Elgin O'Hare Western Access Tollway

Challenge: The Illinois Tollway Authority specifications for compaction quality required the contractor to implement intelligent compaction measurements independently calibrated to pavement design modulus (e.g., modulus of subgrade reaction) values with a minimum R² >= 0.85. Lake County Grading (LCG) company performed initial calibration testing with two index-value based intelligent compaction systems, using nuclear density gauge and light weight deflectometer. The results did not produce the minimum calibration requirement.

Solution: Ingios® addressed the project challenges being faced by the contractor with a multi-faceted solution of engineering services, training, and technology deployment.

Ingios performed calibration testing with 30 in. diameter static plate load testing to directly measure the modulus of subgrade reaction, k-value, and analyzed results for the two index-based intelligent compaction systems and the Ingios CRT system. Professional Engineering calibration records were produced for each measurement system, per specification requirement, with documentation of the measured versus predicted k-values and the associated statistics. CRT system yielded a R² of 0.98, while the traditional index-value based intelligent compaction system yielded R² of 0.55 and 0.81.

Benefits: The Ingios CRT solution exceeded the project specification requirements for calibration. Using mapping solutions that can provide high degree of confidence in the predicted values and are independently calibrated with direct measurements offers a significant advantage with using CRT technology for agency Quality Assurance. CRT map results showed in real-time areas that required additional compaction and differences in areas with and without lime stabilized subgrade.