TECHNOLOGICAL ADVANCEMENTS IN THE APPLICATION OF ALTERNATE RAW

MATERIALS IN CEMENT MANUFACTURE -NCB'S EXPERIENCE

ASHWANI PAHUJA

Director General

NATIONAL COUNCIL FOR CEMENT AND BUILDING MATERIALS,

Sustainability in Cement and Concrete

Production

• Sustained efforts are required for environmental protection andenergy conservation to combat climate changes in the 21st century.

• The most important present day issues pertinent to cement industryinclude reduction of CO2 emission, utilization of waste materials aswell as conservation of natural resources.

• There is a greater need for enhancing the use of marginal grade andalternate raw materials, alternate fuels, and supplementarycementitious materials in cement and concrete production

• Cement industry can contribute substantially in the on-going SwachhBharat Abhiyan (Clean India drive) in the country by treating largeamounts of hazardous and non-hazardous wastes in safe andenvironmentally sound manner.

KEY ISSUES

• Raw Material Conservation: Limestone – non renewable mineral resource

• Environmental considerations:

• Global emphasis on reducing the emission of greenhouse gases

• Use of alternate raw materials in clinker production

• Producing cements with lower clinker factor

• Gainful utilization and disposal of waste materials

• Circular Economy

• Standard Specifications

• Formulation of standard specifications for newer and more sustainable cements

• Cement properties and concrete performance

• Rate of strength gain of cements at lower clinker contents/ newer cements

• Durability of concrete structures

Low carbon technology roadmap for the Indian cement industry

• NCB has been actively associated with Indian industry members of thecement sustainability initiative (CSI), a part of the world business councilon sustainable development (WBCSD) to assess opportunities for carbonemission reduction and increased resource efficiency.

• This has resulted in a road map for low carbon technology identifyingthe potential levers to improve energy efficiency as well as to reducecarbon emission.

• Five broad technological key levers have been identified• Increased use of alternate fuels and raw materials (AFR)• Improvement in thermal and electrical energy efficiency• Reduction in clinker factor• Recovery of waste heat• Application of newer technologies.

Raw Material Resource – Augmentation & Conservation

• The total estimated cement grade limestone reserves are 124.5 billiontones.

• It is required to broaden the raw material base by utilization of lowgrade deposits and industrial wastes in the manufacture of cements asa component of raw mix.

• Various approaches need careful consideration for utilizing the hugereserves of low/marginal grade limestone.

• it is also imperative that intensive research be conducted to developnewer products depending on the available resources.

LOW/MARGINAL GRADE LIMESTONE RESERVES

Category Reserve (in Million Tonnes)

Proved 6332.48

Probable 9259.94

Possible 32144.99

Total 47737.41

Category Quality RangeCaO%, SiO2%

Reserve (in Million

Tonnes)

III (a) 42-44, 12-14 1904.16

III (b) 40-42, 14-16 1291.90

IV 36-40, 16-20 1966.96

Unspecified - 42574.0

Approaches for Utilization of low/marginal grade limestone

• Beneficiation of low/marginal grade limestone.

• In preparation of synthetic granulated slag.

• Manufacture of reactive belite and sulfoaluminate-belite cement

• Manufacture of LC3 (limestone – calcined clay) cement

• Manufacture of Portland Limestone Cement

• As minor additional constituent in OPC and blended cements

Gainful utilization and disposal of waste materials

• As much as 57 million tonnes of fly ash is consumed by Indian cement industry for makingblended cements. consuming about 28% of the total fly ash generated and the entirequantity of granulated blast furnace slag, the waste generated by steel plants exceeding10 million tones annually.

• As the generation of fly ash, granulated blast furnace slag and other industrial wasteswould increase in coming years, continuous innovative efforts are required to enhancegainful utilization for these wastes.

• Techno-economic feasibility studies for utilization of industrial, agricultural and minewastes such as fly ash, BF slag, sludges, red mud, non-conventional slag, marble dust andchemical industry wastes, rice husk, bagasse etc as raw materials / mineralizers andblending component in the manufacture of OPC and blended cements carried out at NCB

• Use of different sulfate bearing wastes as substitutes for gypsum have also beeninvestigated by NCB.

• Based on detailed investigations carried out at NCB, waste materials such as lead-zincslag, copper slag, LD slag and e-cat have been included for use as performance improverin OPC.

