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47 Case Examples Unbonded Concrete Overlay of Asphalt on U.S. Highway 18 in Iowa Key features: Pilot-car operations with single-lane traffic through work areas, established maximum work zone lengths, a staging plan specifically established for efficient operations and to reduce disruptions, 3D stringless milling operations, 3D stringless paving operations, real- time smoothness measurements, concrete curing and strength gain monitored using maturity sensors for opening to traffic, early-entry saws for cutting transverse and longitudinal joints, portable signs that could be moved with operations, a longitudinal safety wedge along the length of the first paved lane to eliminate drop-off, and public meetings immediately prior to paving operations. Traditionally, the Iowa DOT constructed Portland cement concrete (PCC) overlays of exist- ing pavements on two-lane roads by closing the roadway and providing detours. This option was not always economic or feasible, so the Iowa DOT was looking for practical solutions. The Iowa DOT embarked on a pilot project to demonstrate and document the design and construc- tion of PCC overlays along with other roadway improvements while maintaining traffic with- out detours. A two-lane, 18.82-mi section of U.S. Highway 18 in northeastern Iowa between Fredericksburg and West Union was selected for this pilot project. The planning, design, and construction of the project along with lessons learned were documented by Cable (2012). The report also included a list of 71 recommendations for future construction of such projects. The existing roadway was an 18- to 20-ft-wide thickened-edge PCC pavement constructed in 1938 that had been widened to 24 ft using PCC and overlaid with a total of 6 in. of asphalt over a period of time. Some portions of the roadway had also received a thin surface treatment. Over the length of the project, the existing surface exhibited many distresses, including reflec- tive cracking, transverse and longitudinal crack deterioration, raveling, debonding of the surface treatment, and rutting. Project construction included preparation of the hot-mix asphalt (HMA) surface by milling to grade and placement of a 4.5-in. PCC overlay and 4 ft of widening of the existing pavement on each side for a total pavement width of 32 ft. The project also included installation of longitu- dinal subdrains, full-depth repairs, replacement of bridge approaches, guardrail improvements, drainage repair and improvement, and shoulder surfacing. Most construction, except drainage repair work, was performed using pilot-car operations and single-lane traffic through the work areas. The overlay paving and shoulder work were allowed to have a maximum 3.5-mi work zone length. Crossroad traffic was not allowed when the overlay pavement was being placed and the PCC was being cured. Subdrainage installation and full-depth repair work were allowed to be performed in maximum work zone lengths of 2 mi. C H A P T E R 4
48 Construction and Rehabilitation of Concrete Pavements Under Traffic The original plans called for milling 0.5 in. and overlaying with 4-in. PCC. Because of the dis- tresses on the existing pavement, the contractor offered a VE proposal to profile mill the existing surface to match the new design profile by milling up to 1.5 in. in depth. The contractor proposal saved Iowa DOT hundreds of thousands of dollars in concrete overages that would have been necessary to cover wheel rutting and other irregularities. Because of these savings, Iowa DOT increased the thickness of the new overlay by 0.5 in. to 4.5 in. The original staging plan included working in different portions of the project. Early on in the project, the contractor and Iowa DOT realized that it would be more efficient to perform indi- vidual operations at one end of the project and progress through the project in one time period, so the staging plan was revised to accommodate these changes. The final staging plan included: ⢠Perform subdrainage installation and full-depth repairs using 2-mi work zones allowing for 2-mi gaps between operations and orderly construction by each subcontractor. The subdrain- age installation and full-depth repair work could follow each other with only minor conflict- ing times and locations. ⢠Rehabilitate bridge approaches and railings on four bridges in the western part of the project area. Because bridge work is labor intensive and time consuming, bridge approaches and transition sections were constructed in advance or staged with other items such as subdrain- age installation, full-depth repair, and earthwork. ⢠Mill the HMA surface from one end of the project to the other in one operation. ⢠Place the PCC overlay and shoulder stone from one end of the project to another in one con- tinuous operation. ⢠Complete the construction of paved connections and turn lanes and place required rumble strips on the shoulders. 3D stringless milling was performed on this project with control from total robotic sta- tions using a computer surface model of the longitudinal centerline profile and 2% cross slope (Figure 14). The computer surface model was based on a 9-shot cross section at 50-ft intervals along the existing surface prior to milling. The PCC overlay placement was divided into 3.5-mi paving sections, with the single-lane traffic controlled by stoplights, flagging personnel, and pilot cars. Trucks delivered the concrete directly on grade in front of the paver. Concrete paving operations were performed using a Courtesy CP Tech Center. Figure 14. 3D stringless milling using total robotic stations.
Case Examples 49 single-lane slipform paver in two 16-ft-wide passes with two different pavement depths simul- taneously, 4.5 in. for the roadway and 8 in. for the shoulder. 3D stringless technology (Figure 15) was used for the PCC overlay, allowing accurate place- ment of the concrete to profile and cross slope. Four total stations were used simultaneously for the 3D paving. For typical wider and thicker PCC placement, one worker is sufficient to move the total stations in a leap-frogging process. Because this project had less concrete cross-sectional area being paved at one time, it required two people dedicated to moving the total stations to keep ahead of the paverâs high production rate, which averaged about 8,000 ft/day. The total stations typically needed to be less than 300 ft from the paver, and they were set at staggered control points 500 ft apart on each side of the road, resulting in a control point every 250 ft on one side of the road or the other. Not having a centerline stringline allowed for two-way construction traffic, timely delivery of concrete, and a single lane for the pilot car followed by through traffic on the shoulder/edge of the pavement simultaneously. Stringless paving also allowed for changes to be executed more quickly by immediately implementing the reprogramming of changes into the system. Two paver-mounted, real-time smoothness measurement units were also used to allow the paving crew to monitor smoothness and make adjustments as needed. Iowa DOT offers incentives for an International Roughness Index of less than 26 in./mi, and smoothness on this project aver- aged 18 to 19 in./mi and was as low as 13 in./mi. Typical paving included placing up to a 3.5-mi one-lane section under a single closure, stop- ping paving until the section cured and reached opening strength, and completing shoulder placement and striping before moving to the next section. Once one direction was completed, the operation backed to the beginning of the work and placed the second lane in 3.5-mi sections. Because this process was time consuming and inefficient, especially for the paving crew, the con- tractor opened a second paving section near the middle of the project and operated two sections Courtesy CP Tech Center. Figure 15. Illustration of 3D stringless paving.
