Black Creek

Owner:

City of Chattanooga

Designer:

LaBella / Chazen Group

Paving Contractor:

Robert Smith Inc

Paving Machine:

2009 ABG7820 HD Volvo

Mixing Plant:

A240 Blend

General Contractor:

Chazen Group

Completion Date:

June 15, 2021

Project Details:

Lookout Mountain in Georgia is best known for Rock City, standing at 2,392 feet in elevation, where it is possible to see seven states. Lookout Mountain and all its many attractions shadow its sister mountain in Tennessee, Aetna Mountain which stands at 1,950 feet in elevation and is located just across the interstate. Most of Aetna Mountain remains undeveloped but, more than a decade ago, a part of the I-24 side of the mountain in Chattanooga was purchased and development began.

Planning for this stretch of mountain road started in 2017 and construction began in 2019. Cutting a two-lane road up the side of a mountain was no small feat. Due to the steep incline, safety was a concern. The City of Chattanooga required that the road have two 17-foot-wide lanes with one-foot curbs and gutters plus a median in between. The original plan was for the road to be constructed using heavy-duty asphalt. However, the City of Chattanooga opted to use Roller-Compacted Concrete (RCC), as an alternative for this project.

Robert Smith Inc. (RSI) was hired as the paving contractor for this project. RSI was required by the city to supply a skid-resistant surface. The RCC mix design consisted of granite 89 stone from Dallas, Georgia, and a limestone 67 stone, manufactured sand and Type I/II Buzzi Cement from the Signal Mountain Plant.

The heavy-duty asphalt section had four inches of asphalt to be installed in two lifts, a 2.5-inch lift of binder asphalt and a 1.5-inch lift of surface asphalt. The RCC design required seven inches of concrete in one lift. Both alternatives were placed over six inches of compacted graded aggregate base.  RCC was selected because the City of Chattanooga believed it was the best application for this roadway.

Robert Smith Inc. used an A240 Blend portable mixing plant and positioned it halfway up the mountain road. RSI used a 2009 ABG7820 HD Volvo paver that was able to handle steep grades up to 15 percent with ease. 400 cubic yards were produced each day on average. Small rollers were needed to achieve final compaction of the RCC after placement with a high-density paver.

This project, completed on June 15, 2021, provided steep grades paved with durable RCC, which resulted in magnificent long views a quarter mile above downtown Chattanooga.