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Waste Management of Residual Black Ash in Barium Industries
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ScienceDirect Materials Today: Proceedings 18 (2019) 4810–4815
www.materialstoday.com/proceedings
ICMPC-2019
Waste Management of Residual Black Ash in Barium Industries a
Jyotsna Agarwala
Assistant Professor, MSRUAS, Bangalore-560058, India
Abstract Waste generation is inexorable in industries, it can be controlled but cannot be abolished totally. The aim of the investigation was reclamation of industrial wastes to eliminate heavy metal toxic ions such as barium ions from industrial wastes dumping sites, and it exemplifies very productive, easy and low cost utilisation of barium industrial wastes. Present paper is about the ill effects of barium/barium chemicals and the development of waste management technology by using industrial wastes of barium industries, which helps us to formulate the approach for mitigating the harmful effects of barium ions present in industrial wastes. The outcomes are quite promising. This study is very important for government authorities, industrialist as well as for public, as it possesses manifold benefits: effective utilisation of industrial wastes, positive environmental /ecological effects as wastes are recycled, protects natural resources, efficacious production of cementitious/plastering material with good binding character great strength, etc. In this paper the author tried to achieve the goal of waste minimization through simple but effective way, encouraging others to join the stream. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: Aluminosilicate; black ash; hydraulic mortar; industrial waste; cementitious.
1. Introduction Uncontrolled and hasty industrialization/urbanisation is one of the major cause of rapid environmental degradation. Emitted industrial pollution has done a drastic damage to the environment. The Indian industrial sector generated an estimated 100 million tons/year of non-hazardous solid waste and 8 million tons/year of hazardous solid waste [1]. However no data is available to estimate the amount of industrial waste for reclamation or agricultural purpose. Different industrial activities such as mining, pulverization, metallurgical operation and manufacturing of other chemicals/products have led to release heavy metals into the environment. As heavy metals are not bio-degradable, they bio-accumulate in environment/living organisms reaching levels that cause toxicological effects. Haphazard dumping of industrial wastes results in severe impairment to various components of environment, via soil, air, water along with they pose a serious threat to the human/animal health, agriculture, and ecosystem [2-4]. The industrial wastes especially the metallurgical wastes (highly pulverised and rich in heavy metal contents) affects the environment gravely and are hazardous for human/animal health which can intensify due to the weather, particle size, presence of human habitats, water bodies, agriculture land, etc. near the industries.Thus efforts are to be made to control pollution arising due to waste disposal, by conversion of these unwanted wastes into utilizable raw materials. But ironically there are not many reclamation techniques and those which are available are expensive thus not affordable for developing country like India. According to the ideal Corresponding author E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
Jyotsna Agarwal/ Materials Today: Proceedings 18 (2019) 4810–4815
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industrial location criteria in India, the industry should have enough land available within its premises for the treatment and disposal and or reuse/recycling of the wastes generated from it. But in practice mostly the large scale industries have own proper treatment and disposal facilities including few medium scale industries and none of the small scale industries own the above facilities. Thus small scale industries use easiest and cheapest methods for the disposal of industrial wastes and are not much concerned with the environmental and human/animal health issues. India ranks second in the production of barite in the world and is one of the important barite exporters to the world market [5]. Barium (heavy metal) and its chemicals are very valuable potent chemicals widely used in different industries like paint, paper, medical science, etc. Barium industries produces wastes of different types like low active wastes (mainly due to mechanical operations), arduous wastes, which includes unreacted barite i.e. barium sulphate, treatment residues of barite ore, leaching wastes, barium sulphide i.e. black ash filtration sludge, wastes from cleaning and maintenance of the barium chemicals production area, various impurities, dust etc. Most of the solids wastes are of RCRA