Design and Construction of Concrete Overlays By: James K. Cable, P.E. Cable Concrete Consultation
PCC OVERLAY AGENDA Current design & construction features What is needed in a PCC overlay set of plans? Tie bar insertion approved methods Maturity measurements Stringless paving technology The economics of single vs. two lane overlay paving The future of PCC overlays
Overlay Design Details ACPA bonded overlay design for up to 6 in. AASHTO & Winpas for 6 in. & higher Slab size Max of 1.5 x overlay depth up to 6 inches Lane width for 6 inch or greater depths and lengths of 12-15 feet Joint reinforcement Joint reinforcement Tie bars in longitudinal joints of over 6 in. depth & across widening joints Dowels in transverse joints of 7 in. or greater Consider bar retrofit for premature cracking in 7 inch or greater depths
Tie Bar Insertion Methods
Tie Bar Insertion Methods
Overlay Design Details (continued) Joint preparation Develop 1/8 inch joints x T/3 Blow clean & do not seal Hot pour seal centerline only Surface texture Require longitudinal tining Contractor can grind bumps into incentive pay Pavement widening Mill trench to provide full 8 in. depth widening Staple or epoxy tie bars to existing surface with 3 or more anchors & 18 in. embedment each way Saw longitudinal joint T/3
Overlay Construction Details Surface preparation Broom & air blast Mill to profile grade for a purpose only Difficult to mill to a lift line across a lane Traffic control options 5000 ADT or less, consider: 2 lane paving with single or rolling detour 1 lane paving with pilot car (24/7) 5000 ADT or greater 2 lane paving with head to head traffic & limit construction time
FINAL BID COPY 10/19/10 Late Start Date April 14, 2011 Number of working days 120 Number of Bidders 6 Bid range $8.48 million to 10.51 million Prime Contractor Manatts, Inc., Brooklyn, Iowa DESIGN TEAM LEADER Dave Skogenboe 515-239-1612 800 Lincoln Way Ames, Iowa 50010
Project Location
PROJECT OBJECTIVE DESCRIPTION a. Place unbonded PCC overlay while staging traffic through the project with the aid of a pilot car. b. All preliminary work is to be included in stages one to two prior to overlay paving. c. Transition pavement is required at the BOP, EOP and four bridge sites. d. Microsurfacing to be removed on the west portion (BOP to County W-14) by milling. e. Four paved side roads are affected by the overlay work. SIGNIFICANT CONTRACT ITEMS a. Patches by count - 651 PCC patches, 4-30 foot in length. b. Longitudinal subdrains - 113 locations with lengths of 250-540 feet. c. Temporary barrier rail - 6 locations (BOP, 4 bridges and EOP). d. Temporary traffic signals, bridge approach and railing rehabilitation - 4 bridge locations. e. Shoulder improvement and drainage work - 223 locations. MAJOR CONTRACT QUANTITIES (TOTAL CONTRACT ITEMS) a. Slipform 9.5 inch class 3 durability pavement 6,623 sy - $35/S.Y. b. Concrete Furnish...48,605 cy - $50/C.Y. c. Concrete Place...350,267 sy - $3.85/S.Y. d. Surface preparation...94,681 sy e. Granular shoulder material, placed...67,741 tons f. Patches full depth repair...4,337 sy - $84.65 g. Patches by count...651 each - $52 h. Class 13 widening excavation...12,894 sy - $1.75 i. Pavement Scarification...169,982 sy - $0.45 j. Granular surfacing...2055 tons - $17.70 k. Longitudinal subdrain...48,422 LF - $4.45 l. Pavement removal...23,858 sy - $8.50 m. Temporary barrier rail...5,720 LF - $8.40 n. Longitudinal joint repair.10,920 LF - $3.35 o. Traffic Control...Lump Sum - $125,000 p. Flaggers. 520 ea - $295 q. Pilot cars 260 ea - $445 r. Mobilization.Lump Sum - $170,000
What Information Do You Need To Gather To Design Any Overlay? Planning Information Expected Design Life for the Overlay Current & Projected Traffic ADT & ADTT Directional & lane distribution Current & Expected Adjacent Land Use Maintenance Staff Concerns Pavement Management Data
Overlay Design Information Requirements Existing Pavement History Evaluation Layer material source, depths & age Widening material type, depths, widths, & age History of full depth patching by location, type & age As Built Plan Information Vertical & horizontal alignment Previous test sections in project limits Previous drainage structure remains
