pavements soil cement
TRANSCRIPT
Concrete Airport Pavement Workshop, Nov 4-5, 09
Cement-Stabilized Base CoursesCement Stabilized Base Courses
Fares Y. Abdo, P.E.,Market Manager, PavementsPortland Cement Association
Fundamentals
Cement-Treated Base CoursesFundamentals
Materials
Mix Design
Thickness Designg
Construction
Case StudiesCase Studies
Cement-Based Pavement MaterialsRoller Compacted ConventionalRoller-Compacted Concrete
Conventional Concrete
PerviousConcrete
FAA
FAA C t T t d
Soil-Cementent
FAA Econocrete
P-306
Cement-Treated Base/Subbase
P-301 &P-304 Flowable Fill
Cement-Treated
Base
ent C
onte
Flowable Fill
Cement-ModifiedSoil
Full-DepthReclamationC
em
Water Content
Soil
Definition
Cement-Treated Base – a intimate mixture of native and/or manufactured aggregates with measured amounts of portland cement (and possibly other cementitious materials) and water that hardens after compaction and curing to form a strong durable paving material
What materials can be treated with cement?
Soils (sand, silt, clay)GravelGravelShaleC h d tCrushed stoneSlagRecycled HMARecycled concrete
Are all materials suitable for CTB?
Problem Soils
Organic soils
Acid soils
Sulfate soilsSulfate soils
Uniform sands
Why Use CTB?Economical pavement baseEconomical pavement base
Decreased base thickness compared to unbound aggregate base
Structural properties maintained under varying moisture conditions
High stiffness inhibits fatigue cracking and High stiffness inhibits fatigue cracking and rutting of asphalt surface
Sustainable paving optionSustainable paving option
FAA Base/Subbase Approved FAA Base/Subbase Approved Materials
P f B /S bb CPurpose of Base/Subbase Courses(FAA AC 150/5320-6E)
Flexible pavements
Principal structural components Base
Asphalt
Principal structural components
Distribute the loads to the f d ti
Base
Subbase(Req. if CBR<20)
foundation Subgrade
Improved Performance in Rutting and Fatigue CrackingP P
Cement-Treated BaseUnstabilized Granular Base
P f B /S bb CPurpose of Base/Subbase Courses(FAA AC 150/5320-6E)
Flexible pavements
Principal structural component Base
Asphalt
Principal structural component
Distribute the loads to the f d ti
Base
Subbase(Req. if CBR<20)
foundation
Rigid pavements
Subgrade
Provide uniform stable supportConcrete
Subbase
Subgrade
Materials for Base CourseMaterials for Base CourseFAA AC 150/5320-6E Flexible Pavement Design
I B C M G L d Item Base Course Max. Gross Load, lbs.
P-208 Aggregate Base 60 000P 208 Aggregate Base 60,000
P-209 Crushed Aggregate Base 100,000
P-211 Lime Rock Base N/A/
P-219 Recycled Concrete Aggregate Base 100,000
P-304 Cement Treated Base N/A/
P-306 Econocrete Subbase N/A
P-401 Plant Mix Bituminous Pavements N/A
P-403 HMA Base N/A
Materials for Subbase CourseMaterials for Subbase CourseFAA AC 150/5320-6E Flexible Pavement Design
I S bb C 1 F P i Item Subbase Course1 Frost Penetrating Subbase
P-154 Subbase CourseP 154 Subbase Course
P-210 Caliche Base Course
P-212 Shell Base Course
P-213 Sand Clay Base Course X
P-301 Soil Cement Base Course X
1. Materials acceptable for base course can also be used for subbase course
Materials for Sbbase CourseMaterials for Sbbase CourseFAA AC 150/5320-6E Rigid Pavement Design
I S bb C M G L d Item Subbase Course Max. Gross Load, lbs.
P-154 Subbase Course 100,000,
P-208 Aggregate Base Course 100,000
P-209 Crushed Aggregate Base Course 100,000
P-211 Lime Rock Base Course 100,000
P-301 Soil Cement Base Course 100,000
P 304 Cement Treated Base Course N/AP-304 Cement Treated Base Course N/A
P-306 Econocrete Subbase Course N/A
P-401 Plant Mix Bituminous Pavements N/A
P-403 HMA Base Course N/A
Engineering Properties of CTB
P 1 FAA P 301 FAA P 304 PCA CTBProperty1 FAA P-301(Soil Cement)
FAA P-304(CTB)
PCA CTB
7-Day Compressive N/A2 Under PCC: 300 min.; Strength, psi 500 min.; 1000 max.
