David Peshkin, P.E.Vice PresidentApplied Pavement Technology, Inc.dpeshkin@appliedpavement.com

Rigid Pavement Design Details

Session Overview• Joint considerations

– Joint types and details– Joint spacing and layout– Joint load transfer– Joint sealant and reservoir

• Reinforcement

Joint Considerations• Concrete expands and contracts• Concrete curls and warps

And as any PCC paving contractor will tell you, “concrete cracks”

Joint Types and DetailsThree general joint types

• Isolation Joints– Type A – Thickened Edge

• Contraction Joints– Type B – Hinged– Type C – Doweled– Type D – Dummy

• Construction Joints– Type E – Doweled

Isolation Joints• Sometimes referred to as “expansion joints”• Used to isolate structures with different

movement• Pavements from fixed structures• Pavements from pavements

• Also consider thickened edge for future expansion

• Isolation joints are not doweled or tied to surrounding pavement!

Thickened EdgeIsolation Joint Detail

Reinforced IsolationJoint Detail

Isolation Joint Sealant Detail

Contraction Joints• Provide “controlled” cracking of

pavement• Reduce slab stresses

Contraction Joints (continued)

Contraction Joints (continued)

Construction Joints• Used at end of day’s paving or

between paving lanes• Required when two adjacent slabs are

constructed at different times• Tie slabs together rather than isolate

Construction Joints

Beveled Joints• Intended to reduce chipping and spalling

attributed to snow plows• May also be used where joint fraying or

sliver spalls are common

Joint Spacing• Function of slab thickness, stiffness of

support, and other factors• Generally 12.5 to 25 ft• Length-to-width ratio < 1.25• FAA study found better performance on

20-ft slabs compared to 25-ft slabs• ACPA recommendations

– 25-ft maximum for granular base– 20-ft maximum for stabilized base

Radius of Relative Stiffness

( )41

2

3

112 ⎟⎟⎠

⎞⎜⎜⎝

⎛−

=ku

Ehl

l = radius of relative stiffness, inchesE = PCC elastic modulus (typically 4,000,000 psi)h = slab thickness, inchesu = Poisson’s ratio for PCC (typically 0.15)k = modulus of subgrade reaction, psi/in

Keep L/l between 4 and 6

Joint Spacing Limits

1.0

2.0

3.0

4.0

5.0

6.0

7.0

7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25Joint spacing

L/l

ratio

Thickness = 12 inchesThickness = 13 inchesThickness = 14 inchesThickness = 15 inchesThickness = 16 inchesThickness = 17 inchesThickness = 18 inchesThickness = 19 inches

k = 500 psi/inE = 4,000,000 psi

Joint Spacing Limits

1.0

2.0

3.0

4.0

5.0

6.0

7.0

5 10 15 20 25Slab Size, ft

L/l r

atio

k=700

k=500

k=300

Notes:1.Transverse and longitudinal joint spacing.2.For typical runway and taxiway geometries, the corresponding longitudinal joint spacing is 18.75 ft. (5.7 m).

- Joint spacings shown in this table are maximum values that may be acceptable under ideal conditions.- Smaller joint spacings should be used if indicated by past experience - Pavements subject to extreme seasonal temperature differentials or extreme temperature differentials during

placement may require shorter joint spacings.

Joint SpacingTable 3-16. Recommended Maximum Joint Spacing

6.120>229>9

4.615165-2296.5-9

3.812.51526

MetersFeetMillimetersInches

Joint Spacing1Slab Thickness

Part I, without Stabilized Subbase

6.120>406>165.3217.52343-40613.5-164.615267-33010.5-13

3.812.5203-2548–10MetersFeetMillimetersInches

Joint Spacing1Slab ThicknessPart II, with Stabilized Subbase

Joint Layout• Maintain standard size slabs• Minimize odd-shaped slabs (intersections

and fillets)• Saw joints perpendicular to slab edges• Steel reinforcement in odd shaped slabs

Joint Layout

Fillet Construction (Option 1)

Fillet Construction (Option 2)

δL = 20 mils(Loaded)

0% Load transfer

100% Load transfer

δU = 0 mils(Unloaded)

δL = 10 mils(Loaded)

δU = 10 mils(Unloaded)

Joint Load Transfer

• Purpose• Methods• Measurement of Load

Transfer Efficiency

100×=loaded

unloadedLTEδδ

To Dowel or Not to Dowel• Doweled joints

– All construction joints– Within three joints of free edge

• Undoweled joints– Transverse contraction joints

• Tied joints– Intermediate (sawed) longitudinal joints

• Alternative: dowel all joints

Dowel Details• Dowel diameter, length, and spacing a

function of slab thickness and shearing and bending stresses

• Stress on concrete should not cause failure of slab

• Proper performance requires proper construction

Table 3-17 from 5320-6E

18 in24 in2 in21 to 24 in18 in20 in1 ½ in17 to 20 in15 in20 in1 ¼ in13 to 16 in12 in19 in1 in8 to 12 in12 in18 in¾ in6 to 7 in

Dowel SpacingDowel LengthDowel Diameter1Slab Thickness

1 Dowels may be solid bar or high-strength pipe. High-strength pipe dowels must be plugged on each end with a tight-fitting plastic cap or mortar mix.

