||A series of laboratory tests on precast concrete slabs was conducted in the United Kingdom to develop a computer design program to study the impact of slab thickness, steel reinforcement, and subbase and subgrade characteristics on the performance of precast slabs.|
|Correa and Wong
||The design and construction practices of full-depth repair were summarized. Full-depth patches are a repair alternative for the following distresses in jointed concrete pavements: low severity (or more severe) blowup, corner break, medium-severity (or more severe) D-cracking, deterioration adjacent to existing repair, joint deterioration, spalling, reactive aggregate, transverse cracking, and high-severity longitudinal cracking. For a standard lane width of 3.6 m (12 ft), the length of the full-depth patch and the remainder are recommended not to be shorter than 1.8 m (6 ft) to provide stability and prevent longitudinal cracking. The length of the patch should also not exceed the length of the existing slab. The use of three dowel bars along each wheelpath was generally found sufficient; however, the use of four or five dowel bars along each wheelpath is recommended for interstate highways. The dowel diameter of 38 mm (1.5 in.) was found to be most cost effective.|
|Grimsley and Morris 1975||Interstate in an urban area in central Florida||A precast slab was used to replace the entire distressed slab, 3.7 m (12 ft) wide, 6.1 m (20 ft) long, and 200 mm (8 in.) thick. After removal of the existing slab, the precast slab was placed approximately 13 mm (0.5 in.) lower than regular surrounding elevation. The precast slab was slab-jacked to appropriate elevation. The construction caused 8 hours of nighttime traffic closure (10 p.m. to 6 a.m.).|
|Hachiya et al. 2001||Taxiway at the Sendai Airport, Japan||The construction project was to replace distressed slabs at the Sendai Airport taxiway with a series of pretensioned slabs connected at transverse joints through the application of posttensioning. Each slab was 10 m (33 ft) long, 2.5 m (8 ft) wide, and 240 mm (9.5 in.) thick. An appropriate posttensioning force was applied to prevent joint opening due to typical negative temperature gradients at the construction site. The entire construction process from removal of distressed slab to interconnection of slabs through posttensioning was completed within 10 nighttime hours, from 9 p.m. to 7 a.m.|
|Lane and Kazmierowski 2005||Highway 427, Toronto, Canada
||The trial project investigated the efficacy of three precast concrete full-depth repair methods along Highway 427 in Toronto. The methods were the Fort Miller Super Slab™ continuous method, the Fort Miller Super Slab™ intermittent method, and the Michigan method. Based on the initial structural evaluation, it was concluded that all joints met the minimum 70% load transfer efficiency requirement. The precast repairs were similar in both ride and appearance to fast-track repairs along the same section of the highway. For acceptable elevation matching it was recommended that the proper preparation of the base layer is very essential.
|Merritt, McCullough, and Burns 2003||Frontage road along northbound I-35 near Georgetown, Texas||The study was to demonstrate a construction method to replace the entire distressed portland cement concrete (PCC) pavement system through the use of a prestressed (both pretensioning and posttensioning) system. A series of 200-mm (8-in.) pretensioned precast slabs of varying sizes (pretensioning strands were in the traffic direction) were attached together through continuous shear key. When all pretensioned slabs were positioned, posttensioning strands in the transverse direction were stretched to tighten the slab together and then the posttensioning ducts were grouted. The reduction of the time delay of traffic is the main benefit of the proposed construction method.|
|Meyer and McCullough 1983||Eastbound of IH-30 near Mt. Pleasant, Texas||The construction was to repair 200-mm (8-in.) continuously reinforced concrete pavements with the use of precast slabs, 3.7 m by 3.7 m (12 ft by 12 ft) and 1.8 m by 1.8 m (6 ft by 6 ft). Polymer methyl-methacrylate was also used in the concrete. The construction process consisted of four steps: destroying the failed slab, removing the failed slab, installing and aligning the precast slab using a wooden frame and a crane, and connecting steel using welding and U-bolts. It was found that the connection of steel may not be necessary if the polymer is used in the concrete. The plan was to evaluate long-term performance of the repairs.|
