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62-50 The Civil Engineering Handbook, Second Edition
FIGURE 62.30 Minimum percent reinforcement to satisfy crack-spacing criteria. (Source: AASHTO. 1993. AASHTO
Guides for Design of Pavement Structures. Copyright 1993 by the American Association of State Highway and Trans-
portation Officials, Washington, D.C. Used by permission.)
TA BLE 62.18 Shrinkage and Thermal Coefficient
of Portland Cement Concrete
Indirect Tensile Strength (psi) Shrinkage (in./in.)
(a) Approximate Relations between Shrinkage and Indirect
Te nsile Strength of Portland Cement Concrete
300 (or less) 0.0008
400 0.0006
500 0.00045
600 0.0003
700 (or greater) 0.0002
Type of Coarse Aggregate
Concrete Thermal
Coefficient (10
–6
/˚F)
(b) Recommended Value of the Thermal Coefficient of
Concrete as a Function of Aggregate Types
Quartz 6.6
Sandstone 6.5
Gravel 6.0
Granite 5.3
Basalt 4.8
Limestone 3.8
Source: AASHTO. 1993. AASHTO Guides for Design of
Pavement Structures. Copyright 1993 by the American Asso-
ciation of State Highway and Transportation Officials, Wash-
ington, D.C. Used by permission.
12.0
11.0
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1/2
5/8
1.50
1.00
.75
.50
.9
.8
.7
.6
.5
.4
.0004
.0006
.0008
280
800
700
500
400
240
160
120
80
T
L
T
L
T
L
T
L
UndesirableUndesirable
Percent Steel, P
Crack Spacing, X (ft.)
2.0
a
s
/a
c
Ratio
Bar Diameter, f (in.)
3/4
Concrete Shrinkage at 28 Days, Z (in./in.)
.0002
Tensile Stress Due to Wheel Load, s
w
(psi)
200
600
Concrete Tensile Strength at 28 Days, f
t
(psi)
Highway and Airport Pavement Design 62-51
CRCP Reinforcements Based on Steel Stress: (P
min
)
3
. To guard against steel fracture and excessive per-
manent deformation, a minimum amount of steel (P
min
)
3
is determined according to Fig. 62.33. Input
variables Z, s
w
, and f
t
have been determined earlier. For the steel stress s
s
, a limiting value equal to 75%
of the ultimate tensile strength is recommended. Table 62.19 gives the allowable steel working stress for
grade 60 steel meeting ASTM A615 specifications. The determination of (P
min
)
3
also requires the com-
putation of a design temperature drop given by
(62.29)
where T
H
= the average daily high temperature during the month the pavement is constructed
T
L
= the average daily low temperature during the coldest month of the year
FIGURE 62.31 Chart for estimating wheel load tensile stress s
w
. (Source: AASHTO. 1993. AASHTO Guides for
Design of Pavement Structures. Copyright 1993 by the American Association of State Highway and Transportation
Officials, Washington, D.C. Used by permission.)
13
12
11
10
9
8
7
6
5
4
600
550
500
450
400
350
300
250
200
150
EXAMPLE:
D = 9.5 in.
WHEEL LOAD = 20,000 lb.
k = 170 pci
SOLUTION:
σ
w
= 230 psi
6,000
8,000
10,000
12,000
14,000
16,000
18,000
20,000
22,000
24,000
WHEEL LOAD
MAGNITUDE
(POUNDS)
Design Slab Thickness, D (inches)
Wheel Load Tensile Stress σ
w
(psi)
EFFECTIVE
MODULUS OF
SUBGRADE
REACTION k (pci)
500
400
300
200
100
50
DT
D
T
H
T
L
–=
62-52 The Civil Engineering Handbook, Second Edition
FIGURE 62.32 Minimum percent steel reinforcement to satisfy crack-width criteria. (Source: AASHTO. 1993.
AASHTO Guides for Design of Pavement Structures. Copyright 1993 by the American Association of State Highway
and Transportation Officials, Washington, D.C. Used by permission.)
FIGURE 62.33 Minimum percent reinforcement to satisfy steel–stress criteria. (Source: AASHTO 1993. AASHTO
Guides for Design of Pavement Structures. Copyright 1993 by the American Association of State Highway and Trans-
portation Officials, Washington, D.C. Used by permission.)