characteristic hazardous waste, carrying waste code D005 (EPA). Knowingly or unknowingly without realizing the hazardous effects, it is a normal trend for the workers and management of barium industries, to store these untreated wastes at unprofessional and non-eco-friendly dumping sites in an open area (mainly inside the factory premises or a nearby water body), ultimately which sways the environment and posed threats on the human, plants, water, air, soil etc. as a whole. And surprisingly (according to the survey done by author), no change in current production/dumping practices are anticipated for the near future. Once barium (in any form) enters in human body it may cause gastrointestinal disturbance, muscular weakness, hypertension, baritosis (physical irritation and benign pneumoioniosis) etc. Animal studies have shown intravenous infusion of barium chemicals results in increased blood pressure, cardiac arrhythmias, inflammatory responses, granuloma formation in the lungs, etc. Although data are limited but dissolved barium in aquatic environment may represent a risk to aquatic organisms such as daphnids. Similarly some plants are known to accumulate barium from the soil [6-11]. Therefore there is an urgent need of proper use and disposal of the resulting residues in order to contribute more towards sustainable production. Sensitized by this malpractice the author has done some experimental investigations. It was observed by the author that in barium industries, dumped waste materials, (mainly insoluble part of black ash) after sometime set into a hard mass on their own. This gave a clue that these waste materials probably possess binding characteristics on account of siliceous materials and alkalis originating from coal ash and barite [12-14]. If so then these siliceous materials should exhibit binding characteristics in the form of lime/cement and industrial waste mortars. Results are far better with lime and residual wastes rather than cement and residual wastes. Residual wastes are the mixture of water soluble barium sulphide and water insoluble or difficult soluble compositions like amorphous silica, silicates, sulphides, oxides etc. The latter materials react with lime in a faster and better way being amorphous in nature, but it is not so with cement due to the formation of sulphoaluminates and sulphosilicates of calcium in the blocks [15]. To meet the object experiments were carried out with industrial wastes, cement and lime in order to reclaim the industrial waste. The outcomes are fairly supportive. 2. Materials and methods To investigate the binding characteristics of residual wastes of Barium industries experiments were conducted as follows. Materials used for study were acquired from the following sources: 2.1. The raw materials used for study were as follows: 2.1.1. Residual waste (powdered form): After the extraction of barium sulphide (water soluble) from the black ash [16] the residue thus obtained is the main raw material along with residue of carbothermaly reduced barite, broken earthen pots, etc. Barium sulphide which is also known as black ash (used to prepare barium sulphide extract) was prepared by the author in lab by carbothermal reduction of barite. 2.1.2. Lime: Lime (mainly composed of calcite) was procured from local market of Jaisalmer (Rajasthan) act as a basic binding material. Chemical composition of the lime used has been given in Table 1.
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Jyotsna Agarwal/ Materials Today: Proceedings 18 (2019) 4810–4815
Table 1. Chemical composition of lime used in mortar Type of oxide
CaO
MgO
SiO2
Al2O3
Fe2O3
Weight %
53.42 to 54.88
0.30 to 1.0
0.70 to 1.54
0.23 to 0.86 0.12 to 0.26
2.1.3. Cement: Cement which is usually compounds and combinations of metallic oxides like CaO, Al2O3, Fe2O3, H2O, P2O5, SO3, CO3 etc. was Ultra Tech cement of OPC-43 Grade as defined in IS 8112:1989. 2.2. Experimental Procedures Experiments were conducted to study the binding ability (in terms of compressive strength) of residual waste (insoluble part of black ash obtained after the extraction of water soluble barium sulphide). 2.2.3. Preparation of blocks: 2.2.3.1. Preparation of blocks using lime and residual wastes/sand: Residual waste of black ash was thoroughly mixed with fine powder of lime in 3:1 ratio (weight of residual waste of black ash is 3 parts). After mixing, the above trial mixture was gauged with minimum amount of water just sufficient to obtain a plastic wet mix of workable consistency. Two sets of three standard blocks of 70.6mm (70.6 X 10 −3 m) cubic size were prepared (from the above prepared pastes) with the help of standard moulds placed on non-absorbent plates. The moulds were filled with the pastes and were consolidated with light pressure. The surface is made smooth with the blade of trowel. Similarly two sets of 3 standard blocks of 70.6mm cubic size were prepared by mixing sand and lime in 3:1 ratio. 