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Exploratory study on the effect of waste rice husk and sugarcane bagasse ashes in burnt clay bricks
Author’s Accepted Manuscript Exploratory Study on the Effect of Waste Rice Husk and Sugarcane Bagasse Ashes in Burnt Clay Bricks Syed Minhaj Saleem Kazmi, Safeer Abbas, Muhammad Junaid Munir, Anwar Khitab www.elsevier.com/locate/jobe
PII: DOI: Reference:
S2352-7102(16)30071-7 http://dx.doi.org/10.1016/j.jobe.2016.08.001 JOBE162
To appear in: Journal of Building Engineering Received date: 2 July 2016 Revised date: 13 July 2016 Accepted date: 1 August 2016 Cite this article as: Syed Minhaj Saleem Kazmi, Safeer Abbas, Muhammad Junaid Munir and Anwar Khitab, Exploratory Study on the Effect of Waste Rice Husk and Sugarcane Bagasse Ashes in Burnt Clay Bricks, Journal of Building Engineering, http://dx.doi.org/10.1016/j.jobe.2016.08.001 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Exploratory Study on the Effect of Waste Rice Husk and Sugarcane Bagasse Ashes in Burnt Clay Bricks Syed Minhaj Saleem Kazmi1, Safeer Abbas2, Muhammad Junaid Munir1, Anwar Khitab1 1
Department of Civil Engineering, Mirpur University of Science and Technology, Mirpur, AJK, Pakistan.
2
Department of Civil Engineering, University of Engineering and Technology, Lahore, Pakistan.
Abstract Burnt clay brick is the commonly used construction material across the world. In most of countries including Pakistan, brick manufacturing is ignorant of modern day improvements and innovations. Utilization of waste materials in manufacturing of clay bricks is not only helpful in disposal of wastes safely but also imparts useful properties to the burnt clay bricks. In this study, the use of waste materials (rice husk ash and bagasse ash) for brick production has been attempted. Clay bricks were prepared incorporating 5% by clay weight of rice husk ash (RHA) and sugarcane bagasse ash (SBA) to investigate the mechanical and durability properties. It was observed compressive strength and modulus of rupture decreased with incorporation of RHA and SBA in burnt clay brick. However, compressive strength and modulus of rupture satisfied the requirements of building bricks according to Pakistan building code and ASTM standard guidelines. Furthermore, clay bricks incorporating RHA and SBA can be potentially used in the production of lighter bricks. Lighter weight of bricks can result in reduction of structural loads and helpful in achieving economy. Test results confirmed the use of clay bricks incorporating RHA and SBA as moderate weather resistive bricks. Moreover, resistance against efflorescence was improved after incorporating RHA and SBA. The microstructure was examined by scanning electron microscopy (SEM) and found that burnt clay bricks incorporating RHA and SBA were more porous than burnt clay bricks. Based on this study, it can be concluded that the addition of 1
RHA and SBA is not only helpful in controlling environmental pollution but also results into a more sustainable and economical construction. Keywords: Bricks; sugarcane bagasse ash; rice husk ash; mechanical properties; durability. 1. Introduction Clay has been used as a construction material since 8000 BC [1]. It is a naturally occurring finely grained material which becomes plastic after adding water and hardens when heated at a specific temperature [2]. It is considered as the major raw material in the construction of bricks. Clay brick is the commonly used material in the construction of buildings, tunnels and bridges across the world. The history of burnt clay bricks is almost 6000 years old and traces of that have been found in the Babylonia [3]. It is considered as the world oldest industries [4]. In the start, hand making was the way of brick manufacturing. In 1619, first time clay working machine was used [5]. Until 1958, the molded clay was fired in ordinary kilns that were not much effective [3]. Hoffman was the first person to introduce a proper kiln in which all the firing processes occur continuously and connectively [6]. Due to continuous fire, the kiln is heated one time only and the heat is utilized properly before releasing to the surrounding atmosphere [5]. In 19th century, British engineer "Bull" introduced a modified and cheaper version of Hoffmann kiln named as Bull trench kiln [6]. The properties of clay bricks vary depending on various factors including raw material properties, manufacturing method and burning process [7]. The soil properties play an important role in brick properties. Higher energy is required if quantity of lime and moisture content is more to decompose calcium contents and to remove the water from bricks [5]. Similarly, temperature of firing plays a role in bond development. For bond development generally additives are added inside clay bricks. Material production from recycling has been the focus of
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research from decades [8]. These days, addition of waste materials as an additives in bricks is the focus of research [9-10]. High strength and low absorption clay bricks can be produced by using waste glass as an additive [11]. Similarly, the use of fly ash in clay bricks is very common [1213]. In the past researches, an increased compressive strength with decrease in thermal conductivity was observed with small quantity (i.e. 5% by clay weight) of rice husk ash [14-15]. Sugarcane bagasse ash can also be used to produce lighter bricks [16]. Pakistan is one of the country in which burnt clay bricks are commonly used in the construction activities. Approximately, 12000 brick kilns are present in Pakistan with yearly production of 59 billion fired clay bricks [5]. In Pakistan, the kilns are mostly Bull trench kiln, however other types like Hoffmann kiln and vertical shaft brick kiln are also present rarely [3]. Approximately, 99% of brick kilns in Pakistan use hand molding technique for brick production [5]. Coal, timber, tyre/rubber, furnace oil and rice husk are the commonly used fuel sources [3]. Approximately, 1.6 million tons of coal is used as a fuel for brick making around Pakistan [5]. Pakistan being 14th largest rice producing country, yields 1.15 million tons of husk annually [17]. This husk is used as a fuel source in various locations especially in brick kilns. Rice husk ash is obtained as a result of combustion. Similarly, Pakistan being 15th largest sugarcane producing country, produces 50 million tons of sugarcane annually [18]. Bagasse is also used as a fuel source and in Pakistan annually 0.26 million tons of bagasse ash is produced [19]. The disposal of these wastes is of great importance regarding environmental pollution. In most of countries including Pakistan, brick manufacturing is ignorant of modern day improvements and innovations [5]. Because of using rice husk and bagasse as a fuel sources, rice husk ash and sugarcane bagasse ash are commonly available at brick kilns. Keeping in view, these ashes can be economically used in clay bricks. Moreover, being earthquake affected area 3
lighter bricks have a lot of importance in Pakistan. There is scant knowledge available regarding the use of waste materials in clay bricks. In this study, the use of these wastes (rice husk ash and bagasse ash) for brick production has been attempted. 2. Materials and Methods 2.1.
