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Precast Concrete Panel Systems for Full-Depth Pavement Repairs: Field Trials

Appendix B

Construction Guidelines Presentation

Construction Guidelines Presentation
1 Slide 1 - Precast Panel System for Full Depth Pavement Repairs-Construction Guidelines. Two photographs: (1) workers align a precast panel as it is inserted into the pavement; (2) a stretch of concrete in poor condition. Three logos: Federal Highway Administration, Michigan State university, and Civil and Environmental Engineering. This presentation is intended to provide guidance on the installation of precast concrete panels as a full-depth repair alternative.
2 Slide 2 - Acknowledgements. The project team would like to acknowledge the financial support of the Federal Highway Administration and the Michigan Department of Transportation. The project was sponsored by the Federal Highway Administration under the Concrete Pavement Technology Program Task 7. Additional financial assistance was provided by the Michigan Department of Transportation, which also provided the project sites along M-25 and I-675.
3 Slide 3 - Why use "Fast Track" Repairs? Three photographs: (1) conventional paving of a single lane, using a concrete mixing truck; workers' vehicles are parked on the adjacent, finished lane, and two other finished, closed lanes appear in the background; (2) four lanes of moving traffic are shown next to a concrete barrier, separating them from newly constructed, closed lanes; the four open lanes are temporarily marked for bidirectional traffic; (3) two-lane, bumper-to-bumper, traffic congestion is shown adjacent to closed lanes under construction. The traditional practice of rehabilitating existing concrete pavements is an excellent method to extend the remaining service life of the overall network. However, increasing traffic volumes and sensitivity to user delays and costs have required pavement construction and rehabilitation to be put on a "fast track" as much as possible.
4 Slide 4 - Potential Advantages of Precast Panels. Minimize curling of the slab. Improved material properties. Reduce traffic delays and user costs. Improve construction uniformity. Structural precast concrete elements have been successfully used in the building and bridge industry. Precast concrete elements are constructed under controlled curing conditions, resulting in improved short- and long-term durability properties. Since the panels are cured under controlled conditions the mechanical properties of the resulting concrete are not compromised. Since multiple slabs are fabricated at the same time, this leads to uniformity of construction.
5 Slide 5 - "Typical" Candidate Distresses. Four photographs: (a) deteriorated join with an asphalt cold patch, (b) medium-severity mid-panel cracking with associated spalling, (c) high-severity transverse cracking, and (d) deteriorated joint (sealant damage) with associated spalling. Typical distresses include (a) deteriorated joints with asphalt cold patch (b) medium severity mid panel cracking with associated spalling, (c) high severity transverse cracking, and (d) deteriorated joint (sealant damage) with associated spalling.
6 Slide 6 - Precast Panel Structural Details. Diagram. A single precast panel, 6 ft wide by 12 ft long, is shown from above between two existing slabs. Four clusters of three dowel bars (1.25 or 1.5 in. in diameter) each (two clusters in each wheelpath) are spaced 12 in. on center. The slab contains 4 lift hooks, each about 2 ft. from a corner as well as #5 epoxy-coated bar, with additional bars near the joint edges of the panel. Three 1.25" diameter dowels (10" thick slab) or 1.5" diameter dowels (12" thick slab) are placed at 12" on center along the wheel path. This placement is very similar to dowel bar retrofit construction. The mid panel temperature steel is optional. The temperature steel consists of 3/8" steel bars placed at 6" on center held together by ¼" ties. The panels are 6 feet long and 12 feet wide.
7 Slide 7 - Construction Sequence using HDP foam (typical). Activities are listed. Offsite activities: (1) casting of the panels (precast or ready-mix plant) and (2) storage of fabricated precast panels. Onsite activities: (1) documentation of distresses (type, extent, and severity levels); (2) slab (existing) demolition (saw cutting of the repair boundaries; saw cutting of dowel slot outlines in the existing panel; removal of distressed panel). The construction process includes a variety of operations.
8 Slide 8 - Construction Sequence (typical). Onsite activities, continued. (3) initial cleaning of the base layer (removal of debris; dewatering (if needed); (4) cutting (jack hammering) of dowel slots to specification depth; (5) final cleaning and grading of base layer; (6) cleaning (pneumatic) and sand blasting of dowel slots.
9 Slide 9 - Construction Sequence (typical). Onsite activities, continued. (7) check base grade and elevation; (8) transport precast panel to the repair site and check initial panel alignment and elevation; (9) conduct final adjustments; (10) final placement of panel; (11) drill holes for the injection of HDP foam; (12) inject HDP foam to stabilize and level the panel; (13) grout dowel slots and lift hook holes; (14) seal joints and open to traffic.
10 Slide 10 - . Fabrication of Precast Panels-Offsite Activity. Two photographs: (1) placement of panel steel and dowel bars-a worker is shown positioning dowel bars in a mold that already contains rebar and chairs; (2) completed mold for precast panels with dowel bars, rebar and chairs, and four lift hooks. The precast panels can be fabricated at either a precast plant or a ready-mix concrete yard. A series of slab forms are fabricated with the appropriate joint and panel reinforcement.
