Concrete Materials Information
for
Construction Academy
Michael (Mike) Bergin, P.E.
State Concrete Engineer
State Materials Research Park
August 10, 2015
michael.bergin@dot.state.fl.us
Special Guest: Craig Roberts
FIELD OPS SPEC III-PRECAST
Florida Department of Transportation
Lets Talk!!
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This should be inter-active
Share your stories
Ask questions (anytime)
I don’t have all the answers, but someone does!
Florida Department of Transportation
Topics
• Fundamentals of Good Concrete
• A better understanding of w/c ratio
• Slump of Concrete
• Water added at the site
• Penalties
• Water for hydration
• Drilled shaft concrete and slump loss
• Mass concrete
• Other specification changes
Topics
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346 changes based on 7/15 lettings
Performance Based Concrete Pavement, Section 350
Slab Replacement Concrete, Section 353 (proposed changes)
Sampling Steel
Acceptance of Precast Products
• New Ideas, Concepts and Research
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Internal curing
Roller compacted concrete (RCC)
Self consolidating concrete (SCC)
Ground Glass in Concrete
GTR in Concrete
Water Cementitious Materials Ratio and
the Velcro Approach
What is the w/c ratio ?
Cementitious Materials
 Includes:
◦ Cement
 Type I, II, III
 Particle size; ∼ 25 to 40 microns
◦ Pozzolans,
 Fly ash, Class F and C
 Ground glass
 Rice hull ash
 Sugar Cane Ash
 Highly reactive pozzolans
 Particle size, ∼ 0.1 to 50 microns
◦ Slag
 GGBFS, grade 100 or 120
 Particle size, ∼ 20 to 40 microns
Pozzolans and ‘Particle Packing’
 Straight cement and high w/c (>0.41)
◦ Particles separated by high water content
◦ Shrinkage
◦ Excessive bleed water
 Straight cement and low w/c (≤0.41)
◦ Particles closer together, tighter bond
◦ A little more durable
 Cement and pozzolans with low w/c
◦ Particles closer together,
 size more distributed,
 very tight bond
◦ Durability has arrived!
High w/c Ratio
• Water - Concrete needs it but too much increases
volume
• Increase in ‘bleed water?’
• Delays finish work
• Unwanted surface conditions and less durable concrete
• Cracking ;
• High water content  drying shrinkage
• Lack of curing  surface cracking
Low w/c Ratio
• How much water is needed to hydrate cement?
• Concrete maintains its volume
• A little more is needed for pozzolans or slag
• Reduces the pathways for bleed water
• More durable concrete
• Increase in density
• Less surface defects on finished concrete
• Fines reduce bleed water ( particle packing)
Add Fly Ash or Slag to low w/c
• We have additional fine particles for packing and to
provide pozzolanic activity
• Particle packing helps minimize voids in the paste/matrix
• Pozzolanic activity -concrete continues to hydrate (react)
• continues as long as there is calcium, silica and moisture in
the matrix.
• Cement and fly ash both provide calcium and silica.
• Moisture already available in mix and moist curing ???
• Some method of curing.
Add Fly Ash or Slag to low w/c
• Best particle packing
• Less water between particles
• Additional moisture (if needed) comes with wet
curing or covering the surface to prevent moisture
loss.
• Wind
• Heat
• Dry conditions and low humidity
Water/Cement Ratio
Cement particle
Cement particle
High W/C
Low W/C
Hydration
Hydration
Plastic shrinkage cracking ?
Or tearing of the concrete?
Drying Shrinkage Cracking
Water Added at the Job and Slump
of Concrete
Sect. 346
• Target Slump and Tolerance Range
• Here’s a helpful graphic to clarify the issue (346, Table 6)
• Graphic illustrates target slump value
Slump Range
TOLERANCE SLUMP RANGE (3”)
REJECT
1-1/2” DRY
1-1/2” WET
ACCEPT – WATER MAY
BE ADDED
TARGET
SLUMP
REJECT
When the Contractor adds water…
• For initial tests
• Determine the slump (7.6)
• Place concrete, if OK
• For QC tests, target slump must be within tolerance of mix
design
• Perform other plastic properties;
• Air
• Temperature
• Determine w/c ratio
• What happens when water is added and no QC test planned??
346-6: Control of Quality
• 346-6.4 Tolerances: When slump is outside the
tolerance range,
• Make cylinders
• Contractor rejects concrete
• He notifies the concrete production facility to adjust the
concrete mixture
• He tests each subsequent load and the first adjusted load
from the plant
346-12: Penalty occurs…
• If contractor places concrete when any of the plastic
properties are outside the limits of the approved mix
design,…
• He not only assumes risk of placing non compliant
concrete, the contractor is penalized the invoice price of
concrete, unless the Engineer approves.