Under HMA:750 min.; 1000 max.
800 max.
Elastic Modulus, ksi 250 500 600-1000
Poisson’s Ratio 0.20 0.20 0.15
1. Refer to FAA AC 150/5320-6E for durability requirements2. FAA recommendations for P-301 are based on wet-dry and freeze-thaw tests
and strength should increase with age
CTB Mix Design
St i f B l B tStrive for a Balance BetweenStrength and Performanceg
Mixture Design-Step 1Determine moisture-density relationship
Select expected median cement content Select expected median cement content (e.g. 6% by estimated dry weight)
Perform standard or modified Proctor test Perform standard or modified Proctor test (ASTM D558 or ASTM D1557)
Construct moisture-density curve
Determine optimum moisture content and maximum dry density
Moisture-Density Relationship
Mix Design-Step 2Mold specimens for compressive strength testing
Select range of cement contents ( 4% 6% d 8% b d i ht f t i l) (e.g. 4%, 6% and 8% by dry weight of material) Use percent OMC from Step 1 and Mold two specimens per cement content (ASTM specimens per cement content (ASTM D559/560 or ASTM D1632) Perform compressive strength testing Perform compressive strength testing (ASTM D1633)Plot cement content versus compressive Plot cement content versus compressive strength
Strength Testing
Strength vs. Cement Content1000
800
900
ngth
, psi
600
700
ssiv
e St
ren
400
500
y C
ompr
es
200
3007-da
y
3 4 5 6 7 8 9
Cement Content, %
Mix Design-Step 3Determine moisture-density relationship of target cement content
Perform standard or modified Proctor test (ASTM D558 or ASTM D1557)
Construct moisture-density curve
Determine optimum moisture content and Determine optimum moisture content and maximum dry density
Durability TestingSpecimens containing various cementitious contents molded per ASTM D558 and tested per:
ASTM D559; wet-dry cycles
ASTM D560; freeze-thaw cyclesASTM D560; freeze thaw cycles
Select min. cement content that meets weight loss limits set by agency having jurisdictionloss limits set by agency having jurisdiction
Thickness Design
Thickness Design■ FAA: FAARFIELD Computer Program
■ PCA Methods of Thickness Design ■ PCA Methods of Thickness Design
■ Experience
M h i ti E i i l M th d■ Mechanistic-Empirical Methods
■ AASHTO MEPDG (guide accepted)
■ PCA-Pave (near completion)
Thickness Design■ Factors
■ Subgrade Strength■ Subgrade Strength
■ Pavement Design Period
T ffi■ Traffic
■ Typical Thickness
■ Heavy traffic: 6 to 9 inches
■ Highways and airport runways and g y p ytaxiways: 6 to 12 inches
Construction
Construction
■ Two methods
■ Plant Mix
Road Mix (in place)■ Road Mix (in-place)
Plant Mix: PuggmillHigh production
Usually close or on-site
Mob/demob cost
Continuous Pugmill Mixing Chamber
■ Highly accurate Plant Mix: Central Concrete Batch Plant
■ Highly accurate proportioning
■ Local availability■ Local availability
■ Smaller output capacitycapacity
■ Longer mix times than conventional concreteconventional concrete
■ Frequent cleaning
■ Dedicated production
Plant Mix: Dry Concrete Batch Plant■ Highest local availability
■ Desirable method for the smaller-sized jobs
■ 2-step process
■ Feed into transit mixers
■ Discharge into dumps
■ Low production■ Low production
■ Frequent cleaning
S i■ Segregation
Construction - Road Mix
■ In-situ or mixed in place materials
■ Wider variety of materials
■ Dry or slurry cement application methody o s u y ce e t app cat o et od
Road Mix Method
1. Spread cement
2. Add water if necessary and mix
3. Compactp
4. Grade
5 Cure5. Cure
Portland Cement Addition
Dry spread
Slurry spread
Addition of Water
Gravity dump and mix
Via drum of mixer
Road Mixing
With water
Without water
Traffic loading/agency requirements
Plant vs. Road Mix ConsiderationsTraffic loading/agency requirements
FAA P-304 spec includes plant mix only
Quality of in-situ materialsQ y
Cost
Haul distances: material sources, plant, jobsitep j
Design thickness (one or multiple lifts)
Sustainable considerations (Reduce, Reuse and Recycling)
Dust controls/location of project
Plant vs. Road Mix ConsiderationsDust controls/location of project
Tuscaloosa, AL Palo Verde, AZ
Spreading/Placing
Grading/Compaction
Compaction
■ High density is critical for strength and durability
■ Steel-drum
■ Rubber-tire roller
■ Sheepsfoot roller■ Sheepsfoot roller
Curing
■ Required for surface durability and normal strength gaing
■ Needed to retain moisture
■ Three methods:■ Three methods:
▪ Moist Cure
▪ Concrete Curing Compound▪ Concrete Curing Compound
▪ Asphalt Emulsion
Moist Cure
■ Continuous ■ Continuous operation
P t i ■ Prevent excessive drying
Concrete Curing Compound
■ White-pigmented concrete curing compounds
■ Provide adequate coverage
■ May form a bond breaker
Bituminous Curing Compound
E ll t ■ Excellent moisture barrier
G d f h lt ■ Good for asphalt cap
Applications
L l r d
Where are stabilized materials used?Low volume roadways
Residential streets
State routesState routes
Interstate highways
Airport runways and taxiwaysAirport runways and taxiways
Parking lots
Industrial storage facilitiesIndustrial storage facilities
Port facilities
Truck terminalsIn other words…
Truck terminals
Commercial sites any pavement structure!