50 Construction and Rehabilitation of Concrete Pavements Under Traffic at the same time. Moving the paver was relatively easy because equipment design allowed for moving the paving train from one site to another in less than one day and the stringless paving process enabled the contractor to make moves quickly. A texture/cure machine followed the paver and applied a transverse line to the 12-ft driv- ing lane and conventional white-pigmented spray-on cure. Wheels attached to the sensors on the texture/cure machine allowed steering and grade to be referenced off the new overlay. The concrete curing and strength gain were monitored using maturity sensors placed into the edge of the new pavement; these were used to determine when live cross traffic, construction traffic, and two-lane traffic could be placed on the new concrete. Early-entry saws were used to cut the transverse and longitudinal joints. The plans called for allowing through traffic at all times with minimum delays and pilot-car operations 24/7 (Figures 16 and 17). This was achieved using manual traffic controls and flaggers at each end of each work zone section. Side roads were closed off during the concrete paving operations until the concrete gained the strength specified for opening to traffic as monitored using the maturity sensors. The 2-mi work zones for subdrainage, full-depth repairs, and miscellaneous work were con- trolled with portable signs that could be moved with the operations. The work zones were also coordinated to reduce potential congestion in overlapping work areas. Iowa DOT required a longitudinal safety wedge along the length of the first paved lane to eliminate the 4.5-in. drop-off between the lane open to traffic and the new concrete pavement in case a vehicle accidentally veered on or off the new pavement. The contractor created a form box that was attached to the back of the paver and used a skid loader to dump concrete from the front of the paver into the box. The concrete in the box was vibrated before being placed on top of a bond-breaker fabric. When it was time to pave the second lane, the concrete wedge was removed using a motor grader and loaders and hauled away. Iowa DOT conducted a public meeting prior to the paving project to communicate plans for concrete placement and curing that affected access for 1 to 3 days until adequate gain in concrete Courtesy CP Tech Center. Figure 16. Work zone concrete paving operations with live traffic in adjacent lane.
Case Examples 51 strength. The meeting was announced through a flyer that was hand delivered to each local residence prior to the meeting and included visual displays of the paving schedule. The contrac- tor also contacted local residents immediately in advance of the concrete paving to make them aware of the temporary loss of access. Special allowances, such as gaps in the paving operations, were made to maintain access for special vehicles at all times. The contractor also provided spe- cial assistance to farmers and other residents needing access. The project used many technologies, processes, and procedures that enabled construction of a concrete overlay on an existing roadway while maintaining traffic in the adjacent lane, dem onstrating that this is feasible and can be done economically. Many lessons were learned and documented, together with a number of recommendations for future similar projects (Cable 2012). Replacement of Four Traffic Lanes Using Precast Concrete Panels on Interstate 66 in Virginia Key features: Precast prestressed concrete pavement (PPCP) lane replacement, nighttime construction only with at least one travel lane open at all times and all lanes open during the daytime, use of temporary panels and cold patches in blockouts for opening to traffic in the morning, use of high-performance rapid-setting grout for post-tensioning ducts, blockouts, and closure pours. Interstate 66 in Fairfax County, just west of the Interstate 495 Capital Beltway, is a busy high- way carrying mostly commuter traffic between Washington, D.C., and the suburbs of northern Virginia, with average annual daily traffic in 2008 of 184,000 vehicles per day with 5% trucks (Rao et al. 2013). The westbound direction had evening peak traffic of about 7,000 vehicles per hour and a nighttime low of about 500 vehicles per hour. Weekend traffic was approximately 150,000 vehicles per day. Westbound traffic was carried on three travel lanes and an auxiliary shoulder lane or rush-hour lane, which was open to traffic from 2:00 p.m. to 8:00 p.m. Given these traffic levels, shutting down even portions of the roadway for extended periods of time would have substantially affected the traveling public. Courtesy CP Tech Center. Figure 17. Concrete paving operations in the right lane with live traffic in adjacent lane.
52 Construction and Rehabilitation of Concrete Pavements Under Traffic This section of Interstate 66 was 9-in. JRCP built in the early 1960s (Figure 18). It was highly deteriorated and exhibited extensive joint and mid-panel cracking and spalling along with many full-depth repairs. With partial funding from the FHWA under the Highways for LIFE program, the Virginia DOT used PPCP to replace all four lanes of a 1,020-ft portion of the pavement. Virginia DOT adopted a unique contracting approach by limiting the total contract value to $5 million for the entire project, which also included some ramp repairs. The rehabilitation plan outlined the required rehabilitation areas and optional rehabilitation areas. The contract was awarded to the bidder proposing the largest total area of pavement replacement. Virginia DOTâs goal on the project was to reduce construction congestion by at least 50%. The traffic analysis showed that for traditional cast-in-place construction, lane transitions due to reduction in number of available traffic lanes would create queuing problems of approximately 1.5 to 2.0 mi during the evening peak rush hour that would last several hours. For the PPCP construction, queuing was expected to be about 0.1 mi long during the peak night hours when only one lane was open to traffic. The contractor was granted flexibility to plan and stage the construction within the restrictions of the minimum number of lanes open to traffic during construction and the times when all lanes needed to be opened to traffic. Two lanes were allowed to be closed at 9:00 p.m., and a third lane was allowed to be closed at 10:00 p.m. All lanes were to be opened by 5:00 a.m. to accommodate the morning rush-hour traffic. Since the first installation of PPCP in 2002 in Georgetown, Texas, PPCP has been used on projects in California, Missouri, Florida, Iowa, Alaska, Delaware, and other states. For the Inter- state 66 project, the contractor was required to perform a trial installation at a nearby location. The trial installation enabled Virginia DOT to evaluate PPCP construction and identify potential problems and address them prior to mainline construction. The construction was staged in two phases, as shown in Figure 19. Phase I included repairs to the inside shoulder and replacement of lanes 1 and 2 using 12-ft-wide panels. The contractor had the option of replacing one lane at a time or both lanes together and would still be within Virginia DOTâs lane requirements. The contractor initially replaced one lane at a time for a short segment and then changed to replacing both lanes in parallel. Phase II included the replacement of lane 3 and the rush-hour lane using 27-ft-wide panels. The panels for the PPCP were fabricated at a nearby precast plant and delivered to the project site for installation. PCC removal typically began after 10:00 p.m. following closure of the third Courtesy Virginia DOT. Figure 18. Photo of project location for Interstate 66 precast pavement construction.
Case Examples 53 lane. The panels were usually set between 11:30 p.m. and 2:00 a.m. Grouting of panels, followed by breaking down of the traffic control, was done between 2:00 a.m. and 5:00 a.m. The panels were pre-tensioned in the precast plant in the transverse direction (perpendicular to the direction of traffic) and post-tensioned in the longitudinal direction (parallel to traffic flow) during field installation. Each panel was partially post-tensioned in a process called âtem- porary post-tensioningâ using minimal post-tensioning forces on threaded bars at two of the post-tensioning ducts. Temporary post-tensioning helped adjust the alignment of each panel as it was installed and held the panels tightly together so that the roadway could be opened to traffic prior to final post-tensioning. After the placement of all 16 panels within a 160-ft section, a final post-tensioning operation was performed from the end. A high-performance grout material approved by Virginia DOT was used to grout the post-tensioning ducts to create a bonded system that would permit future PCC removal if needed. The grout also protects the tendons from corrosion. A single layer of polyeth- ylene sheeting was placed underneath the panel to allow the panel to slide while post-tensioning. Expansion joints were provided at the ends of each 160-ft section. A temporary panel was neces- sary to open the roadway to traffic in the morning after the end of each nightâs installation. The PPCP installation of lanes 1 and 2 was performed in the following sequence (Rao et al. 2013): 1. Close two traffic lanes at 9:00 p.m. and a third lane at 10:00 p.m. 2. Remove existing pavement in lanes 1 and 2. 3. Grade and level using stringline, straight edge, and No. 10 aggregate. 4. Spread polyethylene sheeting over the graded base to reduce friction beneath the panels for sliding during post-tensioning. 5. Install 12-ft-wide PPCP panels in lanes 1 and 2, along with initial post-tensioning following placement of each panel (Figure 20). 6. Complete post-tensioning and duct and panel grouting. Fill post-tensioning blockouts and closure pour following placement of each 160-ft section. 7. Place temporary panel and cold patch in blockouts before opening all lanes to traffic at 5:00 a.m. each morning. 8. Repeat steps 1 through 7 for the entire length of the project. 9. Grind all traffic lanes to meet smoothness requirements. The PPCP installation for lanes 3 and 4 was performed similarly, except that 27-ft-wide panels were used instead of the 12-ft-wide panels. As the project progressed, the contractor Courtesy Virginia DOT. Figure 19. (left) Phase I repairs of inside shoulder and replacement of inside lanes 1 and 2 using 12-ft-wide panels. (right) Phase II replacement of outside lanes 3 and 4 using 27-ft-wide panels.
