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Concrete Technology Cementitious Materials, Admixtures & Beyond

Presented by: Joe Dan Johnson Sika Corporation Sr. Sales Rep.

A heterogeneous system of solid, discrete, gradiently sized, inorganic (mineral) aggregates, usually plutonic (feldspatho-silicaceous of ferromagnesian) or sedimentary calcareous in origins, embedded in a matrix compound of synthesized polybasic alkaline and alkaloidal silicates held in aqueous solution and coprecipitate dispersion with other amphoteric oxides, this matrix being originally capable of progressive dissolution, hydration, reprecipitation, gelatinization, and solidification through a continuous and coexistent series of crystalline, amorphous, colloidal, and crytocrystalline states and ultimately subject to thermoallotriomorphic alteration, the system when first conjoined being transiently plastic during which state it is impressed to a predetermined form into which it finally consolidates, thus providing a structure relatively impermeable and with useful capacity to transmit tensile, compressive, and shears tresses.

Concrete is……

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Agenda

Concrete Components Cementitious Materials

– Portland Cement • Cement Chemistry for Mill Certifications

– Fly Ash – Slag Cement – How/why mineral components work?

Water Aggregates Chemical Admixtures Color Curing

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Little known fact….

Concrete is the second most consumed product in the

world next to…..

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Concrete Components

• Portland Cement • Water • Aggregates • Admixtures Chemical Mineral

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Supplementary Cementitious Materials….

Fly Ash 10 - 30%

Slag Cement (GGBFS) 15 - 50%

Silica Fume 3 - 8 %

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Silca Fume • By-product of producing silicon metal or

ferrosilicon alloys The “smoke” produced by the smelter is silica fume

• Ultra fine silca (85-96%) between 50 and 100 times finer then OPC

• Specific Gravity is 2.2 • Black in color • Good for high strength concrete • Can make plastic concrete “sticky”

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Slag Cement…. What is it?

•Co-product of the iron making process •Non-metallic, consisting mostly of silicates and aluminosilicates of calcium •Hydraulic cement •Concrete enhancer •ASTM C 989

GGBFS (Ground Granulated Blast

Furnace Slag)

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Grinding to Cement Fineness

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Slag Activity Index (SAI) ASTM C 989

Grade 7 Day SAI 28 Day SAI

80 --- 75

100 75 95

120 95 115

ASTM Minimum Requirements

SAI % = (SP/P) * 100% of Compressive Strength of Reference OPC mix

How Do Mineral Components Work in Concrete?

Free Lime

Portland + water = CSH + Ca(OH)2 (Free Lime)

Free Lime = higher permeability and susceptibility to chemical attack

CSH-Calcium Silicate Hydrate Water or Void Calcium Hydroxide

Coarse Aggregate

• More CSH (Calcium Silicate Hydrate) is formed. • Reacts with calcium hydroxide and alkali. • Hydrates are more gel-like. • Rate of heat liberation is a two-stage effect.

OPC + water = CSH + Ca(OH)2 + GGBFS = CSH = lowered permeability, less susceptible to attack

Coarse Aggregate

How Do Mineral Components Work in Concrete?

Slag and/or Fly Ash in the mix?

CSH-Calcium Silicate Hydrate Water or Void Calcium Hydroxide

Coarse Aggregate

Coarse Aggregate

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Portland GGBFS Class F Cement Cement Fly Ash SiO2 20.0 35.20 56.51 Al2O3 3.0 11.00 32.19 Fe2O3 5.0 1.28 4.27 CaO 65.0 42.62 0.86 MgO 1.1 6.70 SO3 2.6 1.69 0.15 Na2O 0.6 0.20 LOI 1.8 0.00 6.0 Fineness % Ret. 325 92.0% 0.75% 21.38%

OPC vs GGBFS vs Fly Ash

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Particle Shape

OPC

Fly Ash GGBFS

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Performance

• Higher Ultimate Strengths • Lower Heat Generation • Lower Permeability • Improved Sulfate Resistance • Alkali-Silica Reactivity Reduced ADDITIONALLY • Whiter/Brighter Color • Better Workability & Finishability • Environmentally beneficial material

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Plastic Properties

•Reduced water demand •Better slump retention •Enhanced workability •Enhanced flowability •Easier consolidation •Superior finishability

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Mixture Proportioning

• Concrete is proportioned by the same methods as portland cement concrete. • Keep in mind, with slag cement:

Water demand is usually reduced Paste volume is increased

– Difference in Specific gravity - portland cement - 3.15 vs. 2.88 or 2.4-2.7

Coarse/fine aggregate will need adjustment Admixtures may need adjustment Set time may increase, especially in cooler weather

• Determine target values of slag or fly ash substitution to achieve desired effects.

Slag Dosage: 10 – 80% Fly Ash: 10 – 30 %

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The “Opportunities” The Use of Mineral Components in Cement and Concrete can:

• Help minimize CO2 Emissions • Minimize use of raw materials • Reduce energy consumption • Make use of a recycled product – less waste and landfill • Make concrete lighter & more reflective (with slag) • Engineers can obtain specialized results with readily

available materials, (meet type II, type IV and type V requirements).

MAKE BETTER CONCRETE Improve strength, durability & overall sustainability!