• On-going drilled shaft placement
• Large footer (don’t want a cold joint)
• Disposition of defective materials (DDM) is required
Slump loss, a major concern for
drilled shafts.
Slump Loss? Elapsed Time?
• Time it takes to loose slump - drops from 10” to 5”
• Indicates how long the contractor has to place the
concrete, set bolts, remove temporary casing.
• Concrete producer uses water reducing admixtures and
water to get slump.
• (SCC in the future)
Or this!
Q: What is the minimum clear cover (in inches) over steel?
Drilled Shaft Concrete should not
look like this!
Some Probable Causes?
• Concrete not workable?
• Slump loss not accurate for this placement? Need new slump loss?
• Contractor not ready for concrete?
• Rebar spacing too tight?
• Engineers increasing capacity
• Second truck delayed?
• How was the deficiency determined?
High Slump Concrete used in DS
• High slump concrete, 7” to 10” may have lumps and balls.
• Use a grate with max opening size of 2.5” in either direction
• Placement continues but,
• Lumps and balls are removed
• Contractor still responsible for strength
• Engineer can make cylinders anytime
• Department personnel to monitor
• Notify DMO if balls and lumps are present
High Slump Concrete
• If you see lumps and balls,…
• DMO will evaluate the plant to ensure compliance with QC
plan
• Plan indicates how they are to batch high slump concrete
• DMO can verify if the plant was producing in compliance with their
plan
• If problems persist, the DMO may revoke the plants QC
plan
346 Changes
Beginning Jan 2016
Section 346-2 Materials
• 346-2.2 Type II cement replaced with Type II (MH), moderate
heat
• Required for mass (v/sa ≥ 1.0) concrete placements
• 346-2.3
• Fly ash or slag is required for all concrete.
• Not required for dri-cast precast elements.
New cement type is added, Type IL
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• Ternary blends allowed in all classes of concrete
• Highly reactive pozzolans (HRP) are identified (SF, Metak, UFFA)
346-3.1 General
• Acceptance of concrete is based on contract
requirements.
• Say contract requires C-II, 3400 psi
• A higher strength (C-IV, 5500 psi) is substituted
• Compressive strength results are 5,100 psi
• Does the concrete pass or fail?
346-3.1 General
• 5,100 psi meets contract requirements
• Concrete is accepted at FULL PAY
• But wait a minute !!!!
346-3.1 General
• The minimum required f ’c for the C-IV was 5,500 psi - only
achieved 5,100 psi
• Notify DMO that concrete did not meet mix design target strength
• DMO will investigate concrete producer
• QC Program issue at the plant, not an acceptance issue
346-3.2 Drilled Shaft Concrete
• Allows for slump loss test to be performed in the lab
• Less than 30 cubic yards, or
• Less than a maximum elapsed time of 5 hours
• Concrete placed in hot weather (temp > 85F) perform
slump loss test at hot weather conditions.
• DMO will assist
346-3.3 Mass Concrete
• Mass concrete is indicated on the plans (v / sa ≥ 1.0)
• Control concrete temperature
• Max 180F (> 180F, what happens?)
• ΔT≤ 35F (interior to exterior)
• If exceeded, contractor must take action
• How would contractor control temp???
346-3.3 Mass Concrete
• New language is added for multiple elements;
• One plan for All elements;
• Same size,
• Same mix,
• Same R value
• Ambient temp within minus 10F or plus 5F
• All need to be instrumented
• Why would we want all instrumented???
346-3.3 Mass Concrete
• Not required for drilled shafts used to support;
• Sign, signals, lighting or intelligent transportation structures
• Must meet the following for substructures;
• X sect. area ≤ 6’
• R value = 2.5
• Environment; SA or MA
• Mix in compliance with 346-2.3 for mass elements
• Total cementitious content ≤ 752 lbs.
• If max core temp or diff. temp is exceeded, plan is revoked
346-3.3 Mass Concrete
• Construction Staff must inspect all mass concrete
elements:
• after forms have been removed and
• prior to the element being backfilled.
• LOOK for Cracks!
346-5: Sampling and Testing
Methods
• Table 5 –
• If pressure meter is used, must have an aggregate
correction factor on mix design
• Curing facilities have capacity to hold all QC and
V cylinders
• V will use same air meter and cylinder size as QC
• Can take entire concrete sample at one time from
middle of load, ASTM C172
346-7 Mixing and Delivering
• Transit time, reject trucks exceeding the maximum transit
time
• Typically 90 minutes (agitator truck, HRWR)
• DMO may approve longer haul times
• Construction personnel need to notify the District
Materials Office of concrete placements
• To witness complicated placements
• Mass concrete
• Structural Drilled Shafts
• To IA, QC and V technicians
346-7 Mixing and Delivering
• 346- 7.3 Batching at the Site: This is indicated in the
Contractors QC plan.