Overlay Design Quantity Information Requirements Existing Pavement Condition Evaluation Surface distress identification by type, severity & extent Visual survey of transverse joints to estimate of number & distribution of full depth patches required. (Spring & Fall) Evaluation of structural capacity by FWD in each lane (2-3 tests/lane/mile) Rut depth & cross slope (Winter & Summer) Coring by lane & direction (2-3 /lane/mile) & in widening joint deterioration areas
Iowa 175, Rutting
US 18 Pavement Surface and Widening Units
Falling Weight Deflectometer FWD/GPR Use to get existing HMA elastic modulus HMA modulus is temperature sensitive
Overlay Planning Considerations Consider PCC Alternate Designs for any Rehabilitation Involving Overlays Consider Inlays/Overlays at Existing Paved Intersections Evaluate the Closed/Two Lane Paving vs. Open/One Lane Paving Options
IA 175 Two Lane Paving With Detour
US 65 Single Lane Paving With Detour
US 18 Single Lane Paving With Through Traffic
Required PCC Overlay Plan Items 1.Title sheet 2.Typical Cross Sections 3. Estimate of Project Quantities & Notes 4.County Road Map 5. Special Drawings & Tabulations 6. Traffic Control Plan Notes & Limitations. 7. Profile Tabulation w/vertical & Horizontal Curve Data Tabulation 8. Vertical/Horizontal Control Points (x,y,z).
Required PCC Overlay Plan Items 9. Tabulation of Special Events 10. General Staging Notes & Limitations 11. Intersection & Pavement Jointing Plans 12. Bridge Rehab Details. 13. Reference list Pollution Prevention Plan. List of Road Standards & Applicable Drawings
Project Location Maps
How is the Overlay Depth & Joint Spacing Determined? Establish goals w/field staff on milling vs. no milling Determine the bond breaker need, material type & depth Determine type of overlay to be used: bonded or unbonded and why? Developed overlay depth, consider multiple designs & compare to agency goals (ACPA, AASHTO or MEPDG) Limit joints spacing in feet to 1.5 x depth in inches Consider use of fibers with increased joint spacing Communicate the depth limitations to field staff
Stage Work to Meet Both Public & Construction Goals Stage I Prepaving Items (patching, subdrainage, grading & ditches, erosion control, & survey control) Stage II Bridge approaches & paving notches, bridge railing, shoulder strengthening & transitions Stage III Milling & Intersection preparation Stage IV Paving, shouldering & pavement marking.
Join the Paving Plan & Traffic Control Plan to Create an Efficient Construction Project Allow & encourage multiple work zones for each construction activity Shoulder & mark as maturity is reached Use the pilot car 24/7 to eliminate centerline wedge construction Encourage bridge transition & approach construction by mainline paving equipment Close only cross roads in paving area & only one paved cross road per 5 miles of construction area
Pilot Car Impact * Thru traffic reduced 10% with pilot car introduction 6-8 vehicle queue with 2 mi. workzone 15+ vehicle queue with 3.5 mi. workzone
US 18 Lessons Learned Transition Construction Transition from the low point of bridge approach to the end of transition at a 1 inch per 25 foot of transition Use the bridge approach & transition slab to develop an approach vertical curve of 300 ft or greater. Coordinate the bridge approach vertical curve with the pavement model profile. Design bridge approaches & transition pavements for machine paving
Surface Survey vs. Desired Concrete Yield Contract required a three line survey for profile establishment. Contract required 1/2 milling depth to remove surface treatment on west 2/3 of project. Project team conducted one mile test section on various line options & different cross section spacing (25 & 50 ) to assess yield and overruns Optimum yield was obtained with 9 line profile at 50 ft. intervals before milling Milling limits where 1/2 to 1 1/2 deep at centerline and 2% cross slope. Yield changed from 26% average overrun to average of 6% after milling to new profile depth.