Collection of the Materials
The clay used during this study, was taken from the brick kiln located in Mirpur Azad Kashmir, Pakistan (Fig. 1 (a)). Rice husk ash was obtained from a brick kiln, near Wazirabad, Pakistan (Fig. 1 (b)) whereas, sugarcane bagasse ash was obtained from Khazana sugar mill, Charsadda, Peshawar (Fig. 1 (c)). The chemical composition of the raw materials used is shown in Table 1. It was observed that clay has rich silica content along with small proportion of oxides of aluminum, iron, and calcium. Clay can be refereed as low refractory calcareous material as the oxides of calcium are greater than 6% and total concentration of calcium, potassium, iron, magnesium and titanium oxides are greater than 9% [20-21]. In Pakistan, it is preferred that SiO2 should be present in soil within the range of 50-60% and Fe2O3 should be more than 3% [5]. Clay used during this study satisfies the ranges. Similarly, RHA and SBA used during the study were composed of SiO2. The x-ray diffraction (XRD) scans of clay, RHA and SBA were shown in Fig. 2 (a-c). The XRD pattern of the clay indicated the presence of highest proportion of quartz (SiO2) along with corundum (Al2O3) and hematite (Fe2O3). Whereas, RHA comprised of quartz (SiO2) in excess with discrete presence of hematite (Fe2O3). In SBA, quartz (SiO2) was present in excess with discrete presence of calcite (CaCO3), corundum (Al2O3) and halite (NaCl).
4
Particle size distribution of raw material has been presented in Fig. 3. Results showed that clay and RHA are naturally well graded whereas the SBA was gap graded. Soil has plastic index of 8.61. Specific gravity for clay was 2.57 whereas, RHA and SBA have specific gravity of 2.44 and 1.99, respectively (Table 1). As far as unit weight is concerned, RHA and SBA has 51% and 77% less unit weight than clay, respectively. Therefore, lighter bricks could be prepared by using RHA and SBA. 2.2.
Preparation of Bricks
For brick manufacturing, RHA (5% by clay weight) and SBA (5% by clay weight) were mixed in desired proportions with the clay to form the mixture (Fig. 4). Afterwards, water was added in the mixture. The mixture was left for 2-3 hours and the balls of the clay mix were then prepared. Afterwards, the brick molds of size 9" x 4.5" x 3" were poured with clay balls. Hand molding was done to prepare the specimens. Bricks were sun dried for 10 days (Fig. 5) and transported to the brick kiln. A total of 100 bricks were prepared by placing them in kiln for 45 days. 5 specimens of each combination were tested for each test. The bricks were fired by burning the coal (Fig. 6). 2.3.
Methodology
The series of physico-mechanical tests were carried out in accordance ASTM standards to determine weight per unit area (ASTM C 67 [22]) compressive strength (ASTM C 67) and flexural strength (ASTM C 67). The durability tests including water absorption (ASTM C 67)], initial rate of absorption (ASTM C 67), apparent porosity (ASTM C 20 [23]), sulfate resistance, freeze and thaw (ASTM C 67) and efflorescence (ASTM C 67) were also carried out on the developed bricks. The sulfate
5
solution was prepared by using ASTM C 1012 [24]. After 30 days of immersion, bricks were dried at 110 oC, weighed and tested for compressive strength. The effect of RHA and SBA incorporation in clay bricks was also examined using ultrasonic pulse velocity (ASTM C 597 [25]). Color of burnt clay and modified brick specimens was examined by visual inspection. Scanning electron microscopy was used to examine the microstructure of clay and modified brick specimens. 3. Results and Discussion 3.1.
Weight per Unit Area
Table 2 shows the results of weight per unit area of clay bricks incorporating RHA and SBA. It was observed that for modified bricks, weight per unit area of specimens decreased as compared to control specimens leading to lighter bricks. For example, 6% lighter bricks can be prepared after incorporating RHA and SBA. This is may be due to the lesser unit weight of RHA and SBA. Similar observations were also reported in previous studies [15]. Lighter weight bricks are helpful in reducing the structural load which has a lot of importance in earthquake affected areas. Moreover, labor cost on the construction site is dependent on weight of material. Therefore, lighter bricks can be helpful in reducing the laborer cost. 3.2.
Compressive Strength
Table 2 shows the results of compressive strength of clay bricks incorporating RHA and SBA. It was observed that for bricks incorporating RHA and SBA, compressive strength decreased as compared to control specimens. For example, compressive strength for RHA and SBA incorporated bricks reduced from 8.38 MPa to 5.10 MPa. This may be due to the increased porosity after incorporating RHA and SBA. These results are similar to the past researches [26-
6
27]. Although, a reduction in strength was achieved with incorporation of RHA and SBA in clay brick; however, it still satisfied the minimum compressive strength according to Pakistan standards for building bricks (i.e. 5 MPa) [28]. Therefore, these modified bricks can be used as a more sustainable bricks. 3.3.
Modulus of Rupture
Table 2 shows the results of flexural strength of clay bricks incorporating RHA and SBA. It was observed that for bricks incorporating RHA and SBA, flexural strength decreased as compared to control specimens. For instance, flexural strength for RHA and SBA incorporated bricks reduced from 1.49 MPa to 0.72 MPa (Fig. 7). These results are similar to the previous study [29]. Although, a reduction in flexural strength was observed with incorporation of RHA and SBA in clay brick; however, it still satisfied the minimum flexural strength according to ASTM C67 guidelines for building bricks (i.e. 0.65 MPa) [13, 22]. 3.4.