• Contractor may have a batch plant at the project
• 346-7.6 Adding Water:
• Any water missing from the saddle tanks is;
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Assumed to be in the batch and
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Is added to the jobsite water on the delivery ticket and included in
the w/c ratio.
346-7 Mixing and Delivering
• Changes
• No water added to truck after 130 revs on the drum
• Truck has started to place within 90 min.
• has 15 additional min to complete the placement
• If 120 min haul time already approved, no additional time
allowed.
Bottom Up Pumping
346-8 Plastic Concrete Sampling and Testing
• Truck Mixer Identification Card?
• Inspector should request to see this.
• If no card, truck cannot deliver for FDOT - reject concrete
• Contractor is responsible to remove this if there are deficiencies with
the truck that cannot be repaired immediately.
• Contractor to forward id card to DMO
• When any 5 loads within 2 days are outside the specified tolerancesnotify DMO, they will suspend QC plan of the plant!
346-9: Acceptance Sampling and
Testing
• When a mix is used for a different application, the
LOT is defined by that application.
• Class II concrete is placed for use as Class I Pavement.
• Lot size for this Class II concrete is defined as 2000 sy, or 1
days production, since its placed as pavement
346-9: Acceptance Sampling and
Testing
• Acceptance is typically a 50 yd3 lot size
• 346-9.2.1 Contractor may request to reduce
acceptance tests to 100 yd3 if there is consistency in
strength tests (same mix, same plant, same contract)
• Need 2 Sdev (95% of data) above the minimum
required strength based on the class of concrete
346-9: Acceptance Sampling and
Testing
• For Class IV or higher, need ten consecutive strength
tests to determine reduced frequency
• For Class III or lower, need five consecutive strength
tests to determine reduced frequency
• Lab providing the data must be approved,
• Must meet Section 105
Why would a concrete producer not want the
contractor to use the “reduced frequency” option?
Performance Based Pavement
• Section 350 DEV allows contractor more flexibility,
and responsibility
• 350 DEV Projects
• I-4, from SR 44 to I-95, Deland
• I-275, area north of I-4, Tampa
• 9B, Jacksonville
350 DEV Mix Design
 Minimum compressive strength (4000 psi)
 W/cm ≤ 0.50
• Material sources must be approved
◦ Can use a commercial mix
◦ Mix will be approved by DMO;
 Requires LIMs entry
350 DEV Mix Design
• Plant approval
• Central batch plant
• Develop Sdev for plant with 30 data points
• Previous data - OK
• Provides the overdesign needed for mix approval
• Ready mix plant
• Overdesign is still required – Why??
350 DEV Equipment
 Slip form paver;
◦ On board vibrators
 frequency is calibrated
 recording device used to monitor frequency
 Forms may be used where needed;
◦ Must be steel, straight and designed for concrete.
◦ Curing compound spraying equipment, must be
mechanically driven.
350 DEV Placing Concrete
• Thickness cannot deviate by more than ½ inch
• Delivery ticket
• Still required (modified tix) for contractors using central
batch plant, unit price/syd
• Required for each load of concrete
350 DEV Sampling and Testing
• QC is temperature control of the concrete and
making and curing cylinders
• Cylinders may need to be vibrated
• A LOT is 2000 syd or 1 days production
• Partial LOTs (<500 syd) are combined with previous
LOT for acceptance purposes.
• Testing may be reduced to 4000 syd, with
consistent strength data (similar to reduced
sampling frequency)
350 DEV Finishing and Curing
• Finish the concrete with a burlap drag.
• Curing will be with white pigmented curing compound
• 1 gal/ 200 ft2
• If forms are used, apply curing compound to the sides of the
concrete when forms are removed.
• Saw the joints when the sheen has left the concrete
surface.
• Soff-cut saw or early entry saws - OK
• We want to control where the concrete cracks!
350 DEV Thickness
• Core the pavement to determine thickness of
concrete (ASTM C174), need 2 cores
• The department has trialed the Probe
Method (FM 5-596) to verify the thickness
• Use 12 points to verify thickness by the probe method.
• The hope is to use this to verify thickness, instead of
coring
Concrete Probe (thickness)
Changes to Section 353
• Concrete Pavement Slab Replacement
• Fibers may be used
• Concrete Mix Proportions;
• Use an approved mix with minimum 1,600 psi at opening to
traffic – determine by maturity meter.
