it is about recycling of aggregate

1. Batching Effects on Properties of
Recycled Aggregate Concretes for
Airfield Rigid Pavements
Dr. Andres Salas
Prof. David Lange
Prof. Jeff Roesler
2010 FAA Technology Transfer Conference and Exposition
April 22, 2010

2. O’Hare Modernization Program
(OMP)
The purpose is to reconfigure the intersecting
runways at O’Hare International Airport into a
more modern parallel layout.
Prior to this O’Hare had not added a new
runway since 1971.
Project budget of $6.6 billion.

3. O’Hare Modernization Program
(OMP)

4. Sustainable practices are desirable
Reuse and conserve natural resources
Cost savings over traditional methods
Use of RA in concrete and asphalt
showed comparable performance over
virgin aggregates.
Why Recycle?

5. Resistance to change
Lack of experience
Inadequate codes, specifications
and standards
Inconsistent aggregate grading
Lower and variable quality
Challenges for using RecycledChallenges for using Recycled
Concrete AggregatesConcrete Aggregates

6. Recycled Concrete Aggregates atRecycled Concrete Aggregates at
AirportsAirports
Commonly used for base and subbase
Not used on airport concrete surface before in
U.S.?
Technical issues for surface applications
Durability, shrinkage, premature cracking

7. Two-Stage Mixing Approach, TSMATwo-Stage Mixing Approach, TSMA (Tam et al. 2005):
 Mixing process divided into two parts with required
water proportionally split and added at different timing.
 Initial water used for the formation of thin layer of
cement slurry on the surface of RA.
Permeate into old porous cement mortar, filling up
the old cracks and voids.
 Do the aggregates have to be dry, partially-saturated, or
saturated+surface moisture?
A new idea about mixing with RCAA new idea about mixing with RCA

8. Mixture ProcedureMixture Procedure
(Two-Stage Mixing Approach)(Two-Stage Mixing Approach)
Recycled coarse + cementing material 1 min 50% water 1 min Virgin coarse + sand+ 50%water 2 min
mix mix mix
* Control concrete (VAC)
was mixed following the
commonly used mixing
procedure

9. O’Hare Aggregate PhysicalO’Hare Aggregate Physical
PropertiesProperties
Aggregate BSG
Absorption
Capacity
Sand 2.57 2.43%
CA-16 2.68 2.73%
CA-7 2.67 1.90%
Recycled Agg. 2.41 5.51%

10. Mixture DesignMixture Design
Virgin
(CA-7) 43% 1429 30% 997 21% 713 21% 712 0% 0 0% 0 0% 0
Virgin
(CA-16) 12% 400 9% 283 6% 202 6% 201 0% 0 0% 0 0% 0
Recycled 0 0 17% 495 28% 825 28% 823 55% 1649 55% 1647 55% 1649
45% 1439 45% 1439 45% 1439 45% 1437 45% 1439 45% 1437 45% 1439
VAC
217
414
103
0Silica Fume
Coarse
Aggregate
Water
Type I Cement
Class C Fly ash
0
217
414
103
0 16
217
398
103
16
217
414
103
0
217
414
103
0
0Synthetic Macrofibers
Fine aggregate
0 00
100% RAC
FRC
217
398
103
3
Material
Content (lb/yd3
)
0
217
414
103
0
70-30
Blend
50-50
Blend
50-50
Blend+SF
100% RAC
100% RAC+
SF
w/cm = 0.42
The recycled aggregates sprayed to approximately fill 80% of the total absorption capacity.

11. Fresh PropertiesFresh Properties
Slump for 100% RA was higher than expected. Nearly saturated aggregates
reduces effects of RA absorption
MIX
SLUMP
(in)
AIR
CONTENT
(%)
UNIT
WEIGHT
(lb/ft3
)
UNIT
WEIGHT
(kg/m3
)
VAC 5 3.2 146.4 2345
70-30 BLEND 6.5 3.2 147.2 2358
50-50 BLEND 4.5 3.2 145.8 2335
50-50 BLEND + SF 2.5 2.5 146.2 2342
100% RA 7 3.4 149.2 2390
100% RA+ SF 3 2.5 142.8 2287
100% RA + FIBERS 2.2 2.5 145 2323

12. 1 day
7 days
28 days
90 days
0
1000
2000
3000
4000
5000
6000
7000
0
30
50
50+SF
100
100+SF
100 +
FIBERS
CompressiveStrength of Recycled Aggregate
Concrete(psi)
1 day
7 days
28 days
90 days
0
1000
2000
3000
4000
5000
6000
7000
0
30
50
50+SF
100
100+SF
100 +
FIBERS
CompressiveStrength of Recycled Aggregate
Concrete(psi)