2.2.3.2. Preparation of blocks using cement and residual wastes/sand: Similarly as mentioned above two sets of 3 standard blocks of 70.6mm cubic size were prepared by mixing residual wastes and cement in 3:1 ratio (weight of residual waste of black ash is 3 parts) and two sets of 3 standard blocks of 70.6mm cubic size were prepared by mixing sand and cement in 3:1 ratio. The above prepared cubes (total four sets of three each lime with residual wastes/sand and cement with residual wastes/sand) were placed at 27 ± 3⁰ (for about 21 days) under water, after 24 hrs of air curing. Once curing was done under identical conditions these cubes were subjected to compression in a compressive strength testing machine. This is done by using Universal Testing Machine model no.UTM40, Yama Engineers Kolhapur make. The compressive strength of these cubes were found by applying compression gradually and smoothly, just sufficient to crush them with standard compressive strength testing machine. The crushing loads were noted at the interval of 7 days and 30 days. Average strength of three trial cubes was used to tell the compressive strength of the blocks (unit-kg/cm2). 3. Results and discussion Corresponding findings of compressive strength of the blocks of lime vs residual wastes, lime vs sand, cement vs residual wastes and cement vs sand are recorded in Table 2 and Table 3 respectively. Table 2. Compressive strengths of the blocks of lime – insoluble black ash residue Vs lime – sand mortars Surface area: 50cm2 Composition of Block
Approx. ratio
Compressive strength in kg/cm2 after 7 days
Residual wastes/Lime
3:1
Sand/Lime
3:1
3.86 broken even without application of load
after 30 days 7.50 3.90
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Table 2 reveals the compressive strength of the blocks of residual waste material - lime mortars and sand - lime mortars prepared as per the standard procedures. Results shown are average of three blocks (one set of 3 blocks was used after 7 days and one set of 3 blocks was used after 30 days respectively for both compositions). It is clear from Figure1 that water insoluble part of black ash shows excellent binding characteristics with lime. It is far better than sand - lime mortars with respect to its compressive strength taken either 7 or 30 days.
7.5 Compressive Strength in Kg/Cm2
8 7 6 5 4 3 2 1 0
3.9
3.86
0
After 7 days
After 30 days Sand/Lime Mortar(3:1)
Fig. 1 Compressive strength of mortars of residual waste black ash/lime and sand/lime in kg/cm2.
Probable cause for this fact may be, black ash formed due to prolonged (48 hrs) carbothermal reduction of barite and carbon in the pit furnace, resulting in the formation of water soluble barium sulphide on one hand and water insoluble or difficult soluble compositions like amorphous silica, silicates, sulphides, oxides etc. on the other. The latter materials react with lime in a faster and better way because of their amorphous character when compared to the weathered gravel which is of crystalline texture. At ordinary temperature, the latter materials react with lime to form calcium silicate, calcium aluminate, calcium aluminosilicate etc. These different types of lime bearing phases are subsequently hydrated with water which changes them into compounds with cementitious properties and is responsible for development of strength in the mortar. Thus higher compressive strength of the water insoluble black ash and lime mortar is expected. Sulphides also reacted with lime to form insoluble phases of calcium sulphide and hence their damaging effects towards the mechanical strength of the matrix is nullified. Proposed reactions are as follows: Silica Ca (OH) 2 → Calcium silicates --------- (1) (Insoluble) CaO
+
H2O
→
Ca (OH) 2
-------- (2)
(Sulphide) Ca (OH) 2 Ca (OH) 2 + CO2 (Unused)
→
CaS + H2O etc. (Insoluble) →
CaCO3 + H2O (Insoluble)
-------- (3) -------- (4)
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Jyotsna Agarwal/ Materials Today: Proceedings 18 (2019) 4810–4815
Earlier strength (recorded after 7 days) is mainly due to (3) reaction, but gradually other reactions also go on side by side and are responsible for higher ultimate strength (recorded after 30 days). Table 3. Compressive strengths of the blocks of cement – insoluble black ash residue Vs cement – sand mortars Surface area: 50cm2 Composition of Block
Compressive strength in kg/cm2
Approx. ratio
Residual wastes/Cement
3:1
Sand/Cement
3:1
after 7 days
after 30 days
18.0
39.0
25.0
48.0
Table 3 shows the average compressive strength of three blocks (one set of 3 blocks was used after 7 days and one set of 3 blocks was used after 30 days respectively) of residual waste material - cement mortars and sand - cement mortars prepared as per the standard procedures. Figure 2 is reflecting the comparative strength of above discussed mortars.