54 Construction and Rehabilitation of Concrete Pavements Under Traffic made significant improvements to processes and procedures that increased productivity by the third week from fewer than 8 panels per night to 10 panels per night. By the end of the project, up to 12 panels were placed per night for the 12-ft-wide panels and 6 panels per night for the 27-ft-wide panels. Virginia DOT learned many lessons through this project and concluded that impacts to the road user were comparable to cast-in-place concrete as the lane closure times were comparable. However, Virginia DOT expects overall longevity of the PPCP system to be better than cast-in- place concrete, and thus the long-term impacts on traffic are expected to be much less since there will be reduced needs for maintenance and rehabilitation in the future. This project demonstrated that precast concrete pavement systems that include PPCP, jointed precast concrete pavements, and incrementally connected precast concrete pavements are options for overnight replacement of traffic lanes on high-volume roadways and opening to traffic the following day. Using precast concrete pavement systems allows an agency to replace entire lanes of deteriorated sections of existing roadway while eliminating the time needed for in-place setting and strength gain of concrete as compared to cast-in-place concrete. Concrete Pavement Widening on Interstate 75 in Ohio Key features: Construction partnering and sharing a field office between agency and con- tractor for rapid communications and quick responses, formal partnering and coordination between multiple contractors of all four adjacent contracts, a certified work-site traffic super- visor, transition zones between adjacent contract areas for independence of MOT operations, crossover construction with a minimum of two lanes of traffic open at all times in each direc- tion, A+B bidding with the contractor proposing the number of days for substantial completion and bids adjusted to compare bids, incentives for early completion and disincentives for not meeting bid number of days, 3D grading and paving, and a public outreach program with a dedicated website and informational videos updated regularly with new traffic patterns. The 32-mi section of Interstate 75, between Findlay and Perrysburg, just south of Toledo, carries traffic ranging from 55,000 to 65,000 vehicles per day on a four-lane roadway with up to Courtesy Virginia DOT. Figure 20. Placement of PPCP panel with three lanes closed and traffic in the fourth.
Case Examples 55 30% trucks. In 20 years, the traffic is projected to grow to almost 80,000 vehicles per day, with peak-hour traffic of about 7,000 vehicles per hour. To accommodate current and future traffic needs, Ohio DOT widened this portion of the Interstate from a four-lane highway to a six-lane highway through four different contracts comprising four portions of the section. The project also included some resurfacing and new interchange configurations. A contract for the 6.6-mi-long, northernmost of the four projects was awarded in May 2014, and the project was completed in 2017. The existing four-lane roadway consisted of 9-in. JRCP that had been overlaid over the years with a total of more than 8 in. of asphalt pavement. The new pavement design called for removal of all pavement layers, including shoulders and the 6-in. aggregate base beneath the JRCP, grading and compaction of the subgrade, installation of under- drains, placement of a 6-in. aggregate base over the subgrade, and placement of 13.5-in. of JPCP over the aggregate base. In each direction, the new pavement was designed to accommodate three 12-ft lanes, a 12-ft inside shoulder, a 12-ft outside shoulder, and merge and exit lanes as needed. The project included construction partnering and sharing of a field office by Ohio DOT and the contractors to support rapid communication and make it easier for all parties to quickly respond to issues. The minimum requirements for the office space were specified in the plans. Although each of the four concurrent contracts had its own beginning and ending points on the 32-mi section, Ohio DOT noted that overall success from the perspective of the travel- ing public was due to the success of all four projects. Therefore, cooperation, communication, interaction, and coordination between all four contractors were requirements of the contracts, based on the partnering concept. A combined, facilitated partnering session between the four contractors was held as soon as all four contracts were executed. Partnering discussions at the session included public relations, emergency response, access issues, coordination of MOT oper- ations, and scheduling of individual ramp/interchange closures. Since there would be a possibil- ity of two adjacent interchanges being closed at the same time, all ramp/interchange closures, MOT activities, and detour routes were coordinated between Ohio DOT and all four contractors through the partnering process. Each contractor was also required to have a certified work-site traffic supervisor approved by Ohio DOT. The project plans contained areas of interaction between adjacent projects in which one con- tractor could enter an adjacent contractorâs project limits to address MOT items such as signage and pavement markings. Estimated duration for all ramp/interchange closures along the full corridor comprising all four contracts was provided in the contract documents for each contract so that emergency access issues and planned detours could be addressed. The project plans also contained details for each contractor to install transition zones at the ends of each project area to allow independence of MOT operations between adjacent project areas. The transition zones were to be constructed within 120 days of the notice to proceed for each individual project. The transition zones allowed traffic to flow between adjacent MOT phases without interrupting the construction schedules of adjacent project areas. The overall project was constructed using crossover construction with a minimum of two lanes of traffic required to be maintained at all times in each direction, with some planned excep- tions, and permitted overnight lane closures to minimize the impact to the traveling public. The construction included diverting traffic to the southbound side, maintaining four lanes of bidirectional traffic on the southbound side, constructing the northbound lanes, diverting traffic to newly constructed northbound lanes, maintaining four lanes of bidirectional traffic on the northbound side, and constructing the southbound lanes (Figure 21). Through the partnering process, Ohio DOT worked with the contractors to get three lanes (instead of two lanes) open to traffic in each direction prior to the end of 2016, which reduced restrictions to the traveling public and maintained effective snowplow operations. The contractor
56 Construction and Rehabilitation of Concrete Pavements Under Traffic also partnered with Ohio DOT to make sure that weekend closure of a ramp was not needed by adjusting the phasing and slightly accelerating work in the area of the ramp during its specified 120-day closure period. The contraflow configuration seemed to confuse motorists and cause several crashes and near crashes at the decision point. Through the partnering process, additional signs were fabricated and striping changes made in the area to get traffic out of the contraflow configura- tion sooner. Because two of the interchange ramps needed 120-day closures, Ohio DOT and a contractor worked together to fabricate early warning signs, which were not in the plans, to detour travelers before they arrived at the closed ramps and reduce traffic backups. The contract was procured using A+B bidding, and contractors were required to propose the number of days for substantial completion for four segments subject to the specified minimum and maximum number of days, along with I/D for each segment, as shown in Table 12. For purposes of comparing bids, Ohio DOT adjusted the bids to include consideration of the days bid and the I/D value for each specified segment. Courtesy Ohio DOT. Figure 21. Photo of construction of the northbound lanes with four lanes of bidirectional traffic crossed over to the existing southbound lanes. Courtesy Ohio DOT. Note: STA = station. Contract Segment â Location of Critical Work Minimum Days Maximum Days I/D $ per Day Maximum Incentive $ Segment 1: closure and reconstruction of NB I-75/SR 582 on- and off-ramps per MOT Stage 3 or 4 10 45 2,500 25,000 Segment 2: closure and reconstruction of SB I-75/SR 582 on- and off-ramps per MOT Stage 7 10 45 2,500 25,000 Segment 3: closure and reconstruction of NB I-75 to WB I-475, EB I-475 to NB I-75, SB I-75 from STA. 1309+00 to STA. 1403+00 per MOT Stage 5 and 6 60 120 10,000 500,000 Segment 4: closure and reconstruction of WB I-475 to SR 25 exit per MOT Stage 7 4 14 10,000 100,000 Table 12. I/D plan for four construction segments.