.10
.09
.08
.07
.06
.05
.04
.03
.02
.01
3/4
5/8
1/2
800
700
600
500
400
.9
.8
.7
.6
.5
.4
T
L
T
L
Crack Width, CW (in.)
Bar Diameter, f (in.)
Tensile Stress Due to Wheel Load, s
w
(psi)
Concrete Tensile Strength, f
t
(psi)
Percent Steel, P
280
240
200
160
120
80
30
20
35
55
75
45
65
100
300
800
700
600
500
400
220
140
60
.0002
.9
.8
.7
.6
.5
.4
.0005
.0008
40
50
60
70
80
90
100
110
120
Undesirable
Steel Stress, σ
s
(ksi)
Design Temperature Drop, DT
D
(°F)
Concrete Shrinkage at 28 Days, Z
-
(in/in)
Tensile Stress Due to Wheel Load, σ
W
(psi)
Concrete Tensile Strength, f
t
(psi)
Percent Steel, P
T
L
T
L
T
L
Highway and Airport Pavement Design 62-53
Reinforcement Design. Based on the three criteria discussed above, the design percent steel should fall
within P
max
and P
min
given by
(62.30)
(62.31)
If P
max
is less than P
min
, a design revised by changing some of the input parameters is required. With
P
max
greater than P
min
, the number of reinforcing bars or wires required, N, is given by N
min
£ N £ N
max
,
where N
min
and N
max
are computed by
(62.32)
(62.33)
where W
s
= the width of pavement in inches
D = the slab thickness in inches
f = the reinforcing bar or wire diameter in inches
Example 62.19
This example concerns longitudinal steel reinforcement design for CRCP. Design data are D = 9 in., a
s
=
5 ¥ 10
–6
in./in./˚F, a
c
= 5.3 ¥ 10
–6
for concrete with granite coarse aggregate (see Table 62.18), f
t
= 600 psi
at 28 days, Z = 0.0003 (see Table 62.18), maximum construction wheel load = 18,000 lb, effective k =
100 pci, and design temperature drop = 55˚F.
Try steel bar diameter f = 0.5 in. (a) Crack spacing control. s
w
= 240 psi, from Fig. 62.31. With (a
s
/a
c
) =
0.94, obtain (P
min
)
1
< 0.4% for X = 8 ft, and (P
max
)
2
= 0.49% for X = 3.5 ft from Fig. 62.30. (b) Crack
width control. Obtain (P
min
)
2
= 0.40% from Fig. 62.32. (c) Steel stress control. s
s
= 67 psi, from
Table 62.19. Obtain (P
min
)
3
= 0.45%. Hence, overall (P
min
) = 0.4% and (P
max
) = 0.49%. For a pavement
width of 12 ft, apply Eqs. (62.32) and (62.33), N
min
= 29.7, N
max
= 32.3. Use 30 numbers of 0.5-in. bars.
PCA Thickness Design Procedure for Rigid Highway Pavements
The thickness design procedure published by PCA [1984] was developed by relating theoretically com-
puted values of stress, deflection, and pressure to pavement performance criteria derived from data of
(1) major road test programs, (2) model and full-scale tests, and (3) performance of normally constructed
pavements subject to normal mixed traffic.
Traffic-loading data in terms of axle load distribution are obtained in the usual way as described earlier
in this chapter. Each axle load is further multiplied by a load safety factor (LSF) according to the following
recommendations: (1) LSF = 1.2 for interstate highways and other multilane projects with uninterrupted
TABLE 62.19 Allowable Steel Working Stress, ksi
Indirect Tensile Strength of
Concrete at 28 days, psi
Reinforcing Bar Size
No. 4 No. 5 No. 6
300 (or less) 65 57 54
400 67 60 55
500 67 61 56
600 67 63 58
700 67 65 59
800 (or greater) 67 67 60
Source: AASHTO. 1993. AASHTO Guides for Design of
Pavement Structures. Copyright 1993 by the American Asso-
ciation of State Highway and Transportation Officials, Wash-
ington, D.C. Used by permission.
