Makara Journal of Science Makara Journal of Science
Volume 26
Issue 4 December Article 7
12-30-2022
Feasibility Studies for Use of Copper Slag in Clinker Manufacture Feasibility Studies for Use of Copper Slag in Clinker Manufacture
Suresh Vanguri
National Council for Cement and Building Materials, Ballabhgarh, Faridabad, Haryana 121004, India Suresh Palla
National Council for Cement and Building Materials, Ballabhgarh, Faridabad, Haryana 121004, India, [email protected]
Gonthi Prasad
National Council for Cement and Building Materials, Ballabhgarh, Faridabad, Haryana 121004, India Sanjeev Kumar Chaturvedi
National Council for Cement and Building Materials, Ballabhgarh, Faridabad, Haryana 121004, India Bibekananda Mohapatra
National Council for Cement and Building Materials, Ballabhgarh, Faridabad, Haryana 121004, India
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Recommended Citation Recommended Citation
Vanguri, Suresh; Palla, Suresh; Prasad, Gonthi; Chaturvedi, Sanjeev Kumar; and Mohapatra, Bibekananda (2022) "Feasibility Studies for Use of Copper Slag in Clinker Manufacture," Makara Journal of Science: Vol.
26: Iss. 4, Article 7.
DOI: 10.7454/mss.v26i4.1306
Available at: https://scholarhub.ui.ac.id/science/vol26/iss4/7
This Article is brought to you for free and open access by the Universitas Indonesia at UI Scholars Hub. It has been accepted for inclusion in Makara Journal of Science by an authorized editor of UI Scholars Hub.
Feasibility Studies for Use of Copper Slag in Clinker Manufacture
Suresh Vanguri, Suresh Palla
*, Gonthi Prasad, Sanjeev Kumar Chaturvedi, and Bibekananda Mohapatra
National Council for Cement and Building Materials, Ballabhgarh, Faridabad, Haryana 121004, India
*E-mail: [email protected]
Received January 4, 2022 | Accepted December 30, 2022
Abstract
This study investigated the feasibility of using copper slag (CS-C) as a raw material in the production of Portland cement (PC). The effect of addition of 0%-3.5% CS-C on the clinkerization process, mineralogy, microstructure, and compressive strength development was studied. The Presence of CS-C in the raw mix resulted in the reduced temperature of clinker- ization by about 50 °C. The quality of clinker prepared from the raw mix containing 3% CS-C and burned at 1400 °C was comparable to that of clinker prepared from the raw mix containing no CS-C and burned at 1450 °C. Gradual polymorphic modification of alite phase from rhombohedral to monoclinic upon the addition of CS-C was confirmed by X-ray diffrac- tion (XRD) study. XRD and optical microscopy studies revealed the formation of more alite in the clinker prepared, at 1400 °C, from the raw mix containing 3% CS-C compared with the clinker prepared, at 1450 °C, from the raw mix containing no CS-C. This finding indicated the mineralizing effect of CS-C on clinkerization. Well-developed and large- sized alite grains were observed in the clinker samples prepared using CS-C. Portland clinker, prepared using CS-C as a raw mix component showed better mechanical performance characteristics than the control clinker. These results clearly establish the beneficial role of CS-C as a raw mix component in clinkerization and can replace conventional sources of iron such as laterite.
Keywords: alite, clinkerization, mineralizers, mineralogy and microstructure, monoclinic (M3), rhombohedral, slag
Introduction
Concrete is the world’s second most consumed commodity after water. Cement, which is the pivotal component in concrete, is manufactured by the combustion of limestone (CaCO3), which results in the generation of CO2 [1]. Further, the manufacturing process of cement is highly energy consuming (requires temperature ~1450 °C) with contribution of ~ 6%-7% to the world’s total man-made CO2 emissions. With the rising environmental concerns about the effects of CO2
on world climate, cement manufacturers have directed their efforts to decrease fuel use, use energy efficient technologies, and re-use “waste” materials in the cement production [2, 3]. Among the various alternatives available for reduction of greenhouse gas emissions from cement manufacturing, the use of industrial waste materials/by-products is beneficial from the economical and sustainability points of view. Especially in India, as limestone and coal are becoming dearer day by day, conversion of these natural resources is essential for sustainable construction.
