- Email: [email protected]
Effect of calcination temperature on the pozzolanic activity of sugar cane bagasse ash
Construction and Building Materials 23 (2009) 3301–3303
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Effect of calcination temperature on the pozzolanic activity of sugar cane bagasse ash G.C. Cordeiro a,*, R.D. Toledo Filho b,1, E.M.R. Fairbairn b,1 a
Laboratory of Civil Engineering, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Av. Alberto Lamego, 2000, Parque Califórnia, CEP 28013-602, Campos dos Goytacazes/RJ, Brazil b Program of Civil Engineering, COPPE/Universidade Federal do Rio Janeiro, Av. Brigadeiro Trompovski S/N, Centro de Tecnologia, Bloco I-2000, Sala 216, CEP 21941-970, Rio de Janeiro/RJ, Brazil
a r t i c l e
i n f o
Article history: Received 6 April 2008 Received in revised form 29 December 2008 Accepted 6 February 2009 Available online 2 July 2009 Keywords: Sugar cane bagasse ash Pozzolan Calcination Characterization methods Microstructure
a b s t r a c t This work presents the results of the processing of sugar cane bagasse ash (SCBA) under controlled calcination conditions in order to obtain materials with optimum pozzolanic activity. Bagasse samples were burnt in an aired electric oven with a heating rate of 10 °C/min, at 350 °C for 3 h, and at different temperatures ranging from 400 to 800 °C for another 3 h. For all calcination temperatures the pozzolanic activity, structural state of silica and loss on ignition of the ashes were determined. Moreover, the SCBA with greater pozzolanicity was characterized by using chemical analysis, scanning electron microscopy, density, specific surface area and chemical reactivity. Ó 2009 Published by Elsevier Ltd.
1. Introduction Sugar cane bagasse ash (SCBA) is generated as a combustion byproduct of sugar cane bagasse. Composed mainly of silica, this byproduct can be used as a pozzolan in cement based paste, mortar and concrete. Several authors [1–6] have found that the use of SCBA as a partial Portland cement replacement can improve the mechanical and durability properties of cementitious materials. The benefits provided by SCBA are due to both physical and chemical effects. The physical effects are mainly associated with their influence on the packing characteristics of the solid mixture [3]. On the other hand, the chemical effects (also called pozzolanic effects) are linked to their capability of providing amorphous silica that will react with Ca(OH)2 in the presence of water during cement hydration. SCBA is usually obtained under uncontrolled burning conditions in boilers of the cogeneration processes. Thus, the ash may contain black particles due to the presence of carbon and crystalline silica, when burning occurs under high temperature (above 800 °C) or for a prolonged time. The quality of the ash can be improved by the controlling parameters such as temperature, rate of heating, soaking time and atmosphere, as was reported for rice husk ash (RHA) [7–10] – a highly pozzolanic material. Considering only the Brazil* Corresponding author. Tel./fax: +55 22 27241019. E-mail address: [email protected] (G.C. Cordeiro). 1 Tel.: +55 21 25628474; fax +55 21 25628484. 0950-0618/$ - see front matter Ó 2009 Published by Elsevier Ltd. doi:10.1016/j.conbuildmat.2009.02.013
ian production of sugar cane, approximately 2.5 million tonnes of sugar cane bagasse ash were generated in 2006. This ash contains few mineral fertilizers for soils. In the present work, processing and characterization of highly reactive SCBA are studied. Initially, different calcination temperatures were allowed to obtain SCBA with amorphous silica and low carbon content. Detailed measurements of structural state, pozzolanic activity and loss on ignition were carried out in order to compare the performance of the different SCBAs. Subsequently, one optimal SCBA was characterized according to pozzolan specifications.
