2/12/2015

1

Cementitious Materials

2

Concrete Materials

• Cementitious Hydraulic Cement (C150, C595, C1157)

Other Supplementary Cementitious Materials (SCM’s) • Pozzolans (Fly Ashes), C618 • Slag Cement, C989 • Silica Fume, C1240

These SCM’s are commonly referred to as Mineral Admixtures

• Aggregates Coarse and Fine (Rock & Sand), C33

• Chemical Admixtures, C494 & C260

Water Reducers, Retarders, Accelerators, Air Entrainment, and etc.

• Water

2/12/2015

2

3

Learning Objectives

Develop a basic understanding of:

Portland cement, C150

Pozzolans Fly Ash, C618

Silica Fume, C1240

Slag Cement, C989

4

Joseph Aspdin 1824

Aspdin’s early cement was nothing more than a hydraulic lime, but in 1824 his patent gave him the use of the term Portland cement

Lea’s Chemistry of Cement

Early Cement Works

2/12/2015

3

5

Rotary Kiln

Thomas Edison takes advantage of the horizontal rotary kiln Cement manufacture changed from a batch process to a continuous process

1900 1885 England Frederick Ransome patented rotary kiln (18 inch X 15 ft)

Rotary Kilns

6

Portland Cements

2/12/2015

4

7

Typical Cement Plant

8

Raw Material Mining & Processing

2/12/2015

5

Two Major Raw Materials Components in Hydraulic Cement

Calcareous Component Argillaceous Component(providing CaO) (providing SiO2 Al2O3 & Fe2O3)

limestone claymarly limestone shale

chalk (generally easy to grind) calcareous marlcoral limestone marl

marble marly claylime-sand tuff, ash

shell deposits etc phyllite. Slate etc.

Calcium oxide Silicon oxide

Calcium Silica

10

Four Principle Oxides

Calcium oxide 64% CaO "Lime" CSilicon oxide 22% SiO2 "Silica" S

Aluminium oxide 6% Al2O3 "Alumina" A

Iron oxide 3% Fe2O3 "Iron" F

Major Components

Na2O, K2O "Alkali"

SO3 "Sulphur"

MgO "Magnesium"

TiO2 "Titanium"

Minor components

2/12/2015

6

Grinding Mill

Blending and Storage Silos

Lim

esto

ne

Shal

e

Iron

O

re

Sand

Raw Material Proportioning

Raw Meal Pump

Dust Collector

To Preheater

or Kiln

After analysis, the raw materials are proportioned, ground to fine powder, and blended. Some cement

plants add water to the material during grinding, then blend and store it as a slurry.

Raw Material Proportioning & Blending

12

Two Types of Cement Kilns

• Wet Process Kiln Mix is a Slurry (30% - 40% water)

• Advantages more uniform raw material may already contain moisture

• Disadvantage higher energy use

• Dry Process Kiln Mix is a Dry Powder

• Advantages preheating done outside the kiln efficiency shorter kiln length

• Disadvantage alkalies, sulfur, chlorides tall, sophisticated

2/12/2015

7

13

Inside the Kiln

14

Low red -- dark red 875-1200 F bright red -- orange 1500-1650 F orange -- yellow 1650-2000 F light yellow - white 2400-2800 F

Heat Zone Inside the Kiln

2/12/2015

8

15

Voila Clinker!!

C3S (alite)

C2S (belite)

C3A

C4AF

Most important clinker constituent that governs strength

2/12/2015

9

17

C3S Alite...Contributes to early and late strength (1-3-5 day - ...)

Increases heat of hydration

C2S Belite... Contributes to late strength (28 day + ...)

C3A Contributes to very early strength (1 - 3 day)

Increases heat of hydration Impairs resistance to sulfate attack (durability)

C4AF Little effect (mostly color). (Higher C3A, lower C4AF generally more reactive)

Significance of Clinker Minerals for Cement Properties

Grinding Clinker & Gypsum

Kiln

Clinker Cooler Grinding

Mill Bulk

Clinker Gypsum Dust Collector

Loading Cement Pump

Storage Silos

Bagging Facility

2/12/2015

10

Turning Clinker into Cement 

Kiln

Clinker Cooler Grinding

Mill Bulk

Clinker Gypsum Dust Collector

Loading Cement Pump

Storage Silos

Bagging Facility

20

Sulfate (Gypsum) for Set Control

• Gypsum, or naturally occurring anhydrite • Reacts with aluminate phases • Controls chemical reactions • Proper balance needed for good

performance Slump loss Fast set Slow set Slow strength Gain

2/12/2015

11

21

Finish Mill

22

CPU 301 October 10 -12, 2007

THE RECIPE

2/12/2015

12

23

Hydraulic Cement

ASTM C150 “Portland Cement”

ASTM C595 “Blended Cement”

ASTM C1157 “Performance Cement”

AASHTO American Association of State Highway &

Transportation Officials

M85 / M240

AASHTO & ASTM are equal or similar specifications

No AASHTO equal for C1157

Cement Standards

24 ASTM C150 Cement Types

• Type I - No restrictions regarding clinker minerals • Type II - Moderate Sulfate resistance

C3A max. 8 %

• Type III - High early strength

C3A max. 15 %

• Type IV - Low heat of hydration No longer available

C3S max. 35 % (alite) C2S min 40% (belite) C3A max. 7 %

• Type V - High Sulphate resistance C3A max. 5.0 % C4AF + 2 C3A max. 25 % or C4AF + C2F max. 25 %

No Type I-II

2/12/2015

13

25

CPU 301 October 10 -12, 2007

Material Certification Report

2/12/2015

14

27 Supplementary Cementitious Materials (SCMs)

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

28

Slag Cement

• ASTM C 989 Standard Specification for Slag Cement for Use

in Concrete and Mortars (classified by Strength Activity Index compared to a reference Portland Cement) Grade 80 (SAI @ 28days = 75%)