Water Absorption
Table 2 shows the results of water absorption of clay bricks incorporating RHA and SBA. Increase in water absorption was observed after incorporating RHA and SBA. For example, water absorption for control bricks and bricks incorporating RHA and SBA were approximately 17% and 21%, respectively. This is may be due to increased porosity for bricks incorporating RHA and SBA [30]. According to ASTM C62 [31], bricks with water absorption less than 17% and 22% are classified as severe weathering resistance bricks and moderate weathering resistance bricks. Therefore, bricks incorporating RHA and SBA can be used in moderate weather.
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3.5.
Initial Rate of Absorption
Table 2 shows the results of initial rate of absorption of clay bricks incorporating RHA and SBA. It was observed that initial rate of absorption increased with incorporation of RHA and SBA. For instance, initial rate of absorption value for control bricks was 0.46 g/min/cm2, which increased to 0.65 g/min/cm2 for bricks incorporating RHA and SBA. This can be attributed to the increased porosity in RHA and SBA bricks. Similar results were reported in previous study [32]. It is generally considered that clay bricks having initial rate of absorption more than 0.15 g/min/cm 2 should be wetted before laying to avoid the absorption of water from cement mortar paste [33]. Therefore, both control bricks and RHA and SBA incorporated bricks should be wetted before laying. 3.6.
Apparent Porosity
Table 2 shows the results of apparent porosity of clay bricks incorporating RHA and SBA. It was observed that apparent porosity increased with incorporation of RHA and SBA. For example, porosity for control bricks was 35.83%, which increased to 39.71% after incorporation of RHA and SBA (Fig. 8 (a)). This can be attributed to the increased amount and size of pores after incorporating RHA and SBA [34]. Results are similar to that in past researches [15]. Porous bricks are generally preferred because of their insulating properties [35]. Therefore, bricks incorporating RHA and SBA can be used where resistance to heat is required. 3.7.
Efflorescence
Table 2 shows the results of efflorescence of clay bricks with RHA and SBA. It was observed that efflorescence reduced due to incorporation of RHA and SBA. For example, 10% efflorescence was observed after 45 days on control brick specimens. However, no efflorescence was observed on brick specimens incorporating RHA and SBA. Generally, calcium oxide (CaO) 8
and iron oxide (Fe2O3) play a role in causing efflorescence [20, 36]. Quantity of CaO and Fe2O3 decreases after incorporation of SBA and RHA in clay bricks, as a result efflorescence reduces. Similar results were reported in in past researches [16, 33]. Therefore, clay bricks incorporating RHA and SBA can be used effectively in controlling the efflorescence. 3.8.
Freeze and Thaw
Table 2 shows the results of freeze and thaw test of clay bricks with RHA and SBA. It was observed that weight loss due to freeze and thaw increased with the incorporation of RHA and SBA. For example, after 50 cycles, weight loss due to freeze and thaw was 8.32% and 13.85% for control and bricks with RHA and SBA, respectively. According to ASTM C 67, if specimens cracks during freeze and thaw or weight loss increases by 3%, then brick specimens can be considered as fail. No cracks were observed in both control and bricks having RHA and SBA after 50 cycles. However, tested brick specimens showed weight loss greater than 3% after 30 cycles. This can be attributed to the increased porosity, as it plays a key role in the intensity of stress caused by freezing [20, 37]. Therefore, it can be concluded that bricks incorporating RHA and SBA can be used in moderate weather areas (temperature higher than freezing point) instead of severe weather conditions. 3.9.
Sulfate Test
Table 2 shows the results of sulfate resistance of clay bricks incorporating RHA and SBA. It was observed that the tested bricks with RHA and SBA showed reduction in compressive strength; whereas, weight gained with incorporation of RHA and SBA. For example, after 30 days of sulfate immersion, strength reduction was 24.78% and 20.85% for control and bricks incorporating RHA and SBA, respectively. Whereas, weight gain was 17.07% and 22.5% for
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control and modified bricks, respectively (Fig. 8 (b)). As a result of sulfate immersion, sulfate crystals fill inside the pores and micro cracks leading to weight gain [38]. Moreover, crystallization of sulfate salts generates pressure within the pores leading to micro-cracking and reduction in compressive strength [38]. 3.10. Ultrasonic Pulse Velocity Test Table 2 shows the results of ultrasonic pulse velocity test (UPV) of clay bricks having RHA and SBA. It was observed UPV decreased with the incorporation of RHA and SBA. For instance, UPV values reduced from 1643 m/s to 1162 m/s after incorporating RHA and SBA. Generally, pulse velocity is directly related to porosity and the results are also confirming the relation [39]. 3.11. Microscopic Analysis and Color Fig. 9 shows the scanning electron microscopic images of both burnt clay bricks and bricks incorporating RHA and SBA. Porous structure was observed in clay brick specimens. However, the microstructures of burnt clay bricks incorporation RHA and SBA are more porous than burnt clay bricks. The results are in accordance with the porosity and water absorption results as observed in past research [30]. Color of clay brick is also an important parameter to classify bricks [40]. Iron oxide content is considered as responsible for color [41]. The bricks without waste showed a similar color after waste addition. No stains on the surface and black core defects were observed in any brick specimens. 4. Conclusions In this study, the properties of clay bricks after incorporating rice husk ash (RHA) and sugarcane bagasse ash (SBA) were investigated. Utilization of RHA and SBA wastes in the manufacturing 10
of clay bricks not only helpful in disposal of these wastes safely but also imparts useful properties to the burnt clay bricks. From the experimental results, it can be concluded that: 1. Clay bricks after incorporation of RHA and SBA can be potentially used in the production of lighter bricks. Addition of these wastes result into 6% lighter bricks. This decrease in the weight of bricks can result in the reduction of structural loads and helpful in achieving economy. 2. Compressive strength and modulus of rupture decrease after addition of RHA and SBA in brick clay. However, the results still satisfy the requirements of building bricks according to Pakistan building code and ASTM standard guidelines. 3. Porosity and water absorption increases after incorporation of RHA and SBA. However, modified bricks can be used as moderate weather resistive bricks. Freeze and thaw results also confirm the suitability of bricks in moderate weather environment. Porous bricks usually have better insulation properties than control bricks. Scanning electron microscopy also confirmed the increase in porosity after incorporating RHA and SBA. 4. The resistance against efflorescence has been improved after incorporation of RHA and SBA in clay bricks. However, the use of modified bricks under severe sulfate attack is not preferred. Based on the observations, RHA and SBA addition in burnt clay bricks is recommended. The addition of RHA and SBA is not only helpful in controlling environmental pollution but also improves durability properties of burnt clay bricks.
