Nevada Infrastructure Concrete Conference, Oct. 2008 Real Solutions for Concrete Mix Designs - James M. Shilstone, Jr. www.shilstone.com 1 Real Solutions for Real Solutions for Concrete Mix Design Concrete Mix Design - James M. Shilstone, Jr. James M. Shilstone, Jr. “ Either you Either you’ re part of the solution, re part of the solution, or you or you’ re part of the problem. re part of the problem.” -Eldridge Cleaver Eldridge Cleaver Pogo - 1971 Know your needs Know your needs – Write your spec Write your spec Strength Shrinkage Permeability Freeze-thaw resistance Abrasion resistance ASR resistance Sulfate resistance Specs in balance Specs in balance Low w/cm Low permeability No cracks Higher cement More heat Greater shrinkage Higher cost Concrete is Part of a System Concrete is Part of a System
Transcript
Nevada Infrastructure
Concrete Conference, Oct. 2008
Real Solutions for Concrete Mix Designs
- James M. Shilstone, Jr.
www.shilstone.com 1
Real Solutions for Real Solutions for
Concrete Mix DesignConcrete Mix Design
-- James M. Shilstone, Jr.James M. Shilstone, Jr.
““Either youEither you’’re part of the solution, re part of the solution,
or youor you’’re part of the problem.re part of the problem.””
--Eldridge CleaverEldridge Cleaver
Pogo - 1971
Know your needs Know your needs ––
Write your specWrite your spec
Strength
Shrinkage
Permeability
Freeze-thaw resistance
Abrasion resistance
ASR resistance
Sulfate resistance
Specs in balanceSpecs in balance
Low w/cm
Low permeability
No cracks
Higher cement
More heat
Greater shrinkage
Higher cost
Concrete is Part of a SystemConcrete is Part of a System
Nevada Infrastructure
Concrete Conference, Oct. 2008
Real Solutions for Concrete Mix Designs
- James M. Shilstone, Jr.
www.shilstone.com 2
““He that is good with a hammer He that is good with a hammer
tends to think everything is a nail.tends to think everything is a nail.””
-- Abraham MaslowAbraham Maslow
THOU THOU THOU THOU SHALTSHALTSHALTSHALT
HAVE A LOWHAVE A LOWHAVE A LOWHAVE A LOW
WATERWATERWATERWATER----
CEMENTCEMENTCEMENTCEMENT
RATIO.RATIO.RATIO.RATIO.
How did they get 0.26 w/c?How did they get 0.26 w/c?
• PCA Bulletin 29 – “The Nonevaporable
Water Content of Hardened Portland-Cement Paste”–TC Powers
• Grind a cement sample
in water for 4-5 days
• Mix a small bit of cementin a large volume of water
Results of a low Results of a low w/cw/c
• Add more cement
• Generate more heat
• More thermal expansion
• More autogenous shrinkage
• More cracking
• Greater alkalis (ASR potential)
• Higher cost
• Less sustainable concrete
W/C vs. Strength W/C vs. Strength –– DCCM 2DCCM 2
We have found We have found nono
pavement failures in the pavement failures in the
U.S. due to low concrete U.S. due to low concrete
strength.strength.
Nevada Infrastructure
Concrete Conference, Oct. 2008
Real Solutions for Concrete Mix Designs
- James M. Shilstone, Jr.
www.shilstone.com 3
Cement efficiencyCement efficiency
400 450 500 550 600 650 700
Plain cement Cement + Admix
Cement + Ash Cement + Admix + Ash
What problems do we face?What problems do we face?
• Cracking
• Sulfate attack
• Chloride attack
• ASR
• Freeze-thaw
• Abrasion
Types of crackingTypes of cracking
• Plastic shrinkage (bleeding & evaporation)
• Drying shrinkage (excess water)
– Differential moisture shrinkage (curling)
• Thermal shrinkage
– Differential thermal shrinkage
• Autogenous shrinkage
• D-cracking
• Stress cracking
Drying shrinkageDrying shrinkage
• Water has 2 purposes
– Combine with cement
– Lubricate the mix
• Drying shrinkage – excess water
• Total water is the key
• Curling – finer mixes slow bleeding
• Increasing cement can increase thermal
and autogenous shrinkage
Keys to decreasing waterKeys to decreasing water
• Admixtures are a partial solution (can
increase shrinkage)
• Increase maximum aggregate size
– Soft aggregate / cleavage planes
– D-cracking
• Increase coarse aggregate
• Optimize aggregate grading (particle shape and texture affect water demand)
WATER DEMANDWATER DEMAND
Nevada Infrastructure
Concrete Conference, Oct. 2008
Real Solutions for Concrete Mix Designs
- James M. Shilstone, Jr.
