1. Concrete Materials Information for Construction Academy
Michael (Mike) Bergin, P.E.,
State Structural Materials Engineer
FDOT, State Materials Research Park
August 20, 2014

2. Topics Fundamentals of Good Concrete
A better understanding of w/c ratio
Slump of Concrete
Water added at the site
Penalties
Available water for hydration
Drilled shaft concrete and slump loss
Mass concrete
Specification changes

3. Topics New Ideas, Concepts and Research
346 changes based on 1/15 lettings
Performance Based Concrete Pavement, Section 350
Slab Replacement Concrete, Section 353 (proposed changes)
Sampling Steel
New Ideas, Concepts and Research
Internal Curing
Roller compacted concrete (RCC)
Self consolidating concrete (SCC)
Ground Glass in Concrete
GTR in Concrete

4. Water Cementitious Materials Ratio and the Velcro Approach
What is the w/c ratio ?

5. 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

6. 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

7. High w/c Ratio Water Increase in ‘bleed water’
Increases initial volume
Collects in lens under the surface
Lens is a problem when traffic is placed on it
Lens may be under reinforcement
Increase in ‘bleed water’
Delays finish work
Unwanted surface conditions and less durable concrete
Shrinkage
Surface cracking
Scaling

8. High w/c Ratio Fines help reduce bleed water
Cementitious plus fine aggregate
60% coarse/40 fines is a good ratio.
Rate of bleed water evaporating is regulated by external conditions (weather)
A need for curing

9. 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
Still need some bleed water
More durable concrete
Increase in density
Less surface problems on finished concrete

10. Add Fly Ash or Slag
We have additional fine particles for packing and to provide pozzolanic activity
Particle packing helps minimize voids in the paste
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.

11. Add a low w/c ratio 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

12. Water/Cement Ratio High W/C Low W/C Hydration Hydration
Cement particle
Cement particle
High W/C
Low W/C
Hydration
Hydration

13. High w/c ratio equates to lots of shrinkage cracking

14. Shrinkage Cracking

15. 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

16. TOLERANCE SLUMP RANGE (3”)
REJECT
1-1/2” DRY
1-1/2” WET
REJECT
ACCEPT – WATER MAY
BE ADDED
TARGET
SLUMP

17. When the Contractor adds water…
Determine the slump
If within the Target Slump Value
Perform other plastic properties;
Air
Temperature
Determine w/c ratio

18. 346-6: Control of Quality
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
Test each load to ensure only concrete meeting the specification is placed. The Engineer will take into consideration trucks already in route from the concrete production facility after the facility has been notified. If the Contractor does not implement adjustments at the earliest possible time, the Engineer will reject the concrete and terminate further production until the Contractor makes corrections.

19. 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

20. The discussion of w/c ratios, slump, slump loss, and elapse time are a major concerns for drilled shafts.

21. 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.
to get slump, producer uses water reducing admixtures and water.

22. Drilled Shaft Concrete should not look like this!

23. Or this!
Q: What is the minimum clear cover (in inches) over steel?

24. 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?

25. High Slump Concrete
high slump concrete (≥7.5 ”) 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

26. 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

27. For lettings beginning Jan 2015
346 Changes
For lettings beginning Jan 2015

28. Section Materials
Type II cement replaced with Type II (MH), moderate heat
Required for mass (v/sa ≥ 1.0) concrete placements
Fly ash or slag is required for all concrete.
Not required for dri-cast precast elements.
New cement type is added, Type IP
Ternary blends allowed in all classes of concrete
Highly reactive pozzolans (HRP) are identified (SF, Metak, UFFA)

29. 346-3.1 General Substituting higher strength for lower strength
Can be used in two applications if approved by the Engineer
1. For Structural Concrete a Higher Strength can be used in lieu of Lower Strength
2. Structural Concrete can be used in lieu of Non-Structural Concrete

30. 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?

31. 346-3.1 General 5,100 psi meets contract requirements
Concrete is accepted at FULL PAY
But wait a minute !!!!