A potential future shortage of low-cost raw materials is the first aspect that should be considered in the context of
the cement and concrete industry, because of its huge consumption of conventional limestone-based materials.
Cement rotary kiln provides an effective way of harmless treatment and resource utilization for several industrial wastes. Industrial wastes from several sectors and processes have been identified as potential alternate fuels and alternative raw materials in Portland cement (PC) production [4]. Industrial wastes/by-products contains certain metal oxides, which even at low concentrations exert a remarkable effect on the sintering process of cement raw mixes [5-6]. Such compounds may modify the temperature of first liquid phase formation, and amount of melt, change the rate of reactions occurring in the solid state within the liquid phase or at the liquid-solid interface, alter the viscosity and surface tension of the melt and affect crystal growth and morphology [7–9].
Kiln conditions are very important for the formation and growth of clinker phases [10–15]. Presence of minerals like fayalite and magnetite have beneficial influence by substituting their natural mineral resources in the manufacture of cement clinker. The benefits of such substitution include lower production costs and energy savings. Their use leads to the question of where trace elements, such as copper that are present in such waste materials are absorbed in the clinker. The present paper
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investigated the binding tendency of copper in different phases of clinker.
Copper slag (CS-C) is a type of industrial byproduct produced during the copper-making process. CS-C is a massive metallurgical residue obtained from the transformation of copper ore concentrates into metallic copper in copper smelters [16]. Slag is disposed in landfills that occupy large areas of land. Their chemical composition is rich in iron, and silicon. Utilization of the CS-C is of increasing interest owing to environmental concerns and the sustainable development requirement in the copper and cement industries. CS-C has been used in cement and concrete materials, for instance, as supplementary cementing materials [17], coarse or fine aggregates in concrete [18–20]. However, given the relatively poor hydraulic and pozzolanic properties of CS-C, the quantity of CS-C used as a replacement for PC was limited [17–21]. Shi et al. reviewed the characteristics of CS-C from different industries and its applications in cement and concrete [18]. M. M Ali et al studied the utilization of CS-C as a raw mix component (up to 2.5%) for manufacture of clinker. However, the characteristics of slag depend on its manufacturing process and varies significantly from industrial production [7]. This paper concerned the addition of CS-C as a raw mix component for clinker and studied its effect on clinker phase formations and physical properties.
Materials and Methods
Raw materials, such as high-grade limestone, (LS-HG), low grade limestone, (LS-LG), laterite, (LAT), red ochre, (RO), bauxite, (BAU), CS-C, coal, and gypsum, were analyzed for their chemical composition as per the respective standard procedures. The unreacted lime (free lime) in clinker was determined in accordance with the standard ethylene glycol method. The crystalline phase composition of the material was investigated using an X- ray diffractometer. (Rigaku International, Japan, D-Max 2200 V/PC, using CuKα radiation (λ =1.5405 Å)
.
Based on the chemical compositions of raw materials, theoretical raw mixes were designed with gradual replacement of LAT with CS-C by maintaining the alite content, alumina modulus (AM) and silica modulus (SM)
constant. The designed raw mixes included the control sample labeled as RM-0 and CS-C containing samples (1.5, 2.5, 3.0, and 3.5 wt%) was labeled as RM-1, RM-2, RM-3, and RM-4, respectively. All the raw materials were separately ground in laboratory ball mill, and retention at 90 µm was maintained in the range of 15% - 18%. Based on the weight proportions given in Table 1, all the raw materials were weighed, thoroughly blended, and ground to achieve the desired fineness in terms of percentage retention at 212 and 90 µm, which were maintained in the range of 4.50%-5.25% and 22%-23%, respectively. The 10 mm nodules of raw mix samples were prepared by mixing and drying at ambient temperature. These nodules were subjected to thermal treatment at temperatures of 1350 °C, 1400 °C, and 1450
°C by retention for 20 min in a laboratory furnace. The ambient-cooled fired nodules were then analyzed for free lime content to study the degree of lime assimilation in the development of clinker mineral phases.
Mineralogical and granulometric analysis of clinker samples (CLs) was carried out using optical microscope.
The samples were analyzed for heavy elements using an inductive coupled plasma-optical emission spectrometer (model Vista-MPX, made by Varian) as per the procedures laid down in ASTM D-5233 (ASTM, 1995). Physical performance characteristics of Ordinary PC (OPC) samples were studied as per Indian standard specification IS: 4031 (BIS, 1989, 1998). The burned clinker nodules were ground and evaluated for free lime content.