Dowel Bars at Slab Corners• Issue: spacing pattern at joint intersection can

lock joint

Tie Bars• Used at longitudinal contraction joints• Inhibit instead of allow movement• Allows load transfer by aggregate interlock• Common use is #5 (5/8 in) deformed bars,

30 in long on 30-in centers• Do not tie together more than 75 ft

Jointing Arrangement

Joint Sealant• All joints sealed• Sealant types

– Hot-poured– Silicone– Preformed– Fuel resistant sealants– Jet blast resistant sealants

Joint Seal Details

Joint Seal Details

Reinforcement• Purpose• Types• Use for

– Odd shaped slabs– Where L:W exceeds 1.25

• Jointed reinforced concrete pavements (JRCP)

• Continuously reinforced concrete pavements (CRCP)

Reinforcement does not increase strength!

Purpose• Does not prevent cracking• Keeps cracks that form tightly closed• Maintains joint interlock• Minimizes infiltration of debris• Allows longer joint spacing/fewer joints

Types• Welded wire fabric or bar mats

• End laps• Minimum of 12 inches, but not < 30 times the

diameter of reinforcement• Side laps

• Minimum of 6 inches, but not < 20 times the diameter of reinforcement

• Side and end clearance• Maximum of 6 inches and minimum of 2 inches

to allow for adequate concrete cover

Spacing• Longitudinal

• Not less than 4 inches nor more than 12 inches apart

• Transverse• Not less than 4 inches nor more than 24

inches apart

Odd-Shaped Slabs• Amount of steel

• 0.050 percent steel in both directions• When L:W exceeds 1.25

• Location• Per the spacing guidelines, but enough to

fulfill the area of steel requirement

Amount of Steel

where:

As = area of steel per foot of width or length, square inches

Ps = percentage of steel based on length of slab, %

L = length or width of slab, feet

t = thickness of slab, inches

fs = allowable tensile stress in steel, psi

ss

fLtLA )7.3(

=s

sft

LLP

8.30(%) =

Minimum percentage of embedded steel is 0.05 percent!

Table 3-18 from 5320-6E

Based on current specifications and accounting for 2/3 of the yield strength of the steel to calculate the fs.

Table 3-19 from 5320-6E

Table 3-20 from 5320-6E

Welded Wire Fabric• Use of smooth or deformed wire is option

of designer• Minimum sizes

• Transverse: not < W4 or D4• Longitudinal: not < W5 or D5

• Minimum area should not be < 0.05 %

JRCP• Steel contents typically 0.15 to 0.20% of

cross sectional area• Can use up to maximum 75 feet joint

spacing with load transfer• Use spacing details shown in Figure 3-11

Figure 3-11 from 5320-6E

CRCP• Steel contents typically 0.6 to 0.7% of

cross sectional area• Eliminates transverse joints• Develops transverse cracks every 2 to

10 feet• Continuous reinforcement keeps cracks

tightly closed

CRCP Design• Foundation requirements per rigid design• Thickness requirements same as plain

PCC• Transverse Steel Design

• Located either above or below longitudinal steel but must have a minimum of 3 inches cover

• Spacing at 12 inches or greater

CRCP Design (continued)• Longitudinal Steel Design

• Resist subgrade restraint• Resist temperature effects• Concrete to steel strength ratio• Located mid-depth of slab or above• Spacing every 6 to 12 inches• Overlap greater of 25 bar diameters or 16

inches

Steel to Resist Subgrade Restraint

where:

Ps = percentage of embedded steel, %

F = friction factor of subgrade

ft = tensile strength of concrete, psi

fs = allowable working stress in steel, psi

s

ts

ffFP )2.03.1((%) −=

Recommended friction factor is 1.8Recommended fs is 75 percent of specified minimum yield strengthft may be estimated at 67 percent of concrete flexural strength

Steel to Resist Temperature Effects

where:

Ps = percentage of embedded steel, %

T = maximum seasonal temperature differential for pavement, °F

ft = tensile strength of concrete, psi

fs = allowable working stress in steel, psi

TffP

s

ts

19550(%)−

=

Recommended fs is 75 percent of specified minimum yield strengthft may be estimated at 67 percent of concrete flexural strength

Concrete to Steel Strength Ratio

where:

Ps = percentage of embedded steel, %

ft = tensile strength of concrete, psi

fy = minimum yield strength of steel, psi

y

ts

ffP 100(%) =

Transverse Steel Design

where:

Ps = percentage of embedded steel, %

fs = allowable working stress in steel, psi

Ws = width of slab, feet

F = friction factor of subgrade

1002

(%)s

ss

fFWP =

Recommended fs is 75 percent of yield strength

CRCP Jointing• Construction joints

• Longitudinal joints between paving lanes• Transverse construction joints between

paving days• Warping joints

• See Figures 3-12 and 3-13

Figure 3-12 from 5320-6E

Figure 3-13 from 5320-6E

CRCP Terminal Treatment• Needed when CRCP meets other

pavements or structures• End movements can be expected around

2 inches• Allows ends to expand and contract• Figure 3-14 shows the detail with a

flange beam

Figure 3-14 from 5320-6E

Summary• Many other features to consider in FAA

design besides thickness• All components need to be considered

together

Questions?