• 3,000 psi at 28 days
• Contractor must place a demonstration slab
New 353
• Batching and Mixing Concrete;
• All materials added at batch plant except for accelerator
• Plastic properties verified at job site prior to addition of
accelerator
• Accelerator is added
• Amount of accelerator is indicated on delivery ticket
• Amount cannot exceed the manufacturer’s recommended
dosage
• Based on Tech Data sheet of manufacturer.
New 353
• Test Requirements;
• Plastic properties verified at job site prior to addition of
accelerator, follow 346-8 and 346-9
• Accelerator is added;
• Acceptance cylinders are made
• QC and V comparison samples are made in accordance
with 346-9.
• 3 cylinders for testing, 1 for ‘hold’
New 353
• Uncontrolled Cracks are the responsibility of the
contractor
• “Controlled Cracks” are defined as;
• “cracks that are designed to occur at specific locations
based on the pavement design. All other cracks in the
pavement are uncontrolled cracks”
• Uncontrolled cracked slabs are repaired by removing and
replacing across the full width and depth of the slabs
New 353
• Curing
• Use a Type I curing compound with a fugitive dye. Why?
• Apply within one- half hour of finishing
• Apply two layers of a white burlap- polyethylene curing
blanket
• Blanket stays in place until the Maturity Meter indicates
slab has met the minimum 1,600 psi.
New 353
• Joints
• Bond breaker is approved by the Engineer
• Applied to vertical faces of existing concrete
• Dowels; new language indicating orientation of dowels and
the allowable tolerance from parallel to the travel surface.
• Epoxy for dowels
• Dispensed from a dual cartridge system
353 Concrete is almost ready to be placed.
What’s missing?
Sampling Steel on the project
Reinforcement?
Post tensioning strand?
Stressing bars?
Sampling Reinforcing Steel
• Project personnel need to collect;
• 3 pieces, at randomly selected
• Mill Certificate w/ Buy America clause
• Cert in envelope, firmly attached to steel
• Do not cut sample with a torch!
• Send 1 bar, hold 2 (a check may be needed)
• A bar not selected by you is not random!
• No ‘test bars’, ‘splice bars’, or ‘FDOT test samples’
Sampling Reinforcing Steel
• Job Guide Schedule indicates amount of steel on the
job
• Look for total quantity (usually in lbs)
• Take the total ÷ 2000 lbs to get tons
• Divide that number by 80 to get the samples needed
• Randomly sample during project
• Not while project is being certified!
Sampling Reinforcing Steel
• Rebar (#3 to #18)
• A sample is 3 bars – 7’ long –
• 1 per 80 tons
• Sample most frequently used bar size
• Bend and tensile test
• If bar passes, give the other 2 bars to contractor,
or discard.
• Foreign bars indicate country of origin
Sampling Steel Strand
• 7 wire strand (prestress and PT)
• A sample is 3 strands, 5’ long
• Mill cert in an envelope attached to the sample
• 1/ shipment
• Send 1, hold 2 (may need a check sample)
• Again, must be a random sample
Sampling Steel Stressing Bars
• Threaded stressing bars
• A sample is 3 bars, 4’ long
• Mill cert in an envelope attached to the sample
• 1/ heat/ shipment/ job or JGS
• Send 1, hold 2
• Random, selected by you
Sampling Steel - Review
• Take 3 pieces of steel from project at a
frequency indicated in JGS.
• No torching of bars
• Send 1 to SMO, hold 2
• Send mill cert in envelope firmly attached to
the sample
• Sample to match mill cert
Precast Concrete Drainage
Structures
A Brief Introduction of on-site
acceptance of products
Contents
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Purpose
References
Plant Qualification
Producers with Accepted Quality Control Programs
Pre-shipment Requirements
 Quality Control Stamp
 Shipping Documentation
 Delivery Acceptance Requirements
 Points of contact for any questions or concerns
 Questions
Purpose
To discuss the inspection
requirements for acceptance of
precast concrete drainage structures
at the project site.
References
 Materials Manual Sections 6.2 & 6.3 Volumes I & II.
 Design Standards Topic No. 625-010-003, Florida Department of Transportation and
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any revisions to this document.
American Society for Testing and Materials (ASTM) Standard Test Methods and
Specifications, Philadelphia, Pennsylvania.
American Association of State Highway and Transportation Officials (AASHTO), Part I
Specifications, and Part II Tests, Washington, D.C.
Florida Department of Transportation Standard Specifications for Road and Bridge
Construction.
Approved Products List, Florida Department of Transportation.