Scanning electron microscopy (SEM) studies of the samples were carried out using JEOL 6510 LV.
Secondary electron images were obtained to study the sample morphology and microstructure. Optical microscopic studies for investigation of the microstructure and granulometry of clinker phases were carried out using a Nikon Polarizing Microscope, E 600 POL. The CLs were fixed in molds, ground to prepare smooth cross sections, etched with HF, and studied under reflection mode.
Raw Mix Design
Table 2 provides the chemical compositions of all raw materials. Different raw mixes (RM-0 to RM-3.5) were designed using CS-C, LS-LG, LS-HG, LAT, RO, BAU, Table 1. Weight Proportions of Designed Raw Mix Compositions
Raw Mix Raw Materials Proportions (Wt. %) CA (%)
CS-C LS-HG LS-LG LAT RO BAU 1.53
RM-0 0.0 13.5 80.5 5.0 0.5 0.5 1.53
RM-1.5 1.5 13.4 80.8 2.5 1.8 0.0 1.53
RM-2.5 2.5 12.05 82.55 0.87 0.0 2.03 1.53
RM-3.0 3.0 12.2 82.4 0.1 0.5 1.8 1.53
RM-3.5 3.5 28.2 65.4 0.0 2.4 0.5 1.53
Table 2. Chemical Composition of Limestone, Additives, CS-C and CA Samples Oxide
constituents
Percentage (%)
LS-HG LS-LG LAT RO BAU CS-C GYP CA
LOI (%) 42.53 35.29 13.25 22.21 26.24 7.48 17.16* 2.27
CaO (%) 52.52 44.58 4.41 1.67 1.9 1.63 28.28 9.84
SiO2 (%) 1.88 15.52 23.85 11.48 3.96 25.35 12.44# 50.68
Al2O3 (%) 0.39 1.94 15.67 47.77 52.11 4.09 0.51 18.49
Fe2O3 (%) 0.12 0.74 39.20 4.31 3.97 64.00 0.40 4.67
MgO (%) 2.18 1.11 1.36 0.45 0.36 0.81 0.74 0.64
SO3 (%) 0.05 0.07 0 0 0 0.0 40.19 10.46
Na2O (%) 0.22 0.22 0.21 0.14 0.17 0.29 0.05 0.55
K2O (%) 0.04 0.24 0.14 0.02 0.02 0.54 0.04 1.06
Free silica (%) 1.46 11.69
*Combined water, #Silica + Insoluble Residue
Table 3. Potential Phase Composition of Clinker Phases, as per Bogue’s Method
S. No. Sample No. Percentage Liquid Content
C3S C2S C3A C4AF (%)
1. CL-0 55.93 20.97 5.57 12.28 25.69
2. CL-1.5 55.82 20.67 5.65 12.32 25.82
3. CL-2.5 55.86 20.46 5.65 12.37 25.85
4. CL-3.0 55.82 20.29 5.63 12.49 26.00
5. CL-3.5 55.72 18.85 5.97 13.56 27.88
and coal ash (CA) (Table 2). The CS-C content was varied from 0% to 3.5%. RM-O, was prepared with conventional source of iron (laterite) and without the addition of CS-C. The CA absorption was uniformly kept at the level of 1.53% in all mixes. Clinker parameters, such as limestone saturation factor (LSF), SM, and AM, were in the ranges of 0.93-0.94, 2.22-2.53 and 1.14-1.16, respectively (Table 3). The potential phase compositions of tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF), as estimated by Bogue’s method, were in the range of 55.72%–55.93%, 18.85%–20.97%, 5.57%–5.97% and 12.28%–13.56%, respectively. The liquid content varied from 25.69%–27.88 %.