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[13] A. Shakir, S. Naganathan, K. Mustapha, Properties of bricks made using fly ash, quarry dust and billet scale, Construction and Building Materials 41 (2013) 131-138. [14] A. More, A. Tarade, A. Anant, Assessment of suitability of fly ash and rice husk ash burnt clay bricks, International Journal of Scientific and Research Publications 4 (7) (2014) 1-6. [15] D. Tonnayopas, P. Tekasakul, S. Jaritgnam, Effects of rice husk ash on characteristics of lightweight clay brick, Proceedings of the Technology and Innovation for Sustainable Development Conference, Thailand, 2008, pp. 36-39. [16] S.M.S. Kazmi, S. Abbas, M.A. Saleem, M.J. Munir, A. Khitab, Manufacturing of sustainable clay bricks: Utilization of waste sugarcane bagasse and rice husk ashes, Construction and Building Materials 120 (2016) 29-41. [17]
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[24] ASTM C1012, Standard test method for length change of hydraulic-cement mortars exposed to a sulfate solution, American Society for Testing and Materials, Philadelphia PA, 2003. [25] ASTM C597, Standard test method for pulse velocity through concrete, American Society for Testing and Materials, Philadelphia PA, 1998. [26] G. Gorhan, O. Simsek, Porous clay bricks manufactured with rice husks, Construction and Building Materials 40 (2013) 390-396. [27] I. Demir, Effect of organic residues addition on the technological properties of clay bricks, Waste Management 28 (2008) 622-627. [28] National Engineering Services of Pakistan, Building Code of Pakistan – Seismic Hazard Evaluation Studies, Ministry of Housing and Works, Government of Pakistan, Pakistan, 2007. [29] E.I. Ugwu, A. Dickson, Analysis of the effect of blending Nigeria pure clay with rice husk: a case study of Ekulu clay in Enugu state, American Journal of Materials Engineering and Technology 2 (3) (2014) 34-37. [30] K. Faria, R. Gurgel, J. Holanda, Recycling of sugarcane bagasse ash waste in the production of clay bricks, Journal of Environmental Management 101 (2012) 7-12. [31] ASTM C62, Standard specification for building brick (solid masonry units made from clay or shale), American Society for Testing and Materials, Philadelphia PA, 2013. [32] T. Banu, B. Muktadir, G. Fahmida, A. Kurny, Experimental studies on fly ash-sand lime bricks with gypsum addition, American Journal of Materials Engineering and Technology 1 (3) (2013) 35-40. [33] B.E. Hegazy, H.A. Fouad, A.M. Hassanain, Incorporation of water sludge, silica fume, and rice husk ash in brick making, Advances in Environmental Research 1 (1) (2012) 83-96. [34] C.A. Garcia-Ubaque, G. Liliana, C.M. Juan, Quality study of ceramic bricks manufacture with clay and ashes from the incineration of municipal solid wastes, Afinidad LXX 561 (2013) 61-66. [35] G. Majkrzak, J. Watson, M. Bryant, K. Clayton, Effect of cenospheres on fly ash brick properties, Proceedings of World Coal Ash, Covington, Kentuck, USA, 2007.
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[36] P. Velasco, M. Ortiz, M. Giro, L. Velasco, Fired clay bricks manufactured by adding wastes as sustainable construction material – A review, Construction and Building Materials 63 (2014) 97-107. [37] J.I. Davison, Linear expansion due to freezing and other properties of bricks, Proceedings of Second Canadian Masonry Symposium, Carleton University, Ottawa, Canada, 1980. [38] N. Naik, B. Bahadure, C. Jejurkar, Strength and durability of fly ash, cement and gypsum bricks, International Journal of Computational Engineering Research (IJCER) 4 (5) (2014) 14. [39] S.R. Koroth, P. Fazio, D. Feldman, Evaluation of clay brick durability using ultrasonic pulse velocity, Journal of Architectural Engineering 4 (1998) 142-147. [40] A.C. Dunham, Developments in industrial mineralogy: The mineralogy of brick-making, Proceedings of the Yorkshire Geological Society 49 (2) (1992) 95-104. [41] S.O. Yakubu, M.Y. Abdulrahim, Suitability of Birnin Gwari and Maraban Rido clays as refractory materials, American Journal of Engineering Research (AJER) 3 (3) (2014) 8-15.
