Cement and PozzolansBen Blankenshipp

Technical Services Manager

OutlineOutline

• Overview of Cement ProductionOverview of Cement Production• Common Types of Cements• Fly Ash, Slag, and Other Pozzolans

True or False?True or False?

Cement and concrete are the same thing.

☺Nearly all cement is called portland cement.

Portland cement comes from Portland, Oregon.

☺Concrete is the most widely used building material in the world.

Portland, Blended, and Other Hydraulic Cements

Portland cement is a fine powder that when mixed with water becomes the glue that holds aggregates together in concrete.

C tCementM f t iManufacturing

ProcessProcess

Alamo Roman & Portland Cement Company,San Antonio, Texas

Started January 1880:“Texas’ First Cement Plant”Texas First Cement Plant

and “America’s Second Cement Plant” Kiln Stack

Vertical KilnVertical Kiln

Cement Process Terminology(Commonly Used Terms)

Raw MixWet Process (Slurry)Dry Process yKilnClinkerClinkerCalciningClinkering / SinteringClinkering / Sintering Preheater – PrecalcinerCement Kiln DustCement Kiln Dust

Cement Process TerminologyCement Process Terminology

Raw Mix - blend of raw materials, ground todesired fineness, correctly proportioned, andblended ready for burning in a kiln for themanufacture of cement clinker.

Primary Components of Raw MaterialsPrimary Components of Raw Materials Necessary for Portland Cement

ManufactureManufacture

CalciumSilicaAluminaIronIron

Calcium Iron Silica Alumina Sulfate

Sources of Raw Materials Used in Manufacture of Portland Cement

Calcium Iron Silica Alumina SulfateAlkali wasteAragonite

Blast-furnace flue dust

Clay

Calcium silicateCement rock

Aluminum-ore refuse

B it

Anhydrite

CalciteCement-kiln

dustC t k

y

Iron ore

Mill scale

ClayFly ash

Fuller’s earth

BauxiteCement rock

ClayC l

Calcium sulfate

GCement rockChalkClay

F ll ’ th

Mill scale

Ore washings

Pyrite cinders

LimestoneLoessMarl

Copper slagFly ash

Fuller’s earthG di it

Gypsum

Fuller’s earthLimestone

MarbleM l

Pyrite cinders

ShaleOre washings

QuartziteRice-hull ash

GranodioriteLimestone

LoessO hiMarl

SeashellsShaleSl

SandSandstone

Shale

Ore washingsShaleSlag

S liSlag SlagTraprock

Staurolite

Quarry

Limestone, a primary raw material providing calcium in making cement, is quarried near the cement plant. Quarry rock is trucked to the primary crusher.

Cement Process TerminologyCement Process Terminology

Wet Process - a cement manufacturingWet Process - a cement manufacturingprocess in which 30% to 40% water isadded to the raw mix to form a slurry andadded to the raw mix to form a slurry andthen fed into a (wet process) kiln.

Dry Process - a cement manufacturingprocess in which the raw mix enters a (dryprocess) kiln system in dry powdered form.

Wet Process Kiln SystemWet Process Kiln System

Kiln St kStacksCrusher Limestone Quarry

Slurry Tanksy(Raw Mix) Rotary

KilnsRaw Material

Storage

Clinker Coolers

Dry Process Kiln System P h t P l i

Stack

Preheater Precalciner

Kiln Dry Raw Mix Silo

Clinker Cooler

Traditional Manufacture of Portland CementPage 22 Design & ControlPage 22 Design & Control

Wet Kiln System

1 Stone is first reduced to 125 mm (5 in )1. Stone is first reduced to 125 mm (5 in.) size, then to 20 mm (3/4 in.), and stored.

2. Raw materials are ground to powder and blended.

or2. Raw materials are ground, mixed with

water to form slurry, and blended.

Cross-Belt Analyzer for measurement of ychemical composition of raw materials

Cement Process TerminologyTerminology

C t ”Kil ” kil ( t t ) i hi h thCement ”Kiln” - a kiln (rotary type) in which theground and proportioned raw mix is dried, calcined,and burned or sintered into clinker at a temperature ofand burned or sintered into clinker at a temperature of26000 to 30000 F; in essence a cement kiln is a hugeheat exchanger.g

3. Burning changes raw mix chemically and h i ll i t t li kphysically into cement clinker.

Page 22 Design & ControlW t Kil S tWet Kiln System

Cement Process Terminologygy

Calcining - to alter composition or physical stateby heating below the temperature of fusion. Thezone in the kiln system where carbon dioxide(CO2 ) is liberated from the raw materials (1100 -1650 degrees F).