www.shilstone.com 4
RESULTS OF GAP GRADINGRESULTS OF GAP GRADING HAYSTACK HAYSTACK -- ““OptimumOptimum””
Hydration of Portland CementHydration of Portland Cement
Cement + Water
C-S-H + Ca(OH)2 + Other
C
C
C
C
C
C
C
Hydration of Portland CementHydration of Portland Cement
PozzolanicPozzolanic Reaction in ConcreteReaction in Concrete
Ca(OH)2 + Pozzolan
more….. C-S-H
C C
CC
C
Effect of Effect of PozzolanicPozzolanic ReactionReaction
Nevada Infrastructure
Concrete Conference, Oct. 2008
Real Solutions for Concrete Mix Designs
- James M. Shilstone, Jr.
www.shilstone.com 7
Marin Airport, PRMarin Airport, PR
RCP variations RCP variations –– 28 day28 day
500
1500
2500
3500
4500
5500
6500
7500
8500
5 sk 6 sk 7.5 sk 6 sk +
mfg sand
Cement Cem + ash Cem + air
Examine the combined mixExamine the combined mix
Alkali Silica ReactivityAlkali Silica Reactivity
• ASR Requirements
– Reactive silica
– High alkali pore solution
– Moisture
• Increasing cement increases alkalis
• Adding Class F fly ash or GGBFS can reduce ASR
• Lithium can mitigate ASR
FreezeFreeze--Thaw ResistanceThaw Resistance
• Original studies show need for 9% air as a
percent of mortar or 16% air in paste
• Air void spacing is critical
• Air Void Analyzer has shown importance
of bubble sizes
• FT damage is a function of paste and aggregate permeability
Does PCC need air entrainment?Does PCC need air entrainment?
A PCA publication contains the results of tests on high-strength concrete for frost and scaling resistance. All tests were made on concretes with portland cement as the only cementitious material. … Durability factors [for freeze-thaw] close to 100 were only achieved without air entrainment when the water-cement ratio was equal to or less than 0.35. … Resistance to scaling of non-air-entrained concrete was only achieved when the water-cement ratio was reduced to 0.25.
www.cement.org/bridges/br_QA_air_entrainment.asp
Air loss in concreteAir loss in concrete
• Losses of 3-5% reported behind paver or
after pumping
• Segregation of concrete during placement
and at vibrator trails
• Wisconsin DOT reports well-graded aggregate mixes tend to segregate less
• Ohio DOT reports well-graded aggregate
mixes tend to lose less air
Nevada Infrastructure
Concrete Conference, Oct. 2008
Real Solutions for Concrete Mix Designs
- James M. Shilstone, Jr.
www.shilstone.com 8
Abrasion resistanceAbrasion resistance
ICAR Study ICAR Study -- High fines High fines
manufactured sandmanufactured sand
• Proposed revision to ASTM C-33
• Allow up to 18% passing #200
• Dust of fracture only
• Can increase strength, decrease permeability
• Requires increased Super-P dosage
• Particle shape critical
Concrete & Concrete &
SustainabilitySustainability
Reducing ConcreteReducing Concrete’’s Impact s Impact
on Sustainabilityon Sustainability
• Consider entire life cycle
• Minimize impact on:
– Environment & Natural Resources
– Economics
– Aesthetics & Human Factors
• Cement production impact
• Transportation and processing impact
Current practices provide no Current practices provide no
incentive for innovation incentive for innovation ––
in fact, they stifle innovation.in fact, they stifle innovation.
• Incorporate recycled crushed concrete and reclaimed fresh concrete
• Encourage innovations
• Improve our understanding of concrete
PigmentsPigments PigmentsPigments
Shift to PerformanceShift to Performance
• Strength
• Modulus of elasticity
• Durability
• Low shrinkage/cracking
• Workability
• Stability & uniformity
• Protect reinforcing steel
Nevada Infrastructure
Concrete Conference, Oct. 2008
Real Solutions for Concrete Mix Designs
- James M. Shilstone, Jr.
www.shilstone.com 10
JEDDAH INTERNATIONAL JEDDAH INTERNATIONAL
AIRPORT AIRPORT -- 19751975
Severe mix segregation due to use of
aggregate grading standards in a region for which they were not suited.
Blind Men & the ElephantBlind Men & the Elephant
Traditional methods Traditional methods
causing problemscausing problems
Fixed weights of
variable materials result in a
variable product.
Design of Concrete MixturesDesign of Concrete MixturesD.A. Abrams, Lewis Inst. Bulletin 1D.A. Abrams, Lewis Inst. Bulletin 1
“It is a matter of common experience that the method of arbitrary selection in which fixed quantities of fine and coarse aggregates are mixed without regard to the size and grading of the individual materials is far from satisfactory.”
SmartPlant: The Next GenerationSmartPlant: The Next Generation
Aggregates Cement Fly Ash Admixtures
Materials Statistics Construction Maturity
SmartPlant
Fixed weights vs. AdjustedFixed weights vs. Adjusted