2. Materials and methods The bagasse (raw material) used came from a sugar and alcohol factory in the State of Rio de Janeiro (Brazil). It was washed in the laboratory with distilled water and dried at 45 °C in a ventilated oven to remove impurities. Subsequently, the bagasse samples were burnt in an aired electric oven with a 10 °C/min heating rate, first at 350 °C for 3 h, and then at different temperatures ranging from 400 to 800 °C, at increments of 100 °C, for another 3 h. The ashes are designated as SCBA-T, where T is the maximum temperature. The ratio of sample to internal chamber volumes was maintained at 0.036 for all burning processes. The burning was performed in two steps in accordance with the efficient results obtained by Sugita [10] with RHA. After calcination and cooling inside the oven, the samples were subjected to dry grinding using a planetary mill (Restch PM-4) with alumina jar operating with 300 rpm and 25% filling of alumina spheres as grinding media. Particle sizes were measured using a laser diffraction analyzer (Mastersizer 2000, Malvern Instruments) and the loss on ignition (LOI) was determined by heating the sample up
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G.C. Cordeiro et al. / Construction and Building Materials 23 (2009) 3301–3303
to 1000 °C according to ASTM C-114 recommendations [11]. X-ray diffraction patterns (powder method) were taken using a Rigaku Miniflex diffractometer with Cu–Ka radiation. The chemical composition was determined by X-ray fluorescence (XRF) using a Phillips PW2400 spectrometer and the specific surface area was measured according to the N2 adsorption (BET) using a Gemini 2375V5. The density was determined using an Accupic Micromeritics helium picnometer. The morphology of SCBA particles was investigated using scanning electron microscope (Jeol JXA840A) images coupled to microanalysis by energy-dispersive spectroscopy (EDS). The samples were carbon-coated under vacuum. The reactivity of the SCBAs was evaluated by two methods: mechanical test (pozzolanic activity index) and chemical analysis (Chapelle method). The principle of determining the pozzolanic activity index is to compare the compressive strength of an ISO mortar with that of a mortar where 35% of the cement volume is replaced by SCBA, as described in Brazilian Standard NBR 5752 [12]. The ISO mortar was prepared with sand–cement and water–cement ratios of 3 and 0.52 (in mass), respectively. The pozzolanic activity was also determined based on CaO fixation by ash in the Chapelle method [13]. The test consisted of heating a solution of 1.0000 g of CaO, 1.0000 g of ash and 250.0 g of water up to 90 °C and keeping this temperature constant for 16 h. The free CaO amount was then measured by titration and the fixed CaO was estimated.
Table 1 Physical properties of SCBAs produced under different burning conditions. Samples
LOI (%)
P10 (lm)
P50 (lm)
P90 (lm)
PAI (%)
SCBA-400 SCBA-500 SCBA-600 SCBA-700 SCBA-800
84.5 14.0 5.7 3.0 1.3
1.78 1.69 1.23 1.14 0.88
12.20 11.27 11.56 12.31 10.10
29.78 28.17 29.05 29.14 27.99
28 73 77 63 69
3. Results and discussion The particle size distributions of the ground SCBAs are shown in Fig. 1. The ashes present similar particle size distributions, with average sizes (P50) varying from 7 to 12 lm (Table 1). Other characteristic sizes such as P10 (10% passing size) and P90 (90% passing size) are almost the same (Table 1). The similar particle size distributions displayed in Fig. 1 is an important characteristic of the ashes aiming the evaluation of its pozzolanic activity. Similar particle sizes correspond to similar physical packing what emphasizes the chemical effect of the pozzolan in the mechanical behavior of the material. The values of LOI decrease with increasing temperatures, as shown in Table 1. These results indicate also that the calcination conditions adopted are sufficient to remove the carbon and volatile compounds, mainly for temperatures greater than 600 °C. The XRD patterns displayed in Fig. 2 indicate the variation of the crystallinity of the silica as a function of temperature (see reference [9]). The SCBA-400 and SCBA-500 are amorphous, with a diffused halo between 2h 20° and 30°. Above 600 °C, the ashes exhibit an incipient crystallization of phosphates (Ca9MgK[PO4]7 and KAlP2O7). The crystallization of silica in cristobalite is observed in the SCBA800. Temperatures of calcination higher than 800 °C are not used in this work. The results of pozzolanic activity index (PAI) are given in Table 1. The PAI of the SCBA produced by burning at 400, 500 and 600 °C increases with increasing calcination temperatures due to signifi-
2.5
SCBA-4 0 0 SCBA-50 0
Frequency (%)
2.0
SCBA-6 0 0 SCBA-70 0
1.5
SCBA-8 0 0
1.0 0.5 0.0 0.1
1.0
10.0
Particle size ( µm)
100.0
Fig. 1. Particle size distributions of SCBAs.