Results and Discussion
Chemical and mineralogical evaluation of raw materials. Given the substantial amount (64.0%) of iron- (III) oxide in CS-C, it can be explored for the replacement of conventional iron-bearing natural raw materials for the manufacture of clinker. Although the silica content in CS-C is as high as approximately 25%, it is in not in its most inert form (quartz) and may not pose a problem in clinkerization. In addition, the presence of amorphous contents, as evident from X-ray Diffraction (XRD) studies, CS-C may contain reactive silica, which is more reactive and can aid the burnability of the raw mix, to a certain extent. The chemical and mineralogical characterization of CS-C and other raw materials established its suitability as a raw material with 64.0%
Fe2O3 existing mainly in the form of phases, such as
fayalite (Fe2(SiO4) and magnetite (Fe3O4). Along with iron oxide, CS-C contains 0.20% titanium dioxide (TiO2), 0.03% manganese (III)-oxide (Mn2O3), and 0.46% phosphorus pentoxide (P2O5), along with 0.01%
MnO, and 0.56% of sulfide sulfur. These oxides are known for their mineralizing effect, which can help in melt formation at early temperatures and improve the kinetics of formation of clinker phases. Inductive coupled plasma spectrometric studies of CS-C, estimated the contents of Ba (0.02%), Cd (0.001%), Co (0.026%), Cu (0.96%), Cr (0.052%), Zn (0.139%), Mn (0.021%), Mo (0.298%), Ni (0.026%), and Sr (0.009%). Although these elements also have a positive influence on clinkerization, to a certain limit, their effect in this case may be negligible due to their low concentrations and considering the small addition levels of CS-C in the raw mix.
Burnability investigations of designed clinkers. In cement raw mix, the formation of dicalcium silicate (C2S), occurs followed by its conversion into tricalcium silicate (C3S) via the further reaction between C2S and CaO. Therefore, the unreacted CaO, called free lime, is a measure of completeness of the clinkerization reaction that leads to the formation of C3S phase. The lower the quantity of free lime, the greater is completeness of clinkerization reaction. Burnability investigations are therefore important to assess the reactivity of constituent oxides and thermal energy requirements in the formation of clinker mineral phases and depend considerably on the raw mix design, i.e., LSF value, SM, AM and liquid content during clinkerization reaction in the kiln.
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Table 4. Burnability Studies of Prepared Raw Mixes Raw
Mixes
Free CaO (%)
1300 °C 1350 °C 1400 °C 1450 °C
CL-0 3.19 1.28 0.72 0.55
CL-1.5 2.85 1.18 0.54 0.30
CL-2.5 2.74 1.14 0.41 0.26
CL-3.0 2.45 1.06 0.36 0.24
CL-3.5 2.41 1.06 0.31 0.24
Figure 1. Change in the f-CaO Content with the Amount of CuO
Table 4 shows the obtained free lime of the designed raw mixes. CS-C-containing raw mixes showed a slightly better rate of lime assimilation in the CL compared with the control sample at all temperatures. Alite content increased in the presence of CS-C at all temperatures.
The free lime content at 1350 °C more than 2% and reduced to less than 1% in all the raw mixes. At 1400 °C, the free lime content in CLs was reduced from 0.72% to 0.31% with the increase in CS-C content. Similarly at 1450 °C, the free lime content in CLs reduced from 0.55% to 0.24% with the increase in CS-C content. This finding can be attributed to the mineralizing effect of CS- C. Figure 1 displays the variations in the content of free- CaO in the clinker with the amount of CS-C at 1400 °C.
Lime assimilation increased with the increase in CS-C content. The positive effect of CS-C on the clinker burning process can be attributed to the decrease in temperature of liquid phase formation and an increase in its quantity [12, 14, 22].
Optical microscopy.Microstructural studies of CLs, including control clinker, CL-0 to CL-3.5, have indicated definite improvement in the microstructure of clinker phases with the addition of copper CS-C. The microstructure of CL-0 (Figure 2a) fired at 1400 °C
indicated moderately developed and inhomogeneously distributed clinker phases with lath-shaped alite grains.
The optical micrograph of CL-1.5 prepared with the addition of 1.5% CS-C and fired at 1400 °C showed improvement in phase formation (Figure 2b). Micrographs of clinker CL-2.0, which was prepared by incorporation of 2.0% CS-C in the raw mix and firing at 1400 °C, exhibited further improvement in phase formation with the formation of round C2S grains and euhedral C3S grains (Figure 2c). The micrograph of CL-3.0, showed perfect hexagonal alite grains with micro-sized inclusions (Figure 2d). Numerous semi-crystalline belite grains were also observed. A sharp increase was observed in the development of alite and belite phases compared with CL-2.5 prepared at the same temperature. A similar trend was noted in the development of mineral phases in CL- 3.5 (Figure 2e). The comparative evaluation of all CLs indicated that in general, the quality of clinker produced upon the addition of CS-C in the raw mix improved continuously with the increase in CS-C addition up to 3.50%. Table 5 shows the results of quantitative analysis of clinker phases along with granulometry.
