Marked up map of Levee Road and Brooks Road shows test sections, control sections, designated entrances and a tree protection zone

West Campus Roads to Close April 30-May 2 for Pavement Research

Putah Creek Riparian Reserve Trailhead Parking Temporarily Impacted

  • by Katie Hetrick

The University of California Pavement Research Center, or UCPRC, in collaboration with CalRecycle and Caltrans, is testing innovative pavement materials made from end-of-life tires to enhance the sustainability and performance of California’s roads. To support this work, a few roads near the UC Davis Airport will be closed morning to evening to vehicle, bicycle, and pedestrian traffic from April 30 to May 2 (details below).

The closures include Hopkins Road (south of the airport), Levee Road, and Brooks Road leading up to the Putah Creek Reserve. Road closures will begin on April 30 at 6 a.m. and continue to 6 p.m. Closures will resume on May 1 at 6 a.m. and continue overnight until work is complete at 6 p.m. on May 2. This work includes a closure of the Putah Creek Riparian Reserve trailhead parking area on Levee Road between Hopkins Road and Brooks Road.

Employees who need to access their workplace along the closure will be given controlled access. All other traffic will be directed to detour routes via Hutchison Drive. Community members are encouraged to plan alternate routes during the closure. The temporary closure is necessary to ensure the safety of construction crews and the integrity of the testing process. 

Why This Matters 

This project showcases the latest advancements in pavement innovation, including the use of asphalt mixes containing recycled tires. By testing these materials, UCPRC aims to develop longer-lasting, cost-effective, and environmentally friendly road surfaces. Key highlights of the project:

  • Cold Recycling Technology: Repurposes existing road materials, reducing waste and greenhouse gas emissions.
  • Recycled Tire Asphalt Mixes: Incorporates waste tires to enhance durability and sustainability.
  • Life-Cycle Assessment Tools: Evaluates environmental impacts of pavement designs.

Campus Collaboration 

This project is made possible by a unique partnership with UC Davis Design and Construction Management’s Campus Planning unit. By utilizing the campus as a living laboratory, UC Davis is enabling real-world research that advances sustainability and innovation in infrastructure development.

“Our collaboration with the Pavement Research Center exemplifies how the university infrastructure can benefit while serving as a resource for innovative research,” said Lucas Griffith, campus planning executive director. “These efforts align with UC Davis’s commitment to sustainability and provide valuable insights that benefit the campus and the entire state.” 

About the UC Pavement Research Center 

The UCPRC is a leader in advancing pavement innovation, sustainability, and cost-effectiveness. Through partnerships with Caltrans, CalRecycle, and industry leaders, the center develops and implements cutting-edge materials and processes for roadway construction and maintenance. Learn more.

Additional Project Background

A dense graded rubberized hot mix asphalt (RHMA-D) is an HMA that contains recycled tires rubber. RHMA-D is not currently specified by Caltrans, but may be beneficial for several reasons including increasing recycling, meeting legislative mandates, improving mix performance and service life, and reducing the overall environmental impact. There may also be benefits to local governments that are looking for an alternative to gap-graded hot mix asphalt (RHMA-G) for use on their networks.

Funded by Caltrans and CalRecycle, the UCPRC has evaluated the use of rubber in dense grade mixes. Phase 1 of the research (2022-2023) focused on constructability and preliminary laboratory testing of RHMA-D. Phase 2, ongoing, includes a comprehensive lab characterization of RHMA-D mixes produced in the laboratory. Phase 2 is expected to be accomplished by June-2024. A total of nine rubber products have been evaluated in Phases 1 and 2. The nine products fall in one of the following technology groups:

  • Wet process, terminal blend: 3 products (TRMAC, Sigmabond, and ViaTec)
  • Modified wet process, by diluting the asphalt rubber binder used in conventional RHMA-G (18-20% rubber content)
  • Modified wet process, by quick blending of crumb rubber modifier (CRM) with plain binder; no need for interaction tank
  • Dry process, CRM/GTR: 2 sizes (passing #40 / 0. 425 mm and #60 / 0.25 mm)
  • Dry process, engineered CRM/GTR (ECRM/EGTR): 3 products (SmartMIX, RARx, Elastiko ECR)

Location and Overview

The proposed pilot project location is a 1.1 mile stretch of a Full Depth Recycled with Cement (FDR-C) service road to the Southwest of the main UC Davis campus (Brooks-Levee Road). Phase 3 of the research includes the evaluation of RHMA-D in a field pilot project. The field sections are the following:

  1. 950 tons of HMA Type-A with 25% RAP and PG 58-22 Base Binder
  2. 950 tons RHMA-D with 25% RAP and 10-20% rubber by total weight of binder:
    • 238 tons of Wet process, terminal blend #1 (Wright Asphalt TRMAC)
    • 238 tons of Wet process, terminal blend #2 (US Polyco Sigmabond)
    • 238 tons of Modified wet process (CRM 40 mesh in conventional rubber blending unit with <10min reaction time, no 45 min requirement)
    • 238 tons of Dry process, ECRM (RARx 30 mesh)

Goals of the Project

The goals of this field pilot are to understand the following:

  1. How will the new HMA with fine rubber in a dense gradation (RHMA-D) affect the performance?
    • Will this mix help to increase the use of rubber in Caltrans below-surface lifts and maintenance work?
    • Will this mix help to increase the use of rubber in local governments?
  2. Mechanistic Properties of Plant Produced Mix:
    • Establish the CalME Standard Materials Library Design Inputs from Plant Produced Mix.
    • Establish the BMD Tests (IdealCT, HWTT, etc.) and Fundamental Tests (4PB, AMPT, etc.)
  3. Constructability at the Plant and Field:
    • Asphalt Plant considerations and modifications for fine rubber in dense graded HMA
    • Paving considerations
    • Cost considerations
  4. Environmental Impacts:
    • Estimated EPD for each rubber product (reported by each participating supplier)
    • Impact of the addition of rubber to total mix EPD