48 Compressive Strength in Kg/Cm2
50
39
40 30
25 18
20 10 0 After 7 days Sand/Cement Mortar(3:1)
After 30 days Residual Waste/Cement Mortar (3:1)
Fig. 2 Compressive strength of mortars of residual waste black ash Vs cement and sand Vs cement in kg/cm2.
Figure 2 patently specifies that along with cement, black ash residues do contribute to the compressive strength but to a less extent as compared to cement-gravel mortars. Probable cause for this fact appear to be the less percentage of sand in the black ash residue then that in the gravel. In addition available sulphide in the black ash residues (though in very small extent), pose adverse effect on the setting and binding behaviour of Portland cement. Thus decrease in strength of the blocks made up of black ash insoluble residues is expected. This phenomenon can be explained on the basis of formation of sulphoaluminate and sulphosilicate of calcium in the blocks made by cementblack ash residue mortars. However, smooth physical appearance of the cement-black ash residue blocks even after keeping the blocks in water for over one month is suggestive of their more water tightness as compared to cement-gravel blocks which are found to be more porous. This is also explicable on similar reasons as mentioned above.
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4. Conclusions Water insoluble black ash residue in powdered form is better substitute of gravel in mortars based on hydraulic lime. Within the experimental limitations water insoluble contents of black ash in powdered form, forms hydraulic mortar with lime of better strength than that formed by gravel (sand). Though compressive strength of cement-black ash residue blocks is less as compared to that of the cement-gravel blocks, water tightness of the former is more than that of the latter. Except for heavy duty purposes water insoluble residue of the black ash is a very good substitute of the gravel. Cement-black ash insoluble residue mortars can be effectively used for plastering purpose for their smoothness, particularly in the buildings of dark rooms. References [1] Snapshot Waste Management in India, European Business and technology centre, www.ebtc.eu.pdf 2011. [2] CPCB, Inventorisation of hazardous waste generating units in Orissa, Hazardous Waste Management Series, 2003. [3] K.K. Wankhade., The dangers of hazardous waste, www.toxiclink.org. 2004. [4] J.P. Lehman, Hazardous Waste Disposal, Vol. 4. Plenum Press, New York, 1981. [5] IBM., 2011. Indian Mineral Year Book, fifty ed. Nagpur. [6] G. Clayton and F. Clayton. Patty’s industrial hygiene and toxicology, third ed. John Wiley & Sons, New York, 1981. [7] F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, fourth ed. John Wiley, New York, 1980. [8] IPCS, Barium and Barium Compounds, World Health Organization, Geneva, 2001. [9] NLM, The hazardous substances data bank: barium sulphate, Bethesda, MD: National Library of Medicine, 1991. [10] A.L. Reeves et al. (Eds.), Handbook on the Toxicology of Metals, second ed., Amsterdam, Elsevier, 1986. [11] US EPA, Health effects assessment for barium. Washington, DC, 1984. [12] U. Barbier, Industrial Italian. Laterizi, (1986) pp 40 - 53. [13] J.D. Watt, D.J. Thorne, J. App. Chem., 15, (1996) 585. [14] Ozlem Cizer., Koenraad Van Balen., Dionys Van Gemert., Jan Elsen., 2006. Carbonation reaction of lime hydrate and hydraulic binders at 20°C in ACEME. [15] MDA Thomas, Delayed ettringite formation in concrete. Recent developments and future directions, Department of civil engineering, University of Toronto 1998. [16] International Organization for Standardization, ISO 5877:1971 Barium sulphide, technical (black ash), New Delhi, 1971.
ScienceDirect Materials Today: Proceedings 18 (2019) 4810–4815
www.materialstoday.com/proceedings
ICMPC-2019
Waste Management of Residual Black Ash in Barium Industries a
Jyotsna Agarwala
Assistant Professor, MSRUAS, Bangalore-560058, India
Abstract Waste generation is inexorable in industries, it can be controlled but cannot be abolished totally. The aim of the investigation was reclamation of industrial wastes to eliminate heavy metal toxic ions such as barium ions from industrial wastes dumping sites, and it exemplifies very productive, easy and low cost utilisation of barium industrial wastes. Present paper is about the ill effects of barium/barium chemicals and the development of waste management technology by using industrial wastes of barium industries, which helps us to formulate the approach for mitigating the harmful effects of barium ions present in industrial wastes. The outcomes are quite promising. This study is very important for government authorities, industrialist as well as for public, as it possesses manifold benefits: effective utilisation of industrial wastes, positive environmental /ecological effects as wastes are recycled, protects natural resources, efficacious production of cementitious/plastering material with good binding character great strength, etc. In this paper the author tried to achieve the goal of waste minimization through simple but effective way, encouraging others to join the stream. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: Aluminosilicate; black ash; hydraulic mortar; industrial waste; cementitious.
