Minnesota District 7 hired Braun Intertec to perform Cold In-place Recycling (CIR) laboratory mix designs for 9 different district projects since 2018. CIR has become a desired rehabilitation alternative for cost, environmental, and performance advantages compared to standard practices. For this process, a laboratory mix design is performed before production to predetermine the type and optimal amount of engineered emulsion to be used in the remixing component of the process.
One of District 7 projects was TH 99 from TH 13 to TH 21 in Le Sueur County. This section was approximately 8 miles in length. TH 99 is a high-volume roadway with an average daily traffic of approximately 2,000 and a design speed of 60 mph. With a CIR depth of 4 inches, TH 99 consisted of approximately 100,500 square yards of CIR.
Representative samples of the in-place bituminous (bituminous cores) were collected by MnDOT and were picked up by Braun Intertec and shipped to our lab in Bloomington, Minnesota. The pavement design included 2 ½ inches of pre-milling followed by 4 inches of CIR. To replicate field condition in the lab, the top 2 ½ inches of the cores were trimmed and discarded and the next 4 inches were cut and cold-crushed and used in the CIR mix design.
Through the CIR mix design, it was determined that an Engineered Emulsion with a base binder of PG 58-28 needs to be used. The optimum emulsion content was determined to be 2% based on the weight of the RAP which is equal to 1 gallon per square yard for the planned CIR depth.
The CIR portion of the project was performed by Midstate Reclamation and Trucking, Inc. in 2019. Midstate hired Braun Intertec to perform quality control (QC) testing during the construction. Quality control of construction materials is essential requirement for obtaining improved and uniform standard of road construction. Several testing and measurements were performed throughout the project in accordance with 2018 SALT Schedule of Materials Control. The QC testing included performing control strip, depth checks, moisture testing, density measurement, and yield control which were all within the specification limits.
Braun Intertec is an industry leader in asphalt recycling design and testing services, with a wide range of quality control and assurance services. If you have any questions, please reach out to us.