|Overacker 1974||Niagara Section of the New York State Thruway, New York||Existing pavements that exhibited high-severity fatigue cracking were replaced with pretensioned precast slabs with slab sizes varying from 3.7 m by 6.1 m by 225 mm (12 ft by 20 ft by 9 in.) to 4.0 m by 9.1 m by 225 mm (13 ft by 30 ft by 9 in.). The construction work was only allowed from 6:30 p.m. to 6:30 a.m. and from 9 a.m. to 3:30 p.m. to avoid traffic congestion during commuter hours. The construction process consisted of three steps: the distressed roadway was sawed and removed, the precast slabs were installed, and the repair areas were overlaid with asphalt concrete.|
|Sharma 1990||I-90 between STH 30 and USH 18 in Dane County, Wisconsin||Eight different construction variations were used to repair distressed joints. One repair method used precast slabs. The precast patch was 1.8 m (6 ft) wide and 8.5 in. (216 mm) thick and was without any load transfer device. A leveling bed of 13 mm (0.5 in.) of portland cement mortar grout was laid before the precast slab was placed. As compared with sections with load transfer devices, the precast section and other sections without load transfer devices were found to fault more in 5 years.|
|Simonsen 1971||M-59 about 2.5 miles east of I-96 in Livingston County, Michigan||Four distressed joints were replaced with precast slabs, 3.4 m (11 ft) long, 1.8 m (6 ft) wide and 200 mm (8 in.) thick. Dowel bars were used as a load transfer device for two of the slabs, while epoxy mortar and filler were used in the other two slabs. The construction process consisted of three steps: sawing distressed joints with the use of a propelled saw; removing failed slabs with the use of an air hammer, a crane, and a truck; and installing precast slabs with the use of a drill frame and four screw jacks. The lane closure times were about 3.5 and 2.5 hours for doweled and undoweled sections, respectively. It was found that partial-depth sawing and breaking up the slab with a pavement breaker resulted in undercutting and cracking of the existing slab. The plan was to construct more precast slabs along I-75–US-23 near Flint in Genesee County, Michigan.|
||I-75–US-23 west of the Flint in Genesee County, Michigan
||This was phase II of the M-59 project. A similar technique was used to repair 24 lane joints with precast slabs. Unlike the M-59 project, this project experienced high traffic volumes where the traffic disruption period was required to be short. All the repairs were 3 m (10 ft) long and 3.7 m (12 ft) wide with varying thicknesses. A crew of seven completed the construction in 2 days. The average times for the entire process from the removal of the distressed slabs to the installation of the precast slabs were 2.5 and 4.25 hours for undoweled and doweled sections, respectively. The problem of traffic control was encountered as no work was permitted for several periods of time. The plan was to evaluate the performance of the repairs under high-volume traffic.|
|Speir et al. 2001||La Guardia Airport, New York||A feasibility study was conducted to provide preliminary design details for two precast PCC slab construction options and an asphalt concrete approach. The precast options were
The initial cost of the asphalt concrete option was found to be the lowest among the three construction approaches. However, based on a 40-year life cycle cost comparison, both precast approaches were found to be more cost effective.
- conventional plain jointed panels in two sizes (3.8 m by 3.8 m [12.5 ft by 12.5 ft] and 7.6 m by 7.6 m [25 ft by 25 ft]) and slab thicknesses ranging from 30.5 to 40.6 cm (12 in. to 16 in.).
- posttensioning of multiple slab panels to provide an effective slab size of 7.6 m by 7.6 m (25 ft by 25 ft).
|Tyson 1976||Culpeper, Richmond, and Fredericksburg, Virginia||Four full-depth pavement repair procedures were investigated, including rehabilitation by stress relief, cast-in-place restoration, precast replacement, and cast-in-place replacement. Elimination of curing time and potentially better concrete quality were emphasized as two major advantages of the precast procedure over the cast-in-place procedure. The main processes for the precast replacement procedure included precast slab fabrication, pavement removal, and precast slab installation. Since no dowel bars were used, the deflection test using the Benkelman beam was conducted. The results indicated that the precast slabs performed satisfactorily and had about three times smaller deflections than adjacent slabs. Three months after the construction, a precast slab was lifted to investigate the condition of the interface between the underlying mortar and the slab, which was found to be unbonded. It was recommended that the bedding mortar should have a slump exceeding 200 mm (8 in.) to provide uniform seating.|