XRD analysis. Mineralogy characterization of all the samples was carried out by powder XRD, and the X-ray diffractograms of all the samples are given in Figure 2.
Qualitative X-ray diffractogram of all the samples showed the presence of alite, belite, aluminate, ferrite and free lime. The obtained hkl values or 2-theta diffractograms of all the CLs were matched the standard peak positions in the ICDD data base pdf card numbers of 013-0272 (alite), 01-083-0461 (larnite or belite), 038- 1429 (C3A), and 030-0226 (C4AF) and trace amount of 01-081-0065 (quartz). The reference data card standard peak positions were also provided at the bottom of the XRD. From these results, the XRD of CLs indicated the formation of well-developed crystalline clinker phases.
Qualitative XRD analysis indicated the presence of alite, belite, aluminate, ferrite, and quartz phases in all the CLs (Figure 3). Quantitative XRD analysis of CLs showed the formation of more alite phase in CL-3-1400 than the reference sample CL-0-1450. Quantitative XRD analysis demonstrated the positive effect of CS-C addition on the formation of alite phase. The effect of CS-C addition on alite polymorph was studied by monitoring the peak at 2θ
= 51°–53°, which was the independent peak of alite in the clinker XRD pattern without any overlap from other clinker phases. With the increase in the CS-C content, changes in alite polymorph were observed. A gradual change in the peak shape at 2θ = 51°-53° from almost a singlet to a well-defined doublet indicated the alite polymorphic transformation from rhombohedral (R) form to monoclinic (M3) form (Figure 4). The M3 form of alite is considered to be more reactive than its R form [22]. The increase in alite content coupled with polymorphic transformation to a more reactive form can result in better physical performance of CLs.
Figure 2a. Distribution of Alite and Belite Grains in CL-0 at 1450 °C (20x)
Figure 2b. Distribution of Alite and Belite Grains in CL-1.5 at 1450 °C (20x)
Figure 2c. Distribution of Alite and Belite Grains in CL-2.0 at 1450 °C (20x)
Figure 2d. Distribution of Alite and Belite Grains in CL-2.5 at 1450 °C (20x)
Figure 2e. Distribution of Alite and Belite Grains in CL-3.5 at 1450 °C (20x)
SEM analyses. CLs prepared without and with different doses of CS-C were examined under SEM, and the micrographs are given in Figure 5. The portions of samples presented in the micrographs were selected as representative in regard to the size and shape of the alite and belite grains. Alite grains in CL-0-1450 were developed in euhedral to subhedral form (Figures 5e and 5f). Some alite grains were found in fused form. A few belite grains were present in clusters, which may affect the grindability and reactivity of belite. Lath-shaped C3A and C4AF phases were observed around the grains of alite and belite. With the increase in CS-C content, more regular and well-developed alite and belite grains were
observed along with the fused grains (Figures 5a, 5b, and 5c). Alite grains in CL-3.0-1400, which was prepared using 3.0% CS-C fired at 1400 °C, developed into more euhedral form and were larger size (Figures 5a and 5c) than those of CL-0-1450, which was prepared without CS-C and fired at 1450 °C. Figure 5d shows the well- developed alite grains in CL-4-1400. The alite grain size was in the range of 4µm-20µm in CL-1-1450 and 5µm- 30µm in CL-4-1400. The increase in compaction of the clinker phases and grain size with the increased use of CS-C can result in a lower grindability and lower reactivity of the alite phases. However, evident from XRD studies, that the polymorphic modification of the
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alite phase to a more reactive form along with the increased quantity of alite with increased CS-C content can nullify the effect of increased alite grain size on clinker reactivity.
Performance evaluation of OPC samples. Bulk OPC samples, OPC-C (control cement prepared using CL-0- 1450), and OPC-4 (prepared using CL-3.0-1400) were prepared and evaluated for their physical properties as per the relevant Indian standard test procedures. The results indicated that changes in clinker properties due to the addition of CS-C had minimal effect on the water demand for normal consistency of cement samples. The consistency of both cement samples was approximately 25.0% when tested as per Indian standard (IS: 4031(4)).
