30-Year Old Two-Life Pavement Case Study

Florida Econocrete Road:
Performance After 30 Years
Presented by
Roger Schmitt, P.E.

The FDOT in conjunction with the FHWA
and the ACPA initiated the “Econocrete
Test Road” demonstration research
project in 1974.

What prompted this project ?
• Shortage of high quality aggregates and energy
crisis in the early 70’s
• Depletion of many supply sources of high
quality aggregates in Florida
• Increase in aggregate transportation cost, and
• Energy savings envisioned i in 70’s by use of
econocrete

Purpose :
This project was to determine the feasibility of
construction, and to evaluate the structural
and performance characteristics of a composite
concrete pavement system consisting of a
relatively thin wearing concrete course over an
econocrete base layer.

Project Description
• Contractor
• Completed 1978
Ballenger Paving
• Length
6.5 65 Miles es( (initially)
ta • Southbound Lanes 2
• Test Sections
• Typical Test Section
• Design Life
33 (initially)
2,000 ft
20 years

Project Location :
The project is on US 41/SR45 in Charlotte
County, Florida, between the cities of Punta
Gorda to the North and Fort Myers to the
South. It includes the two southbound lanes of
a four lane divided highway.

US 41/SR 45
Project Alignment

• Twelve (12) test sections remain in
service today:
-2 (control section)
- 3A, 3B, 3B-1S, 3B-2S, 3C
- 4A, 4B, 4C
- 5A, 5B, 5BT

• Section 2 (Control):
9 in PCC
6 in Cement treated subgrade
20 ft slabs, right angle joints

• Sections 3A, 3B, 3C, 3B1S, 3B2S:
3 in PCC
9 in Econocrete (A=2,000 psi, B=1,250 psi, C=750 psi)
6 in Stabilized subgrade
15 ft slabs, skewed joints
3B1S & 3B2S– have tied econocrete shoulder
with and without rumble strips, respectively .

• Sections 4A, 4B, 4C:
3 in PCC
9 in Econocrete (A=2,000 psi, B=1,250 psi, C= 750 psi)
6 in Cement treated subgrade
15 ft slabs, right angle joints

• Sections 5A, 5B, 5BT:
3 in Dowelled PCC ( 1in dowels @ 12” c/c)
9 in Econocrete (A=2,000 psi, B=1,250 psi)
6 in Stabilized subgrade
20 ft slabs, right angle joints

Condition Survey Results

Cracking
50.0
45.0
40.0
Cracked Slab bs (%)
35.0
30.0
25.0
20.0
15.0
10.0
50 5.0
0.0
2 3A 3B 3B1S 3B2S 3C 4A 4B 4C 5A 5B 5BT
Test Sections
Corner Longitudinal Transverse

Cores from Well Performing
Cement Treated Subgrade Sections

Cores from Well Performing
Stabilized Subgrade Sections

Cores from Longitudinal Cracked
Sections
3 C 4 A
4 B 4 C

Smoothness
220
200
180
160
140
IRI (in/mile)
120
100
80
60
40
20
0
2 3A 3B/ALT. 3B1S 3B2S 3C 4A 4B 4C 5A 5B 5BT
Test Sections

FAULTING IN OUTSIDE WHEEL PATH (in).
0.60
0.55
0.50
Faulting > 0.5 in typically requires reconstruction/slab replacement
Faulting (in n) -
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
Faulting > 0.15 in typically requires diamond grinding /other rehabilitation
2 3A 3B 3BIS 3B2S 3C 4A 4B 4C 5A 5B 5BT
Test Section
Avg.
Max.

Observations:
• This project has surpassed its 20 year design life, and
continues to perform well.
• Pavement sections made up of a concrete layer laid
bonded to an econocrete layer, have generally shown
better performance than the standard design section (ie
Section 2).
• Pavement sections on stabilized subgrade have very little
or no cracking and better smoothness compared to
pavement sections on cement treated subgrade.

Observations (Continued):
• Composite pavement sections on cement treated
subgrade with 15 ft joint spacing have higher load
transfer efficiency compared to the rest of the test
sections
• All test sections have minimal faulting, except for
sections 2 and 4C which require grinding.
• Examination of core samples show that uniformity and
control of the stabilized subgrade material is necessary
to ensure good pavement performance.

Upcoming activities:
• Coring of test sections 2, 5A and 5B
• Testing of cores: compressive and flexural
strength, coefficient of thermal expansion,
and modulus of elasticity of composite
layers
• Analysis of model predicted performance
vs field performance

Thank You !