HIGHLIGHTS OF NCB’s WASTE UTILIZATION STUDIES

Waste MaterialsUtilization Levels in Specific Studies

Lead-Zinc Slag Utilization up to 6% in cement raw mix

5% as performance improver in OPC

Copper slag Utilization up to 2.5% in cement raw mix

5% as performance improver in OPC

Steel slag Utilization up to 2.0% in cement raw mix

5% as performance improver in OPC

E-cat from oil refinery Utilization up to 10-15% in the manufacture of blendedpozzolanic cement

Marble dust from marbleindustries

Utilization up to 5-15% as replacement of limestone incement manufacture (in raw mix, asperformance improver, as substitute for limestonein Portland limestone cement )

Further Reduction of the Clinker Factor of Cements

• CO2 emissions from the Indian cement industry currently average to

0.72 t CO2/ t cement, targeted to be further reduced to 0.35 t CO2/

t of cement by 2050, as estimated in the technology road map.

• The present production of blended cements in India has been around

65-70% as against only 36% in 2000-2001. Accordingly, the current

clinker factor is 0.77.

• Further reduction of clinker factor is crucial for achieving the target

reduction in CO2 emission

Utilization of Fly Ash

• Indian Standard IS 1489 (Pt.1)-2015 (Portland Pozzolana Cement –

Specifications) specifies 15-35 % fly ash in cement and as cement replacement

material in concrete.

• European standard EN-197 permits maximum 55 percent pozzolana in

pozzolanic cement.

• Only fly ash meeting the requirements of Indian Standard IS 3812 (Pt.1)-2013

can be used in manufacture of PPC and for OPC replacement

• At present less than 50% of the total fly ash generated (~ 200 million tonnes

per annum) gets utilized

• Various technological options need to be explored for enhancing the utilization

level of fly ash.

Utilization of Fly Ash in Cement and Concrete

• The properties of Indian fly ash are significantly different from those of

European fly ash, especially in terms of glass and lime content.

• NCB has investigated a number of approaches for enhancing utilization of fly

ash in cement and concrete

• Improved clinker quality, finer grinding of cement and use of chemical and

mineral activators have been found helpful in enhancing fly ash addition level

in cement and concrete.

• Activation of relatively poor quality fly ash and bottom ash through

processing may enable their utilization.

• Improving the quality of fly ash at thermal power plant has also been

considered.

Enhancing the Utilization of Fly Ash in Cement and Concrete

PROCESSING OF BOTTOM ASH FOR IMPROVED REACTIVITY

• Of the total ash generated, approximately 20% is bottom ash and It generally has

little pozzolanic reactivity.

• Bottom/pond ash fraction has been used in applications like raw material in tiles

and bricks and mineral admixture in cement and concrete

• Replacement of fine aggregate in concrete by bottom ash have shown promising

results

• Indian Standard IS 3812 (Part 1): 2013 excludes use of bottom ash as pozzolanic

‘cement replacement material’ in cement mortar and concrete.

• If sufficient pozzolanic character is obtained through processing, e.g. drying and

grinding, bottom ash could find use as a pozzolanic cement replacement material.

Enhancing utilization of fly ash in PPC blends- Use of Bottom Ash as Pozzolanic Material

• In a joint study with SINTEF, Norway, two bottom ash samples were

systematically characterized and tested as supplementary cementitious

materials.

• Binary blends of OPC and bottom ash were prepared by replacing equal

amount of OPC.

• Ternary blends were prepared by including micro silica in the binary blends

as replacement of OPC.

• The material characterization and evaluation of cement blends were

carried out at the National Council for Cement and Building Materials.

• The results indicated feasibility of using bottom ash after activation by

grinding, as pozzolanic material in cement blends

PHYSICAL PROPERTIES OF GROUND BOTTOM ASH SAMPLES

PROPERTY BA1bc BA1bf BA2

FINENESS, m2/kg 228 331 282

LIME REACTIVITY, N/mm2 4.4 4.8 6.0

COMPRESSIVE STRENGTH AT 28 DAYS, % 83 89 84

PARTICLES RETAINED ON 45µ, % 58 37 34

AUTOCLAVE EXPANSION, % 0.17 0.16 0.04

LE-CHATELIER EXPANSION , mm 2 2.5 1.0

SPECIFIC GRAVITY 2.59 2.61 2.64

Compressive Strength of Cement Blends At Different

Contents of Bottom Ash

0

10

20

30

40

50

60

70

80

1D 3D 7D 28D 90DAge (Days)

Co

mp

ress

ive

Str

egth

(M

Pa

)

BA1cem;0BA1cem;5BA1cem;10BA1cem;20

TERNARY BLENDS FOR ENHANCED LEVELS OF FLYASH UTILIZATION

• High fly ash content in cement and concrete bring down the rate of strength

gain leading to relatively lower strengths at early ages.