Table 1-Chemical and physical properties of the constituents Components SiO2 (%) Al2O3 (%) Fe2O3 (%) CaO (%) MgO (%) TiO2 (%) P2O5 (%) SO3 (%) MnO (%) Na2O (%) K2O (%) LOI (%) pH Liquid Limit Plastic Limit Plastic Index
Soil 58.05 10.91 4.56 9.28 2.5 0.7 0.15 0.07 1.81 2.26 9.49 8.5 30 21.39 8.61
15
RHA 77.31 6.77 4.64 3.7 1.39 0.43 1.23 2.6 4.7 -
SBA 86.92 2.89 2.7 2.55 0.73 0.14 0.26 0.32 10.25 -
Unit Weight (Kg/m3) Specific Gravity
1123 2.57
549.74 2.44
253.9 1.99
Table 2-Mechanical and durability properties of normal and modified clay bricks Property Weight per unit area (Kg/m2) Compressive strength (MPa) Modulus of rupture (MPa) Water absorption (%) Initial rate of absorption (gm/min/cm²) Apparent porosity (%) Area affected by Efflorescence (%) Freeze and Thaw weight Loss after 50 cycles (%) Sulfate Resistance Strength reduction (%) (MPa) Weight gain (%) Ultrasonic pulse velocity (m/sec)
Normal Clay Bricks 97.13 8.38 1.49 17.45 0.46 35.83 10 9.12 23.78 17.87 1643
Modified Clay Bricks 91.15 5.1 0.72 20.93 0.65 39.71 Nil 13.85 20.85 22.5 1162
FIGURES
(a)
(b) Fig. 1 – Raw materials (a) Soil, (b) RHA and (c) SBA
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(c)
(a)
(b)
(c) Fig. 2 – XRD patterns of a) clay, b) RHA and c) SBA
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Fig. 3 - Particle Size Distribution
Fig. 4 – Manual mixing of raw materials for brick manufacturing
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Fig. 5 – Fresh molded control and modified bricks
Fig. 6 – Unit weight of control and modified bricks
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Fig. 7 – Mechanical properties of control and modified bricks
Fig. 8 – Durability properties of control and modified bricks
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Fig. 9 – Initial rate of absorption of control and modified bricks
Fig. 10 – Ultrasonic pulse velocity of control and modified bricks
21
(a)
(b) Fig. 11 – SEM micrographs of the a) clay brick and b) clay brick incorporating RHA and SBA
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Highlights:
Brick production using agricultural wastes such as RHA and SBA was investigated.
Mechanical and durability properties of bricks were studied.
Utilization of RHA and SBA in brick production can lead towards economical and sustainable construction.
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PII: DOI: Reference:
S2352-7102(16)30071-7 http://dx.doi.org/10.1016/j.jobe.2016.08.001 JOBE162
To appear in: Journal of Building Engineering Received date: 2 July 2016 Revised date: 13 July 2016 Accepted date: 1 August 2016 Cite this article as: Syed Minhaj Saleem Kazmi, Safeer Abbas, Muhammad Junaid Munir and Anwar Khitab, Exploratory Study on the Effect of Waste Rice Husk and Sugarcane Bagasse Ashes in Burnt Clay Bricks, Journal of Building Engineering, http://dx.doi.org/10.1016/j.jobe.2016.08.001 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Exploratory Study on the Effect of Waste Rice Husk and Sugarcane Bagasse Ashes in Burnt Clay Bricks Syed Minhaj Saleem Kazmi1, Safeer Abbas2, Muhammad Junaid Munir1, Anwar Khitab1 1
Department of Civil Engineering, Mirpur University of Science and Technology, Mirpur, AJK, Pakistan.
2
Department of Civil Engineering, University of Engineering and Technology, Lahore, Pakistan.
Abstract Burnt clay brick is the commonly used construction material across the world. In most of countries including Pakistan, brick manufacturing is ignorant of modern day improvements and innovations. Utilization of waste materials in manufacturing of clay bricks is not only helpful in disposal of wastes safely but also imparts useful properties to the burnt clay bricks. In this study, the use of waste materials (rice husk ash and bagasse ash) for brick production has been attempted. Clay bricks were prepared incorporating 5% by clay weight of rice husk ash (RHA) and sugarcane bagasse ash (SBA) to investigate the mechanical and durability properties. It was observed compressive strength and modulus of rupture decreased with incorporation of RHA and SBA in burnt clay brick. However, compressive strength and modulus of rupture satisfied the requirements of building bricks according to Pakistan building code and ASTM standard guidelines. Furthermore, clay bricks incorporating RHA and SBA can be potentially used in the production of lighter bricks. Lighter weight of bricks can result in reduction of structural loads and helpful in achieving economy. Test results confirmed the use of clay bricks incorporating RHA and SBA as moderate weather resistive bricks. Moreover, resistance against efflorescence was improved after incorporating RHA and SBA. The microstructure was examined by scanning electron microscopy (SEM) and found that burnt clay bricks incorporating RHA and SBA were more porous than burnt clay bricks. Based on this study, it can be concluded that the addition of 1
RHA and SBA is not only helpful in controlling environmental pollution but also results into a more sustainable and economical construction. Keywords: Bricks; sugarcane bagasse ash; rice husk ash; mechanical properties; durability. 1. Introduction Clay has been used as a construction material since 8000 BC [1]. It is a naturally occurring finely grained material which becomes plastic after adding water and hardens when heated at a specific temperature [2]. It is considered as the major raw material in the construction of bricks. Clay brick is the commonly used material in the construction of buildings, tunnels and bridges across the world. The history of burnt clay bricks is almost 6000 years old and traces of that have been found in the Babylonia [3]. It is considered as the world oldest industries [4]. In the start, hand making was the way of brick manufacturing. In 1619, first time clay working machine was used [5]. Until 1958, the molded clay was fired in ordinary kilns that were not much effective [3]. Hoffman was the first person to introduce a proper kiln in which all the firing processes occur continuously and connectively [6]. Due to continuous fire, the kiln is heated one time only and the heat is utilized properly before releasing to the surrounding atmosphere [5]. In 19th century, British engineer "Bull" introduced a modified and cheaper version of Hoffmann kiln named as Bull trench kiln [6]. The properties of clay bricks vary depending on various factors including raw material properties, manufacturing method and burning process [7]. The soil properties play an important role in brick properties. Higher energy is required if quantity of lime and moisture content is more to decompose calcium contents and to remove the water from bricks [5]. Similarly, temperature of firing plays a role in bond development. For bond development generally additives are added inside clay bricks. Material production from recycling has been the focus of