CaCO3 + HEAT CaO + CO2 (gas )

Calcium Fuel, BTU’s Calcium Carbon Carbonate Oxide Dioxide

3. Burning changes raw mix chemically and physically into cement clinkerphysically into cement clinker.

Page 23 Design & Control

(Note four stage preheater, flash furnaces, and shorter kiln.)(Note four stage preheater, flash furnaces, and shorter kiln.)

Rotary kiln (furnace) for manufacturing portland cement clinker.

view inside the kiln

Three Major Heating ZonesThree Major Heating Zones

Drying or preheating zone (700F to 11000F)Drying or preheating zone (70 F to 1100 F) evaporation of water from raw materials

C l i i (11000F t 16500F) l fCalcining zone (11000F to 16500F) removal of carbon dioxide (CO2 gas ) from calcium carbonate in limestonecarbonate in limestone

Clinkering or burning zone (22000F to 28000F) g g ( )raw materials undergo complex chemical & physical changes

Drying or Preheating Zone(700F to 11000F)

Calcining ZoneCalcining Zone (11000F to 16500F)

Flame 3,5000 FFlame 3,500 F

3500 degree flameburner pipe

3500 degree flame

2800 degree clinker

refractory brick

rotating steel cylinder (kiln)

Cement ProcessCement Process Terminology

Portland Cement “Clinker” - a partially fused(sintered) product of a rotary kiln, consisting(sintered) product of a rotary kiln, consistingprimarily of hydraulic calcium silicates; whichis ground to make cementis ground to make cement.

4. Clinker with gypsum is ground into gyp gportland cement and shipped.

Page 22 Design & Control

Import CementImport Cement

• In markets where there is not adequate domestic production

• Cement can be imported from all over the world.

• Houston Cement Company has one of the

t d d i tmost advanced import facilities in the world!

Import CementImport Cement

• Auger unloading arm is d t l d hi tused to unload ships at

an average rate of 700 mtph

• Ship takes on average 3.5 to 4 days to unloadShi t i ll h ld• Ships typically hold between 40,000 to 60,000t of cement

• Can achieve as much as 1500 mtph.

Types of Portland Cements And SpecificationsSpecifications

Types of Portland CementASTM C 150 (AASHTO M 85)ASTM C 150 (AASHTO M 85)

(Eight Types of Portland Cements)

I NormalIA Normal, air-entraininggII Moderate sulfate resistanceIIA Moderate sulfate resistance, air-entrainingIII High early strengthIII High early strengthIIIA High early strength, air-entrainingIV Low heat of hydrationV High sulfate resistance

Hydraulic Cements ASTM C 1157

Thi i th fi t f ifi tiThis is the first performance specificationfor hydraulic cements.Cements meet physical performance testrequirements rather than prescriptive

t i ti i di t trestrictions on ingredients or cementchemistry as in other cement specifications

h ASTM C150such as ASTM C150.Provides for six types.

Portland and Blended Hyd. Cements ASTM C 1157ASTM C 1157

• Type GU--General useType GU General use• Type HE--High early strength• Type MS--Moderate sulfate resistanceType MS--Moderate sulfate resistance• Type HS--High sulfate resistance• Type MH Moderate heat of hydration• Type MH--Moderate heat of hydration• Type LH--Low heat of hydration• Option (R) Low reactivity with reactive• Option (R)--Low reactivity with reactive

aggregates

Blended CementsClinkerGypsumP tl d C tPortland CementFly ashSlaggSilica FumeCalcined Clay

Sh i bl d d t ( t ) d d b ( i ht dShown is blended cement (center) surrounded by (right andclockwise) clinker, gypsum, portland cement, fly ash, slag, silicafume, and calcined clay. ASTM C 1157 allows the use andoptimization of all these materials, simultaneously if necessary,to make a cement with optimal properties.

Blended Cements - ASTM C 595

T IP (%) P tl d P l• Type IP (%) – Portland PozzolanCement

• Type IS (%) – Portland Slag Cement• Type IT (%%) Portland Ternary• Type IT (%%) – Portland Ternary

Blended Cement• Type IL – 15% Limestone Portland

Cement

Fl A h Sl Sili F d N t lFly Ash, Slag, Silica Fume, and Natural Pozzolans

Also known as —

Supplementary Supplementary Cementing Materials (SCMs)

— a material that, when used in conjunction with portland cement, contributes to thewith portland cement, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity, or both.

