Author: Albert Marshall BleakleyPublisher:
ISBN:
Category :
Languages : en
Pages : 668
Book Description
Reclaimed Asphalt Pavement (RAP) is produced by milling during resurfacing operations. Finding innovative ways to incorporate RAP into highway base course applications will provide both environmental and economic benefits by allowing in situ recycling of material for projects such as widening or shoulder addition. RAP is a well-drained granular material which is already on site, however 100% RAP is low bearing strength and creeps under load. The objective of this research was to develop methods to improve RAP's strength while reducing creep to an acceptable level through blending with high quality crushed limestone aggregate and/or by chemical stabilization with asphalt emulsion, Portland cement, or lime. RAP/aggregate blends with and without chemical stabilization were compacted by modified Proctor, Marshall, or gyratory methods, cured, and tested for strength and creep. Strength tests included limerock bearing ratio (LBR), a variant of the CBR test, unconfined compression, Marshall compression, and indirect tensile tests. Strength specimens were tested dry and soaked to evaluate retained strength. One dimensional creep testing was performed using seven day oedometer tests. RAP/aggregate blends have the potential to be used successfully as a base course material. Blends of RAP with 50% limerock base material attained a soaked LBR strength of 100 and acceptable levels of creep with the addition of 1% of either asphalt emulsion or cement. Blends of RAP with 75% or more limerock attained a soaked LBR close to 100 and low levels of creep without any chemical stabilizer. In general adding RAP to limerock blends increased the soaked retained strength and improved permeability compared to 100% limerock. Gyratory compaction achieved higher densities than modified Proctor or Marshall compaction and improved RAP's strength by a factor of two to three compared to modified Proctor compaction at the same density but had less effect on creep. Field testing is required to determine whether it is feasible to reproduce the gyratory compaction results on an actual construction site. Significant variability was noted between results with different blends, compaction methods, and stabilizing agents. Site specific performance testing should be conducted to establish the viability of blending RAP into a base or subbase.