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research from decades [8]. These days, addition of waste materials as an additives in bricks is the focus of research [9-10]. High strength and low absorption clay bricks can be produced by using waste glass as an additive [11]. Similarly, the use of fly ash in clay bricks is very common [1213]. In the past researches, an increased compressive strength with decrease in thermal conductivity was observed with small quantity (i.e. 5% by clay weight) of rice husk ash [14-15]. Sugarcane bagasse ash can also be used to produce lighter bricks [16]. Pakistan is one of the country in which burnt clay bricks are commonly used in the construction activities. Approximately, 12000 brick kilns are present in Pakistan with yearly production of 59 billion fired clay bricks [5]. In Pakistan, the kilns are mostly Bull trench kiln, however other types like Hoffmann kiln and vertical shaft brick kiln are also present rarely [3]. Approximately, 99% of brick kilns in Pakistan use hand molding technique for brick production [5]. Coal, timber, tyre/rubber, furnace oil and rice husk are the commonly used fuel sources [3]. Approximately, 1.6 million tons of coal is used as a fuel for brick making around Pakistan [5]. Pakistan being 14th largest rice producing country, yields 1.15 million tons of husk annually [17]. This husk is used as a fuel source in various locations especially in brick kilns. Rice husk ash is obtained as a result of combustion. Similarly, Pakistan being 15th largest sugarcane producing country, produces 50 million tons of sugarcane annually [18]. Bagasse is also used as a fuel source and in Pakistan annually 0.26 million tons of bagasse ash is produced [19]. The disposal of these wastes is of great importance regarding environmental pollution. In most of countries including Pakistan, brick manufacturing is ignorant of modern day improvements and innovations [5]. Because of using rice husk and bagasse as a fuel sources, rice husk ash and sugarcane bagasse ash are commonly available at brick kilns. Keeping in view, these ashes can be economically used in clay bricks. Moreover, being earthquake affected area 3
lighter bricks have a lot of importance in Pakistan. There is scant knowledge available regarding the use of waste materials in clay bricks. In this study, the use of these wastes (rice husk ash and bagasse ash) for brick production has been attempted. 2. Materials and Methods 2.1.
Collection of the Materials
The clay used during this study, was taken from the brick kiln located in Mirpur Azad Kashmir, Pakistan (Fig. 1 (a)). Rice husk ash was obtained from a brick kiln, near Wazirabad, Pakistan (Fig. 1 (b)) whereas, sugarcane bagasse ash was obtained from Khazana sugar mill, Charsadda, Peshawar (Fig. 1 (c)). The chemical composition of the raw materials used is shown in Table 1. It was observed that clay has rich silica content along with small proportion of oxides of aluminum, iron, and calcium. Clay can be refereed as low refractory calcareous material as the oxides of calcium are greater than 6% and total concentration of calcium, potassium, iron, magnesium and titanium oxides are greater than 9% [20-21]. In Pakistan, it is preferred that SiO2 should be present in soil within the range of 50-60% and Fe2O3 should be more than 3% [5]. Clay used during this study satisfies the ranges. Similarly, RHA and SBA used during the study were composed of SiO2. The x-ray diffraction (XRD) scans of clay, RHA and SBA were shown in Fig. 2 (a-c). The XRD pattern of the clay indicated the presence of highest proportion of quartz (SiO2) along with corundum (Al2O3) and hematite (Fe2O3). Whereas, RHA comprised of quartz (SiO2) in excess with discrete presence of hematite (Fe2O3). In SBA, quartz (SiO2) was present in excess with discrete presence of calcite (CaCO3), corundum (Al2O3) and halite (NaCl).
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Particle size distribution of raw material has been presented in Fig. 3. Results showed that clay and RHA are naturally well graded whereas the SBA was gap graded. Soil has plastic index of 8.61. Specific gravity for clay was 2.57 whereas, RHA and SBA have specific gravity of 2.44 and 1.99, respectively (Table 1). As far as unit weight is concerned, RHA and SBA has 51% and 77% less unit weight than clay, respectively. Therefore, lighter bricks could be prepared by using RHA and SBA. 2.2.
Preparation of Bricks
For brick manufacturing, RHA (5% by clay weight) and SBA (5% by clay weight) were mixed in desired proportions with the clay to form the mixture (Fig. 4). Afterwards, water was added in the mixture. The mixture was left for 2-3 hours and the balls of the clay mix were then prepared. Afterwards, the brick molds of size 9" x 4.5" x 3" were poured with clay balls. Hand molding was done to prepare the specimens. Bricks were sun dried for 10 days (Fig. 5) and transported to the brick kiln. A total of 100 bricks were prepared by placing them in kiln for 45 days. 5 specimens of each combination were tested for each test. The bricks were fired by burning the coal (Fig. 6). 2.3.
Methodology
The series of physico-mechanical tests were carried out in accordance ASTM standards to determine weight per unit area (ASTM C 67 [22]) compressive strength (ASTM C 67) and flexural strength (ASTM C 67). The durability tests including water absorption (ASTM C 67)], initial rate of absorption (ASTM C 67), apparent porosity (ASTM C 20 [23]), sulfate resistance, freeze and thaw (ASTM C 67) and efflorescence (ASTM C 67) were also carried out on the developed bricks. The sulfate
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solution was prepared by using ASTM C 1012 [24]. After 30 days of immersion, bricks were dried at 110 oC, weighed and tested for compressive strength. The effect of RHA and SBA incorporation in clay bricks was also examined using ultrasonic pulse velocity (ASTM C 597 [25]). Color of burnt clay and modified brick specimens was examined by visual inspection. Scanning electron microscopy was used to examine the microstructure of clay and modified brick specimens. 3. Results and Discussion 3.1.
Weight per Unit Area
Table 2 shows the results of weight per unit area of clay bricks incorporating RHA and SBA. It was observed that for modified bricks, weight per unit area of specimens decreased as compared to control specimens leading to lighter bricks. For example, 6% lighter bricks can be prepared after incorporating RHA and SBA. This is may be due to the lesser unit weight of RHA and SBA. Similar observations were also reported in previous studies [15]. Lighter weight bricks are helpful in reducing the structural load which has a lot of importance in earthquake affected areas. Moreover, labor cost on the construction site is dependent on weight of material. Therefore, lighter bricks can be helpful in reducing the laborer cost. 3.2.
