Optimal proportioning for hot recycled mix design under Superpave mix design consideration

While performing recycled (central plant) hot mix design as per Superpave mix design criteria, the quantity of reclaimed asphalt pavement (RAP) is either assumed fixed, or estimated from other fixed parameter(s). In either of the cases, the constituent (RAP, virgin binder, and virgin aggregates) proportions may not necessarily represent a cost-optimal situation. The present paper develops a generalized formulation for preliminary constituent proportioning of hot recycled mix following Superpave criteria. Through this formulation an optimal solution for mix proportion can be obtained, where the total material cost is minimized while satisfying all the binder and mix property requirements.

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Construction Quality Control of Unbound Base Course using Light Weight Deflectometer where Reclaimed Asphalt Pavement Aggregate is Used as an Example

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120934473 ◽

2020 ◽

Vol 2674 (10) ◽

pp. 989-1002

Author(s):

Emre Akmaz ◽

Saad Ullah ◽

Burak F. Tanyu ◽

Erol F. Guler

Keyword(s):

Quality Control ◽

Asphalt Pavement ◽

Field Measurements ◽

Design Criteria ◽

Reclaimed Asphalt Pavement ◽

Light Weight ◽

Reclaimed Asphalt ◽

Light Weight Deflectometer ◽

Base Course ◽

Unbound Aggregate

Reclaimed asphalt pavement (RAP) is already being recycled as a construction and building material. One of the commonly considered applications is to create an unbound aggregate from this material. However, since the particles of RAP have binder coatings, traditional quality control procedures applied during construction such as use of a nuclear density gauge does not provide accurate results. Therefore there is a need to find another method that can be applied during construction to confirm that the placement in the field meets the design criteria. For this reason, in this study, the suitability of using light weight deflectometer (LWD) has been investigated. The presented methodology outlines how to implement the use of LWD to create a target modulus in the laboratory as part of design criteria and compare with the field measurements. In the field, depending on the thickness of the constructed aggregate layer, the LWD measurements may be influenced by more than just the layer of interest. The presented methodology also provides a solution for such multilayer conditions. Although the study primarily focuses on using RAP as the investigated material, the methodology developed in this study can be applied to any type of unbound aggregate as demonstrated in this study.

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A Method to Quantify Reclaimed Asphalt Pavement Binder Availability (Effective RAP Binder) in Recycled Asphalt Mixes

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198118821366 ◽

2019 ◽

Vol 2673 (1) ◽

pp. 205-216 ◽

Cited By ~ 7

Author(s):

Fawaz Kaseer ◽

Edith Arámbula-Mercado ◽

Amy Epps Martin

Keyword(s):

Asphalt Pavement ◽

Economic Benefits ◽

Binder Content ◽

Mix Design ◽

Void Content ◽

Reclaimed Asphalt Pavement ◽

Asphalt Mixes ◽

Reclaimed Asphalt ◽

State Highway ◽

Asphalt Mix

State highway agencies recognize the environmental and economic benefits of utilizing reclaimed asphalt pavement (RAP) in asphalt mixes. Currently, most agencies assume all of the RAP binder content is available for mix design purposes. However, the percentage of available or effective RAP binder in the asphalt mix is usually less than 100% and not quantified, which could yield dry asphalt mix with a high air void content, potentially leading to premature distress. The term available or effective RAP binder refers to the binder that is released from the RAP, becomes fluid, and blends with virgin binder under typical mixing temperatures. This study proposes a method to estimate the RAP binder availability factor (BAF) which can be used to adjust the virgin binder content in RAP mixes to ensure that the mix design optimum binder content is achieved. In this method, asphalt mixes were prepared so that, after mixing and conditioning, the RAP material can be separated from the virgin aggregate, which allows for a thorough evaluation of the extent of RAP binder availability in the asphalt mix. This method was verified in a preliminary experiment and then used to estimate the BAF of RAP from different sources, and a correlation between RAP BAF and the high temperature performance grade (PG) of each RAP source was established. Finally, factors affecting the RAP BAF were also evaluated such as mixing temperature, conditioning period, the use of recycling agents (or rejuvenators), and the method of adding the recycling agent to the mix.

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