Grade 100 (SAI @ 7days = 75% & 28days = 95%)

Grade 120 (SAI @ 7days = 95% & 28days = 115%)

Slag Cement is a hydraulic cement

2/12/2015

15

29

Blast furnace

Iron ore, coke and limestone added to the top

Molten slag and iron flow from the bottom

Blast Furnace Slag (BFS)

3000 oF +/-

30

Molten Blast Furnace Iron & Slag

2/12/2015

16

31

Slag

Granulated Blast-Furnace Slag (GBFS) Molten slag is quenched with a large quantity of water, about a 10:1 ratio

“Shock” of the water vitrifies the slag into a glassy sand like material

Water

32

US Steel GRANULATION TANK STACK

DEWATERING PLANT

2/12/2015

17

33

Dewatering Plant

34

Dewatering Drum

2/12/2015

18

35

Slag Cement Grinding Plant

36

Ball Mill

Slag Cement

Ground Granulated Blast-Furnace Slag

2/12/2015

19

37

Slag - Features and Benefits

• Benefits for Hardened Concrete Later age strength Increased flexural strength Lighter, brighter color (substitute for white

cement) Increased ability to reflect solar heat Reduced permeability and increased durability Increased resistance to alkali silica reaction

25% to 70%

Increased sulfate resistance (low alumina slag) 40% to 70%

38

Slag - Cautions • As cement replacement

rates increase, freeze/thaw durability can be reduced (on flat work)

• Sensitive to cold weather, below 40 deg F(set time and early strength)

• As levels of unoxidized sulfide sulfur increase, a temporary greening of the hardened concrete may occur

2/12/2015

20

39

Pozzolans

• ASTM C618 Standard Definition “pozzolan, n. a siliceous or siliceous and aluminous material

which in itself possesses little or no cementitious value but which will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide to form compounds possessing cementitious properties”

40

Fly ash • A by-product produced

at coal-fired electric generating power plants

• Residue (or ash) from the combustion of ground or powdered coal…in other words coal ash

2/12/2015

21

41

Fly Ash Flow Process

Coal/Source Coal Pulverizer

Boiler

Electrostatic Precipitation

Fly Ash Silo

Customers

Fly Ash

Fly Ash: A finely divided residue that results as a product from the combustion of pulverized coal in electric generating power plants. Class C Fly Ash: Most often comes from the burning of sub-bituminous coal and generally has a calcium oxide content above 20%. Class F Fly Ash: Most often comes from the burning of bituminous coal and generally has a calcium oxide content of less than 10%.

•Bituminous coal (F)

•Subbituminous coal (C )

Younger coals - western - North America

Older coals - eastern - North America and on the west coast

2/12/2015

22

43

ASTM C 618/AASHTO 295 Specification Classes

Fly Ash

• Class F—Fly Ash with pozzolanic properties

• Class C—Fly Ash with

pozzolanic and cementitious properties

44

Fly Ash

• Class C “C” ash is cementitious and pozzolanic Class C ash contains higher CaO contents

• (8% - 40%) High lime content, light color

• Due to lower carbon and iron contents ASTM C 618

• Medium – High CaO ( 18 - 40+% )

2/12/2015

23

45

Fly Ash

• Class F “F” ash is pozzolanic Class F ash contains low CaO content

• ( 1-15% ) Low lime content, dark color

• Due to presence of unburned carbon ASTM C 618

• Low CaO ( 2-15% )

Type F ash is usually preferred for durability, (ASR)

46

Fly Ash - How Does it Work?

• Fly ash reacts with the cementitious free lime during the cement hydration process to enhance the density of crystal growth and realize concrete strength gain.

2/12/2015

24

47

Primary cement reaction (fast):

C3S (and C2S) + water = C-S-H gel

Byproduct from hydration = Calcium Hydroxide

Pozzolanic reaction (slow):

Fly Ash + Calcium Hydroxide = C-S-H gel

Reactions

48

Fly Ash - Features and Benefits

• Improved concrete mix workability • Reduced permeability • Increased resistance to alkali-silica reactivity &

sulfate conditions with Class F • Reduced heat of hydration

Primarily Class F more so than Class C

2/12/2015

25

49

Fly Ash - Cautions

• Fly ash can affect air entrainment dosages

• Increase initial set time • Lower early age strengths

Especially w/ Class F

50

Other Considerations • Must accommodate specific gravity difference

when batching with fly ash and slag cement specific gravity of fly ash = 2.2 - 2.8 specific gravity of slag cement = 2.6 - 2.9 specific gravity of Portland cement = 3.15

• Must adequately cure concrete when slow hydration occurs

2/12/2015

26

51

Fly Ash - Potential Uses

• Primary Applications Concrete Concrete Products

52

Silica Fume

(microsilica): pure, amorphous silica with particle size of 0.1-0.2 m, collected during the manufacture of silicon and ferrosilicon alloys

2/12/2015

27

53

Specification for Silica Fume

ASTM C1240 finely divided residue resulting from the

production of silicon, ferro-silicon, or other silicon-containing alloys that is carried from the burning surface area of an electric-arc furnace by exhaust gases.

54

Silica Fume Basics

• Typical amounts used in concrete 5% to 10% • Adds to strength gain • Reduces permeability • Reduces Alkali Silica Reactivity

2/12/2015

28

55

Conclusions

• Portland cement is a complex material that is manufactured from natural materials

• Pozzolans and Slags are by-products of manufacturing processes

• The use of SCM’s can benefit concrete by improving the desired engineering properties

• SCM’s also provides an environmental benefit.

56

QUESTIONS?