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 and energy conservation to combat climate changes in the 21st century. The most important present day issues pertinent to cement industry include reduction of CO 2 emission, utilization of waste materials as well as conservation of natural resources. There is a greater need for enhancing the use of marginal grade and alternate raw materials, alternate fuels, and supplementary cementitious materials in cement and concrete production Cement industry can contribute substantially in the ongoing Swachh Bharat Abhiyan (Clean India drive) in the country by treating large amounts of hazardous and nonhazardous wastes in safe and environmentally 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 the cement sustainability initiative (CSI), a part of the world business council on sustainable development (WBCSD) to assess opportunities for carbon emission reduction and increased resource efficiency. This has resulted in a road map for low carbon technology identifying the potential levers to improve energy efficiency as well as to reduce carbon 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 billion tones. It is required to broaden the raw material base by utilization of low grade deposits and industrial wastes in the manufacture of cements as a component of raw mix. Various approaches need careful consideration for utilizing the huge reserves of low/marginal grade limestone. it is also imperative that intensive research be conducted to develop newer products depending on the available resources.
LOW/MARGINAL GRADE LIMESTONE RESERVES Category Proved 6332.48 Probable 9259.94 Reserve (in Million Tonnes) Possible 32144.99 Total 47737.41 Category Quality Range CaO%, SiO2% Reserve (in Million Tonnes) III (a) 4244, 1214 1904.16 III (b) 4042, 1416 1291.90 IV 3640, 1620 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 sulfoaluminatebelite cement Manufacture of LC 3 (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 making blended cements. consuming about 28% of the total fly ash generated and the entire quantity of granulated blast furnace slag, the waste generated by steel plants exceeding 10 million tones annually. As the generation of fly ash, granulated blast furnace slag and other industrial wastes would increase in coming years, continuous innovative efforts are required to enhance gainful utilization for these wastes. Technoeconomic feasibility studies for utilization of industrial, agricultural and mine wastes such as fly ash, BF slag, sludges, red mud, nonconventional slag, marble dust and chemical industry wastes, rice husk, bagasse etc as raw materials / mineralizers and blending 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 been investigated by NCB. Based on detailed investigations carried out at NCB, waste materials such as leadzinc slag, copper slag, LD slag and ecat have been included for use as performance improver in OPC.
HIGHLIGHTS OF NCB s WASTE UTILIZATION STUDIES Waste Materials Utilization Levels in Specific Studies LeadZinc 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 Ecat from oil refinery Utilization up to 1015% in the manufacture of blended pozzolanic cement Marble dust from marble Utilization up to 515% as replacement of limestone in industries cement manufacture (in raw mix, as performance improver, as substitute for limestone in Portland limestone cement )
Further Reduction of the Clinker Factor of Cements CO 2 emissions from the Indian cement industry currently average to 0.72 t CO 2 / t cement, targeted to be further reduced to 0.35 t CO 2 / t of cement by 2050, as estimated in the technology road map. The present production of blended cements in India has been around 6570% as against only 36% in 20002001. Accordingly, the current clinker factor is 0.77. Further reduction of clinker factor is crucial for achieving the target reduction in CO 2 emission
Utilization of Fly Ash
Utilization of Fly Ash in Cement and Concrete Indian Standard IS 1489 (Pt.1)2015 (Portland Pozzolana Cement Specifications) specifies 1535 % fly ash in cement and as cement replacement material in concrete. European standard EN197 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.
Enhancing the 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.
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, m 2 /kg 228 331 282 LIME REACTIVITY, N/mm 2 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 LECHATELIER EXPANSION, mm 2 2.5 1.0 SPECIFIC GRAVITY 2.59 2.61 2.64
Compressive Stregth (MPa) 80 70 60 50 40 30 20 10 0 Compressive Strength of Cement Blends At Different Contents of Bottom Ash BA1cem;0 BA1cem;5 BA1cem;10 BA1cem;20 1D 3D 7D 28D 90D Age (Days)
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.
