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Highways for LIFE

Arrow California Demonstration Project: Pavement Replacement Using a Precast Concrete Pavement System

Project Overview and Lessons Learned

Project Overview

The project consisted of rehabilitating 4.7 mi (7.4 kilometers (km)) of I-15 near the city of Ontario in Riverside County between Route 60 and the San Bernardino–Riverside County line at Seventh Street just north of the I-10/15 interchange. This segment of I-15, about 40 mi east of Los Angeles, is a major route for Las Vegas traffic and carries very heavy traffic. I-15 has four mainline lanes in each direction at this location with auxiliary lanes accommodating merging traffic from area crossroads. The average daily traffic (ADT) is about 200,000 vehicles with six percent trucks. The area also has a concentration of commercial activities, including two shopping malls, auto centers, airports, a National Association for Stock Car Auto Racing (NASCAR) speedway, railroads, and warehouses. The presence of the interchange is an added challenge to maintaining traffic during construction; as many as six lanes approach the interchange. A large amount of traffic merges in and out of I-15; Route 60 at the south end of the project carries six to eight lanes of traffic and I-10 toward the north end of the project carries eight lanes of traffic.

The two outer lanes were rehabilitated in both directions under this project, which amounted to about 12 lane-mi of continuous lane replacement and intermittent slab replacement. Other roadway portions that underwent rehabilitation included interchange ramps, freeway-to-freeway connectors, and asphalt shoulders. To support the major rehabilitation activities and accommodate traffic flow or traffic detours during the construction work, the project also entailed median paving, new median barriers, widening of the inside shoulder, bridge widening, and structure crossings. Other bridgework was included in the project, which consisted of deck rehabilitation, replacement of structure approach slabs, and upgrading of bridge approach rails.

Project Innovations

The magnitude of work involved on this project required Caltrans to do a great deal of planning. The agency performed a detailed evaluation of available technologies to optimize project resources for the best outcome, which involved several aspects of the project. Caltrans considers the following technologies as innovative approaches that contributed to the project's success, especially in meeting the HfL objectives:

  • Precast concrete pavement system (PCPS) technology for rapid slab replacement within short work windows. PCPS reduced traffic delays and improved safety and performance (long service life) of the pavement. PCPS technology, planned during the design stage, was the primary innovation Caltrans listed to qualify for HfL funding.
  • The road safety audit (RSA) procedure to critically examine each design detail to identify potential safety concerns and provide mitigation strategies. An RSA audit was performed on the project during the construction stage.
  • Construction Analysis for Pavement Rehabilitation Strategies (CA4PRS) schedule and traffic analysis software that helps planners and designers select the best alternative to reduce highway construction time and its impact on traffic. The CA4PRS analysis was performed by Caltrans independent of the HfL funding approval and was the basis for selecting the rehabilitation strategy for developing the project funding and the bid documents.
  • Dynameq™ staging and traffic simulation software to evaluate congestion relief strategies and lane management. Again, Caltrans completed Dynameq analysis before, and independent of, the HfL funding application or funding.
PCPS

Traditional practice for the rapid repair of concrete pavements on heavily congested highways in California involves the use of a fast-setting concrete mix so that slab replacement can be performed within tight work windows. Caltrans uses the Rapid Set® Concrete (RSC) referred to as "4x4 mix" because the concrete is designed to achieve at least 400 pounds per square inch (psi) flexural strength within 4 hours. While Caltrans has had much success with this mix design, the agency believes the service life of the 4x4 mix may be influenced by unpredictable site conditions affecting both the casting and curing processes. The primary concerns are associated with difficulty of placement and curing and shrinkage issues.

Caltrans has explored the use of PCPS for slab replacement on other projects. The I-15 project was the first project District 8 considered for the application of PCPS technology. The traffic patterns and limitations in lane closures made this project a select candidate for evaluating the feasibility of using PCPS technology. Caltrans recognized at the outset that the initial cost for Super-Slab® is higher than traditional methods (i.e., rapid-set concrete placed in night closures) of rehabilitating roadways, but the life cycle costs appeared to be closer.