11 Slide 11 - Fabrication of Precast Panels-Offsite Activity. Two photographs: (1) placement of fresh concrete-a worker spreads concrete in the mold as it pours from a concrete mixer truck; (2) completed precast panel-a filled mold is shown and another mold is being filled. It is recommended that fresh concrete property tests be performed. The mechanical property tests should include flexural and compressive strength tests.
12 Slide 12 -  Fabrication of Precast Panels-Offsite Activity. Two photographs: (1) surface texturing-a worker is texturing a panel's concrete surface with a broom-like tool; (2) concrete curing-several panels are shown covered with tarps. It is recommended that the completed panels be textured and cured.
13 Slide 13 - Typical PCC Mixture Design: Note. All weights are for 1 cubic yard of concrete. Cement (type I): 500-650 lb; water: 200-250 lb; coarse aggregate: 1500-2000 lb; fine aggregate: 1200-1400 lb; admixtures: AEA, WRA (if needed); target 28-day f'c3: 4000-6000 psi; target slump: 1-3 in. Standard concrete paving mixture designs are suitable for precast concrete fabrication.
14 Slide 14 - Installation of Precast Panels-On site activities. Two photographs: (1) saw-cutting of panel boundaries in the existing pavement, with a worker guiding a saw-cutting machine; (2) dowel slots cut into the panels are shown. The slab removal boundaries are outlined and saw cut. The limits of the pavement area to be removed are sawed in the transverse direction.
15 Slide 15 - Installation of Precast Panels-On site activities. Two photographs. Removal of distressed panel. (1) the prongs of a forklift are being inserted under the edge of a panel; (2) the forklift, with workers watching, removes a chunk of the panel. Following the saw cutting operation, the lift hooks are inserted and the distressed slabs are removed using a front-end loader. During this process, the outline for the dowel slots in the adjacent panels are also cut.
16 Slide 16 - Installation of Precast Panels-On site activities. Four photographs. Initial cleaning and grading of base course. (1) concrete and other debris is shown where the panel has been removed; (2) a worker has removed the debris onto a front-end loader; (3) two workers with shovels clean the base course; (4) workers grade and tamp the course as another uses a level. It is recommended that the base be excavated 1.5-2" below the bottom of the existing slab to accommodate the precast panel. The base should be cleaned and dewatered (if necessary).
17 Slide 17 - Installation of Precast Panels-On site activities. Two photographs. Jack hammering of dowel slots. (1) a worker begins jack hammering two slots; (2) two completed dowel slots are shown with debris and a shovel in the base course. The dowel slot cutting and preparation includes (i) initial grooving to the required depth with a concrete saw; (ii) jack hammering of the concrete to carve out the dowel slot.
18 Slide 18 -  Installation of Precast Panels-On site activities. Two photographs. Sandblasting of dowel slots. (1) a worker blasts out a dowel slot; (2) the base course with 12 clean dowel slots is shown. The dowel slot preparation also includes (i) air cleaning of dowel slot to remove debris and any loose concrete pieces; and (ii) sand blasting of the dowel slots. The dowel slots are approximately 4" wide and 5.25" deep (base of the slot cut).
19 Slide 19 - Installation of Precast Panels-On site activities. Diagram. Schematic cross-section of the dowel assembly. A side view of base, existing panel, and newly installed precast panel is shown. Graded aggregate base underlies both sections. The precast panel is a bit thicker than the existing pavement and a flowable fill or HDP underlies it, above the base. The existing pavement has a dowel slot cut into it, and the 18-in. dowel bar extends from the precast panel into the slot, with about half on either side.
20 Slide 20 - Installation of Precast Panels-On site activities. Placement of precast panel. Four photographs: (1) a front-end loader is carrying a panel by its four lift-hooks; (2) the panel is being lifted toward the prepared base opening; (3) workers steady and align the panel as it is dropped into the opening; the panel placement is completed. The precast panels are transported from the flat-bed truck to the excavation using a front-end loader.
21 Slide 21 - Installation of Precast Panels-On site activities. Elevation adjustment of precast panel using HDP foam. Four photographs. (1) a worker drills a hole in the panel; (2) a panel with holes and leveling instruments is shown; (3) workers insert material; (4) the completed panel with filled holes is shown. A series (approximately 4-6 holes/panel) of holes (5/8" in diameter) are drilled to inject the foam. The polyurethane foam is made from two liquid chemicals that combine under heat to form a strong, lightweight, foam-like substance. The chemical reaction between the two materials causes the foam to expand and fill the voids. According to the manufacturer's specification, the HDP foam sets in approximately 15 minutes (approximately 90% of full compressive strength), and the precast panel is ready to carry load. For the purpose of slab stabilization, the foam density is about 4 lbs/ft³ with a compressive strength range of 60 psi to 145 psi.