Compressive Strength (MPa) 80 70 60 50 40 30 20 10 0 Compressive Strength of Ternary Cement Blends at 25% Bottom Ash Content BA2cem; 25 BA2cemSF5; 25 BA2cemSF10; 25 1D 3D 7D 28D 90D Age (Days)
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 nonportland cements such as geopolymeric cements. Blended cement types like Portland limestone cements which are already in use in European countries, are yet to be adopted, standardized and produced in India. Their production would provide additional avenue for lowering clinker factor 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 Slag Minimum Maximum IS 16415 : 2015 Fly ash Maximum Constituent Content, % Minimum Clinker/ OPC 35 65 Fly ash 15 3 5 Clinker / OPC Minimum Maximum GBFS 20 50 0 20 40 60 80
Composite Cement Indian Standard Specification IR, Max Min PSC PPC CC 4.0 X+((4(100x/100) 0.7X Chemical Requirements X+((4*(100x/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 Specific Surface Area m 2 /Kg Setting Time IST,Min. (Mts.) FST,Max.(Mts.) PSC PPC CC 225 300 300 Physical Requirements 30 600 30 600 30 600 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 Compressive Strength, MPa 3days 7days 28days 16 22 33 16 22 33 16 22 33
HIGH VOLUME FLY ASH CEMENT Fineness 330 ± 10 m 2 /kg Fineness 400 ± 10 m 2 /kg Compressive Strength, MPa 50 45 40 35 30 25 20 15 IS 1489 PPC 35 PPC 40 PPC 45 PPC 50 Compressive Strength, MPa 55 50 45 40 35 30 25 20 IS 1489 PPC 35A PPC 40A PPC 45A PPC 50A 10 15 3 7 Age, days 28 3 7 28 Age, days
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 claylimestone (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 CaCO 3 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 GRADE AND DOLOMITIC LIMESTONE MULTICOMPONENT BLENDED CEMENTS CALCINED CLAY & LIMESTONE COMBINATION IMPROVING THE PERFORMANCE OF COMPOSITE CEMENT SEPARATE FINE GRINDING OF CONSTITUENTS, CONTROL OF PSD OF INDIVIDUAL 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 mineral additives 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 Multicomponent blended cement Calcined claylimestone cement Geopolymeric binders
Thank You
CHEMICAL COMPOSITION OF DIFFERENT TYPES OF SLAG SAMPLES CONSTITUENTS (%) LEADZINC SLAG COPPER SLAG STEEL SLAG BLAST FURNACE SLAG GOI / LOI 5.68 6.65 1.08 1.14 SiO 2 18.08 25.14 12.24 31.86 CaO 17.91 1.09 47.44 38.51 Al 2 O 3 8.17 1.78 2.00 19.78 Fe 2 O 3 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 Cement Composition as per EN 19711 Main Constituents Composite Cement CEM V/A Composite Cement CEM V/B Clinker 4064 2038 Granulated Blast furnace slag Siliceous fly ash/ natural pozzolana/ natural calcined pozzolana 1830 3149 1830 3149
Ternary Blended Cements ASTM C 595 14 Type of mineral additive combinations Limit of mineral additives Two different pozzolanas Maximum content of pozzolana 40 % Slag and pozzolana Pozzolana and limestone Slag and limestone Maximum content of limestone 15 % Total content of pozzolana, limestone and slag not more than 70%
Main Constituents Pozzolana Flyash Cement Type Designation Notation Clinker GGBS Silica Fume Natural Industrial Siliceous Clacare ous Burnt Shale Limestone Minor Additional Constituent Portland Slag Cement II/AS II/BS 8094 6579 620 2135 05 05 Portland Silica Fume Cement II/AD 9094 610 05 Portland Pozzolana Cement II/AP II/BP II/AQ II/BQ 8094 6579 8094 6579 620 2135 620 2135 05 05 05 05 Portland Flyash Cement II/AV II/BV II/AW II/BW 8094 6579 8094 6579 620 2135 620 2135 05 05 05 05 Portland Burnt Shale Cement II/AT II/BS 8094 6579 620 2135 05 05 Portland Limestone Cement II/AL II/BL 8094 6579 620 2135 05 05 II Portland Composite Cement II/AM II/BM 8088 6579 05 05 2135 1220 Portlandcomposite cement Composition as per EN 19711
Portland Composite Cement Composition as per EN 19711 Main Constituents CEM II / AM CEM II / BM Clinker 8088 6579 Granulated Blast furnace slag Calcareous fly ash Siliceous fly ash Natural pozzolana Natural calcined pozzolana 1220 2135 Silica fume Burnt shale Limestone