P
max
P
max
()
1
=
P
min
max P
min
()
1
P
min
()
2
P
min
()
3
,,{}=
N
min
0.01273P
min
W
s
D
f
§
2
=
N
max
0.01273P
max
W
s
D
f
§
2
=
62-54 The Civil Engineering Handbook, Second Edition
traffic flow and high volumes of truck traffic; (2) LSF = 1.1 for highways and arterial streets with moderate
volumes of truck traffic; and (3) LSF = 1.0 for roads, residential streets, and other streets with small
volumes of truck traffic. The flexural strength of concrete is determined by the 28-day modulus of rupture
from third-point loading according to ASTM Test Method C78. Subgrade and subbase support is defined
in terms of the modulus of subgrade reaction k.
The design procedure consists of a fatigue analysis and an erosion analysis, which are considered separately
using different sets of tables and design charts. The final thickness selected must satisfy both analyses.
Fatigue Design
Fatigue design is performed with the aim to control fatigue cracking. The slab thickness based on fatigue
design is the same for JRCP, for JPCP with doweled and undoweled joints, and for CRCP. This is because
the most critical loading position is near midslab and the effect of joints is negligible. The presence of a
tied concrete shoulder, however, must be considered since it significantly reduces the critical edge stress.
The analysis is based on the concept of cumulative damage given by
(62.34)
where m = the total number of axle load groups
n
i
= the predicted number of repetitions for the ith load group
N
i
= the allowable number of repetitions for the ith load group
The steps in the design procedure are:
1. Multiply the load of each design axle load group by the appropriate LSF.
2. Assume a trial slab thickness.
3. Obtain from Table 62.20(a) or (b) the equivalent stress for the input slab thickness and k, and
calculate the stress ratio factor as
(62.35)
4. For each axle load i, obtain from Fig. 62.34 the allowable load repetitions N
i
.
5. Compute D from Eq. (62.34). If D exceeds 1, select a greater trial thickness and repeat steps 3
through 5. The trial thickness is adequate if D is less than or equal to 1.
Erosion Design
PCA requires erosion analysis in pavement thickness design to control foundation and shoulder erosion,
pumping, and faulting. Since the most critical deflection occurs at the corner, the presence of shoulder
and the type of joint construction will both affect the analysis. The concept of cumulative damage as
defined by Eq. (62.34) is again applied. The steps are:
1. Multiply the load of each design axle load group by the LSF.
2. Assume a trial slab thickness.
3. Obtain from Table 62.21(a), (b), (c), or (d) the erosion factor for the input slab thickness and k.
4. For each axle load i, obtain from Fig. 62.35(a) or (b) the allowable load repetitions N
i
.
5. Compute D from Eq. (62.34). If D exceeds 1, select a greater trial thickness and repeat steps 3
through 5. The trial thickness is adequate if D is less than or equal to 1.
Example 62.20
Determine the required slab thickness for an expressway with the design traffic shown in the table below.
The pavement is to be constructed with doweled joint but without concrete shoulder. Concrete modulus
of rupture is 650 psi. The subgrade k is 130 pci.
D
n
i
N
i
-----
i 1=
m
Â
=
Stress ratio factor
Equivalent stress
Concrete flexural strength
--------------------------------------------------------------=
Highway and Airport Pavement Design 62-55
A trial-and-error approach is needed by assuming slab thickness. The solution is shown only for slab
thickness h = 9.5 in.
For an expressway, the LSF = 1.2. The design load is equal to (1.2 ¥ axle load). From Table 62.20,
equivalent stress for single axle is 206 and for tandem axle is 192. The corresponding stress ratios are
TABLE 62.20 Equivalent Stress for Fatigue Analysis
Slab
Thickness
(in.)