32. General
The minimum required for the C-IV was 5,500 psi - only achieved 5,100
Notify DMO that concrete did not meet mix design target strength
DMO will investigate concrete producer
QC Program issue, not acceptance issue

33. 346-3.1 General Section 347 governs non-structural concrete
Do not test concrete based on 346
Acceptance based on delivery ticket, signed by batcher and QC certifying minimum 2,500 psi

34. 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 an maximum elapsed time of 5 hours
Concrete used during the summer, temp > 85F, perform slump loss test at hot weather conditions.

35. 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)
Interior stays hot, exterior cools
If exceeded, contractor must take action
How would contractor control temp???

36. 346-3.3 Mass Concrete New language is added; Same size elements
One plan can be used
2 elements could be placed at one time
2nd needs to be started within 1 hour of the first.
Both need to be instrumented
Why would we want both instrumented???

37. 346-5: Sampling and Testing Methods
Table 5
Added testing requirements for self consolidating concrete (SCC)
Also indicates that QC will use the same type of air meter as V.
Static Segregation of Self Consolidating Concrete using Column Techniques ASTM C 1610
Slump Flow of Self Consolidating Concrete ASTM C 1611
Passing Ability of Self Consolidating Concrete by J-Ring ASTM C 1621
Use the same type of meter for QC tests as the Department uses for Verification testing. When using pressure type meters, use an aggregate correction factor determined by the concrete producer for each mix design to be tested. Record and certify test results for correction factors for each type of aggregate at the concrete production facility. **The Department will use the same size cylinder molds as the Contractor uses for his QC tests.. Use 4 x 8 or 6 x 12 inch cylinders for determination of the compressive strength.

38. 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

39. 346-7 Mixing and Delivering
Transit time, reject trucks exceeding the maximum transit time
Typically 90 minutes (agitator truck, HRWR)
Construction personnel need to notify the District Materials Office of concrete placements
To witness complicated placements
Mass concrete
Structural Drilled Shaft
To IA QC or V technicians

40. 346-7 Mixing and Delivering
Mixing at the Site: This is indicated in the Contractors QC plan.
Adding Water:
Any water missing from the saddle tanks is;
Assumed to be in the batch and
is added to the jobsite water on the delivery ticket and included in the w/c ratio.

41. 346-7 Mixing and Delivering
Changes
No water added to truck after 130 revs
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.

43. 346-7 Mixing and Delivering
Sample Location: Sample Correlation required when contractor can’t sample at the point of final placement.
Need 5 samples, one sample per load
What is a sample?
DMO will help with this process

45. Bottom Up Pumping

46. 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.
He is to forward id card to DMO
When any 5 loads within 2 days are outside the specified tolerances- notify DMO, they will suspend production from the plant!

47. 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, its placed as pavement

48. 346-9: Acceptance Sampling and Testing
Acceptance is typically a 50 cyd lot size
Acceptance Tests can be reduced 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
When ten consecutive strength test results from a Class IV or higher class of concrete are produced at the same concrete production facility, on a given Contract have all been verified and have attained an average strength greater than two standard deviations above the specified minimum, then the LOT may represent a maximum production quantity of 100 yd3. In addition, when five consecutive strength test results from a Class III or lower class of concrete is produced at the same concrete production facility on a given Contract have all been verified and have attained an average strength greater than two standard deviations above the specified minimum, the LOT may represent a maximum production quantity of 100 yd3.
The average of the consecutive compressive strength test results, based on the class of concrete, can be established using historical data from the previous project. The data must also represent the same prime/subcontractor. The last test from the previous job must be within the last 60 calendar days or may also be established by a succession of samples on the current project. Only one sample can be taken from each LOT. Test data must be from a laboratory meeting the requirements of 6-9.
If at any time a strength test is not verified and/or the average strength of the previous ten or five consecutive samples based on the class of concrete described above, is less than the specified minimum plus two standard deviations, the maximum production quantity represented by the LOT will return to 50 yd3.