Case Examples 57 A B B Bn n[ ][ ] [ ]( ) ( ) ( )= + Ã + Ã + ÃAdjusted bid I D I D . . . I D1 1 2 2 where A = Sum of the estimated unit quantities multiplied by the respective unit prices bid, Bn = Number of calendar days bid to complete segment n, (I/D)n = The listed I/D value for segment n, and n = Number of segments. Unless specified in the plans, the beginning date for charging calendar days to a segment was the date when traffic on the segment was affected by the construction. Once the construction of a segment was substantially complete, Ohio DOT used the information in Table 12 to compute I/D payments based on the number of days bid by the contractor for that segment. The plans allowed for the contractor to perform 3D construction using GPS. The contrac- tor used both GPS and Universal Total Stations to perform survey layout, grading, and paving; improve construction efficiency; and construct within schedule. Ohio DOT had a public outreach program that included a dedicated web page with links to construction updates and other pertinent information (Figure 22), and it also provided infor- mational video channels to communicate with the traveling public (Figure 23). Ohio DOT, its public information officers, and the contractors worked with local police departments, fire departments, first responders, and the state highway patrol to keep the traveling public and stakeholders up to date on any major changes to the project. Ohio DOT also held quarterly meetings to keep stakeholders updated on emergency points of contact and what upcoming work would need to be more closely monitored. Reconstruction and Widening of Interstate 90 at the Illinois Tollway, Illinois Key features: Temporary warm-mix asphalt lane construction along the full length of one direction to widen roadway, crossover construction with a minimum of two lanes of traffic open at all times in each direction, a unique MOT plan over a series of multiple contracts and staged construction, MOT coordination among multiple contracts, performance-related specification with quality incentives and disincentives, removal and recycling of existing pavement in place, and optimized mix designs. The 60-mi segment of Interstate 90 (Jane Addams Memorial Highway) between Interstate 39 at Rockford, Illinois, and the Kennedy Expressway in Chicago was constructed by the Illinois State Toll Highway Authority (Tollway) using 10-in. JRCP and was opened to traffic in 1959. Since that time, much of the original JRCP had received full-depth repairs, and the entire road- way had been overlaid multiple times with asphalt. The average pavement Condition Rating Survey value had deteriorated to around 7 (out of 100) in 2011. The original concrete pavement was severely deteriorated to the point where asphalt overlays had short service lives. Traffic ranged from 40,000 vehicles per day on the westernmost locations to 170,000 vehicles per day on the easternmost locations. Traffic levels were also expected to increase, requiring placement of additional lanes to maintain acceptable levels of service. The Tollway Authority elected to reconstruct the Interstate 90 pavements and replace them with a widened pavement section to provide the most benefit to Tollway customers. The 37-mi western portion of the segment was rebuilt and widened from two to three lanes in each direction in 2013 and 2014, with JPCP thicknesses ranging from 11.25 to 13.0 in. Tem- porary warm-mix asphalt pavement was built the full length along the inside shoulder of the
58 Construction and Rehabilitation of Concrete Pavements Under Traffic Courtesy Ohio DOT. Figure 22. Ohio DOT web page providing links and communications on the Interstate 75 widening project.
Case Examples 59 Courtesy Ohio DOT. Figure 23. Ohio DOT informational video channel for communications on the Interstate 75 widening project.
60 Construction and Rehabilitation of Concrete Pavements Under Traffic westbound side to accommodate four lanes of traffic. Traffic was diverted to the westbound side, with two lanes of traffic in each direction, while the eastbound lanes were constructed (Figure 24). Once the eastbound lanes were completed, all traffic was diverted to the eastbound side, with two lanes of traffic in each direction, while the westbound lanes were constructed. Because the work zone was separated from traffic, there was sufficient room to allow for two- lift PCC/PCC composite pavement construction, use of performance-related specifications for materials, and chemical soil stabilization, with minimal impact to traffic. The 22-mi eastern portion of the segment was rebuilt and widened using 13-in. JPCP, from three to four lanes in each direction in 2015 and 2016, with a unique MOT plan to reduce traf- fic impacts and maintain three lanes of traffic in each direction at all times (Figure 25). During the first year of construction, traffic was squeezed into the inside lanes as widening and recon- struction were performed on the outside lanes in both directions. During the second year of construction, the three lanes of traffic in each direction were shifted onto the new pavement on the outside lanes, while the inside lanes and median were reconstructed. The project allowed for managed lanes to be constructed, was designed to accommodate driverless cars in the future, and used performance-engineering specifications for the PCC mix and performance-related specifications for PCC pavement construction. Chemical soil stabilization was also used on this project. Both projects were completed through a series of multiple contracts over a 4-year period and included various stages of construction on various portions of the roadway. The individual con- tracts were divided based on traffic phasing (e.g., different contracts for widening, westbound paving, eastbound paving, reconstruction of inside lanes, and reconstruction of outside lanes) rather than location (e.g., from point A to point B). Because multiple sections of the roadway were being constructed concurrently under different contracts, the contractors were required to coordinate MOT with each other and cooperate with each other in the phasing and performance of the work without delay, interruption, or hindrance to the work being performed by the other contractors. The contractors were also required to provide access to contractors from adjacent Courtesy Illinois Tollway. Figure 24. Construction of the western portion of Interstate 90 with four lanes of traffic (two in each direction) on the westbound side and construction activities on the eastbound side.
Case Examples 61 projects as appropriate. If any conflicts were to arise, they were to be resolved at the direction of the Tollway. Whenever possible, the existing pavement was removed and recycled in place (Figure 26). Recycling in place reduces the impact to traffic otherwise caused by haul vehicles traveling in and out of the work zone. These pavements were also designed and built with sustainable con- crete mixes with optimized gradations and with more supplementary cements to provide better Courtesy Illinois Tollway. Figure 25. Construction of the eastern portion of Interstate 90 with widening and reconstruction being performed on the outside lanes. Courtesy Illinois Tollway. Figure 26. In-place recycling of existing pavement.
