WORLD BANK

TCP Design(THIN CONCRETE PAVEMENTS)

Juan Pablo Covarrubias

Washington

2008

Type of Pavement we are Talking About

PERFORMANCE OF CONCRETE PAVEMENTS

The basic performance principles of Concrete Pavements

In Chile, the slabs are always curled with the edges lifted up, day and night.

DEFORMATION OF A SLAB15 cm thick, 4 m. long

EFFECT OF SUBGRADE STIFFNESS

5,5 5,5 / 11 11 / 16,6 16,6 /22,1

22,1

K (kg/cm3)

% cracked slabs

Armaghani 1993

EFFECT OF SUBGRADE STIFFNESS

cantilever

Granular CBR 40

cantilever

CTB

Not bonded (polyethylene)

EFFECT OF SLAB LENGTH

cantilever

1/3 L

cantilever

1/3 L

cantilever

1/4 L

cantilever

1/4 L

Length 4,5 m. cantilever = 1,13 m

Length 1,8 m. Cantilever = 0,45 m

EFFECT OF SLAB LENGTH ON SHRINKAGE AND CURLING

a > 1

450 cm x350 cmThickness= 18 cmDelta T°=-14 C° LinearCurling = 2.41 mm

140 cm x175 cmThickness= 18 cmDelta T°=-14 C° LinearCurling = 0.49 mm

EFFECT OF SLAB LENGTH ON CURLING

SLAB LENGTH AND CURLING

Holland 2002

3,8 m 4,5 m

Hiller and Springenschmid, 2004Hiller and Springenschmid, 2004

CrackingCracking

EFFECT OF TIE BARS ON CRACKING OF SLABS

Development of the Designby TCPavements

• Research at the University of Illinois

• Generate Design Method.

• Coordinate tests at international level

Loads of Trucks on Slabs

Dx

L

Dx

L

Minimum Requirement for TCP design:Minimum Requirement for TCP design:

• Maximum slab length less than L Maximum slab length less than L

• Maximum slab width less than Dx (1/2 lane)Maximum slab width less than Dx (1/2 lane)

LOADING OF LONG AND SHORT SLABS

Efect of Loads and Slab Geometry on Stresses

Top 2.47 MpaBottom 0.20 MPa

Top 0.52 MpaBottom 0.24 MPa

One Axel at the Edge

X

LOADS AND STRESSES ON A SLAB WHITH ROCKING

RELATION: length - thickness - tensile stress

Length (m) Thickness (cm) σ (MPa)

4,5 15 4,04,5 12 5,04,5 10 6,04,5 8 7,5

1,75 15 0,61,75 12 0,81,75 10 0,91,75 8 1,1

450 cm x350 cmThickness= 18 cmDelta T°=-14 C° LinearTop Tensile stress= 1.40 MPa

140 cm x175 cmThickness= 18 cmDelta T°=-14 C° LinearTop Tensile stress= 0.18 MPa

EFFECT OF SLAB LENGTH ON CURLING AND OWN WEIGHT STRESSES

Project in GuatemalaSlabs 4,5 m x 3,5 m x 24 cm

THICKNESS (cm) 24

SIZE 450x360

Thermal Gradient °C -14

Elastic Modulus (kg/cm2) 290000

K (kg/cm3) 3

Dowels YES

Load Position I II III IV

Tensions (kg/cm2) 21,9 22,5 19,9 10,6

Position III

Position IV

Position I

Position II

Project in Guatemala Slabs 1,8 m x 2,1 m x 15 cm

Posición III

Posición I

Posición II

THICKNESS (cm) 15

SIZE 210x180

Thermal Gradient °C -14

Modulus of Elasticity (kg/cm2) 290000

K (kg/cm3) 3

Load Transfer LTE 50%

Load Position I II III

Tensions (kg/cm2) 14,5 20,0 22,1

Summary Guatemala Project

Slab Length

m.

Thickness

cm

Tension

Kg/cm2

Traffic

mESALS

4,5 24 22,5 50

1,8 15 22,1 50

Thin slabs with 30 cm widening

FINITE ELEMENTS ANALISIS

Equitensional Curves

0255075

100125150175200225250275300325350375400425450

7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Thickness (cm)

Len

gth

of

slab

(cm

)

20 Kg/cm2

25 Kg/cm2

30 Kg/cm2

35 Kg/cm2

40 Kg/cm2

Thicknesses for Same Stresses and Slab Length

Slab length change from 4,5 to 1,75 m

y = 0,5431x + 2,0129

R2 = 0,9954

0

2

4

6

8

10

12

14

16

18

20

0 5 10 15 20 25 30 35

Slabs 4,5 m

Sla

bs

1,75

m

cm

cm

LOAD POSITION AND SLAB SIZE

Top and Bottom Stresses for Length and Thickness

CHARACTERISTICS of TCP Design• Small slabs (1,8 by 2.4 meters)

• Granular base (fines < 6%) 15 cm thick

• Impermeable layer between the sub grade and sub base, if needed

• Thin joint cut (2 mm thick)

• No joints sealing

• No dowel bars or tie bars

• Lateral confinement with curb, shoulder or vertical steel pins

• Widened outer lane (30 cm)

DesignDesign method being used:

– Design with AASHTO with normal slab size (4.5 m long)

– Determine by finite elements the stresses within the concrete of the slab for the AASHTO design

– Calculate slab thickness by iteration with ISLAB2000 with the new configuration of slab size and wheel positions (one set of wheels on each slab) to obtain the same stresses than the AASHTO design.

