach a clearly defined binary failure state. Accelerated pavement testing provides the necessary link between material properties and full-scale performance. Laboratory results can be interpreted with FWD-backcalculated stiffness, rutting and surface-distress progression, measured structural response, and post-loading forensic observations. This study therefore focused on the direct comparison of field-produced CTA and CS-FDR and on the development of Pavement ME inputs supported by laboratory, FWD, APT, and forensic evidence.