100% recycled hot mix asphalt lab samples were modified with five generic and one proprietary rejuvenators at 12% dose and tested for binder and mixture properties. Waste Vegetable Oil, Waste Vegetable Grease, Organic Oil, Distilled Tall Oil, and Aromatic Extract reduced the Superpave performance grade (PG) from 94–12 of extracted binder to PG 64-22 while waste engine oil required higher dose. All products ensured excellent rutting resistance while providing longer fatigue life when compared to virgin mixtures and most lowered critical cracking temperature. Rejuvenated samples required more compaction energy compared to virgin and some oils reduced moisture resistance slightly.

Influence of Six Rejuvenators on the Performance Properties of Reclaimed Asphalt Pavement (RAP) Binder and 100% Recycled Asphalt Mixtures

A Literature Review on Cold Recycling Technology of Asphalt Pavement

The use of reclaimed asphalt pavement (RAP) materials in road construction has been proven to reduce both the amount of construction debris disposed of in urban landfills and the rate of depletion of natural resources. However, source-dependent product variability, federal and local environmental regulation, and deficient strength-stiffness characteristics often limit RAP applications in road bases. These limitations have led to new research efforts aimed at exploring novel, cost-effective, chemical and/or mechanical stabilization methods to treat RAP materials before their reuse in pavement construction. In this work, a series of tests were performed on RAP aggregate materials treated with different dosages of portland type I/II cement and with alkali-resistant glass fibers. Tests include permeability, leachate, unconfined compression, and small-strain shear moduli through resonant column testing. Leachate tests include pH, total and volatile dissolved solids, total and volatile suspended solids, and turbidity. Test results confirm the potential of cement-fiber-treated RAP material as an environmentally and structurally sound alternative to nonbonded materials for base and subbase applications in pavement engineering. A companion paper presents the results from a comprehensive repeated-load triaxial test program to investigate the resilient modulus characteristics of cement-treated RAP.

Characterization of Cement-Fiber-Treated Reclaimed Asphalt Pavement Aggregates: Preliminary Investigation

Currently, highway agencies in Illinois are exploring the feasibility of using higher amounts of reclaimed asphalt pavement (RAP) in asphalt mixtures. Concerns about variability in aggregate gradation and higher stiffness of aged RAP binder have limited this use, however. This research project was designed to characterize the performance of hot-mix asphalt (HMA) with high amounts of RAP and to identify any special considerations that must be met to utilize these higher RAP contents. Two material sources from two districts were used to prepare eight 3/4-in nominal maximum aggregate size (NMAS) N90 binder mix designs. The mix designs included a control mix with 0% RAP and three HMAs with 30%, 40%, and 50% RAP for each district. A base asphalt binder (PG 64-22) was used in the mix design process; a single-bumped binder (PG 58-22) and a double-bumped binder (PG 58-28) were also used to prepare specimens for performance testing. The tests conducted on the HMAs were moisture susceptibility, flow number, complex modulus, beam fatigue, semi-circular bending, and wheel tracking. All tested HMAs with RAP performed equal to or better than the mixtures prepared with virgin aggregate. The study found that HMAs with high RAP content (up to 50%) can be designed with desired volumetrics. RAP fractionation proved to be very effective. Asphalt binder-grade bumping is vital for HMAs with 30% RAP content and above.

Impact of High RAP Contents on Structural and Performance Properties ofAsphalt Mixtures

In recent years, efforts have been made to incorporate reclaimed asphalt pavement (RAP) into pavement base or subbase applications by means of cement binder stabilization. This approach, however, may not be an environmentally friendly solution due to the high carbon footprint involved in the production of Portland cement. Recycled concrete aggregate (RCA), on the other hand, has been widely accepted in pavement applications. The sustainable solution of blending RAP with RCA was investigated in this research in an attempt to facilitate the usage of this blend as an alternative pavement subbase material. An extensive suite of geotechnical laboratory tests was undertaken on RAP with contents of 100, 50, 30 and 15% in blends with RCA. Results of the research study indicated that RAP/RCA blends with a low 15% RAP content meet the repeated load triaxial requirements for use in pavement subbase layers. Results of field performance of a pavement subbase constructed with untreated 100% RAP, at a private haul road field-demonstration site, confirmed that it had insufficient strength requirements to meet local road-authority pavement-subbase requirements. RAP and RAP/RCA blends, although found in this study to be not fully compliant with the local road-authorities requirements, could be potentially considered for lower traffic usage, such as haul roads and footpaths.