k of Subgrade–Subbase (pci)
50 100 150 200 300 500 700
(a) Equivalent Stress — No Concrete Shoulder (Single Axle/Tandem Axle)
4 in. 825/679 726/585 671/542 634/516 584/486 523/457 484/443
4.5 in. 699/586 616/500 571/460 540/435 498/406 448/378 417/363
5 in. 602/516 531/436 493/399 467/374 432/349 390/321 363/307
5.5 in. 526/461 464/387 431/353 409/331 379/305 343/278 320/264
6 in. 465/416 411/348 382/316 362/296 336/271 304/246 285/232
6.5 in. 417/380 367/317 341/286 324/267 300/244 273/220 256/207
7 in. 375/349 331/290 307/262 292/244 271/222 246/199 231/186
7.5 in. 340/323 300/268 279/241 265/224 246/203 224/181 210/169
8 in. 311/300 274/249 255/223 242/208 225/188 205/167 192/155
8.5 in. 285/281 252/232 234/208 222/193 206/174 188/154 177/143
9 in. 264/264 232/218 216/195 205/181 190/163 174/144 163/133
9.5 in. 245/248 215/205 200/183 190/170 176/153 161/134 151/124
10 in. 228/235 200/193 186/173 177/160 164/144 150/126 141/117
10.5 in. 213/222 187/183 174/164 165/151 153/136 140/119 132/110
11 in. 200/211 175/174 163/155 154/143 144/129 131/113 123/104
11.5 in. 188/201 165/165 153/148 145/136 135/122 123/107 116/98
12 in. 177/192 155/158 144/141 137/130 127/116 116/102 109/93
12.5 in. 168/183 147/151 136/135 129/124 120/111 109/97 103/89
13 in. 159/176 139/144 129/129 122/119 113/106 103/93 97/85
13.5 in. 152/168 132/138 122/123 116/114 107/102 98/89 92/81
14 in. 144/162 125/133 116/118 110/109 102/98 93/85 88/78
(b) Equivalent Stress — Concrete Shoulder (Single Axle/Tandem Axle)
4 in. 640/534 559/468 517/439 489/422 452/403 409/388 383/384
4.5 in. 547/461 479/400 444/372 421/356 390/338 355/322 333/316
5 in. 475/404 417/349 387/323 367/308 341/290 311/274 294/267
5.5 in. 418/360 368/309 342/285 324/271 302/254 276/238 261/231
6 in. 372/325 327/277 304/255 289/241 270/225 247/210 234/203
6.5 in. 334/295 294/251 274/230 260/218 243/203 223/188 212/180
7 in. 302/270 266/230 248/210 236/198 220/184 203/170 192/162
7.5 in. 275/250 243/211 226/193 215/182 201/168 185/155 176/148
8 in. 252/232 222/196 207/179 197/168 185/155 170/142 162/135
8.5 in. 232/216 205/182 191/166 182/156 170/144 157/131 150/125
9 in. 215/202 190/171 177/155 169/146 158/134 146/122 139/116
9.5 in. 200/190 176/160 164/146 157/137 147/126 136/114 129/108
10 in. 186/179 164/151 153/137 146/129 137/118 127/107 121/101
10.5 in. 174/170 154/143 144/130 137/121 128/111 119/101 113/95
11 in. 164/161 144/135 135/123 129/115 120/105 112/95 106/90
11.5 in. 154/153 136/128 127/117 121/109 113/100 105/90 100/85
12 in. 145/146 128/122 120/111 114/104 107/95 99/86 95/81
12.5 in. 137/139 121/117 113/106 108/99 101/91 94/82 90/77
13 in. 130/133 115/112 107/101 102/95 96/86 89/78 85/73
13.5 in. 124/127 109/107 102/97 97/91 91/83 85/74 81/70
14 in. 118/122 104/103 97/93 93/87 87/79 81/71 77/67
Source: Portland Cement Association. 1984. Thickness Design for Concrete Highway and
Street Pavements. With permission.
62-56 The Civil Engineering Handbook, Second Edition
0.317 and 0.295. N
1
for fatigue analysis is obtained from Fig. 62.34. From Table 62.21, the erosion factor
is 2.6 for single axle and is 2.8 for tandem axle. N
2
for erosion analysis is obtained from Fig. 62.35(a).
The results show that the design is satisfactory.
FAA Method for Rigid Airport Pavement Design
Both the thickness design and reinforcement design procedures by the FAA [1978] are presented in this
section.
FIGURE 62.34 Allowable repetitions for fatigue analysis. (Source: Portland Cement Association. 1984. Thickness
Design for Concrete Highway and Street Pavements, p. 15. With permission.)