Compressive Strength
Table 2 shows the results of compressive strength of clay bricks incorporating RHA and SBA. It was observed that for bricks incorporating RHA and SBA, compressive strength decreased as compared to control specimens. For example, compressive strength for RHA and SBA incorporated bricks reduced from 8.38 MPa to 5.10 MPa. This may be due to the increased porosity after incorporating RHA and SBA. These results are similar to the past researches [26-
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27]. Although, a reduction in strength was achieved with incorporation of RHA and SBA in clay brick; however, it still satisfied the minimum compressive strength according to Pakistan standards for building bricks (i.e. 5 MPa) [28]. Therefore, these modified bricks can be used as a more sustainable bricks. 3.3.
Modulus of Rupture
Table 2 shows the results of flexural strength of clay bricks incorporating RHA and SBA. It was observed that for bricks incorporating RHA and SBA, flexural strength decreased as compared to control specimens. For instance, flexural strength for RHA and SBA incorporated bricks reduced from 1.49 MPa to 0.72 MPa (Fig. 7). These results are similar to the previous study [29]. Although, a reduction in flexural strength was observed with incorporation of RHA and SBA in clay brick; however, it still satisfied the minimum flexural strength according to ASTM C67 guidelines for building bricks (i.e. 0.65 MPa) [13, 22]. 3.4.
Water Absorption
Table 2 shows the results of water absorption of clay bricks incorporating RHA and SBA. Increase in water absorption was observed after incorporating RHA and SBA. For example, water absorption for control bricks and bricks incorporating RHA and SBA were approximately 17% and 21%, respectively. This is may be due to increased porosity for bricks incorporating RHA and SBA [30]. According to ASTM C62 [31], bricks with water absorption less than 17% and 22% are classified as severe weathering resistance bricks and moderate weathering resistance bricks. Therefore, bricks incorporating RHA and SBA can be used in moderate weather.
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3.5.
Initial Rate of Absorption
Table 2 shows the results of initial rate of absorption of clay bricks incorporating RHA and SBA. It was observed that initial rate of absorption increased with incorporation of RHA and SBA. For instance, initial rate of absorption value for control bricks was 0.46 g/min/cm2, which increased to 0.65 g/min/cm2 for bricks incorporating RHA and SBA. This can be attributed to the increased porosity in RHA and SBA bricks. Similar results were reported in previous study [32]. It is generally considered that clay bricks having initial rate of absorption more than 0.15 g/min/cm 2 should be wetted before laying to avoid the absorption of water from cement mortar paste [33]. Therefore, both control bricks and RHA and SBA incorporated bricks should be wetted before laying. 3.6.
Apparent Porosity
Table 2 shows the results of apparent porosity of clay bricks incorporating RHA and SBA. It was observed that apparent porosity increased with incorporation of RHA and SBA. For example, porosity for control bricks was 35.83%, which increased to 39.71% after incorporation of RHA and SBA (Fig. 8 (a)). This can be attributed to the increased amount and size of pores after incorporating RHA and SBA [34]. Results are similar to that in past researches [15]. Porous bricks are generally preferred because of their insulating properties [35]. Therefore, bricks incorporating RHA and SBA can be used where resistance to heat is required. 3.7.
Efflorescence
Table 2 shows the results of efflorescence of clay bricks with RHA and SBA. It was observed that efflorescence reduced due to incorporation of RHA and SBA. For example, 10% efflorescence was observed after 45 days on control brick specimens. However, no efflorescence was observed on brick specimens incorporating RHA and SBA. Generally, calcium oxide (CaO) 8
and iron oxide (Fe2O3) play a role in causing efflorescence [20, 36]. Quantity of CaO and Fe2O3 decreases after incorporation of SBA and RHA in clay bricks, as a result efflorescence reduces. Similar results were reported in in past researches [16, 33]. Therefore, clay bricks incorporating RHA and SBA can be used effectively in controlling the efflorescence. 3.8.
Freeze and Thaw
Table 2 shows the results of freeze and thaw test of clay bricks with RHA and SBA. It was observed that weight loss due to freeze and thaw increased with the incorporation of RHA and SBA. For example, after 50 cycles, weight loss due to freeze and thaw was 8.32% and 13.85% for control and bricks with RHA and SBA, respectively. According to ASTM C 67, if specimens cracks during freeze and thaw or weight loss increases by 3%, then brick specimens can be considered as fail. No cracks were observed in both control and bricks having RHA and SBA after 50 cycles. However, tested brick specimens showed weight loss greater than 3% after 30 cycles. This can be attributed to the increased porosity, as it plays a key role in the intensity of stress caused by freezing [20, 37]. Therefore, it can be concluded that bricks incorporating RHA and SBA can be used in moderate weather areas (temperature higher than freezing point) instead of severe weather conditions. 3.9.