https://researchbank.swinburne.edu.au/file/73bec40c-db31-4728-ac16-60b9f257fe7d/1/PDF (Accepted manuscript).pdf

Reclaimed Asphalt Pavement and Recycled Concrete Aggregate Blends in Pavement Subbases: Laboratory and Field Evaluation

A procedure for characterizing the curing process of cold recycled bitumen emulsion mixtures

Evaluation of the durability and the performance of an asphalt mix involving Aramid Pulp Fiber (APF): Complex modulus before and after freeze-thaw cycles, fatigue, and TSRST tests

Quebec roads are subjected to seasonal ambient temperature variations and daily rapid variations of temperature. These significant temperature variations in combination with the moisture in...

Complex Modulus and Fatigue Analysis of Asphalt Mix after Daily Rapid Freeze-Thaw Cycles

This research focused on the stiffening effect of the filler on the asphalt mastic of microsurfacing. One challenge that researchers are faced with in the field of bituminous materials is the interaction between the filler and binder. In this study, a new conceptual model for filler stiffening of the mastic was developed that allows the asphalt mix designer to establish the minimum and maximum filler concentration to incorporate in the asphalt mixture. The proposed model has only one parameter that can be determined using the filler and asphalt emulsion selective properties, such as D10 and pH of the filler and the asphaltene content of the emulsion. A new mechanism for the stiffening effect of filler on mastic was developed based on the physicochemical interaction between filler and bitumen. Based on the model, the increase in mastic stiffness (G*) as a function of the increase in filler concentration can be divided into three regions: diluted region, optimum concentration region, and concentrate...

New conceptual model for filler stiffening effect on asphalt mastic of microsurfacing

In Quebec, for more than 20 years, cold in-place recycling (CIR) and full-depth reclamation (FDR) have been reliable rehabilitation techniques; restoring pavement condition at an affordable cost with a lower footprint on the environment. Experience reveals that CIR and FDR interventions effectively address the issues of reflective cracking and respect Quebec’s Ministry of transportation rutting threshold values. However, despite their commendable performance in the field, the cold recycled emulsified asphalt materials (CRM) has yet to be adequately characterized with respect to their rheological properties. This study was undertaken to evaluate the rheological behavior of the CRM with four different combinations of RAP (50, 75, 85, and 100%). The scope of work for this study consisted of preparing the laboratory compacted CRM specimens, determining the complex modulus (E*) of compacted specimens at various testing temperatures and loading frequencies, analyzing the experimental data with the help of 2S2P1D (2S: two springs, 2P: two parabolic elements, 1D: one dashpot) model and finally, validating the results with pavement design. It was concluded that 100% RAP mixture exhibits extremely high stiffness value at high frequency and low temperature. The results revealed that all four mixtures respect the time–temperature superposition principle with respect to the complex modulus. From a pavement design perspective, the moduli measured in this study do have a big impact. However, since different pavement structure are achieved with those different materials, the stiffest material, the CIR, ended up giving the least performant structure.

Alan Carter

Papers

A procedure for characterizing the curing process of cold recycled bitumen emulsion mixtures

Evaluation of the durability and the performance of an asphalt mix involving Aramid Pulp Fiber (APF): Complex modulus before and after freeze-thaw cycles, fatigue, and TSRST tests

Complex Modulus and Fatigue Analysis of Asphalt Mix after Daily Rapid Freeze-Thaw Cycles

New conceptual model for filler stiffening effect on asphalt mastic of microsurfacing

Rheological behavior of cold recycled asphalt materials with different contents of recycled asphalt pavements