Supplementary CementitiousSupplementary Cementitious Materials (SCMs)

From left to right:• Fly ash (Class C)• Fly ash (Class C)• Metakaolin (calcined clay)• Silica fume• Silica fume • Fly ash (Class F)

Sl• Slag • Calcined shale

PozzolansPozzolans

• A pozzolan is a siliceous or aluminosiliceous pmaterial that, in finely divided form and in the presence of moisture, chemically reacts with the calcium hydroxide to form additional CSH andcalcium hydroxide to form additional CSH and other cementitious compounds.• Fly Ashy• Slag• Silica Fume

C l i d Cl• Calcined Clay

Cement Hydration – Chemical yReaction Between Water &

CementCement

• 70%-90% of the reaction is Calcium Silicate Hydrate (CSH) – strong crystals10% 30% i l i h d id l• 10% -30% is calcium hydroxide – gel

• Calcium hydroxide (gel) + glassy silica from ash & slag= Calcium Silicate Hydrate= More strong crystals!= More strong crystals!

Specifications and Classes of Fly Ash

ASTM C 618 (AASHTO M 295)ASTM C 618 (AASHTO M 295)

• Bi-product of burning coal to produce electricityCl F Fl h ith l i• Class F—Fly ash with pozzolanicproperties• Older Anthracite or Bituminous Coal

• Class C—Fly ash with pozzolanicand cementitious properties• Younger Lignite or Subbituminous Coal• Younger Lignite or Subbituminous Coal

Ground Granulated Iron Blast-Furnace Slag

• Grade 80Slag with a low

ti it i dactivity index• Grade 100

Slag with a moderateSlag with a moderate activity index

• Grade 120Grade 120Slag with a high activity index

ASTM C 989 (AASHTO M 302)ASTM C 989 (AASHTO M 302)

Fluxing StoneCaCO3

M CO

FuelCoke, C

Iron OreFe2O3

SiO MgCO3Coke, CSiO2

Al2O3

Production of GGBF Slag

Air-cooled slag(aggregate)

GGBF Slag

Burden

Expanded slag(lightweight agg)

Blastfurnace

Hot Air

Granulated or pelletized slag( )

MoltenMolten

SlagSlagSt l m kin

MoltenMoltenSlag

Pig Iron

Hot Air

(cement)Steel makingIronIron

Pig Iron

2(iii)-2

To make iron blast furnace slag suitable as a i i l f i bcementing material for concrete it must be:

Q enched (cooled rapidl ) b aterQuenched (cooled rapidly) by water granulation of pelletization

Dried to remove water from the quenching process

Ground to a fine powder

Only in its final form will ground granulated blast furnace slag exhibit sufficient cementitious behaviour

2(iii)-4

Hydraulic Reaction of Hydraulic Reaction of yySlagSlag

Slag is not a pozzolan. It is a latent hydraulic material.

Slag will hydrate when mixed on its own with water, however, the process is very slow

Latent hydraulic materials require the addition of an activator (e.g. lk li li d ) t t i ifi t h d tialkali or lime compounds) to promote significant hydration

The alkalis present in Portland cement and the calcium hydroxide released during its hydration are very effective activators of slagreleased during its hydration are very effective activators of slag

3(iii)-1

Silica FumeSilica Fume

finely divided residue resulting from the

d i f iliproduction of silicon, ferro-silicon, or other silicon containing alloyssilicon-containing alloys that is carried from the burning surface area of an bu g su ace a ea o aelectric-arc furnace by exhaust gases.

ASTM C 1240ASTM C 1240

Natural PozzolansClass N Raw orClass N—Raw or calcined natural pozzolans including:• Diatomaceous earths• Opaline cherts and

shalesshales• Tuffs and volcanic

ashes or pumicites• Calcined clays,

including metakaolin, and shales

Metakaolin

ASTM C 618 (AASHTO M 295)ASTM C 618 (AASHTO M 295)

Nature of the Reaction of Different SCM’sNature of the Reaction of Different SCM’s

Pozzolanic HydraulicPozzolanic HydraulicSilica Fume XXXXX

Low-CaO Fly Ash XXXX

Moderate-CaO Fly Ash

XXXX XIncreasingCalciumContent Ash

High-CaO Fly Ash XXX XX

Slag X XXXX

Content

Slag X XXXX

3(i)-2

Questions!?