Axle Load
(kips)
Design Load
(kips)
Design
Fatigue Erosion
nN
1
(n/N
1
) N
2
(n/N
2
)
52T 62.4T 3,100 800,000 0.004 800,000 0.004
50T 60.0T 32,000 2,000,000 0.016 1,000,000 0.030
48T 57.6T 32,000 10,000,000 0.0032 1,200,000 0.027
46T 55.2T 48,000 Unlimited 0 1,700,000 0.028
44T 52.8T 158,000 Unlimited 0 2,000,000 0.079
42T 50.4T 172,000 Unlimited 0 2,800,000 0.061
40T 48.0T 250,000 Unlimited 0 3,500,000 0.071
30S 36.0S 3,100 25,000 0.124 1,700,000 0.002
28S 33.6S 3,100 70,000 0.044 2,200,000 0.001
26S 31.2S 9,300 200,000 0.045 3,000,000 0.002
24S 28.8S 545,000 800,000 0.682 5,000,000 0.033
22S 26.4S 640,000 10,000,000 0.064 9,000,000 0.071
Total 0.982 0.41
SINGLE AXLE LOAD, KIPS
8
12
14
16
18
22
24
26
28
32
34
36
38
42
44
46
48
52
54
56
58
20
30
40
50
60 120
110
100
90
80
70
60
50
40
30
20
16
10
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
2
4
6
8
100
1000
10,000
100,000
1,000,000
10,000,000
ALLOWABLE LOAD REPETITIONS
1.50
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.25
0.20
0.15
TANDEM AXLE LOAD, KIPS
STRESS RATIO FACTOR
Highway and Airport Pavement Design 62-57
TA BLE 62.21 Erosion Factors for Erosion Analysis
Slab
Thickness
(in.)
k of Subgrade–Subbase (pci)
50 100 200 300 500 700
(a) Erosion Factors — Doweled Joints, No Concrete Shoulder
(Single Axle/Tandem Axle)
4 3.74/3.83 3.73/3.79 3.72/3.75 3.71/3.73 3.70/3.70 3.68/3.67
4.5 3.59/3.70 3.57/3.65 3.56/3.61 3.55/3.58 3.54/3.55 3.52/3.53
5 3.45/3.58 3.43/3.52 3.42/3.48 3.41/3.45 3.40/3.42 3.38/3.40
5.5 3.33/3.47 3.31/3.41 3.29/3.36 3.28/3.33 3.27/3.30 3.26/3.28
6 3.22/3.38 3.19/3.31 3.18/3.26 3.17/3.23 3.15/3.20 3.14/3.17
6.5 3.11/3.29 3.09/3.22 3.07/3.16 3.06/3.13 3.05/3.10 3.03/3.07
7 3.02/3.21 2.99/3.14 2.97/3.08 2.96/3.05 2.95/3.01 2.94/2.98
7.5 2.93/3.14 2.91/3.06 2.88/3.00 2.87/2.97 2.86/2.93 2.84/2.90
8 2.85/3.07 2.82/2.99 2.80/2.93 2.79/2.89 2.77/2.85 2.76/2.82
8.5 2.77/3.01 2.74/2.93 2.72/2.86 2.71/2.82 2.69/2.78 2.68/2.75
9 2.70/2.96 2.67/2.87 2.65/2.80 2.63/2.76 2.62/2.71 2.61/2.68
9.5 2.63/2.90 2.60/2.81 2.58/2.74 2.56/2.70 2.55/2.65 2.54/2.62
10 2.56/2.85 2.54/2.76 2.51/2.68 2.50/2.64 2.48/2.59 2.47/2.56
10.5 2.50/2.81 2.47/2.71 2.45/2.63 2.44/2.59 2.42/2.54 2.41/2.51
11 2.44/2.76 2.42/2.67 2.39/2.58 2.38/2.54 2.36/2.49 2.35/2.45
11.5 2.38/2.72 2.36/2.62 2.33/2.54 2.32/2.49 2.30/2.44 2.29/2.40
12 2.33/2.68 2.30/2.58 2.28/2.49 2.26/2.44 2.25/2.39 2.23/2.36
12.5 2.28/2.64 2.25/2.54 2.23/2.45 2.21/2.40 2.19/2.35 2.18/2.31
13 2.23/2.61 2.20/2.50 2.18/2.41 2.16/2.36 2.14/2.30 2.13/2.27
13.5 2.18/2.57 2.15/2.47 2.13/2.37 2.11/2.32 2.09/2.26 2.08/2.23
14 2.13/2.54 2.11/2.43 2.08/2.34 2.07/2.29 2.05/2.23 2.03/2.19