1. Introduction Uncontrolled and hasty industrialization/urbanisation is one of the major cause of rapid environmental degradation. Emitted industrial pollution has done a drastic damage to the environment. The Indian industrial sector generated an estimated 100 million tons/year of non-hazardous solid waste and 8 million tons/year of hazardous solid waste [1]. However no data is available to estimate the amount of industrial waste for reclamation or agricultural purpose. Different industrial activities such as mining, pulverization, metallurgical operation and manufacturing of other chemicals/products have led to release heavy metals into the environment. As heavy metals are not bio-degradable, they bio-accumulate in environment/living organisms reaching levels that cause toxicological effects. Haphazard dumping of industrial wastes results in severe impairment to various components of environment, via soil, air, water along with they pose a serious threat to the human/animal health, agriculture, and ecosystem [2-4]. The industrial wastes especially the metallurgical wastes (highly pulverised and rich in heavy metal contents) affects the environment gravely and are hazardous for human/animal health which can intensify due to the weather, particle size, presence of human habitats, water bodies, agriculture land, etc. near the industries.Thus efforts are to be made to control pollution arising due to waste disposal, by conversion of these unwanted wastes into utilizable raw materials. But ironically there are not many reclamation techniques and those which are available are expensive thus not affordable for developing country like India. According to the ideal Corresponding author E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
Jyotsna Agarwal/ Materials Today: Proceedings 18 (2019) 4810–4815
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industrial location criteria in India, the industry should have enough land available within its premises for the treatment and disposal and or reuse/recycling of the wastes generated from it. But in practice mostly the large scale industries have own proper treatment and disposal facilities including few medium scale industries and none of the small scale industries own the above facilities. Thus small scale industries use easiest and cheapest methods for the disposal of industrial wastes and are not much concerned with the environmental and human/animal health issues. India ranks second in the production of barite in the world and is one of the important barite exporters to the world market [5]. Barium (heavy metal) and its chemicals are very valuable potent chemicals widely used in different industries like paint, paper, medical science, etc. Barium industries produces wastes of different types like low active wastes (mainly due to mechanical operations), arduous wastes, which includes unreacted barite i.e. barium sulphate, treatment residues of barite ore, leaching wastes, barium sulphide i.e. black ash filtration sludge, wastes from cleaning and maintenance of the barium chemicals production area, various impurities, dust etc. Most of the solids wastes are of RCRA characteristic hazardous waste, carrying waste code D005 (EPA). Knowingly or unknowingly without realizing the hazardous effects, it is a normal trend for the workers and management of barium industries, to store these untreated wastes at unprofessional and non-eco-friendly dumping sites in an open area (mainly inside the factory premises or a nearby water body), ultimately which sways the environment and posed threats on the human, plants, water, air, soil etc. as a whole. And surprisingly (according to the survey done by author), no change in current production/dumping practices are anticipated for the near future. Once barium (in any form) enters in human body it may cause gastrointestinal disturbance, muscular weakness, hypertension, baritosis (physical irritation and benign pneumoioniosis) etc. Animal studies have shown intravenous infusion of barium chemicals results in increased blood pressure, cardiac arrhythmias, inflammatory responses, granuloma formation in the lungs, etc. Although data are limited but dissolved barium in aquatic environment may represent a risk to aquatic organisms such as daphnids. Similarly some plants are known to accumulate barium from the soil [6-11]. Therefore there is an urgent need of proper use and disposal of the resulting residues in order to contribute more towards sustainable production. Sensitized by this malpractice the author has done some experimental investigations. It was observed by the author that in barium industries, dumped waste materials, (mainly insoluble part of black ash) after sometime set into a hard mass on their own. This