1000.0
Fig. 2. X-ray diffraction patterns of SCBAs.
cant removal of carbon. With the formation of crystalline compounds, the values of PAI are slightly decreased. These results show that the temperature of 600 °C is the most appropriated to produce pozzolan from SCBA. At this temperature it is possible to generate an ash predominantly amorphous, with PAI of 77% and LOI of 5.7%. It is important to note that the Brazilian Standard NBR 12653 [14] establishes that 75% is the minimum value required to classify a material as a pozzolan, in analogy to the ASTM C-618 [15]. For the same standard, the LOI should be lower than 6%, which is also indicated by Malhotra and Mehta [16] for pozzolanic materials. The SCBA-600 presents grains of varied shapes and sizes, as can be seen in Fig. 3. There are prismatic particles with well defined edges in contrast to cellular grains with high porosity, typical for organic materials (in details in Fig. 3b). Similar morphologies were observed by Payá et al. [2] in a SCBA from Colombia. The EDS analysis of 180 lm2 area (see green rectangle in Fig. 3b2) shows that the selected prismatic particle contains predominantly silicon and oxygen, with lesser amounts of potassium, sodium, and phosphorus, as can be seen in Fig. 4. The EDS results are in accordance to the chemical composition of the SCBA-600, as shown in Table 2. In this analysis is possible to note that SiO2 (61.0%, in mass) is the main constituent present in the ash, which also contains significant amounts of K2O, P2O5 and CaO. Impurities are observed, such as Na2O3, MnO and Al2O3. In what concerns the physical characteristics, the SCBA-600 presents a density of 2570 kg/m3, a specific surface area of 11887 m2/kg and a gray color. The specific surface area of this sample is significantly larger than that observed for SCBA generated under uncontrolled burning conditions [3–6]. The sample presents Chapelle activity of 421 mg/g, which is significantly higher (28%) than the minimum required for a pozzolanic material [13]. 2 For interpretation of color in Fig. 3, the reader is referred to the web version of this article.
G.C. Cordeiro et al. / Construction and Building Materials 23 (2009) 3301–3303
3303
4. Conclusions The results of the present research indicate that the temperature of calcination is an important parameter for the production of SCBA with pozzolanic activity. Furthermore, the following conclusion can be drawn: the SCBA produced with air calcination at 600 °C for 3 h (3 after hours at 350 °C) with a rate of heating of 10 °C/min presents amorphous silica, low carbon content and high specific surface area. The sample produced with these characteristics presents considerable pozzolanic activity according to both mechanical and chemical methods of evaluation.
Acknowledgements The authors wish to thank the Brazilian Agencies FAPERJ, CNPq, and CAPES for their financial support and also thank the Companhia Açucareira Usina Barcelos for providing the sugar cane bagasse used in the investigation.
References
Fig. 3. Scanning electron microscopy images of the SCBA-600 (a). In details, the prismatic particles (b).
Fig. 4. EDS analysis of the selected area (green rectangle in Fig. 3b) of the SCBA-600.
