This project was awarded by UDOT to Geneva Rock Products, Inc. and the project schedule required the eastbound lanes to be constructed in the fall of 2014 with the westbound lanes being constructed in the spring of the following year. This project included partial depth reclamation (PDR) covered by portland cement concrete pavement (PCCP) and cast in place concrete barrier wall. In addition to the PDR, PCCP, and barrier wall, there was a substantial bridge along the westbound lanes that had to be demolished and reconstructed during the 2015 construction season.
A sustainable construction technology utilized on the project was that of partial depth reclamation of a portion of the existing asphalt. Four inches of the existing asphalt was recycled by pulverizing it with a percentage of portland cement to create a durable paving platform. This was the first project in the history of reclamation, where only a portion of the existing asphalt was used, leaving the other portion in place. The original PDR design specified 9% to 11% portland cement in the reclamation mixture. UDOT required strength values were between 300-500 PSI in 7 days. Geneva Rock however, performed value engineering to optimize the cement content of the PDR. Test strips of PDR were constructed at 7%, 8%, and 9%. It was determined that 7% cement was adequate to meet the UDOT strength requirements. This reduction in cement saved money and reduced the raw materials needed on the project. The PDR proved to be a superior paving base material, holding up well during construction activities and reducing yield loss compared to an aggregate base. Because the existing materials were utilized on this project very little waste was created and subsequently landfilled, thus reducing fuel and hauling and disposal costs which have negative impacts to the environment.
A durable, long lasting concrete pavement was designed to cap the PDR providing a great highway surface for years to come. Mainline concrete pavement design consisted of 12 inches of PCCP placed over 4 inches of the PDR. Off ramps consisted of 10 inches of PCCP on 4 inches of PDR. A central batch plant was set up at west end of the project on UDOT property and produced concrete for the entire project including paving and barrier wall construction. The permanent concrete barrier wall was constructed by a concrete sub-contractor. The narrow canyon provided concrete paving challenges with its limited access to the project and limited to no track grade. The accelerated schedule and the unpredictable mountain weather also proved somewhat challenging.
Concrete mix designs, QC/QA, and performance evaluation
Due to the accelerated construction season in 2014, the eastbound lanes of I-80 were constructed with a traditional concrete paving mixture. The hydraulic binder selected was ASTM C150 Type II/V portland cement. The concrete mixture included 25% Class F fly ash.
The westbound lanes were constructed with a concrete mixture that was designed with sustainability in mind. This mixture utilized Holcim Envirocore cement as the hydraulic binder. Envirocore cement has a lower carbon foot print due to the incorporation of un-calcined high grade limestone, interground with the portland cement clinker. The limestone lowered the CO2 associated with clinker production and helped the concrete by providing nucleation sites of hydration products. The limestone cement is also engineered for use with other supplementary cementitious materials such as fly ash. This concrete mixture also included Class F fly ash used in conjunction with the limestone cement increasing the CO2 reduction by an additional 25%. The Envirocore concrete mixture significantly lowered the environmental impact from traditional concrete mixtures by utilizing blended cements and SCMs.
The two concrete mixtures performed similarly and meet all concrete strength requirements for the project. Concrete batching and placement crews did not see a noticeable difference between the two concrete mixtures. Concrete results of the two mixtures all exceeded design requirements.