62 Construction and Rehabilitation of Concrete Pavements Under Traffic durability and longer life. Optimized mixes allow for more effective designs, limited lane closure times, and expedited schedules. The project was completed successfully and met all of the Illinois Tollwayâs goals for the project in terms of traffic impacts, duration, safety, and quality. Bonded Concrete Overlay of Asphalt on Interstate 70, Missouri Key features: Used existing median crossovers to divert traffic, recycled asphalt pavement millings to stabilize the edge of the outer shoulder, two belt placers to spread concrete along with delivery of two trucks of concrete simultaneously to increase productivity, and stringless paving. In 2011, a 15.2-mi, divided, four-lane, full-depth asphalt pavement section of Interstate 70, spanning Ellsworth and Lincoln Counties in Missouri, was overlaid with a 6-in. bonded con- crete overlay (Figure 27) (LaTorella 2015a, Brown 2012, ForConstructionPros 2012). The main- line was slipformed in a 30-ft-wide pass that included two travel lanes and the inside shoulder. A separate slipform paver was used to construct the 10-ft-wide outside shoulder. To accelerate construction, traffic was diverted across the median, resulting in two-lane, head- to-head traffic separated by a concrete barrier. The approach also allowed the contractor to stay on schedule, especially in transporting more equipment and personnel, thereby improving productivity. The contractor also proposed using an existing active median crossover, resulting in savings of time and money. The width of the mainline slipform paver made it sometimes difficult for trucks to go around the paving train. To address this issue, the contractor recycled asphalt pavement millings to stabilize the edge of the outer shoulder. To boost production and expedite construction, the contractor used two belt placers to spread concrete in front of the paver, which allowed for the delivery of two trucks of concrete simultaneously. The contractor achieved an average profile index of 9.2 in./mi, resulting in significant smoothness incentives. This was achieved by (1) using dual, precisely tensioned aircraft cable stringlines; (2) paying close attention to ensure stringlines were set up correctly, with pins Courtesy Missouri/Kansas ChapterâAmerican Concrete Pavement Association. Figure 27. Construction of bonded concrete asphalt overlay on Interstate 70 in Kansas.
Case Examples 63 placed at 50 ft intervals; and (3) producing and delivering concrete to the paver consistently (in terms of batch plant production, timing of delivery, and slump) so that the paver never stopped. The contractor also used a stringless automated control system for paving over the final 2 mi. Intersection Reconstruction Using Precast Panels on State Route 7, New York Key features: Precast panels at critical areas and cast-in-place concrete at non-critical areas, one lane of traffic maintained in all directions at all times, night work with all lanes open to traf- fic during the day, and occasional use of pilot cars through complex detours. In 2006, a major signalized intersection was reconstructed on a four-lane portion of State Route 7 in Schenectady County, New York (Cuerdon 2015), as part of a reconstruction of several miles of the highway (Figure 28). Being the first intersection off of Interstate 890, and provid- ing access to two major commercial areas, State Route 7 carried 40,000 vehicles per day at this location. At least one lane of traffic was to be maintained in all directions at all times through the intersection. To attain this goal, 9-in. precast concrete panels were placed in critical traffic areas, whereas cast-in-place concrete was used for non-critical areas such as shoulders and turn lanes. The precast panels were placed during a 13-h night work window when one lane was taken out of service. The 12-ft-wide and 10-ft-long slabs were typically installed at a rate of 10 per night. In the morning, at the end of the work window, the traffic control was removed, and all lanes were open to traffic, including lanes with precast panels placed during the previous nightâs work shift. To minimize disruptions and improve work zone safety, traffic had to occasionally be escorted by a pilot car through the sometimes complex traffic detours. Because of the complex geometries, transitions, and superelevations at the intersection, three-dimensional âwarpedâ precast panels specifically designed for each location were used. This also required the use of special grading equipment specifically designed to create the same geometry as the top surface of the precast panels to provide full support. To overcome Courtesy New York ChapterâAmerican Concrete Pavement Association. Figure 28. Reconstruction of urban intersection on State Route 7 in New York.
64 Construction and Rehabilitation of Concrete Pavements Under Traffic obstruction from overhead signal wires in some locations, low-height tow-truck booms were used instead of conventional cranes to set some of the precast panels. Unbonded Concrete Overlay on Interstate 77, North Carolina Key features: Four lanes of traffic maintained much of the time, DB allowed contractor flex- ibility in developing MOT plan and time-saving techniques, two-lane-wide detour along the median for the full length of the project, temporary asphalt pavement, wireless maturity testing, and full-width slipform paving equipped with a spreading plow to spread the concrete before it entered the paver, thereby increasing productivity by eliminating a placing machine. In 2009, a 6.5-mi section of deteriorated, divided, four-lane CRCP of Interstate 77 in Yadkin County was overlaid with an 11-in. unbonded concrete overlay (Figure 29) [Dean (2015), Fisher (2008), Ayers and Harrington (2010)]. The DB project also included full-depth repairs, shoulder widening, ramp work, and guardrail improvements. The project included several traffic consid- erations, including (1) seasonal traffic restrictions, (2) reduction of single-lane patterns to lessen traffic impacts, (3) reduction of temporary pavements and associated costs, and (4) full-width paving to the greatest extent possible to increase productivity and reduce construction time and traffic impacts. The contractor was required to maintain four lanes of traffic much of the time, and the lanes were not allowed to be closed or narrowed during holidays, summer weekends, or other events. The DB process allowed the contractor flexibility to employ a creative MOT plan and time- saving techniques to accelerate construction, resulting in the project being completed almost 6 months ahead of schedule. The contractor built a two-lane-wide detour along the median for the length of the proj- ect; this was facilitated by the extra-wide median. While the plans called for a permanent 10-ft asphalt inside shoulder, the contractor provided and constructed a permanent 12-ft asphalt inside shoulder in the northbound direction. The contractor also placed an additional 13 ft of asphalt pavement on the median side of this inside shoulder, which was milled out at the end of Courtesy Carolinas Concrete Paving Association. Figure 29. Construction of unbonded concrete overlay on Interstate 77 in North Carolina.
Case Examples 65 the project and recycled. The northbound lanes were closed, and two-lane northbound traffic was crossed over on to 25-ft, newly placed asphalt lanes. This allowed for full-width slipform paving of the concrete overlay in the northbound direction, thus reducing traffic impacts and increasing safety. It also improved productivity by making the concrete delivery and paving operations more efficient and allowing for construction during the multiple, short work win- dows associated with the seasonal traffic. When northbound construction was complete, it was opened to northbound traffic, and the southbound traffic was detoured to the asphalt lanes for closing and constructing the southbound lanes. The slipform paver was equipped with a spreading plow that spread the concrete before it entered the paver, thereby increasing productivity by eliminating a placing machine. Wireless maturity testing was used to estimate the time at which the new concrete obtained sufficient strength to allow construction equipment onto the concrete overlay. To meet ride specifications, the concrete pavement surface was diamond ground prior to opening to traffic. Bonded Concrete Overlay of Asphalt on U.S. Highway 2, North Dakota Key features: Field designs for each lane closure segment to optimize construction sequenc- ing, temporary signals, modifications to existing signals, nighttime operations, fast-track mix- tures, maturing testing, and optimized concrete mixtures. In 2012, six intersections on a 5.7-mi stretch of asphalt pavement on U.S. Highway 2 (West Dakota Parkway) in Williston, North Dakota, were overlaid with 6- and 7-in. bonded concrete overlays, while access to the businesses around the intersections was maintained (Figure 30) (Sethre 2015). Because of the heavy truck traffic from oil and gas operations, these intersections had exhibited severe rutting and deterioration. The bonded concrete overlays at the intersections extended an additional 800 ft to accommodate truck breaking and stopping. No advanced field surveys could be performed due to heavy traffic on the road. As such, field designs were required for each lane closure segment. Field adjustments were made to opti- mize the construction sequencing, resulting in a reduction of construction time by 5 weeks. To reduce disruption to traffic and accelerate operations, the construction was performed in over 20 phases. Courtesy North Dakota ChapterâAmerican Concrete Pavement Association. Figure 30. Nighttime construction of bonded concrete asphalt overlay on U.S. Highway 2 in North Dakota.