The initial and final setting times of OPC-C were 110 and
150 min, respectively, compared with those of OPC-4, which were 115 and 160 min (Table 6). The expansion measured in accordance with the Le-Chatelier and autoclave process varied from 1.0 mm and 0.04% for both samples, respectively, whiles the limits according to IS269:2015 were 10mm and 0.8%. The physical performances of control cement without Cu slag (OPC- C) and OPC-4, were comparable in terms of compressive strength. The modifications of clinker mineral phase polymorphism and grain sizes have resulted in the comparable compressive strength development in OPC- 4 compared with OPC-C. Clinker prepared using CS-C as a raw mix component at 1400 °C showed physical performance comparable to that of clinker prepared without CS-C as raw mix component at 1450 °C.
Table 5. Quantitative Estimation and Granulometry of Different CLs using Optical Microscopy
Sample No. Phases Present Quantity (%)
Granulometry (m)
Min. Max. Avg.
CL-0-1450
Alite 50 2 59 27
Belite 35 2 68 35
Interstitial matter 15 - - -
\
CL-1.5-1400
Alite 55 2 60 29
Belite 30 3 62 30
Interstitial matter 15 - - -
CL-2.0-1400
Alite 53 2 65 33
Belite 34 2 69 37
Interstitial matter 13 - - -
CL-2.5-1400
Alite 52 2 60 28
Belite 34 2 55 27
Interstitial matter 14 - - -
CL-3.0-1450
Alite 50 2 62 30
Belite 35 2 59 28
Interstitial matter 15 - - -
CL-3.5-1400
Alite 53 2 67 30
Belite 34 3 59 28
Interstitial matter 13 - - -
Figure 3. X-Ray Diffractogram of CL-0 to CL-3.5 Fired at 1400 °C
Figure 4. Effect of CS-C on the Development of Alite Polymorph, Change in Peak Shape with Increase in CS-C Content
Figure 5. SEM Images of (a) Alite and Belite Grains Along with Interstitial Matter in CL-1-1450, (b) Alite and Belite Grains Along with Interstitial Matter in CL-3-1400, (c) Close-packed Alite and Belite Grains in CL-4-1400, (d) Well- developed Alite Grains in CL-4-1400; (e and f) Alite and Belite Grains in CL-0-1450
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Table 6. Physical Performance of Cement Samples
S. No. Property OPC-C OPC-4 IS:269-2015
1. Blaine’s Fineness (cm2/kg) 3280 3310 2250, Min.
2. Consistency (%) 25.0 25.0
3. Setting Time (Minutes)
4. Initial (IST) 110 115 30, Min.
5. Final (FST) 150 160 600, Max.
6. Compressive Strength (MPa)
7. 3 Days 31.0 31.5 27, Min.
8. 7 Days 43.5 45.2 37, Min.
9. 28 Days 59.3 62.4 53, Min.
10. Soundness
11. Le-Chatelier (mm) 1.0 1.0 10.0, Max.
12. Autoclave (%) 0.04 0.04 0.8, Max.
Conclusion
Burnability studies of raw mixes indicated that the use of CS-C as a raw mix component in clinker preparation resulted in the decreased of clinkerization temperature by approximately 50°C and promoted the formation of alite phase. Systematic polymorphic transformation of alite from R to M3 has been observed with the increase in CS- C content in the raw mix. As the M3 polymorph of alite has a higher reactivity than its R form, the transformation may have positive influence on the properties of the resultant cement. Although the sizes of alite grains were enhanced with the increased content of CS-C, based on the mechanical properties of cement, the effect of this size enhancement on the reactivity of alite grains is negligible or nullified by the effects due to the polymorphic transformation of alite phase. The mechanical properties of clinker prepared using 3% CS- C at 1400OC showed a performance comparable to that of the CL-0 prepared at 1450OC. Changes in clinker properties due to the addition of CS-C had minimal effect on water demand, and normal consistency, of the resultant OPC. These results establish the beneficial role of CS-C as a raw mix component in clinkerization and can replace conventional sources of iron such as LAT.
Acknowledgment
This paper is based on the research and development work carried out at National Council for Cement and Building Materials (NCB), Ballabgarh, Haryana, India.
This paper is published with kind permission of the Director-General, of NCB.
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