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Available Forms of Fly Ash and Slag Cement

Separate Product in Bulk ASTM C 989 (AASHTO M 302) Specification for Ground

Granulated Blast-Furnace Slag for Use in Concrete and Mortars

ASTM C 619 – Specification for Fly Ash in Concrete Blended With Portland Cement

ASTM C 595 (AASHTO M 240) Specification for Blended Hydraulic Cements

ASTM C 1157 Standard Performance Specification for Hydraulic Cement

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BLENDED CEMENT TYPES ASTM C595

Type IS: Portland Blast-Furnace Slag Cement

(25-70% replacement) Type IP: Portland-Pozzolan Cement (15- 40% replacement) Type I(PM): Pozzolan Modified Portland Cement (less than 15%) Type I(SM): Slag Modified Portland Cement (less than 25%) Type S: Slag Cement (greater than 70%)

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The Cake Scenario

ASTM C150

ASTM C595

ASTM C1157

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What is the Most “Expensive”

Ingredient in Concrete ?

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How Water Effects Concrete (based on a 3000 psi mix)

Water Added gal. per/cy

Slump Increase in inches

Percent of strength reduction

Strength loss (lbs) per square inch

1 1 6.7 200

2 2 13.4 400

3 3 20 600

4 4 26.7 800

5 5 33.4 1000

6 6 40 1200

7 7 46.7 1400

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Did You Know? “Adding One Gallon of Water Will” • Increase the slump about ONE INCH • Cut the compressive strength about 200 psi • Wasts the effect of ¼ sack of cement • Increase the shrinkage potential about 10% • Decrease the freeze thaw resistance about 20% • Increase cracking about 10% • Increase air content about 1% • Increase segregation • Increase wear damage from traffic • Increase dusting • Increase finishing time for contractors labor

Is one gallon of water worth all the expense?

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Water/Cement Ratio • Water (lbs)/Cement (lbs) Water Total added water included “free”

mositure from the aggregates “Cement” Total cementitious indcluding any

fly ash, slag, and/or silica fume • Need approximately 25 lbs of water to

hydrate 100 lbs of cement • Higher the w/c ratio the weaker the

concrete.

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Mixing Water

Almost any natural water that is drinkable with no pronounced taste or odor can be used for making concrete

Some waters that are not fit for drinking maybe suitable for concrete if tested by a laboratory

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What Is An Admixture ?

• Snake Oil • Bug Juice • Colored Water • It’s Specified On A Project So I

Have To Use It • Performance, Quality & Cost • As necessary an ingredient as

cement itself!

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Admixtures

Admixtures are those ingredients in concrete other than cement, water, and aggregates that are added to the mixture immediately before or during mixing to give the concrete special

properties or to cut costs.

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Reasons For Using Admixtures

• Increase Strength • Improve Mix Workability • Improve early strengths • Control set time • Reduce Permability • Control Efflorescence • Improve Color Vibrancy • Meet Durability Requirements • Control Shrinkage • Increase Profitability

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Admixture Types

Accelerators Retarders Air Entrainment Water-Reducers

Mid-Range Water-Reducers High-Range Water-Reducers

Viscosity Modifiers (SCC) Efflorescence Control (architectural concrete) Others

Corrosion Inhibitors Anti Wash-out ASR Controlling Shrinkage Reducers Water-Repellent Admixtures

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Set Altering Chemical Admixtures

•Accelerators • Reduce set times while increasing early age strengths but reduced later age strengths • Chloride or Non-Chloride • Hardening Accelerators

•Retarders • Slows set time and produces lower early age strengths but greater later age strengths • Hydration controlling admixtures

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Air Entraining Admixtures Improve durability in environments of freeze-thaw,

deicers Improve Workability

Wood Resins

Synthetic Detergents

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How do AEA’s work?

• Reduce surface tension • Stabilizes millions of air bubbles formed

during mixing. • Semi-microscopic bubbles. • Mechanical, not chemical, action.

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Water Reducers Used to reduce the quantity of mixing water required

to produce concrete of a certain slump

• Reduce water/ cementitious ratio • Increased strength • Replaces cement for equivalent strength. • Increased workability & flowability

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• Polycarboxylate-based –

full range water-reducing admixtures

• Engineered molecules for the desired concrete performance

• Full range water reduction - may be used from 2 -18 oz/cwt depending on application

New Generation WR’s

They make SCC possible!!

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How Polycarboxylate-Based Admixtures Work…???

These products provide significantly improved cement dispersion

due to inherent dual mechanism of electrostatic & steric repulsion Polycarboxylate molecules work by attaching themselves to

cement particles and impart a negative charge that causes cement particles to repel from one another (electrostatic repulsion)

The long side chains on the molecules physically help to keep cement particles apart and totally surround the cement particles (steric hindrance)

This dual mechanism results in improved dispersion, mix lubrication and performance

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Reduce/eliminate bleeding Improve concrete stability Great for use with manufactured sands

Untreated Viscosity Modifiers

Treated

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SCC - We measure spread not slump

•Spread 18” - 26” •Produced with Super P and sometimes a VMA •Requires minimal to no vibration •Non-segregating •Aggregate Gradation is important •Increased cement content isn’t always necessary

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Joe Dan Johnson 512.845.8844 johnson.joedan@us.sika.com