Improving Properties of Reclaimed Asphalt Pavement for Roadway Base Applications through Blending and Chemical Stabilization

Abstract

Finding innovative ways to incorporate reclaimed asphalt pavement (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; however, 100% RAP has low bearing strength and creeps under load. The objective of this research is to develop methods to improve RAP's strength while reducing creep to an acceptable level through blending with high-quality crushed-limestone aggregate, by chemical stabilization with asphalt emulsion or portland cement, or both. RAP–aggregate blends with and without chemical stabilization were compacted by the modified Proctor method, cured, and tested for strength and creep. Strength was tested by the limerock bearing ratio (LBR), a variant of the California bearing ratio test. Specimens were tested dry and soaked to evaluate retained strength. One-dimensional creep testing was performed with 7-day oedometer tests. RAP–aggregate blends have the potential to be used successfully as base course material. Blends of RAP with 50% limerock base material attained acceptable LBR strength and creep with the addition of 1% of either asphalt emulsion or cement. Blends of RAP with 75% or more limerock attained close-to-acceptable LBR and low levels of creep without any chemical stabilizer. Significant variability was noted between results with different blends and stabilizing agents. Performance testing should be conducted to establish the suitability of a specific RAP–aggregate blend.

Investigation of the Effect of Recycled Asphalt Pavement Material on Permeability and Bearing Capacity in the Base Layer

“…e percentage of RAP material in blends exceeds 20-25%, and the expected CBR value for the base course decreases as discussed by several authors [4][5][6][7][8][9][10][11][12]. Some researchers reported that the RAP content of the base mixtures should be limited to a maximum of 50% by weight [7,8].…”

Comportamento mecânico e desempenho estrutural de materiais reciclados e estabilizados com espuma de asfalto.

“…For surface layers, West (2010) says that the average RAP incorporation rate in new asphalt mixes in the United States is between 12% and 15%, with a rate up to 30% resulting in the same performance as conventional mixtures that only use virgin aggregates. Other authors, as Rahman et al (2014), have obtained good results studying permanent deformation in the Hamburg Wheel Tracking Device with RAP percentages of up to 50%, surpassing some of the results of mixes with rates of 10% and 30%.…”

“…The combination of RAP and different proportions of crushed limerock was studied by Bleakley and Cosentino (2012) with the objective of increasing the resistance and bearing capacity of the recycled mix, to be used as a base layer. It was observed that higher proportions of crushed limerock resulted in smaller deformations and higher stiffness.…”

“…Twagira (2010) states that curing is the main process in developing a strong and durable bond between the asphalt binder and the mineral aggregates.…”

“…Twagira (2010) conducted a few triaxial resilient modulus tests to investigate the effect of moisture damage on stiffness for both foamed and emulsion mixtures, with asphalt binder contents of 2.0% and 1% of either cement or lime. The results presented modulus from 300 MPa to 700 MPa for 100% saturated samples for different mixtures.…”