• Approaches used for enhancing the rate of strength gain of fly ash based

cements include use of mineral and chemical activators

• The addition of mineral additives like silica fume, making a ternary blend of

three cementitious minerals, have proved to give promising results.

• Other pozzolanic materials like rice husk ash and bagasse ash may be used

in place of silica fume or microsilica.

0

10

20

30

40

50

60

70

80

1D 3D 7D 28D 90DAge (Days)

Co

mp

ress

ive

Str

eng

th (

MP

a) BA2cem; 25

BA2cemSF5; 25

BA2cemSF10; 25

Compressive Strength of Ternary Cement Blends at 25% Bottom Ash Content

Manufacture of newer and more sustainable cements

• The R&D efforts at NCB in the recent past have been directed towards

producing more sustainable cements through reduction of clinker factor in

cement, enhancing utilization of low grade and waste materials in cement

manufacture and developing composite cements, Portland limestone cements

as well as non-Portland cements such as geopolymeric cements.

• Blended cement types like Portland limestone cements which are already inuse in European countries, are yet to be adopted, standardized and producedin India. Their production would provide additional avenue for lowering clinkerfactor of cement.

• Standardization of low clinker factor cements requires thorough and

systematic research on Indian materials and weather conditions before these

can find application in India.

Composite Cement

•Uses both fly ash and granulated blast furnace slag as the blending

components

• Indian standard specification of composite cement, IS 16415: 2015,

formulated only recently

• The R&D investigations on composite cement carried out at NCB paved

the way for formulation of Indian specifications

•Clinker content of composite cement can be as low as 35 percent;

environment friendly cement for sustainable construction. Physical

properties of composite cement are specified to be at par with those of

PPC and PSC

Composite Cement Composition

0 20 40 60 80

Clinker/ OPC

Fly ash

Slag

IS 16415 : 2015

Constituent Content , %

Clinker/ OPC 35 - 65

Fly ash 15 -3 5

GBFS 20 - 50

Minimum

Minimum

Maximum

Minimum

Maximum

Maximum

Composite Cement Indian Standard Specification

PSC PPC CC

IR, Max

Min4.0 X+((4(100-x/100)

0.7XX+((4*(100-x/100)

0.6X

MgO, Max 10.0 6.0 8.0

SO3, Max 3.5 3.5 3.5

LOI, Max 5.0 5.0 5.0

Chloride 0.1, 0.05 0.1, 0.05 0.1, 0.05

Alkalies 0.6 0.6 0.6

S, Max. % 1.5 - 0.75

Chemical Requirements Physical Requirements

PSC PPC CC

Specific Surface

Area m2/Kg225 300 300

Setting Time

IST,Min. (Mts.)

FST,Max.(Mts.)30

600

30

600

30

600

Compressive

Strength, MPa

3days

7days

28days

16

22

33

16

22

33

16

22

33

HIGH VOLUME FLY ASH CEMENT

10

15

20

25

30

35

40

45

50

IS 1489

PPC 35

PPC 40

PPC 45

PPC 50

Co

mp

ress

ive

Str

eng

th,

MP

a

Age, days3 7 28

Fineness – 330 ± 10 m2/kg Fineness - 400 ± 10 m2/kg

15

20

25

30

35

40

45

50

55

Com

pre

ssiv

e S

tren

gth

, M

Pa

Age, days

IS 1489

PPC 35A

PPC 40A

PPC 45A

PPC 50A

3 7 28

Formulation of Standard Specifications for Newer Cements

• Composite cement using fly ash – limestone

• High volume fly ash cement

• Portland limestone cement

• Multicomponent blended cement

• Performance improvers in PPC & PSC

• Calcined clay-limestone (LC3 Cement)

