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Project Name
Lane Construction I-40/I-77 Concrete Paving Project/First Type IL in NC
Description
The Lane Construction Corporation (Lane CC) is the contractor on the project. Roanoke Cement Company (RCC) is the NRMCA member and the cement supplier.
In 2024, Lane CC completed a $260 million design-built contract at the I-40 and I-77 interchange in Iredell County, NC. The project included the widening of the interstate highways, along with the construction of a partial turbine interchange to decrease traffic congestion and improve safety. This project was the first for NCDOT that used Type IL cement, a low-carbon formulation that provides up to a 10% savings in carbon impact compared to ordinary portland cement. A case study by the company and the University of North Carolina at Charlotte estimated that the project obtained a reduction of carbon emissions by 2,647 tons (compared to the use of Type I cement).
New pavement constructed on I-77 was asphalt pavement, while new pavement construction placed for the I-40 portion of the project was jointed plain concrete pavement. The newly constructed concrete pavement sections on main line I-40 consisted of 14-in. portland cement concrete pavement placed on a 1¼ in. layer of asphalt base, on top of 12 in. of Type I stone base. Ramps were constructed in the same manner but the concrete thickness for ramps was typically 11.5 in.
The project included extensive staging and traffic control to allow both interstates to remain open during the four-year project. Paving lanes were constructed at different times, sometimes over three years apart.
In 2021-22, RCC transitioned their production from Type I/II cements to Type IL. Ongoing paving projects required contractors to prepare for the change in supply through trial batches in communication with suppliers. Agency approvals for Type IL mixtures needed to follow standard procedures; the timing of trial batching and mixture design approvals was critical to the success of the project to avoid interruptions in construction. Lane CC produced approximately 95,179 CY of concrete using Type IL cement for the project.
Prior to construction, the interchange carried more than 70,000 vehicles per day. After completion of the project, a 57% increase in vehicles per day – about 110,000 -- is predicted by 2035.
Evidence
The switch from Type I to Type IL cement occurred mid-project on February 11, 2022 during pavement of the collector lanes on eastbound I-40. Neither the batch plant nor paving operations were stopped during the changeover. Lane CC emptied the final Type I cement pig before filling the next pig with Type II.
Neither the plant operators nor the paving crew noticed a change in workability or finishability at the time of the switch. Since the switch occurred in the middle of the lot, two sets of samples were made for that lot--one for each cement type; no other noticeable changes occurred to batching placement or testing.
The concrete mixture designs for the project were developed by Lane CC. The NCDOT standard specifications for roads and structures requires specific proportions of cement, a maximum W/CM ratio, an air content between 4.5% and 7.5%, a maximum slump of 1.5 in., a minimum flexural strength of 650 lbs./sq. in. at 28 days and a minimum compression strength of 4,500 at 28 days. All mixtures were approved through NCDOT’s standard process, although due to urgency, approvals were allowed with 14-day compressive strength results.
A central mix plant was used to batch the concrete, which was delivered to the site by non-agitating equipment. Concrete was spread in front of the paver via concrete placer. The concrete was finished with the burlap drag and was then hand floated. The pavement was hand tined, and curing compound was spray applied by hand. All segments of pavement were subsequently diamond ground, saw cuts were made at 15-ft. intervals, and joints were later widened and sealed.
No difference was reported between the Type I and Type IL mixtures regarding placement, workability, and early-age strength gain. Lane CC reported that its crews did not notice the switch in cement during the placement on February 11, 2022. Hydration and hardening rates were similar for both types and sawing times were not adjusted.
Overall, smoothness measurements for the travel lanes were excellent with all segments studied exhibiting IRI measurements below 50 in./mi. Notable differences in mean IRI were not observed between Type I or Type IL pairs.
The use of a 28% replacement of fly ash further reduced the embodied carbon associated with both Type I and Type IL mixtures. The use of Type IL cement resulted in a carbon emissions savings of approximately 11%.
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