Field sampling and Testing Manual, Florida Department of Transportation.
Code of Federal Regulations (CFR) and Federal-Aid Policy Guide (FAPG)
Plant Qualification
• Before a precast plant can produce drainage structures and box culverts for
FDOT projects it must have an approved Quality Control Plan (QCP).
• Plant Qualification Review Process:
• Submit QCP
• Review QCP
• Plant qualification review
• Approve QCP
• Placement of plant on Department’s list of producers with
accepted quality control programs.
Producers with Accepted
Quality Control Programs
ftp://ftp.dot.state.fl.us/fdot/smo/website/sources/precast-pipe.pdf
Quality Control Stamp
• The Quality Control Manager or quality control
personnel working under the direct supervision of
the Quality Control Manager shall stamp each
Structure prior to its shipment to the project site.
The quality control stamp indicates that the Plant
certifies that the Structure was manufactured in
conformance with the Plant’s quality control Plan.
Producer’s Quality Control
Stamps
http://www.dot.state.fl.us/statematerialsoffice/quality/programs/qualitycontrol/plantstamps/index.sht
m
Shipping Documentation
• Plant provides a notarized statement at the beginning of each
project to the Project Administrator from a responsible company
representative certifying that the Plant will manufacture the products
in accordance with the requirements set forth in the Contract
Documents and Plant’s approved quality control plan.
• Each shipment of precast concrete products to the project site is
accompanied with a signed or stamped delivery ticket providing the
description and the list of the products.
• Each delivery ticket shall be on the Plant's letterhead and shall
include as a minimum:
• Project Number
• Date shipped
• Serial Number of the Structure section
Delivery and Acceptance
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Review delivery documentation.
Locate and identify proper markings on structure.
Inspect structure for any major or minor defects.
Accept structures that are in compliance with the
requirements of the Contract Documents.
• Reject any structures that are damaged or have any
other defects.
Points of Contact for
Any Questions or Concerns
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Contractor Quality Control Personnel
Project Administer
Precast Producer
District Materials Office
District Construction Office
State Materials Office
Questions
New Research and Concepts
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ICC
RCC
SCC
Ground Glass
GTR
Internal Curing of Concrete
• Use light weight fine aggregate
• About 20% of the total fines in mix
• Provides additional moisture in the mix
• Does not “bleed” out during normal curing
• Remains to provide the additional moisture needed for long term
hydration
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Used by pozzolans long after 28 day strength is determined
Reduce water and have same slump as a control mix
Reduction in shrinkage cracking
Increase in long term strength
Roller Compacted Concrete
• Use cement, good blend of coarse aggregate and a little
water (dry mix)
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Batch materials in a pug mill
Delivered in a dump truck
Placed into a spreader or a high density asphalt paver.
Rolled to a specific density with a steel wheel roller.
Can be smoothed with a rubber tire roller if needed
Finished surface may be rough.
Self Consolidating Concrete
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Very fluid, but thixotropic
Self levels
MM 8.4 - slump flow of SCC is 27” ± 2.5”
Very finicky
• Sensitive to temperature
• Changes to water
Lab Test Methods for SCC
• To verify and approve the mix;
• ASTM C 1610 - Static Segregation of SCC using Column Techniques
• ASTM C 1712 – Dynamic Segregation of SCC (new device)
Static Segregation Test
(ASTM C1610)
Dynamic Segregation Test
Field Test Methods for SCC
• To accept concrete at the project;
• ASTM C 1611 - Slump Flow of SCC
• ASTM C 1621 - Passing Ability of SCC by J-Ring
• Conventional tests;
• Percent air, ASTM C173, or C231
• Temperature
• w/c ratio
Slump Flow (ASTM C1611)
Ground Glass in Concrete
• Glass not used in the past- due to ASR
• What is ASR?
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New research indicates if ground small enough, no ASR
The ground glass actually reacts like fly ash
Can use any color glass, except for Pyrex (very reactive)
Glass has to be cleaned before use
• No residual sugars, other contaminates
Ground Tire Rubber in Concrete
• Several particle sizes were tried
• The best size is a crumb rubber, similar to the size used in
asphalt (≈30 to 60 microns)
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Use about 20% maximum replacement of fine aggregate.
Provides a reduction in strength (less brittle)
The MOE is lower, so slabs are more ‘flexible’
The effort helps to reduce the amount of rubber tires in
landfills.
My Request from You
• In my evaluation, tell me:
• About concrete topics that should be discussed in this
session
• Are there portions of 346 that are confusing and need
clarification?
• Is there additional concrete training or information that are
of special interest to you or others in your work group?
Thanks for your time!