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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 1 of 36
Prepared for the International Conference on Advances in ConcreteTechnology and Sustainability Issues
January 11, 2012, Quito, Ecuador
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 2 of 36
Compatibility and Incompatibility
Compatibility:
Every admixture present in a cementitious mixtureperforms its expected role without negative effects
Incompatibility:
Upon addition of admixture the concrete mixturedoes not behave as expected
The effects of admixtures can be:
detrimental(one or more admixtures do notperform as expected), or synergistic(combinationof admixtures performs better than when used
separately)
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 3 of 36
Robustness
The Robust system small variations in the
dosage of cement, water or admixture havelittle effect on the properties of the mixture
The Non-Robustsystem small variationsin the cement, water or admixture dosageresult in significant (sometimes dramatic)
changes in concrete properties
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 4 of 36
Courtesy of Csar A. Constantino, Titan America
Introduction
Lack of in-depth
knowledge of thematerialsinteractions maylead to
incompatibilitiesbetween variousingredients of the
mixture.
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 5 of 36
Admixture - Cementitious Materials
Interactions
Admixtures interact with components of
cementitious materials and influence cementhydration
Effects depend on:
Type and dosage
Composition
Sequence of addition
w/cm and temperature
Compatibility of admixtures (mixtures of admixtures)
Chemistry and specific surface area of cem. mat.
Courtesy of PCA
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 6 of 36
Background.
Materials incompatibility problems do not
occur in every concrete mixture. However,
when they arise, concrete may experience
undesirable effects, primarily prematurestiffening or severe set retardation.
In addition, difficulties with creating anadequate air void system may be
experienced, resulting in durability problems.
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 7 of 36
Types of Incompatibilities
Resulting from Direct Interactions
Cement-Admixture interaction Admixture-Admixture interaction
Resulting from Indirect Interactions
Typically involve interactions between 2 (ormore) admixtures and 1 or more component ofcementitious system
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 8 of 36
General Trends
Role of C3A:
Uncontrolled hydration of C3A is the major
reason for early stiffening behavior flash set.Delays setting time by preventing hydration of
silicates
Role of sulfates:Sulfate deficient systems - the rapid
hydration of C3A - flash set
Excessive sulfate nucleation and growth ofgypsum crystals - false setting behavior.
The level of soluble sulfates affectsadsorption of admixtures
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 9 of 36
General Trends
Role of alkalis:
Higher alkali cements react faster higherrate of stiffening higher slump loss
Dosage requirement of admixtures are
directly related to alkali content of thesystem.
Low alkali content systems exhibited lowerstability of air void system.
Low alkali cement & synthetic air entrainercombination resulted in severe strength loss
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 10 of 36
General Trends
Role of Fly Ashes:
May introduce reactive aluminate phases(like C3A and Kleins compound)Sulfates and alkalis in fly ash - disturb the
sulfate balanceHigh LOI class F (low lime) ashes
problems with generation and stability of airvoidsCalcium and magnesium ions in the fly ash
affect the air entrainment precipitates withAEAs
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 11 of 36
General Trends
Role of Admixtures:
High alkali contents -increase the amount ofpolycarboxylate type of superplasticizers -optimum fluidityLignin based admixtures reduce the solubility
of sulfates thus disturbing the C3A sulfatebalanceSugar content of the lignin based, water-
reducers linked to set retardation and air
entrainment difficultiesVR + Lignin based WRA - high entrapped air &
reduction in specific surface area of the airvoid system
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 12 of 36
Stages in Hydration Reaction
Iinitial hydration processes (015 min); IIinduction period (15 min4 h); IIIacceleration and setting (48 h); IVdeceleration and hardening (824 h);
Vcuring beyond 1 day.
Jolicoeur et al. 1994, ACI SP-148,pp. 63-88
Solubilization
of cementphases
Cement particles
become coatedwith layer ofhydrates
Critical role ofreactions of
aluminate andgypsum phases
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 13 of 36
Admixture-binder Interactions
Admixtures that modify the properties of
fresh concrete
may cause early stiffeningor retardation of the setting time.
Early stiffening is often caused by changes
in the rate of reaction between tricalciumaluminate (C3A) and sulfate in the cement.
Retardation can result from an overdose ofadmixture or from a decrease in the ambienttemperature. Both delay calcium silicates
hydration.
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 14 of 36
Example: Change in the Rate of
Hydration
Jolicoeur et al. 1994, ACI SP-148,pp. 63-88
Change in the rate of hydration at three different dosages of chemical admixture
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 15 of 36
Critical Role of Sulfate in Controlling
Hydration of C3A
Courtesy of C. Jolicoeur
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Forms of Sulfates
Forms of CaSO4 Solubility (g/100g)
CaSO4 . 0 H20Anhydrite*
0.63
CaSO4 . 1/2 H20
Hemihydrate0.71
CaSO4 . 2 H20Dihydate (gypsum)
0.21
K2SO4, Na2SO4 Highly soluble*Anhydrite can be synthetic (soluble) and natural (less soluble) .