(b) Erosion Factors — Aggregate–Interlock Joints, No Concrete Shoulder
(Single Axle/Tandem Axle)
4 3.94/4.03 3.91/3.95 3.88/3.89 3.86/3.86 3.82/3.83 3.77/3.80
4.5 3.79/3.91 3.76/3.82 3.73/3.75 3.71/3.72 3.68/3.68 3.64/3.65
5 3.66/3.81 3.63/3.72 3.60/3.64 3.58/3.60 3.55/3.55 3.52/3.52
5.5 3.54/3.72 3.51/3.62 3.48/3.53 3.46/3.49 3.43/3.44 3.41/3.40
6 3.44/3.64 3.40/3.53 3.37/3.44 3.35/3.40 3.32/3.34 3.30/3.30
6.5 3.34/3.56 3.30/3.46 3.26/3.36 3.25/3.31 3.22/3.25 3.20/3.21
7 3.26/3.49 3.21/3.39 3.17/3.29 3.15/3.24 3.13/3.17 3.11/3.13
7.5 3.18/3.43 3.13/3.32 3.09/3.22 3.07/3.17 3.04/3.10 3.02/3.06
8 3.11/3.37 3.05/3.26 3.01/3.16 2.99/3.10 2.96/3.03 2.94/2.99
8.5 3.04/3.32 2.98/3.21 2.93/3.10 2.91/3.04 2.88/2.97 2.87/2.93
9 2.98/3.27 2.91/3.16 2.86/3.05 2.84/2.99 2.81/2.92 2.79/2.87
9.5 2.92/3.22 2.85/3.11 2.80/3.00 2.77/2.94 2.75/2.86 2.73/2.81
10 2.86/3.18 2.79/3.06 2.74/2.95 2.71/2.89 2.68/2.81 2.66/2.76
10.5 2.81/3.14 2.74/3.02 2.68/2.91 2.65/2.84 2.62/2.76 2.60/2.72
11 2.77/3.10 2.69/2.98 2.63/2.86 2.60/2.80 2.57/2.72 2.54/2.67
11.5 2.72/3.06 2.64/2.94 2.58/2.82 2.55/2.76 2.51/2.68 2.49/2.63
12 2.68/3.03 2.60/2.90 2.53/2.78 2.50/2.72 2.46/2.64 2.44/2.59
12.5 2.64/2.99 2.55/2.87 2.48/2.75 2.45/2.68 2.41/2.60 2.39/2.55
13 2.60/2.96 2.51/2.83 2.44/2.71 2.40/2.65 2.36/2.56 2.34/2.51
13.5 2.56/2.93 2.47/2.80 2.40/2.68 2.36/2.61 2.32/2.53 2.30/2.48
14 2.53/2.90 2.44/2.77 2.36/2.65 2.32/2.58 2.28/2.50 2.25/2.44
(c) Erosion Factors — Doweled Joints, Concrete Shoulder
(Single Axle/Tandem Axle)
4 3.28/3.30 3.24/3.20 3.21/3.13 3.19/3.10 3.15/3.09 3.12/3.08
4.5 3.13/3.19 3.09/3.08 3.06/3.00 3.04/2.96 3.01/2.93 2.98/2.91
5 3.01/3.09 2.97/2.98 2.93/2.89 2.90/2.84 2.87/2.79 2.85/2.77
5.5 2.90/3.01 2.85/2.89 2.81/2.79 2.79/2.74 2.76/2.68 2.73/2.65
62-58 The Civil Engineering Handbook, Second Edition
FAA Thickness Design Procedure for Rigid Airport Pavements
The FAA thickness design method is based on the Westergaard analysis of an edge-loaded slab on a dense
liquid foundation. The design curves in Figs. 62.36–62.42 have been developed with the assumption that
the landing gear assembly is either tangent to a longitudinal joint or perpendicular to a transverse joint —
whichever produces the largest stress. It is also assumed that 95% of the gross aircraft weight is carried
on the main landing gear assembly. The design curves provide slab thickness T for the critical areas
defined earlier in this chapter. The thickness of 0.9T for noncritical areas applies to the concrete slab
TA BLE 62.21 (continued) Erosion Factors for Erosion Analysis
Slab
Thickness
(in.)