Table 2 Chemical composition of the SCBA-600 (%, in mass). SiO2
Al2O3
Fe2O3
CaO
Na2O
K2O
MnO
MgO
P2O5
LOI
60.96
0.09
0.09
5.97
0.70
9.02
0.48
8.65
8.34
5.70
[1] Martirena Hernández JFM, Middeendorf B, Gehrke M, Budelmann H. Use of wastes of the sugar industry as pozzolana in lime–pozzolana binders: study of the reaction. Cem Concr Res 1998;28(11):1525–36. [2] Payá J, Monzó J, Borrachero MV, Ordóñez LM. Sugar-cane bagasse ash (SCBA): studies on its properties for reusing in concrete production. J Chem Technol Biotechnol 2002;77(1):321–5. [3] Cordeiro GC, Toledo Filho RD, Tavares LM, Fairbairn EMR. Pozzolanic activity and filler effect of sugar cane bagasse ash in Portland cement and lime mortars. Cem Concr Compos 2008;30(5):410–8. [4] Singh NB, Singh VD, Rai S. Hydration of bagasse ash-blended Portland cement. Cem Concr Res 2000;30(9):1485–8. [5] Ganesan K, Rajagopal K, Thangavel K. Evaluation of bagasse ash as supplementary cementitious material. Cem Concr Compos 2007;29(6): 515–24. [6] Cordeiro GC, Toledo Filho RD, Fairbairn EMR. Use of ultra-fine sugar cane bagasse ash as mineral admixture for concrete. ACI Mater J 2008;105(5): 487–93. [7] Mehta PK. Properties of blended cements made from rice husk ash. ACI Mater J 1977;74(40):440–2. [8] Jaubethie R, Rendell F, Tamba S, Cisse I. Origin of the pozzolanic effect of rice husks. Constr Build Mater 2000;14(8):419–23. [9] Della VP, Kühn I, Hotza D. Rice husk ash as an alternative source for active silica production. Mater Lett 2002;57(4):818–21. [10] Sugita S. On the burning principle and the furnace design based on the principle for producing highly active rice husk ash. In: Proceedings of 3rd international conference on the concrete future, Kuala Lumpur, Malaysia; 1994. [11] ASTM C-114. Standard Test Methods for Chemical Analysis of Hydraulic Cement, Annual Book of ASTM Standards; 2007. [12] ABNT NBR 5752. Pozzolans – Pozzolanic activity – Determination of pozzolanic activity index with Portland cement. ABNT (Technical Standards Brazilian Association), Brazil; 1992. [13] Raverdy M, Brivot F, Paillère AM, Bron R. Appréciation de l’activité pouzzolanique de constituents secondaires. In: Proceedings of 7e Congrès International de la Chimie des Ciments, Paris, France; 1980. [14] ABNT NBR 12653. Pozzolanic materials. ABNT (Technical Standards Brazilian Association), Brazil; 1992. [15] ASTM C-618. Standard specification for fly ash and raw calcined natural pozzolan for use as a mineral admixture in Portland cement concrete, Annual Book of ASTM Standards; 2005. [16] Malhotra VM, Mehta PK. Pozzolanic and cementitious materials. 1st ed. Amsterdam: Gordon and Breach Publishers; 1996.
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Effect of calcination temperature on the pozzolanic activity of sugar cane bagasse ash G.C. Cordeiro a,*, R.D. Toledo Filho b,1, E.M.R. Fairbairn b,1 a
Laboratory of Civil Engineering, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Av. Alberto Lamego, 2000, Parque Califórnia, CEP 28013-602, Campos dos Goytacazes/RJ, Brazil b Program of Civil Engineering, COPPE/Universidade Federal do Rio Janeiro, Av. Brigadeiro Trompovski S/N, Centro de Tecnologia, Bloco I-2000, Sala 216, CEP 21941-970, Rio de Janeiro/RJ, Brazil
a r t i c l e
i n f o
Article history: Received 6 April 2008 Received in revised form 29 December 2008 Accepted 6 February 2009 Available online 2 July 2009 Keywords: Sugar cane bagasse ash Pozzolan Calcination Characterization methods Microstructure
a b s t r a c t This work presents the results of the processing of sugar cane bagasse ash (SCBA) under controlled calcination conditions in order to obtain materials with optimum pozzolanic activity. Bagasse samples were burnt in an aired electric oven with a heating rate of 10 °C/min, at 350 °C for 3 h, and at different temperatures ranging from 400 to 800 °C for another 3 h. For all calcination temperatures the pozzolanic activity, structural state of silica and loss on ignition of the ashes were determined. Moreover, the SCBA with greater pozzolanicity was characterized by using chemical analysis, scanning electron microscopy, density, specific surface area and chemical reactivity. Ó 2009 Published by Elsevier Ltd.