49. 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
Data must come from an approved lab (Section 105)
When ten consecutive strength test results from a Class IV or higher class of concrete are produced at the same concrete production facility, on a given Contract have all been verified and have attained an average strength greater than two standard deviations above the specified minimum, then the LOT may represent a maximum production quantity of 100 yd3. In addition, when five consecutive strength test results from a Class III or lower class of concrete is produced at the same concrete production facility on a given Contract have all been verified and have attained an average strength greater than two standard deviations above the specified minimum, the LOT may represent a maximum production quantity of 100 yd3.
The average of the consecutive compressive strength test results, based on the class of concrete, can be established using historical data from the previous project. The data must also represent the same prime/subcontractor. The last test from the previous job must be within the last 60 calendar days or may also be established by a succession of samples on the current project. Only one sample can be taken from each LOT. Test data must be from a laboratory meeting the requirements of 6-9.
If at any time a strength test is not verified and/or the average strength of the previous ten or five consecutive samples based on the class of concrete described above, is less than the specified minimum plus two standard deviations, the maximum production quantity represented by the LOT will return to 50 yd3.

50. 346-9: Acceptance Sampling and Testing
Need prior approval of the Engineer
Provide data prior to approval
CPAM has instructions on the process
Usually includes the DMO to help verify data.

51. Why would a concrete producer not want the contractor to use the “reduced frequency” option?

52. 346-10 Investigate Low Strength Concrete
The 10% (below minimum) was removed and is now 500 psi only.
If the strength of the concrete is within 500 psi below the minimum required;
the contractor cannot core to determine strength
a pay penalty is applied .
Why do we have this caveat??

53. Performance Based Spec. for Pavement
Complete rewrite of Section 350
PB 350 Pilot Projects
I-4, from SR 44 to I-95, Deland
I-275, area north of I-4, Tampa
9B, Jacksonville

54. PB 350 Mix Design Compressive strength (4000 psi)
W/cm not to exceed 0.50
Material sources must be approved
Can use a commercial mix
Mix will be approved by DMO;
Requires LIMs entry

55. PB 350 Mix Design Plant approval Central batch plant Ready mix plant
Develop Sdev for plant with 30 data points
Previous data - OK
Provides the overdesign needed for mix approval
Ready mix plant
Overdesign still required – Why??

56. PB 350 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.

57. PB 350 Placing Concrete
Place concrete by single lane width or full width of the combined travel lanes
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 ready mix
Addition of water does not apply unless concrete is delivered by ready mix truck

58. PB 350 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

59. PB 350 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.
We want to control where the concrete cracks!

60. Add some other pics of shrinkage and other cracking
Stress Crack

61. PB 350 Thickness
Core the pavement to determine thickness of concrete (ASTM C174), need 2 cores
The department will trial the use of the Probe Method (FM) 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

62. Concrete Probe (thickness)

63. 350 Opening to Traffic Concrete strength ≥ 2200 psi
Cylinders cured similar to the slab concrete.
Maturity Method can be used to indicate concrete strength
For opening to traffic
Not for acceptance

64. Changes to Section 353 What is 353 Concrete?
Revising this specification to address current problems
In some cases- high rate of cracked slabs in new concrete
Slab replacement projects are on-going or scheduled to start in almost every district

65. 353 Concrete is almost ready to be placed.
What’s missing?

66. 353 Issues
Opening to traffic, contractor’s major goal (usually night work)
If he places concrete until 4 AM
Does not provide curing time for concrete
Can’t limit truck traffic
Can we limit contractor?
Limit means and methods of contractor?
Require a minimum curing time?

67. 353 Issues Mixes are extremely “hot”
Initial set, 15 to 30 min.
Accelerators are used and are typically placed outside of recommended dosage rates
Revisions needed to ‘cool’ the concrete

68. Now this is HOT!!

69. 353 Revision We’re revising Section 353 to;
Provide construction personnel with guidance on the placement and curing of 353 concrete
Ensure a low percent of failures.
Record admixture dosage
limit dosage to max dosage on tech data sheet.

70. Sampling Steel on the project
How is reinforcement steel sampled? How is post tensioning strand sampled? How are stressing bars sampled?