66 Construction and Rehabilitation of Concrete Pavements Under Traffic The intersections and side streets were paved under traffic, one lane at a time, as there were no viable detours. When possible, traffic was diverted to one side of the divided roadway, resulting in two-lane, head-to-head traffic. Temporary signals or modifications to existing signals were used to control traffic through the construction zones. Nighttime operations were used on some segments of the project to reduce traffic impacts. Fast-track mixtures were used to accelerate concrete strength gain. Maturity testing was used to monitor the strength gain and open completed segments to traffic as soon as possible. Con- crete mixture gradations were optimized to improve workability and productivity. Bonded Concrete Overlay of Asphalt on U.S. Highway 40/287, Colorado Key features: Flaggers and pilot-car operations with time limits and without detours, 24-h traffic control supervisor (TCS), lane rentals, construction equipment and material delivery vehicles not allowed to use lanes open to traffic, illuminated flagger stations, advanced warn- ing measures, and centerline control without a stringline using a ski attachment running over profiled milled pavement. In 2010, an 8.3-mi, two-lane rural asphalt portion of U.S. Highway 40/287 near Boyero was overlaid with a 10.75-in. bonded concrete overlay (Figure 31) (Folkestad 2015a, Ungerman 2015). Portions of the roadway were reconstructed with 12-in. concrete pavement. All paving work was performed during daylight hours. The 40-ft-wide road, with heavy truck traffic, was paved in 20-ft passes using flaggers and pilot-car operations that escorted one-lane traffic in the adjacent open lane. Normal two-way traffic was required to be maintained between December and March. Detours would have presented sight distance issues, and three-phase lane closures would have increased project duration and would also have presented safety issues. To disincentivize construction delays, the contractor was charged a lane rental fee of $2,000 to $2,500 per day of pilot-car operation. The pilot-car specifications also required maintaining a 24-h TCS. For safety reasons, no detours were allowed as part of the pilot-car operations. The pilot car escorted traffic through the work zone at 20 mph and was required to complete a full cycle in 25 min or less. The specifications called for fines or even work stoppages if the 25-min Courtesy Colorado/Wyoming ChapterâAmerican Concrete Pavement Association. Figure 31. Construction of bonded concrete asphalt overlay with traffic in the adjacent lane on U.S. Highway 40/287 in Colorado.
Case Examples 67 time limit was exceeded. The contractor completed this entire project without any pilot-car time-limit violations. Wide-load restrictions limited vehicles that were wider than 12 ft; these were detoured around the project. To reduce traffic disruptions and improve safety, construction equipment and material deliv- ery vehicles were not allowed to use lanes open to traffic. All construction traffic and personnel were required to follow appropriate traffic control protocols before entering the roadway with active traffic. Flaggers were used at crossroads to control traffic access and direct it in the appro- priate pilot-car direction. Radios were used for communication between the project engineer, the pilot-car driver, the TCS, and all flaggers. Flagger stations were illuminated to improve flagger and work zone safety. Advanced warning measures that included a variable message board, centerline controls, a radar speed board, uniformed highway patrol, and temporary rumble strips were set up ahead of the construction zone to alert drivers to the flagger and the stoppage for the pilot-car operations. The contractor had to maintain a minimum of 10 ft for traffic, resulting in insufficient space for setting up a stringline along the centerline. For centerline control without a string- line, a ski attachment, which ran on the trimmed and properly profiled milled pavement, was installed on the paver. A flagger near the paver used an air horn to warn crews of the approaching pilot car. To reduce delays, costs, and the need for 24-h TCS, some construction activities were per- formed without pilot-car operations. The embankment was hauled before paving with simple shoulder closures. Before slipform paving began, milling on the project was conducted under mile-long lane closures. After paving began, milling on the project was done to coincide with the pilot-car operations. Localized traffic control was used to widen structures. Seeding and other cleanup activities were performed under lane closures. Bonded Concrete Overlay of Asphalt on U.S. Highway 385, Colorado Key features: Flaggers and pilot-car operations with time limits and without detours, 24-h TCS, lane rentals, construction equipment and material delivery vehicles not allowed to use lanes open to traffic, illuminated flagger stations, advanced warning measures, and centerline control without a stringline using a ski attachment running over profiled milled pavement. A bonded concrete overlay of asphalt pavement was constructed on a 28-ft-wide section of U.S. Highway 385 near Idalia in Yuma County, Colorado (Figure 32) [Folkestad (2015b), Ungerman (2015)]. A 7.75-in. doweled concrete overlay was placed on the existing asphalt pavement. As in the case of the U.S. Highway 40/287 project (previous case example), speci- fications required one lane to be open to traffic at all times, no traffic was allowed beyond the barriers, and all paving was to be performed during daylight hours. The specifications also included lane rental for pilot-car operations, a 24-h TCS requirement, completion of the pilot- car cycle in 25 min, and an at least 10-ft-wide travel lane. The contractor used a combination of flaggers and the pilot car to manage traffic, reduce disruption, and accelerate construction during asphalt milling and slipform paving operations. Proper staging and well-planned delivery of concrete was necessary for efficient and cost- effective construction. Because of the tight tolerances for the slipform paver, no centerline stringline was used, and the contractor used vertical barrier panels along with a ski attached to the paver for centerline control. Embankment for side slopes was hauled prior to pilot-car operations with simple shoulder closures.
68 Construction and Rehabilitation of Concrete Pavements Under Traffic Bonded Concrete Overlay of Asphalt on State Route 79, Missouri Key features: One-lane traffic with automated timed signal controls, construction partner- ing, coordination with local agencies, and significant public information activities. A 7.7-mi, two-lane portion of State Route 79 in Ralls and Marion Counties, Missouri, was resurfaced in 2013 using a 5-in. concrete overlay on the 12-ft-wide driving lanes (Figure 33) (LaTorella 2015b). The project also included 6-ft-wide paved asphalt shoulders that could be used as bicycle lanes. Because the roadway is vital to the regionâs industry and tourism, provid- ing access during the entire project duration and reducing traffic impacts and construction time were crucial. The project was constructed one lane at a time using a timed signal directing traffic to the adjacent open lane and 10-ft vehicle width restrictions. Oversized vehicles were detoured around the construction zone. The project included significant construction partnering, coordination with local agencies, and public information activities. Based on meetings between Missouri DOT, the construc- tion contractor, and local emergency management officials, special signs, a 24-h hotline, and a Courtesy Colorado/Wyoming ChapterâAmerican Concrete Pavement Association. Figure 32. Construction of bonded concrete asphalt overlay with traffic in the adjacent lane on U.S. Highway 385 in Colorado. Courtesy Missouri/Kansas ChapterâAmerican Concrete Pavement Association. Figure 33. Construction of concrete overlay on State Route 79 in Missouri.