1. Introduction Sugar cane bagasse ash (SCBA) is generated as a combustion byproduct of sugar cane bagasse. Composed mainly of silica, this byproduct can be used as a pozzolan in cement based paste, mortar and concrete. Several authors [1–6] have found that the use of SCBA as a partial Portland cement replacement can improve the mechanical and durability properties of cementitious materials. The benefits provided by SCBA are due to both physical and chemical effects. The physical effects are mainly associated with their influence on the packing characteristics of the solid mixture [3]. On the other hand, the chemical effects (also called pozzolanic effects) are linked to their capability of providing amorphous silica that will react with Ca(OH)2 in the presence of water during cement hydration. SCBA is usually obtained under uncontrolled burning conditions in boilers of the cogeneration processes. Thus, the ash may contain black particles due to the presence of carbon and crystalline silica, when burning occurs under high temperature (above 800 °C) or for a prolonged time. The quality of the ash can be improved by the controlling parameters such as temperature, rate of heating, soaking time and atmosphere, as was reported for rice husk ash (RHA) [7–10] – a highly pozzolanic material. Considering only the Brazil* Corresponding author. Tel./fax: +55 22 27241019. E-mail address: [email protected] (G.C. Cordeiro). 1 Tel.: +55 21 25628474; fax +55 21 25628484. 0950-0618/$ - see front matter Ó 2009 Published by Elsevier Ltd. doi:10.1016/j.conbuildmat.2009.02.013
ian production of sugar cane, approximately 2.5 million tonnes of sugar cane bagasse ash were generated in 2006. This ash contains few mineral fertilizers for soils. In the present work, processing and characterization of highly reactive SCBA are studied. Initially, different calcination temperatures were allowed to obtain SCBA with amorphous silica and low carbon content. Detailed measurements of structural state, pozzolanic activity and loss on ignition were carried out in order to compare the performance of the different SCBAs. Subsequently, one optimal SCBA was characterized according to pozzolan specifications.
2. Materials and methods The bagasse (raw material) used came from a sugar and alcohol factory in the State of Rio de Janeiro (Brazil). It was washed in the laboratory with distilled water and dried at 45 °C in a ventilated oven to remove impurities. Subsequently, the bagasse samples were burnt in an aired electric oven with a 10 °C/min heating rate, first at 350 °C for 3 h, and then at different temperatures ranging from 400 to 800 °C, at increments of 100 °C, for another 3 h. The ashes are designated as SCBA-T, where T is the maximum temperature. The ratio of sample to internal chamber volumes was maintained at 0.036 for all burning processes. The burning was performed in two steps in accordance with the efficient results obtained by Sugita [10] with RHA. After calcination and cooling inside the oven, the samples were subjected to dry grinding using a planetary mill (Restch PM-4) with alumina jar operating with 300 rpm and 25% filling of alumina spheres as grinding media. Particle sizes were measured using a laser diffraction analyzer (Mastersizer 2000, Malvern Instruments) and the loss on ignition (LOI) was determined by heating the sample up
3302
G.C. Cordeiro et al. / Construction and Building Materials 23 (2009) 3301–3303
to 1000 °C according to ASTM C-114 recommendations [11]. X-ray diffraction patterns (powder method) were taken using a Rigaku Miniflex diffractometer with Cu–Ka radiation. The chemical composition was determined by X-ray fluorescence (XRF) using a Phillips PW2400 spectrometer and the specific surface area was measured according to the N2 adsorption (BET) using a Gemini 2375V5. The density was determined using an Accupic Micromeritics helium picnometer. The morphology of SCBA particles was investigated using scanning electron microscope (Jeol JXA840A) images coupled to microanalysis by energy-dispersive spectroscopy (EDS). The samples were carbon-coated under vacuum. The reactivity of the SCBAs was evaluated by two methods: mechanical test (pozzolanic activity index) and chemical analysis (Chapelle method). The principle of determining the pozzolanic activity index is to compare the compressive strength of an ISO mortar with that of a mortar where 35% of the cement volume is replaced by SCBA, as described in Brazilian Standard NBR 5752 [12]. The ISO mortar was prepared with sand–cement and water–cement ratios of 3 and 0.52 (in mass), respectively. The pozzolanic activity was also determined based on CaO fixation by ash in the Chapelle method [13]. The test consisted of heating a solution of 1.0000 g of CaO, 1.0000 g of ash and 250.0 g of water up to 90 °C and keeping this temperature constant for 16 h. The free CaO amount was then measured by titration and the fixed CaO was estimated.
