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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
• 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
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