Case Examples 69 process to allow emergency vehicles to travel against traffic were established. Consistent mes- sages were displayed on websites for local tourist attractions, welcome centers, the chamber of commerce, the city of Hannibal, and Missouri DOT. The consistent messages provided project status updates and also confirmed that local attractions were open during construction. The project was completed 2 weeks ahead of schedule. Reconstruction and Widening of Interstate 15, Utah Key features: Multiple complex phasing plans, a fixed-price-best-design procurement pro- cess, accelerated bridge construction techniques, âpipe jackingâ for installing drainage pipe, stringless paving, grouping work activities, a comprehensive outreach campaign, and formal construction partnering along with emphasis on informal partnering and personal connections. The 24-mi Interstate 15 Corridor Expansion (CORE) DB project south of Salt Lake City, Utah, was completed in 2012 (Figure 34) [McIntyre (2015), Utah Construction and Design (2013), Utah Department of Transportation (2013)]. The highway carries 150,000 vehicles per day through this location and has few alternative routes. This was the largest freeway construction project in Utah history and was completed in less than 36 months, 48 days ahead of schedule and $260 million under budget, due to multiple complex phasing plans that were used to maintain traffic lanes. The mega-scale project incorporated 100 separate pavement segments, 62 full directional lane closures, and 2,500 other lane closures. The entire project had 2.8 million square yards of concrete paved using seven slipform pavers, replacement of 63 bridges, and full reconstruction of 10 interchanges. To increase capacity, two lanes were added to both the northbound and southbound directions of Interstate 15. Utah DOT issued a fixed-price, best-design procurement process in which bidders were required to bid on the amount of highway that could be completed for a predetermined budget. The winning contractor, a consortium of several large firms, bid 24 mi, which was far more than Utah DOT estimated. The winning bid also included a completion date 2 years ahead of Utah DOTâs planned completion date. The winning design used a construction phasing and MOT plan that kept the existing number of lanes (three lanes in each direction) in service and provided a 40-year pavement design, as compared to the required 30-year design. Courtesy Utah ChapterâAmerican Concrete Pavement Association. Figure 34. Construction on Interstate 15 Corridor Expansion project in Utah.
70 Construction and Rehabilitation of Concrete Pavements Under Traffic An additional lane in each direction of the Interstate was provided during construction to reduce delays, thus exceeding contract requirements for number of lanes open during construc- tion. The contractor used accelerated bridge construction techniques extensively throughout the project to expedite the construction schedule. Notably, four bridges were constructed off site, adjacent to Interstate 15, and moved into place using a self-propelled modular transporter overnight with full freeway closure. A new technology used to avoid open cuts in the pavement, which would have required lane closures, was a method of installing concrete drainage pipe called âpipe jacking.â The system uses augers or a tunnel boring machine with a cutting head to excavate under the freeway while simultaneously pushing pipe segments through to the other side. Due to tight paving con- straints and to improve productivity, concrete paving was performed using a stringless paver: a machine-controlled, wireless paving system that eliminates the need for stringlines and staking. The stringless system provided better access for delivery trucks, and operators had better control and precision over the slipform paver. Work activities were often grouped according to the location of each closure, allowing crews to reduce closures and increase productivity. The Utah Highway Patrol helped to adminis- ter slowdowns and work zone speed enforcement and also advised the contractor on ways to improve its MOT strategies. A key part of the project was a comprehensive outreach campaign regarding lane splits around a complex construction zone, which required drivers to know which lanes to use long before they reached that zone so they could exit or stay on the freeway. The MOT and communications team executed the outreach campaign to raise awareness of the traffic configuration and provide information to safely navigate the lane split. The campaign included TV and print news stories, radio advertisements, social media, an online instructional video, direct mail, and even a movie theater ad. Communications also included emphasizing and promoting âTravelWiseâ strategies to individuals and businesses in which road users were encouraged to carpool, telecommute, trip chain, and use flexible work schedules to avoid delays and reduce traffic during construction. The Interstate 15 CORE project also entailed a formal construction partnering process between Utah DOT and the contractor. The field offices as well as the main office for the DOT and the contractor were co-located to encourage face-to-face communications. The collaborative part- nering process enabled decision makers from the DOT and the contractor to work together to set common goals and expectations and established a culture in which issues or challenges could be openly discussed and methods formulated on how to overcome them. As a result, decisions and approvals were made more quickly on the over 125 contract change orders, with zero contrac- tor claims, reducing associated delays. Because of the size and scope of the project, there were occasional disagreements and differing interpretations between the DOT and the contractor, but they were overcome through the partnering process. There was also an emphasis on infor- mal partnering and personal connections to foster teamwork. Partnering meetings included an emphasis on accountability by developing action plans with responsible parties and timelines identified. Subsequent meetings required an accounting of the progress for each action item. Unbonded Overlay and Widening of Interstate 75, Michigan Key features: A temporary movable barrier wall to allow quick changes from two to three lanes in the direction of the heaviest traffic, and a public outreach program. In 2005, six lanes of a 7.2-mi asphalt over 12-in. concrete composite pavement section of Interstate 75 near Birch Run, Michigan, were overlaid with a minimum 8-in. concrete overlay
Case Examples 71 (Figure 35) (ACPA 2015). The project also included widening by adding an 11-in. concrete pavement lane in each direction, for a total of four mainline traffic lanes in each direction. The first step in the MOT was to widen the northbound shoulder under traffic to accommo- date three full lanes of traffic in each direction. This was followed by concrete pavement con- struction in the median. Five lanes of two-directional traffic were then moved to the existing northbound lanes and the newly constructed median for construction of the southbound lanes. To reduce traffic delays and disruptions through the construction zone during this phase, a temporary, movable barrier wall was used to allow quick changes from two to three lanes in the direction of the heaviest traffic. Project progress and lane restrictions were communicated to the traveling public through local media. When construction of the southbound lanes was complete, traffic was diverted from the northbound lanes to the completed southbound lanes and median for construction of the northbound lanes. Unbonded Concrete Overlay on Little Mack Avenue, St. Clair Shores, Michigan Key features: Optimized concrete mixture and leapfrog milling approach. A 2-mi section of Little Mack Avenue in St. Clair Shores, Michigan, was rehabilitated in 2011 with a 4-in. unbonded overlay [Harrington et al. (2014), DeGraff (2011)]. The five-lane urban arterial roadway was originally constructed in 1995, and within 5 years started exhibiting joint distresses that deteriorated considerably in another 5 years. The cause was attributed to poor distribution and reduced amount of entrained air in the upper 3 in. The lower 6 in. of pavement and the foundation were deemed to be sound. The City of St. Clair Shores opted to mill the upper 4 in. of deteriorated concrete and resur- face the remaining concrete with a 4-in. unbonded concrete overlay (Figure 36). The project was completed in two phases while maintaining two-way, two-lane traffic. Southbound traffic was diverted to the northbound direction when constructing the southbound lanes, and north- bound traffic was diverted to the southbound direction when constructing the northbound lanes. The urban location of the project allowed detours to be used around construction at intersections. Courtesy Michigan Concrete Association. Figure 35. Construction of unbonded overlay and widening on Interstate 75 in Michigan.