13. 0
100
200
300
400
500
600
700
800
0
30 50
50+SF 100
100+SF
100 +
FIBERS
Strength(psi)
Splitting Tensile Strength (56 days)
0
100
200
300
400
500
600
700
800
0
30 50
50+SF 100
100+SF
100 +
FIBERS
Strength(psi)
Splitting Tensile Strength (56 days)

14. Drying Shrinkage ResultsDrying Shrinkage Results
 Lower microstrain for 100% RA at 14 days age
RA soaked for 24 hrs while virgin aggregate in oven dry condition
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0 10 20 30 40 50 60
FreeShrinkage(x10-6)
Age (days)
VA
30% RA
50% RA
100% RA
50% RA + SF
100% + SF
100% + FIBERS
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0 10 20 30 40 50 60
FreeShrinkage(x10-6)
Age (days)
VA
30% RA
50% RA
100% RA
50% RA + SF
100% + SF
100% + FIBERS

15. Summary Properties of RACSummary Properties of RAC
(Two Stage Mixing Approach)(Two Stage Mixing Approach)
Similar or higher compressive strength
compared to VAC
Similar shrinkage to VAC at early ages
Reduced bleeding and segregation
Similar concrete workability
Low dosages of silica fume (2 to 3%) enhances
the behavior of RAC

16. Minimize old mortar attached to aggregate
Aggregate grain size distribution and proportions
Aggregate Absorption Capacity
RA should be nearly-saturated conditions to
avoid loss in slump and excessive shrinkage.
Two-Stage Mixing Approach (TSMA) and pre-
soaking treatment method for the production of
RAC are encouraged
Issues to Consider for RACIssues to Consider for RAC

17. Field Testing

18. Pouring Gate F7B at O’HarePouring Gate F7B at O’Hare
Run #1 of RACRun #2 of VAC
 2 strips of 25ft x 125ft x 17in were placed
 Prairie supplied the materials
 Rossi Construction was the contractor
SAM Consultants handled material testing

19. Sensor InstallationSensor Installation
 28 Sensors to measure RH and
Temperature
 7 LVDT sensors to measure lift-off of
the slab

20. Placement and FinishingPlacement and Finishing
 After placement of the RAC
 No bleeding was observed
 Finishing took place almost
immediately after placement
 Very little effort required to finish

21. Field Visits 10/29
RAC (Run #1)VAC

22. Field Visit 11/12
RAC (Run #1)
VAC
VAC (Run #2)
VAC

23. Field Visit 3/18
 Contraction joints remain unchanged
 Some scaling observed in the test strips
VAC
RAC

24. 24
Compare Lab to Field
Mix designs and early age results for the Recycled Aggregate Concrete Mixes. Comparison
between U of I mix designs and Prairie Mix Design
Compressive Strength Design 4000psi
Prairie (RAC) Prairie (VAC) U of I (20%FA) 30% Class C FA 40% Class C FA 50% Class C FA
Water (gal) 28 ~26 ~26 ~26 ~26
Cement (lbs) 490 414 362 310 259
Fly Ash (lbs) 130 103 155 207 259
Air (%) 4.5-7.5 3% 3% 3% 3%
% WRA Variable dosage No No No No
Initial Slump (in) 3±1 4 7.5 8 8
Recycled Coarse (lbs) 1500 1688 1683 1677 1672
Extra Fines (lbs) 400 274 273 272 271
Natural Sand (lbs) 1093 1011 1007 1004 1000
Compressive strength at 3 days (psi) 3547 3581 - - - -
Compressive strength at 7 days (psi) 5190 4855 4700 3978 3830
Compressive strength at 28 days (psi) 6900/5858 5182 5751 5507 5435 5005
Flexural strength at 3 days (psi) 704.5 - - - -
Flexural strength at 7 days (psi) 760 - - - -
Flexural strength at 28 days (psi) 915/1052 826 - - - -
w/cementitious ~0.375 0.42 0.42 0.42 0.42
* Blod and blue represents testing results from SAM Consultants

25. Summary
• Lab test program helps us predict behavior of RAC using
recycled material sources at O’Hare
• Lab test program encourages us to use high(er) volume
of fly ash
• Lab test encourages lower cement than used in the field
RAC
• Testing underscores importance of keeping RA supply
near saturation to control shrinkage
• Field testing confirms that RAC slabs were well-
constructed and not experiencing high deformations
• So far, so good!

26. Acknowledgements