Table 1 Physical properties of SCBAs produced under different burning conditions. Samples
LOI (%)
P10 (lm)
P50 (lm)
P90 (lm)
PAI (%)
SCBA-400 SCBA-500 SCBA-600 SCBA-700 SCBA-800
84.5 14.0 5.7 3.0 1.3
1.78 1.69 1.23 1.14 0.88
12.20 11.27 11.56 12.31 10.10
29.78 28.17 29.05 29.14 27.99
28 73 77 63 69
3. Results and discussion The particle size distributions of the ground SCBAs are shown in Fig. 1. The ashes present similar particle size distributions, with average sizes (P50) varying from 7 to 12 lm (Table 1). Other characteristic sizes such as P10 (10% passing size) and P90 (90% passing size) are almost the same (Table 1). The similar particle size distributions displayed in Fig. 1 is an important characteristic of the ashes aiming the evaluation of its pozzolanic activity. Similar particle sizes correspond to similar physical packing what emphasizes the chemical effect of the pozzolan in the mechanical behavior of the material. The values of LOI decrease with increasing temperatures, as shown in Table 1. These results indicate also that the calcination conditions adopted are sufficient to remove the carbon and volatile compounds, mainly for temperatures greater than 600 °C. The XRD patterns displayed in Fig. 2 indicate the variation of the crystallinity of the silica as a function of temperature (see reference [9]). The SCBA-400 and SCBA-500 are amorphous, with a diffused halo between 2h 20° and 30°. Above 600 °C, the ashes exhibit an incipient crystallization of phosphates (Ca9MgK[PO4]7 and KAlP2O7). The crystallization of silica in cristobalite is observed in the SCBA800. Temperatures of calcination higher than 800 °C are not used in this work. The results of pozzolanic activity index (PAI) are given in Table 1. The PAI of the SCBA produced by burning at 400, 500 and 600 °C increases with increasing calcination temperatures due to signifi-
2.5
SCBA-4 0 0 SCBA-50 0
Frequency (%)
2.0
SCBA-6 0 0 SCBA-70 0
1.5
SCBA-8 0 0
1.0 0.5 0.0 0.1
1.0
10.0
Particle size ( µm)
100.0
Fig. 1. Particle size distributions of SCBAs.
1000.0
Fig. 2. X-ray diffraction patterns of SCBAs.
cant removal of carbon. With the formation of crystalline compounds, the values of PAI are slightly decreased. These results show that the temperature of 600 °C is the most appropriated to produce pozzolan from SCBA. At this temperature it is possible to generate an ash predominantly amorphous, with PAI of 77% and LOI of 5.7%. It is important to note that the Brazilian Standard NBR 12653 [14] establishes that 75% is the minimum value required to classify a material as a pozzolan, in analogy to the ASTM C-618 [15]. For the same standard, the LOI should be lower than 6%, which is also indicated by Malhotra and Mehta [16] for pozzolanic materials. The SCBA-600 presents grains of varied shapes and sizes, as can be seen in Fig. 3. There are prismatic particles with well defined edges in contrast to cellular grains with high porosity, typical for organic materials (in details in Fig. 3b). Similar morphologies were observed by Payá et al. [2] in a SCBA from Colombia. The EDS analysis of 180 lm2 area (see green rectangle in Fig. 3b2) shows that the selected prismatic particle contains predominantly silicon and oxygen, with lesser amounts of potassium, sodium, and phosphorus, as can be seen in Fig. 4. The EDS results are in accordance to the chemical composition of the SCBA-600, as shown in Table 2. In this analysis is possible to note that SiO2 (61.0%, in mass) is the main constituent present in the ash, which also contains significant amounts of K2O, P2O5 and CaO. Impurities are observed, such as Na2O3, MnO and Al2O3. In what concerns the physical characteristics, the SCBA-600 presents a density of 2570 kg/m3, a specific surface area of 11887 m2/kg and a gray color. The specific surface area of this sample is significantly larger than that observed for SCBA generated under uncontrolled burning conditions [3–6]. The sample presents Chapelle activity of 421 mg/g, which is significantly higher (28%) than the minimum required for a pozzolanic material [13]. 2 For interpretation of color in Fig. 3, the reader is referred to the web version of this article.