71. Sampling Steel Project personnel need to collect;
3 pieces, at random by you.
Mill certificate w/ Buy America clause
Cert should identify the steel
Place in envelope, firmly attached to steel
Do not cut sample with a torch!
Send 1 bar, hold 2 (a check may be needed)
Any bar not selected by you is not random!
No ‘test bars’, ‘splice bars’, or ‘FDOT test samples’

72. Sampling 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!

73. Sampling Steel Rebars (#3 to #18) A sample is 3 bars – 7’ long –
Mill cert in an envelope attached to the sample
1 per 80 tons
Submit 1 bar to SMO, hold 2
Sample most frequently used bar size
If bar passes, give the other 2 bars to contractor, or discard.
Foreign bars indicate country of origin

74. Sampling Steel Post tension 7 wire strand
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

75. Sampling Steel 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

76. 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 attached to steel
Sample to match mill cert

77. Internal Curing of Concrete
Use light weight 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 to provide long term hydration
Used by pozzolans long after 28 day strength is determined

78. Roller Compacted Concrete
Use cement, good blend of coarse aggregate and a little water
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.

81. Self Consolidating Concrete
Very fluid
Self levels
Very finicky
Sensitive to temperature
Changes to water
Water additions to load
Changes to aggregate moisture

83. Lab Test Methods for SCC
To verify and approve the mix;
ASTM C Static Segregation of SCC using Column Techniques
ASTM C 1712 – Dynamic Segregation of SCC (new device)

84. Static Segregation Test (ASTM C1610)

85. Dynamic Segregation Test

86. Field Test Methods for SCC
To accept concrete at the project;
ASTM C Slump Flow of SCC
ASTM C Passing Ability of SCC by J-Ring
Conventional tests;
Percent air, Air or pressure meter
Temperature

87. Slump Flow of SCC (ASTM C1611)

88. Passing Ability of SCC through
the J Ring (ASTM C1621)

89. Chap.8.4 of Materials Manual
Prestressed and Precast concrete
A revision to 8.4 allows a change in the slump flow of SCC from 25” to 27” ± 2.5”
Provides a more fluid concrete to reduce bug holes and voids in highly reinforced prestressed elements

90. Ground Glass in Concrete
Glass not used in the past- due to ASR
What is ASR?
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

91. Ground Tire Rubber in Concrete
Several particle sizes were used
The best size is a crumb rubber similar to the size used in asphalt.
Use about 20% maximum replacement of fine aggregate.
Provides a reduction in strength (less brittle)
The MOE is lower, so slabs are able to move a little
The effort helps to reduce the amount of rubber tires going into landfills.

92. LIMS Updates MAC is the new system, and its coming!
But if you have any questions about how to enter a sample in LIMs,….
The SMO is analyzing project data on an annual basis and reporting the results to FHWA as part of the annual Independent Assurance program. For concrete, we will be reviewing compressive strength sample results approved between July 2007 and June We will be considering failures and whether or not the results compared and if they did not, if Resolultion was performed.
In order to do this, I am running reports on LIMS data. Initial data review is showing us that in many cases, the data is incorrect or incomplete. It is essential that this data is logged correctly for this type of analysis.
Mix Design Numbers – Make sure you use the right mix design number. The verification is performed per mix design. We’re seeing a lot of cases where Verification and QC are not even the same mix design.
That means if you change mix designs, you must restart your lot
The biggest issue with plant numbers is the fact that aggregate mines have no dash and concrete plants have a dash and are different facilities in LIMS.
We’re also seeing test results that don’t make a lot of sense. When we try to reconstruct the results from the raw data, we see that the tests containing that data have been killed off the sample. Don’t approve concrete samples that do not have all the data entered.
As we are identifying the problem areas with the data, we are also working on ways to improve the data integrity and user friendliness. When the Concrete Mix Design Module is implemented, we will have a way to assign pass/fail criteria on concrete samples. You will see individual tests results as passing or failing instead of “no limits specified”. We’re working on material specific login screens for concrete and asphalt. When those are implemented, we’ll have a way to filter more data like plant numbers and mix design numbers. The users will see less of what they don’t need and that will mean many of these issues will improve. In the mean time, we need you to be vigilant as PAs when you’re approving samples to make sure all the sample and test data is correct.

93. LIMS
Look up the information at; “Instructions for Samples for Structural Materials” on the SMO website

94. 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?

95. Thanks for your time!