Sulfate Test
Table 2 shows the results of sulfate resistance of clay bricks incorporating RHA and SBA. It was observed that the tested bricks with RHA and SBA showed reduction in compressive strength; whereas, weight gained with incorporation of RHA and SBA. For example, after 30 days of sulfate immersion, strength reduction was 24.78% and 20.85% for control and bricks incorporating RHA and SBA, respectively. Whereas, weight gain was 17.07% and 22.5% for
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control and modified bricks, respectively (Fig. 8 (b)). As a result of sulfate immersion, sulfate crystals fill inside the pores and micro cracks leading to weight gain [38]. Moreover, crystallization of sulfate salts generates pressure within the pores leading to micro-cracking and reduction in compressive strength [38]. 3.10. Ultrasonic Pulse Velocity Test Table 2 shows the results of ultrasonic pulse velocity test (UPV) of clay bricks having RHA and SBA. It was observed UPV decreased with the incorporation of RHA and SBA. For instance, UPV values reduced from 1643 m/s to 1162 m/s after incorporating RHA and SBA. Generally, pulse velocity is directly related to porosity and the results are also confirming the relation [39]. 3.11. Microscopic Analysis and Color Fig. 9 shows the scanning electron microscopic images of both burnt clay bricks and bricks incorporating RHA and SBA. Porous structure was observed in clay brick specimens. However, the microstructures of burnt clay bricks incorporation RHA and SBA are more porous than burnt clay bricks. The results are in accordance with the porosity and water absorption results as observed in past research [30]. Color of clay brick is also an important parameter to classify bricks [40]. Iron oxide content is considered as responsible for color [41]. The bricks without waste showed a similar color after waste addition. No stains on the surface and black core defects were observed in any brick specimens. 4. Conclusions In this study, the properties of clay bricks after incorporating rice husk ash (RHA) and sugarcane bagasse ash (SBA) were investigated. Utilization of RHA and SBA wastes in the manufacturing 10
of clay bricks not only helpful in disposal of these wastes safely but also imparts useful properties to the burnt clay bricks. From the experimental results, it can be concluded that: 1. Clay bricks after incorporation of RHA and SBA can be potentially used in the production of lighter bricks. Addition of these wastes result into 6% lighter bricks. This decrease in the weight of bricks can result in the reduction of structural loads and helpful in achieving economy. 2. Compressive strength and modulus of rupture decrease after addition of RHA and SBA in brick clay. However, the results still satisfy the requirements of building bricks according to Pakistan building code and ASTM standard guidelines. 3. Porosity and water absorption increases after incorporation of RHA and SBA. However, modified bricks can be used as moderate weather resistive bricks. Freeze and thaw results also confirm the suitability of bricks in moderate weather environment. Porous bricks usually have better insulation properties than control bricks. Scanning electron microscopy also confirmed the increase in porosity after incorporating RHA and SBA. 4. The resistance against efflorescence has been improved after incorporation of RHA and SBA in clay bricks. However, the use of modified bricks under severe sulfate attack is not preferred. Based on the observations, RHA and SBA addition in burnt clay bricks is recommended. The addition of RHA and SBA is not only helpful in controlling environmental pollution but also improves durability properties of burnt clay bricks.
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[36] P. Velasco, M. Ortiz, M. Giro, L. Velasco, Fired clay bricks manufactured by adding wastes as sustainable construction material – A review, Construction and Building Materials 63 (2014) 97-107. [37] J.I. Davison, Linear expansion due to freezing and other properties of bricks, Proceedings of Second Canadian Masonry Symposium, Carleton University, Ottawa, Canada, 1980. [38] N. Naik, B. Bahadure, C. Jejurkar, Strength and durability of fly ash, cement and gypsum bricks, International Journal of Computational Engineering Research (IJCER) 4 (5) (2014) 14. [39] S.R. Koroth, P. Fazio, D. Feldman, Evaluation of clay brick durability using ultrasonic pulse velocity, Journal of Architectural Engineering 4 (1998) 142-147. [40] A.C. Dunham, Developments in industrial mineralogy: The mineralogy of brick-making, Proceedings of the Yorkshire Geological Society 49 (2) (1992) 95-104. [41] S.O. Yakubu, M.Y. Abdulrahim, Suitability of Birnin Gwari and Maraban Rido clays as refractory materials, American Journal of Engineering Research (AJER) 3 (3) (2014) 8-15.
Table 1-Chemical and physical properties of the constituents Components SiO2 (%) Al2O3 (%) Fe2O3 (%) CaO (%) MgO (%) TiO2 (%) P2O5 (%) SO3 (%) MnO (%) Na2O (%) K2O (%) LOI (%) pH Liquid Limit Plastic Limit Plastic Index
Soil 58.05 10.91 4.56 9.28 2.5 0.7 0.15 0.07 1.81 2.26 9.49 8.5 30 21.39 8.61
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RHA 77.31 6.77 4.64 3.7 1.39 0.43 1.23 2.6 4.7 -
SBA 86.92 2.89 2.7 2.55 0.73 0.14 0.26 0.32 10.25 -
Unit Weight (Kg/m3) Specific Gravity
1123 2.57
549.74 2.44
253.9 1.99
Table 2-Mechanical and durability properties of normal and modified clay bricks Property Weight per unit area (Kg/m2) Compressive strength (MPa) Modulus of rupture (MPa) Water absorption (%) Initial rate of absorption (gm/min/cm²) Apparent porosity (%) Area affected by Efflorescence (%) Freeze and Thaw weight Loss after 50 cycles (%) Sulfate Resistance Strength reduction (%) (MPa) Weight gain (%) Ultrasonic pulse velocity (m/sec)
Normal Clay Bricks 97.13 8.38 1.49 17.45 0.46 35.83 10 9.12 23.78 17.87 1643
Modified Clay Bricks 91.15 5.1 0.72 20.93 0.65 39.71 Nil 13.85 20.85 22.5 1162
FIGURES
(a)
(b) Fig. 1 – Raw materials (a) Soil, (b) RHA and (c) SBA
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(c)
(a)
(b)
(c) Fig. 2 – XRD patterns of a) clay, b) RHA and c) SBA
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Fig. 3 - Particle Size Distribution
Fig. 4 – Manual mixing of raw materials for brick manufacturing
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Fig. 5 – Fresh molded control and modified bricks
Fig. 6 – Unit weight of control and modified bricks
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Fig. 7 – Mechanical properties of control and modified bricks
Fig. 8 – Durability properties of control and modified bricks
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Fig. 9 – Initial rate of absorption of control and modified bricks
Fig. 10 – Ultrasonic pulse velocity of control and modified bricks
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(a)
(b) Fig. 11 – SEM micrographs of the a) clay brick and b) clay brick incorporating RHA and SBA
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Highlights:
Brick production using agricultural wastes such as RHA and SBA was investigated.
Mechanical and durability properties of bricks were studied.
Utilization of RHA and SBA in brick production can lead towards economical and sustainable construction.
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