Residential Streets
Bells Crossing, Mooresville, NC, 2008
V lExample: County Road Original Design
Value-Engineered
Option■ Upgrade 2-lane to 4-lane route■ Value Engineered Option
3.5”
Asphalt Int. & Surface
■ Value-Engineered Option■ $900,000 savings on
238,000 SY ($3.78/SY) ■ Faster construction (5 months Asphalt Base Crushed
Asphalt Int. & Surface
C t
8” Crushed
(savings)
■ Less mined and processed materials
8”Crushed
Stone BaseCement-
Treated Base
8Stone Base
Subgrade
Subgrade
SC County Road 5
Parking AreasSustainable ContributionsDesign/Bid As ■ Reduced
export/import/fuel use■ Less mined and RCC6” 8”4”4” AsphaltAsphalt4” Asphalt
Design/Bid Section
As Constructed
■ Less mined and processed materials
■ Reduced excavation
RCC
Soil-Cement
6”-8”
6”12”12”Crushed Crushed
44
12”Crushed
4
■ Faster construction■ Cooler pavement■ Used in situ materialsSubgrade
Base612”12” Stone
BaseStone Base
12” Stone Base
■ Used in-situ materials■ Less damage to area
roadsSubgradeSubgradeSubgrade
BMW, SC, 2009
Washington Dulles Airport Runway 4, 2008p y ,
18” PCC w/ dowelled transverse
j i t t 20 ft joints at 20 ft
6” CTB, 6% cement
12” Cement-Stabilized Subgrade,
5% cement
Washington Dulles Airport Runway 4p y
■ Runway 4 completed in 2008■ Runway 12 was completed in
2004
FedEx Hub at Alliance Airport Fort Worth, TX,
Taxiway & Ramp
1997
14” PCC
Taxiway & Ramp
Truck Terminal & C t i St g14” PCC Container Storage
9” CTB10” JRCP
9” Cement-Treated Subgrade
6” Cement-Treated Subgrade
FedEx Hub at Alliance Airport Fort Worth, TX
■ 50-yr design lifeC l t d i 1997■ Completed in 1997
■ 330,000 yd2
■ Cement-treated subgrade■ 7 % cement, 250 psi,
reduced PI from 38 to less than 12
■ Cement treated base■ Cement –treated base■ 750 psi at 28 days
DFW SE Perimeter Taxiway, 2008y,■ First perimeter taxiway in U.S.■ Built for safety and reduce
congestion delays
18” CRCP
congestion delays
18 CRCP
12” CTB
12” Lime-Treated Subgrade
DFW SE Perimeter Taxiway■ Completed in 2008■ 225,000 yd2
■ Data will be analyzed before ■ Data will be analyzed before building the remaining 3 loops
McGhee Tyson AirportKnoxville, TN, 2008■ Completed in 2008■ 9,000 yd2
■ CTB per FAA P 304■ CTB per FAA P-304
16” PCC
6” CTB, 5% (C+FA)
8” Lime-Treated Subgrade
Charlotte-Douglas Airport, 2008■ Completed in 2008■ 256,000 yd2
■ CTB per FAA P 304■ CTB per FAA P-304
Dover AFB, Delaware, 2008■ Old concrete and asphalt
crushed and recycled50% l d d 50% i i ■ 50% recycled and 50% in-situ soil; sandy clays and clear sand
■ CTB 12” thick■ CTB 12 thick■ 42 to 80 lb/SY depending on
the in-situ and recycled materials
■ 300,000 SY ■ 58 days