72 Construction and Rehabilitation of Concrete Pavements Under Traffic An optimized, durable concrete mixture with adequate entrained air and reduced perme- ability was used. The dense, well-graded mixture had reduced paste content and 30% of the Portland cement replaced with ground, granulated blast furnace slag. A 0.25-in. geo- textile fabric separator layer was placed over the existing concrete prior to placement of the unbonded concrete overlay. The project specifications required the maximum ridge height of the milled surface to be less than 0.25 in. to prevent puncturing the geotextile fabric separator layer. Initially, the approach was to mill the 4 in. of concrete in a single pass. To meet the specification expeditiously, the con- tractor recognized that fresh milling teeth would be required for the final finish and performed the milling in two passes: a first pass at a depth of 2 in. and a second pass to final grade with fresh milling teeth. When the fresh teeth were worn to a point that the final milled surface was not acceptable, the machine skipped ahead and continued where the first pass was left off. This process met the tight milling specifications and also reduced construction costs and delays by maximizing the life of the milling teeth. The design, along with the planned milling and associated specifications, allowed the project to be constructed without changing the roadway grade. Consequently, side streets and driveways did not have to be reconstructed, whereas the curb was replaced as an integral curb while placing the concrete overlay. Thus the design, plans, specifications, and construction practices resulted in cost savings and reduced construction time with less disruption to traffic. Unbonded Concrete Overlay on Alma Drive, Plano, Texas Key features: Concrete paid both by volume for the material and by area for the placement; a high-performance, high-strength concrete mixture with fiber reinforcement; a zero-clearance paver; and short joint spacing adjusted to accommodate paving equipment/operation. A 0.7-mi portion of Alma Drive in Plano, Texas, was rehabilitated with a thin (2.5- to 4.5-in.) unbonded concrete overlay in 2007 (Figure 37) (Harrington et al. 2014). The six-lane divided arterial roadway consisted of 3- to 5-in. HMA over 5- to 8-in. concrete. The existing HMA layers were milled, followed by removal and replacement or repair of deteriorated existing concrete. A 0.5-in. HMA separator layer was placed on top of the existing concrete prior to placement of the concrete overlay. Courtesy Michigan Concrete Association. Figure 36. Placement of unbonded concrete overlay on Little Mack Avenue in St. Clair Shores, Michigan.
Case Examples 73 Two-way, two-lane traffic was maintained by diverting southbound traffic to the northbound direction across the median when constructing the southbound lanes. Northbound traffic was diverted to the southbound direction when constructing the northbound lanes. Detours were used around construction at intersections. This project incorporated several features to mitigate risk, improve constructability, and reduce construction time. To accommodate for deviations from estimated quantities due to variability in existing HMA thickness along the project and to eliminate consequent potential delays, payment of the concrete overlay was done as two bid items: (1) by volume for the concrete material and (2) by area for the placement. A high-performance, high-strength concrete mixture with fiber reinforcement was used for the overlay. Strength specifications included both a 28-day minimum requirement and an opening to traffic strength that was not excessive. A zero-clearance paver was used to overcome lateral constraints behind the curb and to facilitate maintenance of traffic through the project. A short transverse joint spacing of 3 ft was used. The design longitudinal joint spacing was also short and was equal to one-third the lane width (approximately 3.67 ft). However, the longitudinal joint spacing was modified during construction. While the outside and inside lanes were constructed with the design 3.67â3.67â3.67-ft longitudinal joint spacing, the middle lane was constructed with 3.5â2.0â2.0â3.5-ft longitudinal joint spacing to accommodate the paving equipment/operation. Roller-Compacted Concrete on State Route 684, Virginia Key features: RCC, weekend-only work, and open to traffic in less than 48 h. Virginia DOT evaluated RCC pavements as a concrete pavement option where disruption to traffic was a consideration (Hossain and Ozyildirim 2015). RCC was used to rebuild a sec- tion of State Route 684 (Staffordboro Boulevard) and roads leading to a commuter parking lot (Park-and-Ride facility) in Stafford, Virginia (Figure 38). In late 2014, the traffic count on Staffordboro Boulevard was expected to go up to 12,800 vehicles per day with 18% buses. Staffordboro Boulevard was also expected to carry heavy commercial trucks. It could not be closed for construction since it is the only access road to the Park-and-Ride facility with direct connection to Interstate 95. A total of 134,000 ft2 was paved with RCC, with roughly half used to rehabilitate the existing Staffordboro Boulevard with 8-in.-thick RCC. The curb and gutter on the existing road helped Courtesy Duit Construction. Figure 37. Zero-clearance paver on Alma Drive in Plano, Texas.
74 Construction and Rehabilitation of Concrete Pavements Under Traffic the construction process by providing a rigid vertical surface against which to pave and compact. The access roads inside the parking lot were paved with 6-in.-thick RCC. RCC is a stiff concrete mixture that is placed using an asphalt paver rather than a slipform paver. It is compacted using vibratory rollers and hardens with properties comparable to that of conventional concrete. Because of the placement technique, RCC does not contain reinforce- ment, tie-bars, or dowels. Due to the low water content and early strength gain, RCC can be placed and opened to traffic in much less time than conventional concrete pavement. RCC typically lacks the smoothness required for high-speed roadways and can undergo raveling or cracking, which could be remedied using a thin asphalt overlay. Construction took more than 1 year of weekend-only work to finish because of traffic and construction constraints. All sections of Staffordboro Boulevard were open to traffic in 48 h or less. Construction usually started on Saturday mornings, and the sections were open to traffic early on Monday mornings. One section was opened to traffic in 5 to 6 h. It was constructed from 7:00 p.m. to 11:30 p.m. on a weekday and opened to traffic the next morning at 5:00 a.m. for commuter traffic composed primarily of passenger vehicles and vans. That section of pave- ment is performing similarly to other sections without any visible distresses. All sections of RCC were overlaid with 2-in. HMA within a few months of RCC placement to achieve a smooth riding surface. Because of the need to open the pavement to traffic in 48 h, the contractor used water curing. There was a concern that the curing compound might create a slick surface when open to traf- fic at an early age. Toward the end of the project, 3-mil polyethylene sheets were used to retain moisture. Initially, a regular saw was used, and cutting was done in 5 to 6 h to avoid raveling. But in the second construction season, an early-entry saw was used to cut the joints in 2 to 3 h or earlier. A high-density asphalt paver is necessary to achieve 90% density behind the paver. It was not possible to get 98% density with the roller unless 90% density was achieved behind the paver. Fly ash was added to the RCC to improve workability, increase fine material for compactabil- ity, and improve durability. The study identified the need for adequate compaction of RCC for strength development, consistent moisture for uniform thickness, and a continuous pavement Courtesy Virginia DOT. Figure 38. RCC paving on State Route 684 (Staffordboro Boulevard) in Virginia.
Case Examples 75 operation to avoid unplanned cracks and poor-performing fresh joints (Hossain and Ozyildirim 2015). A continuous operation pugmill was considered better suited for RCC production, and well-planned coordination between RCC production and hauling was required to maintain a continuous supply of RCC at the site and reduce disruptions and delays. Virginia DOT may consider RCC in future field trials, particularly for applications where fast construction of concrete or composite pavement is needed. In addition to cost competitiveness and early opening to traffic, the authors noted that RCC can provide a rut-free pavement struc- ture for heavily loaded vehicles.