The result, by using this new design approach, is a thinner concrete pavement with the same stresses as

AASHTO design

Construccion Cost

  TCP H° Tradicional Asfalto

EE Diseño EspesorCosto Km-

Pista Espesor Costo Km-Pista H°-TCP % Ahorro EspesorCosto Km-

Pista Asf-TCP%

Ahorro

50,000 8cm $ 69,041 - - - - 5cm $ 71,808 $ 2,767 4%

100,000 8cm $ 75,000 - - - - 7cm $ 86,000 $ 11,000 13%

1,250,000 10cm $ 81,715 15cm $ 113,400 $ 31,685 28% 9cm $ 101,803 $ 20,089 20%

3,000,000 12cm $ 94,389 18cm $ 132,411 $ 38,022 29% 10cm $ 116,165 $ 21,776 19%

15,000,000 15cm $ 113,400 22cm $ 160,000 $ 46,600 29% 13cm $ 137,389 $ 23,989 17%

68,000,000 18cm $ 132,411 28 cm $ 195,782 $ 63,371 32% 18cm $ 186,889 $ 54,478 29%

160,000,000 22 cm $ 157,759 30 cm $ 208,456 $ 50,696 24% 22cm $ 216,885 $ 59,126 27%

*Prices from Chile

Long Term Costs:NPV (%)

Time (years)15 20

Asphalt

Traditional

Concrete

TCP

Research at U. de Illinois

Sub Grade CBR 3%

Geotextile and Granular Base

Granular Base less 6% Fines

Concrete Slabs finished

ATLAS Machine

ATLAS Machine

Experiences

Constructed Projects

Guatemala

• BM3 Acceso CA9 Sur (Puente Villalobos)

• Description– Start Year: end 2005

– Length: 1.68km

– 120.000.000 Esals

– 15 years design

– Ciudad de Guatemala, Guatemala

– Highway

• Pavement structure– 21 cm thick

– Granular base and asphalt base

– 14.40m to 21.60m Witdh

Guatemala• Ruta CA-01 Occidente Ciudad San Cristobal - San

Lucas (Road to Antigua)

• Description– Year 2006

– Length: 11.07km

– 80.000.000 Esals

– Ciudad de Guatemala – Sacatepéquez, Guatemala

– Highway

• Pavement Structure– 17cm thick

– Granular base and asphalt base

– 14.40m Witdh

Configuration of Sugar Cane Vehícle (VCMEM)

TOTAL

Nú

me

ro d

e

Eje

s

1 1 1 1 1 1 1 7

Nú

me

ro d

e

Ne

um

áti

co

s

2 8 8 8 8 8 8 50

Pe

so

Má

xim

o

(To

n)

6 29 25 25 25 25 25 160

Eje

s

Eq

uiv

ale

nte

s a

18

,00

0

lbs

0,26 31 15,9 15,9 15,9 15,9 15,9 111

Lo

ng

itu

d (

m)

18 10 10 38

Tensions with Sugar Cane Vehicle (VCMEM)

THICKNESS (cm) 22

Slab size 180x210

Thermal gradient °C -21 -14 0

Position of load I II III IV I II III IV I II III IV

Tensions (kg/cm2) - K = 3 kg/cm3 16,9 17,1 14,8 14,7 16,5 16,7 14,5 14,3 15,8 16,0 13,8 13,7

Tensions (kg/cm2) - K = 9 kg/cm3 17,9 18,2 15,7 15,5 16,9 17,2 14,8 14,6 14,5 15,1 13,0 12,7

THICKNESS (cm) 18

Slab size 180x210

Thermal Gradient °C -21 -14 0

Position of Load I II III IV I II III IV I II III IV

Tensions (kg/cm2) - K = 3 kg/cm3 25,1 25,4 21,9 21,7 24,4 24,7 21,3 21 23,1 23,4 20,1 19,8

Tensions (kg/cm2) - K = 9 kg/cm3 25,7 26,2 22,6 22,2 24,1 24,5 21,1 20,8 20,6 21,3 17,9 17,5

Conclution

TCP design allows for:

– Reduction in thickness, reducing construction costs and keeping the normal performance as traditional design

– Increase of axel loads, reducing transportation costs, congestion and contamination.

THANK YOU

www.tcpavements.com