Natural anhydrite has slower rate of solution than gypsum, hemihydrate orsynthetic (soluble) anhydrite
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 17 of 36
SO4 Supply/Demand Equilibrium
Courtesy of C. Jolicoeur
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 18 of 36
Superplasticizing Chemicals
Class Origin Structure (typical repeat unit)
Lignosulphonates
Derived fromneutralization,
precipitation, and
fermentation processes
of the waste liquor
obtained duringproduction of paper-
making pulp from woodSulphonated
melamine
formaldehyde (SMF)
or Polymelaminesulfonate (PMS)
Manufactured by normal
resinification of
melamine -formaldehyde
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 19 of 36
Superplasticizing Chemicals
Class Origin Structure (Typical Repear Unit)
Sulphonated
naphthalene
formaldehyde (SNF)
or Polynaphtalene
Sulfonate (PNS)
Produced from
naphthalene by oleum orSO3sulphonation;
subsequent reaction with
formaldehyde leads to
polymerization and the
sulphonic acid isneutralized with sodium
hydroxide or limePolycarboxylic ether
(PCE) orPolycarboxylate
(PC type)
Free radical mechanism
using peroxide initiators isused for polymerization
process in these systems
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 20 of 36
Sulfate related Cement Admixture
Incompatibility
Courtesy of C. Jolicoeur
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 21 of 36
Effect of Calcium Lignosulfonate (CLS)
Dodson, V. 1990. Concrete admixtures,
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PNS adsorption vs. Sulfate Content
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 23 of 36
Role of Alkalis
The soluble alkali content is a key
parameter when studying the compatibilitybetween a cement and a superplasticizer,
The addition of a small amount of sodium
sulfate can reduce the slump loss of asuperplasticized cement paste.
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 24 of 36
Compatibility between cements and PNS
and relation to adsorption behavior
Alkalies C1 C2 C3 C4 C5 C6Na2O eq. 0.31 0.52 0.92 0.74 0.35 0.31
Soluble Alkalies 0.19 0.41 0.57 0.72 0.07 0.06
B.-G. Kim et al. / Cement and Concrete Research 30 (2000) 887893
P f PNS d b d d i i l
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 25 of 36
Percent of PNS adsorbed and mini-slump areaat 30 min for cement pastes with various
Na2SO4 contents.
Alkalies C1 C5 C6
Na2O eq. 0.31 0.35 0.31
SolubleAlkalies
0.19 0.07 0.06
B.-G. Kim et al. / Cement and Concrete Research 30 (2000) 887893
P t f PNS d b d d i i l
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 26 of 36
Percent of PNS adsorbed and mini-slump areaat 30 min for cement pastes with various
Na2SO4 contents.
B.-G. Kim et al. / Cement and Concrete Research 30 (2000) 887893
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 27 of 36
Example of multi-source interactions
Potential incompatibility problems arising in
the cementitious systems containing broadcollection of cements, fly ashes and
chemical admixtures.
Focus on abnormal early age stiffening,
setting behavior and quality of the air voidsystem.
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 28 of 36
Properties Fly ashesF1 Class C ash F2 Class C ash F3 Class F ash
LOI 0.38 (M) 0.25(L) 3.89(H)
SO3 0.53(M) 1.14(H) 0.69(M)
Na2Oeqv 2.18(M) 1.94(M) 2.21(M)
Chemical
propertiesCements
C1 C2 C3 C4
C3A % 9 (M) 10(M) 10.1(M) 7.7(L)
SO3% 3.0(M) 2.4(L) 3.6(H) 3.6(H)
Na2Oeqv% 0.29(L) 0.3(L) 1.04(H) 0.97(H)
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 29 of 36
Chemical Admixtures
Water Reducing Admixtures: (WRA)
Lignin based Type A WRA (W1)
Polycarboxylate Type F superplasticizer (W2)
Air Entraining Admixtures: (AEA)
Synthetic AEA (A1) Vinsol resin (VR) based AEA (A2)
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Work Plan
PHASE IIIPHASE IIPHASE I
Study related torapid slump loss and
abnormal setMore than 100paste and mortarmixtures evaluated
Study related toproblems with
generation &stabilityof air void system18 mortars andslurries evaluated
Verification offindings from
pastes and mortars10 concretemixtures evaluated
Statistical Modeling DEVELOPMENT OF RECOMMENDATIONS
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 31 of 36
Admixture Driven Incompatibilities
W1 + plain C2 severe acceleration while W2 + C2
severe retardation
W1 or W2 + C2 fly ash cementitious system
severe acceleration of set
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Double Dosage of WRA
Aggravated stiffening problem in all the earlystiffening mixtures
Significant changes in SAC curves in 5 out 6mixtures
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 33 of 36
Fly Ash Driven Problems
As the fly ash content increased, the amount
of A1 or A2 (required to attain 18+/-2 % air
content) also increased
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Effect of Class C Ash Content
94% of high (>30%) volume fly ash (HVFA) mixtures
significant acceleration of set
70% HVFA mixtures set time less than 45mins
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 35 of 36
Steps to Identify Incompatibility
Air Void System:
Air content in mortars(ASTM C 185) or Foamindex testing
Foam drainage testing
New Reactive Materials:
Cement: C3A , sulfate & alkali content SCMs: sulfate% & LOIWRAs & AEAs : Varying chemical nature
Potential incompatible combination ???
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International Conference on Advances in Concrete Technology and Sustainability Issues, January 11. 2012, Quito, Ecuador Slide 36 of 36
Steps to Mitigate Incompatibility
Vary the following (one or more at a time) and testagain for potential problems.
Air Void System:
Select a fly ash with low LOI
Change the percentage of flyash replacement
Change the type of air
entraining agent (AEA)Change the type of Waterreducing agent (WRA)
Test the new combination for incompatibility
Potentially incompatible combinations???
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