A 9.3 mile section of State Route 43 in Kern County, CA, had deteriorated to the point that structural improvements were needed to improve rideability. Using a Wirtgen milling machine, PRS removed 1.2 inches of existing asphalt.

Next, as part of the Cold In-Place Recycling (CIR) process, the team crushed and screened the material to a maximum size of 1 inch. An asphalt binder was added to the recycled material and paved as a base course at a depth of 3 to 3.6 inches.

To finish the project, a 1.2 inch rubberized asphalt cap was added and the road was returned to traffic.

The project was in conjunction with Caltrans initiatives brought about by Senate Bill 1, the Road Repair and Accountability Act of 2017 (SB 1). It was signed into law in April 2017. As of Dec. 2020, Caltrans has invested more than $8.2 billion in approximately 1,200 state highway projects.

Additionally, they have spent $8.4 billion for 4,400 city and county projects within the same period. SB 1 invests approximately $5.4 billion each year to fix roads, freeways, bridges, as well as strategically investing in transit. The funds are split equally between state and local projects and will be used to fix more than 17,000 lane miles of pavement, 500 bridges and 5,500 culverts on the state highway system by 2027.

Caltrans utilizes many different pavement rehabilitation methods when rehabilitating their roadways and state highway system. SB 1 references the use of “advanced technologies and material recycling techniques” to reduce costs and greenhouse emissions.

Some of the powerful recycling strategies used by Caltrans to rehabilitate pavement surfaces include Full Depth Recycling (FDR), Cold Central Plant Recycling (CCPR), and Cold In-place Recycling (CIR) which Caltrans now refers to as Partial Depth Recycling (PDR). One strategy may be better suited than another, depending on the pavement engineering assessment of each project’s pavement condition and stress level.

SB 1 calls for the “use of advanced technologies and material recycling techniques that reduce the cost of maintaining and rehabilitating the streets and highways.” Allen King, P.E. is the Senior Transportation Engineer for Caltrans. “CIR (PDR) is a great way for State to decrease its carbon footprint while also realizing a substantial cost savings when compared to a mill/fill strategy with digouts,” says King.

This project was featured in Issue 5 – 2021 of CalContractor magazine. You can read the entire article here.