G.C. Cordeiro et al. / Construction and Building Materials 23 (2009) 3301–3303
3303
4. Conclusions The results of the present research indicate that the temperature of calcination is an important parameter for the production of SCBA with pozzolanic activity. Furthermore, the following conclusion can be drawn: the SCBA produced with air calcination at 600 °C for 3 h (3 after hours at 350 °C) with a rate of heating of 10 °C/min presents amorphous silica, low carbon content and high specific surface area. The sample produced with these characteristics presents considerable pozzolanic activity according to both mechanical and chemical methods of evaluation.
Acknowledgements The authors wish to thank the Brazilian Agencies FAPERJ, CNPq, and CAPES for their financial support and also thank the Companhia Açucareira Usina Barcelos for providing the sugar cane bagasse used in the investigation.
References
Fig. 3. Scanning electron microscopy images of the SCBA-600 (a). In details, the prismatic particles (b).
Fig. 4. EDS analysis of the selected area (green rectangle in Fig. 3b) of the SCBA-600.
Table 2 Chemical composition of the SCBA-600 (%, in mass). SiO2
Al2O3
Fe2O3
CaO
Na2O
K2O
MnO
MgO
P2O5
LOI
60.96
0.09
0.09
5.97
0.70
9.02
0.48
8.65
8.34
5.70
[1] Martirena Hernández JFM, Middeendorf B, Gehrke M, Budelmann H. Use of wastes of the sugar industry as pozzolana in lime–pozzolana binders: study of the reaction. Cem Concr Res 1998;28(11):1525–36. [2] Payá J, Monzó J, Borrachero MV, Ordóñez LM. Sugar-cane bagasse ash (SCBA): studies on its properties for reusing in concrete production. J Chem Technol Biotechnol 2002;77(1):321–5. [3] Cordeiro GC, Toledo Filho RD, Tavares LM, Fairbairn EMR. Pozzolanic activity and filler effect of sugar cane bagasse ash in Portland cement and lime mortars. Cem Concr Compos 2008;30(5):410–8. [4] Singh NB, Singh VD, Rai S. Hydration of bagasse ash-blended Portland cement. Cem Concr Res 2000;30(9):1485–8. [5] Ganesan K, Rajagopal K, Thangavel K. Evaluation of bagasse ash as supplementary cementitious material. Cem Concr Compos 2007;29(6): 515–24. [6] Cordeiro GC, Toledo Filho RD, Fairbairn EMR. Use of ultra-fine sugar cane bagasse ash as mineral admixture for concrete. ACI Mater J 2008;105(5): 487–93. [7] Mehta PK. Properties of blended cements made from rice husk ash. ACI Mater J 1977;74(40):440–2. [8] Jaubethie R, Rendell F, Tamba S, Cisse I. Origin of the pozzolanic effect of rice husks. Constr Build Mater 2000;14(8):419–23. [9] Della VP, Kühn I, Hotza D. Rice husk ash as an alternative source for active silica production. Mater Lett 2002;57(4):818–21. [10] Sugita S. On the burning principle and the furnace design based on the principle for producing highly active rice husk ash. In: Proceedings of 3rd international conference on the concrete future, Kuala Lumpur, Malaysia; 1994. [11] ASTM C-114. Standard Test Methods for Chemical Analysis of Hydraulic Cement, Annual Book of ASTM Standards; 2007. [12] ABNT NBR 5752. Pozzolans – Pozzolanic activity – Determination of pozzolanic activity index with Portland cement. ABNT (Technical Standards Brazilian Association), Brazil; 1992. [13] Raverdy M, Brivot F, Paillère AM, Bron R. Appréciation de l’activité pouzzolanique de constituents secondaires. In: Proceedings of 7e Congrès International de la Chimie des Ciments, Paris, France; 1980. [14] ABNT NBR 12653. Pozzolanic materials. ABNT (Technical Standards Brazilian Association), Brazil; 1992. [15] ASTM C-618. Standard specification for fly ash and raw calcined natural pozzolan for use as a mineral admixture in Portland cement concrete, Annual Book of ASTM Standards; 2005. [16] Malhotra VM, Mehta PK. Pozzolanic and cementitious materials. 1st ed. Amsterdam: Gordon and Breach Publishers; 1996.