• Geopolymer binder & concrete

Performance Improvers in OPC

S. No. Material Specification

1 Fly ash Conforming to IS 3812 (Part 1)

2 Granulated slag Conforming to IS 12089

3 Silica fume Conforming to IS 15388

4 Limestone CaCO3 not less than 75%

5 Rice husk ash Conforming to IS 269

6 Metakaolin Conforming to IS 16354

7 Copper slag Conforming to IS 269

8 Steel slag Conforming to IS 269

9 Lead zinc slag Conforming to IS 269

10 Spent fluidized catalytic cracking

equilibrium catalyst

Conforming to IS 1344

COMPOSITE CEMENT – PATH AHEAD

• USE OF ‘FLY ASH & LIMETONE’ COMBINATION, INCLUDING LOW GRADEAND DOLOMITIC LIMESTONE

• MULTICOMPONENT BLENDED CEMENTS

• ‘CALCINED CLAY & LIMESTONE’ COMBINATION

• IMPROVING THE PERFORMANCE OF COMPOSITE CEMENT

• SEPARATE FINE GRINDING OF CONSTITUENTS, CONTROL OF PSD OFINDIVIDUAL COMPONENTS

• USE OF CHEMICAL ACTIVATORS

• DURABILITY CHARACTERISTICS, INCLUDING CARBONATION

Cement Standards – Path Ahead

• Broadening the range of additives for use in composite cement

•Use of combination of fly ash and limestone as the mineraladditives

•Use of blending additives such as rice husk ash, metakaolin,silica fume, microfine slag/ fly ash, various types of slags

• Portland Composite cements

• Performance Improvers in PPC and PSC

•High volume fly ash cement

• Portland Limestone cement

•Multi-component blended cement

•Calcined clay-limestone cement

•Geo-polymeric binders

Thank You

CHEMICAL COMPOSITION OF DIFFERENT TYPES OF SLAG SAMPLES

CONSTITUENTS

(%)

LEAD-ZINC

SLAG

COPPER

SLAG

STEEL SLAG BLAST

FURNACE

SLAG

GOI / LOI® 5.68 6.65 1.08 ® 1.14

SiO2 18.08 25.14 12.24 31.86

CaO 17.91 1.09 47.44 38.51

Al2O3 8.17 1.78 2.00 19.78

Fe2O3 34.28 68.36 29.89 0.72

MgO 1.93 0.29 2.38 6.76

ZnO 9.21 -- -- --

PbO 1.22 -- -- --

CuO -- 0.58 -- --

Composite CementComposition as per EN 197-11

Main Constituents Composite Cement

CEM V/A

Composite Cement

CEM V/B

Clinker 40-64 20-38

Granulated Blast furnace

slag

18-30 31-49

Siliceous fly ash/ natural

pozzolana/ natural

calcined pozzolana

18-30 31-49

Ternary Blended Cements – ASTM C 595 - 14

Type of mineral additive

combinations

Limit of mineral additives

Two different pozzolanas • Maximum content of pozzolana – 40 %

• Maximum content of limestone – 15 %

• Total content of pozzolana, limestone and slag

not more than 70%

Slag and pozzolana

Pozzolana and limestone

Slag and limestone

Main Constituents

Pozzolana Flyash C

emen

t T

yp

e

Des

ign

ati

on

No

tati

on

Cli

nk

er

GG

BS

S

ilic

a F

um

e

N

atu

ral

Ind

ust

ria

l

Sil

iceo

us

Cla

care

-

ou

s

Bu

rnt

Sh

ale

L

imest

on

e

M

ino

r A

dd

itio

na

l

Co

nst

itu

ent

Portland

Slag

Cement

II/A-S

II/B-S

80-94

65-79

6-20

21-35

-

-

-

-

-

-

-

-

-

-

-

-

-

-

0-5

0-5

Portland

Silica Fume

Cement

II/A-D

90-94 - 6-10 - - - - - - 0-5

Portland

Pozzolana

Cement

II/A-P

II/B-P

II/A-Q

II/B-Q

80-94

65-79

80-94

65-79

-

-

-

-

-

-

-

-

6-20

21-35

-

-

-

-

6-20

21-35

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

0-5

0-5

0-5

0-5

Portland

Flyash

Cement

II/A-V

II/B-V

II/A-W

II/B-W

80-94

65-79

80-94

65-79

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

6-20

21-35

-

-

-

-

6-20

21-35

-

-

-

-

-

-

-

-

0-5

0-5

0-5

0-5

Portland

Burnt

Shale

Cement

II/A-T

II/B-S

80-94

65-79

-

-

-

-

-

-

-

-

-

-

-

-

6-20

21-35

-

-

0-5

0-5

Portland

Limestone

Cement

II/A-L

II/B-L

80-94

65-79

-

-

-

-

-

-

-

-

-

-

-

-

-

-

6-20

21-35

0-5

0-5

II

Portland

Composite

Cement

II/A-M

II/B-M

80-88

65-79

0-5

0-5

21-35

12-20

Portland-composite

cement

Composition as per

EN 197-11

Portland Composite CementComposition as per EN 197-11

Main Constituents CEM II / A-M CEM II / B-M

Clinker 80-88 65-79

Granulated Blast furnace slag

12-20 21-35

Calcareous fly ash

Siliceous fly ash

Natural pozzolana

Natural calcined pozzolana

Silica fume

Burnt shale

Limestone