22 Slide 22 - Installation of Precast Panels-On site activities. Installation of Precast Panels-On site activities. The characteristics of the HDP foam are: Setting time is approximately 15 minutes to achieve 90 percent of full compressive strength. The foam density is about 4 lb/ft3. The injection port hole diameter is 5/8 in.
23 Slide 23 - Installation of Precast Panels-On site activities. Backfilling of dowel slots. Two photographs: (1) a worker pours material into the dowel slots; (2) a worker smooths out filled slots with a trowel while another pours material into a slot. Once the slab elevations are verified and deemed acceptable, the dowel slots are grouted and the joints are sealed.
24 Slide 24 - Installation of Precast Panels-On site activities. Completed precast panel. Two photographs: (1) a closeup view of the panel with filled dowel slots is shown; (2) a more distant view of the completed panel within the existing pavement is shown.
25 Slide 25 - Construction Activity-Typical Timeline. Four activities with their descriptions are listed on this slide: A1-Slab demolition (saw cutting of repair boundaries, saw cutting of dowel outlines, removal of distressed panel); A2-Initial cleaning of the exposed base layer (removal of debris; dewatering (if needed); A3-Cutting (jack hammering) of dowel slots (saw cutting of repair boundaries, saw cutting of dowel outlines, removal of distress panel); A4-Final cleaning and grading of the exposed base layer.
26 Slide 26 -  Construction Activity-Typical Timeline, continued. Four activities with their descriptions are listed on this slide: A5-Air cleaning and sand blasting of dowel slots; A6-Transport, placement, and alignment of precast panels; A7-Drill port holes and inject foam to support and align the panels; A8-Grout dowel slots, seal joints, and open to traffic.
27 Slide 27 - Typical Timeline (I-675)-Example. Gantt chart. The construction times for eight activities in a single panel's installation are shown on a timeline of 0 to 120 minutes. Approximately, they are slab removal, 0-5; dowel slots preparation, 5-45; base cleaning, 45-55; sand blasting, 55-65; flowable fill placement, 75-80; molding of cylinders, 75-80; leveling of fill, 80-110; slab placement, 110-115. Example Gantt Chart illustrating time taken to complete installation of one panel.
28 Slide 28 - Typical Timeline (M-25)-Example. Gantt chart. Activities A1 through A8 (see slides 25-26 for legend) for panels 2 (P2), 3 (P3), and P2 and P3 simultaneously are shown on a timeline from 9 a.m. until 2 p.m. of a single day. Example Gantt Chart illustrating time to complete the installation of two panels (multitasking and overlapping of activities).
29 Slide 29 - Construction Activity-Typical Timeline. Table. Activity code (see slides 25-26), time in minutes, and recommended equipment and labor needs are shown for activities A1-A8. A1, 60 min, Concrete saw (1 labor), front end loader (1 operator); A2, 5 min, nothing specific, 2 labor; A3, 20 min, two pneumatic jackhammers, 2 labor; A4, 15 min, plate compactor, 1 labor; A5, 21 min, sand-blasting equipment, 2 labor; A6, 20 min, front-end loader (1 operator), 3 additional labor to guide the alignment; A7, 25 min, drills and HDP injection equipment, 2 labor; A8, 26 min, grout mixer, 2 labor.
30 Slide 30 - Repair Effectiveness. Measure joint widths along transverse and longitudinal joints. Determine panel deflections using the falling deflectometer (FWD).
31 Slide 31 - Repair Effectiveness-Structural. Two photographs. (1) a pickup truck pulls an FWD behind it, over pavement; (2) a closeup shows the FWD equipment skimming the pavement. Photograph of a falling weight deflectometer (FWD).
32 Slide 32 - Recommended FWD Test Pattern. Diagram. An overhead view of pavement with one direction of travel is shown. There are two existing slabs and a middle slab with an approach joint on the left and a leave joint on the right. Nine spots show the lad positions, one in the center of the middle slab and nine others in or near the wheelpaths, as follows: 1 = Approach OWP (BJT); 2 = Approach OWP (AJT); 3 = Leave OWP (BJT); 4 = Leave OWP (AJT); 5 = Approach IWP (BJT); 6 = Approach IWP (AJT); 7 = Leave IWP (BJT); 8 = Leave IWP (AJT); 9 = Edge. Load positions of the FWD to determine structural effectiveness.
33 Slide 33 - Repair Effectiveness-Structural. Data from [FWD load] locations 1, 2, 3, 4, 5, 6, 7, and 8 can be used to determine approach and leave load transfer efficiencies (LTEs) along the wheelpaths. Equation: LTE(%) = the fraction unloaded side deflection divided by loaded side deflection multiplied by 100.
34 Slide 34 - Repair Effectiveness-Structural. Peak deflections from [FWD load] locations 1, 2, 3, 4, 5, 6, 7, and 8 can be compared with the peak deflection at location 9. This comparison gives information about the uniformity (or lack of it) of support.
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Updated: 09/24/2015
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000