k of Subgrade–Subbase (pci)
50 100 200 300 500 700
6 2.79/2.93 2.75/2.82 2.70/2.71 2.68/2.65 2.65/2.58 2.62/2.54
6.5 2.70/2.86 2.65/2.75 2.61/2.63 2.58/2.57 2.55/2.50 2.52/2.45
7 2.61/2.79 2.56/2.68 2.52/2.56 2.49/2.50 2.46/2.42 2.43/2.38
7.5 2.53/2.73 2.48/2.62 2.44/2.50 2.41/2.44 2.38/2.36 2.35/2.31
8 2.46/2.68 2.41/2.56 2.36/2.44 2.33/2.38 2.30/2.30 2.27/2.24
8.5 2.39/2.62 2.34/2.51 2.29/2.39 2.26/2.32 2.22/2.24 2.20/2.18
9 2.32/2.57 2.27/2.46 2.22/2.34 2.19/2.27 2.16/2.19 2.13/2.13
9.5 2.26/2.52 2.21/2.41 2.16/2.29 2.13/2.22 2.09/2.14 2.07/2.08
10 2.20/2.47 2.15/2.36 2.10/2.25 2.07/2.18 2.03/2.09 2.01/2.03
10.5 2.15/2.43 2.09/2.32 2.04/2.20 2.01/2.14 1.97/2.05 1.95/1.99
11 2.10/2.39 2.04/2.28 1.99/2.16 1.95/2.09 1.92/2.01 1.89/1.95
11.5 2.05/2.35 1.99/2.24 1.93/2.12 1.90/2.05 1.87/1.97 1.84/1.91
12 2.00/2.31 1.94/2.20 1.88/2.09 1.85/2.02 1.82/1.93 1.79/1.87
12.5 1.95/2.27 1.89/2.16 1.84/2.05 1.81/1.98 1.77/1.89 1.74/1.84
13 1.91/2.23 1.85/2.13 1.79/2.01 1.76/1.95 1.72/1.86 1.70/1.80
13.5 1.86/2.20 1.81/2.09 1.75/1.98 1.72/1.91 1.68/1.83 1.65/1.77
14 1.82/2.17 1.76/2.06 1.71/1.95 1.67/1.88 1.64/1.80 1.61/1.74
(d) Erosion Factors — Aggregate–Interlock Joints, Concrete Shoulder
(Single Axle/Tandem Axle)
4 3.46/3.49 3.42/3.39 3.38/3.32 3.36/3.29 3.32/3.26 3.28/3.24
4.5 3.32/3.39 3.28/3.28 3.24/3.19 3.22/3.16 3.19/3.12 3.15/3.09
5 3.20/3.30 3.16/3.18 3.12/3.09 3.10/3.05 3.07/3.00 3.04/2.97
5.5 3.10/3.22 3.05/3.10 3.01/3.00 2.99/2.95 2.96/2.90 2.93/2.86
6 3.00/3.15 2.95/3.02 2.90/2.92 2.88/2.87 2.86/2.81 2.83/2.77
6.5 2.91/3.08 2.86/2.96 2.81/2.85 2.79/2.79 2.76/2.73 2.74/2.68
7 2.83/3.02 2.77/2.90 2.73/2.78 2.70/2.72 2.68/2.66 2.65/2.61
7.5 2.76/2.97 2.70/2.84 2.65/2.72 2.62/2.66 2.60/2.59 2.57/2.54
8 2.69/2.92 2.63/2.79 2.57/2.67 2.55/2.61 2.52/2.53 2.50/2.48
8.5 2.63/2.88 2.56/2.74 2.51/2.62 2.48/2.55 2.45/2.48 2.43/2.43
9 2.57/2.83 2.50/2.70 2.44/2.57 2.42/2.51 2.39/2.43 2.36/2.38
9.5 2.51/2.79 2.44/2.65 2.38/2.53 2.36/2.46 2.33/2.38 2.30/2.33
10 2.46/2.75 2.39/2.61 2.33/2.49 2.30/2.42 2.27/2.34 2.24/2.28
10.5 2.41/2.72 2.33/2.58 2.27/2.45 2.24/2.38 2.21/2.30 2.19/2.24
11 2.36/2.68 2.28/2.54 2.22/2.41 2.19/2.34 2.16/2.26 2.14/2.20
11.5 2.32/2.65 2.24/2.51 2.17/2.38 2.14/2.31 2.11/2.22 2.09/2.16
