This approximately $20 million Design/Build Contract was divided into two sections of work; complete removal and replacement of 3.5 miles of dual lane interstate highway including six ramps at one interchange, and the restoration of four bridges, the other segment consisted of 3.0 miles of concrete pavement patching and correction of super elevation that included concrete and bituminous pavement removal, new concrete valley gutter, and HMA pavement installation.
Schedule and Complexity
This project consisted of lane rental on both sections. When the freeway was closed for reconstruction the charge was $600/hr and when only one lane was closed the charge was $230/hr and these rates were multiplied to how many lane rental hours that the contractor would need to complete the project, this was then added to the project lump sum cost to determine the low bidder. In order to meet the lane rental hours bid into the project the contractor had multiple paving crews and worked 7 days week along with working on both the reconstruction portion and the rehabilitation portion at the same time.
Construction & Innovation
In a Design Build project the contractor is given a set of parameters by MDOT and the contractor designs the project and completes the plans and is paid the lump sum amount as bid for all for all of this work.
Recycling of the entire old concrete pavement for utilization as aggregate for open graded base under all of the new concrete pavement was a major contribution to a sustainable solution, improving the safety, congestion and economy by reducing the number of construction trucks that would be required in the traditional construction methods of hauling and wasting the concrete and bringing new virgin material for base.
Safety was of premium importance for both traveling public and the construction team, resulting in no major accidents and no employee loss of time. To enhance safety and congestion-relief, MDOT set up a bid item to provide wrecker service assuring that disabled vehicles were moved as quickly as possible.
The Contractor's process controls resulted in a high quality project. One-hundred percent of the MDOT incentive for strength was earned for the roadway with the 4400 psi average compressive strength of the concrete for pavement reliably exceeding the contract requirement. Uniformity checks were completed regularly on the concrete mix to insure that the concrete produced was meeting specification. Pavement smoothness requirements were met with a minimum of bump grinding. Smoothness was checked the first thing the next morning using a lightweight profilometer and corrections to the paver, mix or other processes were made immediately to continuously improve the rideability.
For this project the contractor was required to provide a 5 year material and workmanship warranty on the concrete pavement. The Contractor utilizes an internal quality control program that requires the development of a job-specific Quality Control Plan (QCP) to assure that all contract requirements for quality are met and to provide the necessary documentation. A full time project Quality Control Manager reporting directly to the corporate Quality Control Manager is responsible for execution of the project QCP. Two Contractor full-time inspectors had the sole responsibility to assure accurate dowel and tie bar placement, pavement width and thickness, and all other contract requirements for quality were met.
Dowel bar placement by the automatic DBI was assured with wet checks during PCCP placement and the next day after the concrete had hardened with non-destructive methods. Random cores were also taken to check for proper consolidation around the dowel bars.
Methodology and Innovation
Concrete was mixed at the project site with a Rex Model-S central mix plant and delivered to the grade with a steady supply of trucks to maintain a continuous flow to the concrete paver. Aggregate gradation was optimized using a "Shilstone" type process, to provide a mix with excellent workability as well as meeting the performance criteria. This was important in achieving the smoothness with a cost-effective mix. The paving train consisted of a Guntert-Zimmerman 850 paver with a transverse dowel bar inserter (DBI). Directly behind the paver were two straight edge finishers to help take care of any irregularities. The final texture of longitudinal tinning was placed with a Guntert- Zimmerman 4-track cure texture machine.