Survey existing surface Develop database Create profile Reference points are 250 +/- and stagger on opposite sides ATV Laser z coordinates GPS x, y coordinates Survey GPS / Total Stations
US 18 Lessons Learned Prepaving Survey& Model Development vs. Concrete Yield Do paving survey on the surface to receive the overlay prior to all milling Do not mill new bond breaker HMA courses that have been placed Survey goals & methods 1. Speed of construction with minimum survey Measure rut depths & cross slope at 500 foot intervals during summer months Develop profile model & estimate quantity of concrete. Limit pay quantity to 102% of estimated quantity Continue depth checks
US 18 Lessons Learned Prepaving Survey& Model Development 2. Control of overlay depth & yield Conduct 9 shot cross sections at 50 foot intervals Develop profile & estimate quantity of concrete Limit pay quantity to 106% of estimate +/-2% Continue depth checks
US 18 Lessons Learned Surface Preparation Preparation Methods for Overlays Sweep & Air blast Scarify Mill to remove surface or develop profile & cross slope Preparation Goals Remove unstable layers Establish vertical clearance Maintain centerline & shoulder elevations Develop a bonding surface Minimize concrete overruns Maximize surface ride values
US 18 Existing Pavement West & East Ends
US 18 Lessons Learned Milling Considerations Understand existing layer depths & material stability Understand existing rutting movements Assess widening unit movement Understand overlay depth design assumptions Have a plan for layer replacement in case of delamination
Mill Surfaced Resulting In Thin Asphalt Lift Issues
7 wide mill Milling of HMA Minimum ½ to 1 ½ maximum Based on profile grade Centerline pass by total stations (25 to 30 ft. per minute) Remaining removal width by sensor off milled surface (1/2 to 1 mile per day) Added
US 18 Surface Profile Milling
US 18 Milled Surface
US 18 Widening Trench Milling
US 18 Lessons Learned Milling Operations Milling Operations Mill existing pavement widening & proposed widening to the proposed widening depth Mill trench to the profile cross slope Require the vertical edge on the widening trench Require milling to produce an acceptable surface for paving
US 18 Typical Joint & Widening Bar Placement
US 18 Widening Bar Layout
Join the Paving Plan & Traffic Control Plan to Create an Efficient Construction Project Encourage stringless paving to ease thru & construction traffic Consider 5 days/mile construction limit on contract Consider two lane paving vs. one lane Consider a staged (rolling) detour
US 18 Lessons Learned Paving Operations Identify the project paving goals in terms of time & access requirements Require the contractor to develop the paving plan for agency approval Evaluate plans on the basis of contractor ability to deliver pavement, shoulders & markings in a continuous & timely manner Consider haul road needs based on limitations placed on contractor paving plans
Paving Schedule
US 18 Haul Road Map
Paving Average Paving per day 6,800 to 7,500 ft. Depends on distance from plant
Traffic Shift
Stringless Paving for PCC Overlay
PCC Overlay Paving
US 18 Paving Train
Concrete Management Through Maturity Measurements
US 18 Paving Train Cure/Texture/Joint
US 18 Final Product
Where Should You Go From Here With PCC Overlays Consider PCC overlays as an alternative for every rehabilitation concept Establish agency PCC overlay goals Consider the two lane with closed road,& single lane with pilot car operation for each PCC overlay concept Standardize the PCC planning & design process Potential savings in construction cost for two lane/closed road vs. one lane/under traffic overlay paving Build & enjoy the performance of PCC overlays