Caltrans expected to yield a high-quality pavement with a long service life due in part to controlled manufacturing conditions and a high level of quality control. Caltrans anticipates the high-quality PCPS to achieve a lifespan greater than 30 years in contrast to RSC, which has an estimated pavement life of about 10 years. Furthermore, the reduced construction time made possible by the use of Super-Slab® translates to a reduction in the time construction activities impact the traveling public. This results in a lower road-user cost (RUC) from construction delays. Caltrans expected to recover the higher initial cost through a lower life cycle cost compared to traditional rehabilitation strategies.

The chosen PCPS system, Super-Slab® by the Fort Miller Co., Inc., was used to replace slabs along the most critical section of the highway in one northbound lane near the interchange with I-10. The idea was to demonstrate how such a system could allow the contractor to perform continuous and intermittent lane replacement quickly during nighttime and weekend closures while maintaining construction quality and minimizing traffic delays. Since Super-Slab® is a proprietary system, a Public Interest Finding required to justify why this project is specifying this product and was prepared. Super-Slab® was then specified in the contract.

RSA

An RSA is a formal safety performance examination of an existing or future road or intersection by an independent, multidisciplinary team. Through this process, potential road safety issues are estimated and methods for improvement are identified for all road users. An RSA was performed during the early stages of construction by a multidisciplinary team that was not closely associated with the planning and design phases of the project. Caltrans reviewed the team recommendations and incorporated several into the project.

CA4PRS

The application of the CA4PRS software tool in the early design phase of the project helped guide engineers in determining an optimal staging plan for the rehabilitation activities. The program was produced through a pooled fund study among a consortium of four States (California, Minnesota, Texas, and Washington) and supported by FHWA.

CA4PRS was used to help estimate the amount of time necessary to construct each stage of the project, as well as quickly assess multiple alternatives to rehabilitating the pavement. This software was also instrumental in evaluating the production rates for different rehabilitation scenarios. This tool integrates traffic, design, and construction issues to select the most effective and economical rehabilitation strategy from a set of user-defined alternatives. Therefore, CA4PRS allowed a large number of alternatives to be quickly analyzed to determine the most efficient means of construction.

Dynameq

Designers further analyzed the staging and its impacts on traffic using Dynameq software developed by INRO, which combines the advantages of microscopic and macroscopic modeling to create a mesoscopic model. This model provided a level of detail similar to that achieved by microscopic models while achieving the faster, more efficient model runs of macroscopic models. This approach made it more economically feasible to analyze multiple scenarios for staging.

Construction Staging and Schedule

Caltrans received HfL funding of $5 million toward the I-15 project. The construction contractor selected after the bid process was Security Paving Company, Inc. of California with a bid amount of $52 million. The construction sequence involved paving two median lanes and moving traffic over to free two outside lanes in the southbound direction for rehabilitation and slab replacement performed through weekdays and weekends. This process was then repeated for the northbound direction. This staging plan essentially ensured no reduction in lane capacity during the rehabilitation process.

The roadway segment that underwent PCPS slab replacement involved 1.8 mi using 696 slabs of continuous replacement covering an area of 118,400 square feet (ft²). Also, 16 existing panels were replaced at intermittent (noncontinuous) locations. PCPS slab installations were performed mostly during 8-hour nighttime closures and a short portion during 55-hour weekend closures, which was primarily when the ramps and connectors were closed.

The contractor’s bid for the PCPS elements was a unit price of about $1,500 to $1,574 per cubic yard (yd³) (~$2090 per cubic meter (m³) or $418 per square meter (m²)), totaling $4.6 million on the entire project. This price included slab fabrication and shipping to the site, existing pavement removal, installation, grouting, and grinding after installation to meet smoothness requirements. The bid item did not include joint sealing. Joint sealing was paid under a separate item.