12 2.28/2.62 2.19/2.48 2.13/2.34 2.10/2.27 2.06/2.19 2.04/2.13
12.5 2.24/2.59 2.15/2.45 2.09/2.31 2.05/2.24 2.02/2.15 1.99/2.10
13 2.20/2.56 2.11/2.42 2.04/2.28 2.01/2.21 1.98/2.12 1.95/2.06
13.5 2.16/2.53 2.08/2.39 2.00/2.25 1.97/2.18 1.93/2.09 1.91/2.03
14 2.13/2.51 2.04/2.36 1.97/2.23 1.93/2.15 1.89/2.06 1.87/2.00
Source: Portland Cement Association. 1984. Thickness Design for Concrete Highway and Street
Pavements. With permission.
Highway and Airport Pavement Design 62-59
thickness. As in the case for flexible pavement design, stabilized subbase is required to accommodate
aircraft weighing 100,000 lb or more.
Design Loading. The same method of selecting a design aircraft and computing design annual departures
is followed as for the FAA flexible airport pavement design.
FIGURE 62.35 Allowable repetitions for erosion analysis. (Source: Portland Cement Association. 1984. Thickness
Design for Concrete Highway and Street Pavements. With permission.)
FIGURE 62.36 Rigid pavement thickness for single-wheel gear. (Source: Federal Aviation Administration. 1978.
Airport Pavement Design and Evaluation. Advisory Circular AC No. 150/5320-6C. With permission.)
60
50
40
30
20
18
16
14
12
9
816
20
25
30
35
40
50
60
70
80
90
100
110
120
18
10
25
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
SINGLE AXLE LOAD, KIPS
TANDEM AXLE LOAD, KIPS
EROSION FACTOR
ALLOWABLE LOAD REPETITIONS
WITHOUT CONCRETE SHOULDER
100,000,000
8
6
4
2
10,000,000
8
6
4
2
10,000,000
8
6
4
2
100,000
8
6
4
2
10,000
1000
8
6
4
2
60
50
40
30
20
18
16
14
12
9
8
16
20
25
30
35
40
50
60
70
80
90
100
110
120
18
10
25
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
SINGLE AXLE LOAD, KIPS
TANDEM AXLE LOAD, KIPS
EROSION FACTOR
ALLOWABLE LOAD REPETITIONS
WITH CONCRETE SHOULDER
100,000,000
4
2
6
6
4
2
4
10,000,000
1,000,000
2
8
100,000
8
6
4
2
8
6
4
10,000
1000
2
30,000
45,000
60,000
500
300
200
100
k=50 pci
75,000 lbs
0178 E
14
14
15
13
12
11
10
9
13
12
11
10
9
8
7
6
NOTE:
1 inch = 2.54 cm 1 psi = 0.0069 MN/m
2
1 Ib = 0.454 kg 1 pci = 0.272 MN/m
3
16
16
15
14
13
12
11
10
9
8
7
15
14
13
12
11
10
9
8
7
14
13
12
11
10
9
8
7
7
SLAB THICKNESS, in.
CONCRETE FLEXURAL STRENGTH, psi
1200
900
800
700
600
500
3000 6000 15,000 25,000
ANNUAL DEPARTURES
8