As stated earlier, this was a major rehabilitation project and used five major construction stages and 25 substages over 400 working days (about 2 years) and both weekend closures (between late Friday night and early Monday morning) and nighttime closures (between 9 p.m. and 5 a.m.). Eight full roadbed closures were included. Clearly, the challenges for successful completion extended far beyond the use of PCPS for rapid slab replacement. The closure of ramps and connectors at the I-10 interchange over a weekend was, by far, the most critical construction phase because this was expected to create traffic congestion on both highways leading to the intersection. Also, any snag in the planning, scheduling, or execution process could have the highest impact on traffic management.

The CA4PRS analysis was used to justify the estimates for the number of road closure requirements and set the incentive and disincentive clauses in the construction contract. The optimum number of closures offered to the contractor was 32 weekend closures. An incentive of $150,000 per closure was offered for fewer than 26 closures up to a maximum of $900,000 in incentives. The contract also levied a disincentive of $175,000 per closure for every closure over 32. The disincentive included $25,000 for the public awareness campaign to alert the public about the closure. The contractor received the maximum incentive on the project.

HfL Performance Goals

Safety, construction congestion, quality, and user satisfaction data were collected before, during, and after construction to demonstrate that innovations can be an integral part of a project while simultaneously meeting the HfL performance goals in these areas.

  • Safety
    • Work zone safety during construction—Crash rates dropped nearly in half during construction compared to historical rates, which met the HfL goal of achieving a work zone crash rate equal to or less than the preconstruction rate.
    • Worker safety during construction—It is not evident if the contractor was able to meet the HfL goal of less than 4.0 on the OSHA 300 rating. The contractor indicated that the firm does not maintain records on a project basis and instead aggregates safety performance on an annual basis for all construction projects.
    • Facility safety after construction—No direct safety improvements were included in this project, but shoulder widening and increased rideability will likely improve driving conditions. The net effect these improvements will have on the HfL goal of 20 percent reduction in fatalities and injuries in 3-year crash rates after construction is yet to be determined. Caltrans acknowledges that it does not anticipate recording a significant decrease in crash rates because the roadway alignment, lane configurations, and traffic patterns, among other roadway features, have not changed as a result of the rehabilitation. However, it is likely that the improved surface conditions can improve ride quality, which might have a positive impact.
  • Construction Congestion
    • Faster construction—The HfL goal is a 50 percent reduction in the time traffic is impacted compared to traditional construction methods. No factual information was collected during the project to suggest that the use of PCPS reduced construction time because the conventional approach of using fast-setting concrete could allow nighttime construction within the same work windows. However, the construction sequence and staging, especially the paving of two median lanes, certainly reduced construction congestion by virtually maintaining traffic flow similar to preconstruction phases.
    • Trip time—The HfL goal of no more than a 10 percent increase in trip time compared to the average preconstruction conditions was not achieved throughout the construction phase. During the most critical weekend closure, an average increase of 80 percent was noted in the detour for northbound I-15 to westbound I-10 and an increase in 36 percent was noted in the detour for northbound I-15 to eastbound I-10.
    • Queue length during construction—The traffic studies under this project did not explicitly measure queue lengths impacted by the construction activities. Instead, delay times of 3,084 vehicle-hours were estimated on I-15 northbound lanes, which represents the impact of construction during the critical ramp closure.
  • Quality
    • Smoothness—Rehabilitation efforts improved smoothness. IRI decreased from 225 in/mi before construction to 66 in/mi after construction. Motorists will notice a smoother ride, although the HfL goal for IRI of 48 in/mi was not met on this project.
    • Noise—The sound intensity (SI) data showed a noticeable 5.9 dB(A) decrease in noise from a preconstruction value of 108.3 dB(A) to 102.4 dB(A) after construction. Although the new pavement is noticeably quieter, it does not meet the HfL SI requirement of 96.0 dB(A) or less.
    • User satisfaction—Most motorists surveyed were satisfied with the finished highway and the way the project was carried out, which met the performance goal of 4 or more points on a 7-point Likert scale.

Economic Analysis

The costs and benefits of this innovative project approach were compared with those of a project of similar size and scope delivered using a more traditional approach. A comprehensive economic analysis that accounted for construction, road user, and safety costs revealed that the cost of using PCPS was about the same as conventional cast-in-place methods using RSC.

The economic analysis revealed that Mn/DOT’s innovative approach increased project costs by about $2.1 million, or 7 percent, compared to conventional construction practices. User cost associated with detouring traffic to alternate routes during the full closure exceeded the savings in construction costs.

Lessons Learned

Through this project, Caltrans gained valuable insights into the innovative technologies and materials used. The agency learned what contributed to the project's success and what issues need improvement or more careful consideration in future project deliveries. The following are some of the lessons learned:

General
  • On projects of this magnitude, construction experience is important.
  • Breadth of knowledge is required to execute projects that include several engineering aspects—traffic, pavement design, construction, and cost estimation.
  • Team approach and communication across various departments and divisions of an agency are critical. The agency should consider assigning an individual or a team to manage interdepartmental communication and rapport.
  • Innovations may be adopted on large-scale projects if agencies can pay attention to the details and are mindful of the learning curve in adopting new technologies.
  • In retrospect, it appears that production rates during major closures were underestimated, and more can be accomplished in an extended weekend closure than originally anticipated.
Super-Slab®
  • It is possible to use PCPS for rapid slab replacement in heavy traffic areas with short work windows. Planning is critical, as is realizing the significance of crew mobilization on such projects.
  • Accurate thickness data of the existing pavement are critical because the Super-Slab® panels must be cast to match the thickness of the existing panels as closely as possible. Designers should consider maximizing the number of cores taken from the existing pavement to increase the accuracy of design.
  • Designers may wish to consider conducting a 3D survey of the existing pavement during design (in addition to the one required of the contractor), in order to better anticipate faulting, profile issues, and warped panel needs prior to construction
  • Removing the existing panels was the critical task governing the amount of production the contractor could achieve during each closure period.
  • Bedding layer composition may be reconsidered for achieving desired results.
  • Base material grading is a very critical operation in the installation process and for good performance. Caltrans noted a strong correlation between improper grading and slab cracking.
  • Inspectors need to be well trained for PCPS. Typically, inspectors are not familiar with PCPS.
CA4PRS
  • The preconstruction study involving data collection and deciding how the contractor would perform the work was time-consuming because the software analysis setup.
  • Validating the software model took must less time than the preconstruction study.
  • A multidisciplinary team made up of operations, design, and construction experts would likely get the most utility from the CA4PRS software when analyzing a project of this size and complexity.
Dynameq
  • The project demonstrated the application of a mesoscopic scale model for traffic analysis on a large scale project with a very complex construction staging plan.
RSA
  • An RSA looks at project safety at a great level of detail.
  • The use of an independent audit team helps identify issues that may not be apparent to the design and construction planning teams.
  • RSA evaluations might be most useful if performed early in the design process or well before the planning stages. Recommendations, even if considered worthwhile, might be too expensive to incorporate after the plans are finalized or the bidding process is underway.

Conclusions

Caltrans concluded that it is possible to successfully complete the rehabilitation of a heavily congested major urban roadway with minimal disruption to traffic while maintaining high safety standards and designing for a long-life structure. This project highlighted the importance of emphasizing these project goals during the planning, design, and construction phases. The project demonstrated that precast concrete pavement construction can be successfully used for rapid repair of highways in urban areas with heavy traffic. The analyses performed to develop the construction staging plan and to simulate traffic to evaluate the network-wide impact of various construction staging scenarios were useful in developing the incentive and disincentive clauses in the construction contract. Through efficient use of equipment and combining of stages made possible by lower than anticipated traffic impacts, the contractor was able to complete the project with fewer major closures than anticipated. An analysis of these changes provided important lessons that can be utilized in construction planning on future complex projects.

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Contact

Mary Huie
Highways for LIFE
202-366-3039
mary.huie@dot.gov

Updated: 11/28/2012

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United States Department of Transportation - Federal Highway Administration