gave a clue that these waste materials probably possess binding characteristics on account of siliceous materials and alkalis originating from coal ash and barite [12-14]. If so then these siliceous materials should exhibit binding characteristics in the form of lime/cement and industrial waste mortars. Results are far better with lime and residual wastes rather than cement and residual wastes. Residual wastes are the mixture of water soluble barium sulphide and water insoluble or difficult soluble compositions like amorphous silica, silicates, sulphides, oxides etc. The latter materials react with lime in a faster and better way being amorphous in nature, but it is not so with cement due to the formation of sulphoaluminates and sulphosilicates of calcium in the blocks [15]. To meet the object experiments were carried out with industrial wastes, cement and lime in order to reclaim the industrial waste. The outcomes are fairly supportive. 2. Materials and methods To investigate the binding characteristics of residual wastes of Barium industries experiments were conducted as follows. Materials used for study were acquired from the following sources: 2.1. The raw materials used for study were as follows: 2.1.1. Residual waste (powdered form): After the extraction of barium sulphide (water soluble) from the black ash [16] the residue thus obtained is the main raw material along with residue of carbothermaly reduced barite, broken earthen pots, etc. Barium sulphide which is also known as black ash (used to prepare barium sulphide extract) was prepared by the author in lab by carbothermal reduction of barite. 2.1.2. Lime: Lime (mainly composed of calcite) was procured from local market of Jaisalmer (Rajasthan) act as a basic binding material. Chemical composition of the lime used has been given in Table 1.
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Jyotsna Agarwal/ Materials Today: Proceedings 18 (2019) 4810–4815
Table 1. Chemical composition of lime used in mortar Type of oxide
CaO
MgO
SiO2
Al2O3
Fe2O3
Weight %
53.42 to 54.88
0.30 to 1.0
0.70 to 1.54
0.23 to 0.86 0.12 to 0.26
2.1.3. Cement: Cement which is usually compounds and combinations of metallic oxides like CaO, Al2O3, Fe2O3, H2O, P2O5, SO3, CO3 etc. was Ultra Tech cement of OPC-43 Grade as defined in IS 8112:1989. 2.2. Experimental Procedures Experiments were conducted to study the binding ability (in terms of compressive strength) of residual waste (insoluble part of black ash obtained after the extraction of water soluble barium sulphide). 2.2.3. Preparation of blocks: 2.2.3.1. Preparation of blocks using lime and residual wastes/sand: Residual waste of black ash was thoroughly mixed with fine powder of lime in 3:1 ratio (weight of residual waste of black ash is 3 parts). After mixing, the above trial mixture was gauged with minimum amount of water just sufficient to obtain a plastic wet mix of workable consistency. Two sets of three standard blocks of 70.6mm (70.6 X 10 −3 m) cubic size were prepared (from the above prepared pastes) with the help of standard moulds placed on non-absorbent plates. The moulds were filled with the pastes and were consolidated with light pressure. The surface is made smooth with the blade of trowel. Similarly two sets of 3 standard blocks of 70.6mm cubic size were prepared by mixing sand and lime in 3:1 ratio. 2.2.3.2. Preparation of blocks using cement and residual wastes/sand: Similarly as mentioned above two sets of 3 standard blocks of 70.6mm cubic size were prepared by mixing residual wastes and cement in 3:1 ratio (weight of residual waste of black ash is 3 parts) and two sets of 3 standard blocks of 70.6mm cubic size were prepared by mixing sand and cement in 3:1 ratio. The above prepared cubes (total four sets of three each lime with residual wastes/sand and cement with residual wastes/sand) were placed at 27 ± 3⁰ (for about 21 days) under water, after 24 hrs of air curing. Once curing was done under identical conditions these cubes were subjected to compression in a compressive strength testing machine. This is done by using Universal Testing Machine model no.UTM40, Yama Engineers Kolhapur make. The compressive strength of these cubes were found by applying compression gradually and smoothly, just sufficient to crush them with standard compressive strength testing machine. The crushing loads were noted at the interval of 7 days and 30 days. Average strength of three trial cubes was used to tell the compressive strength of the blocks (unit-kg/cm2). 3. Results and discussion Corresponding findings of compressive strength of the blocks of lime vs residual wastes, lime vs sand, cement vs residual wastes and cement vs sand are recorded in Table 2 and Table 3 respectively. Table 2. Compressive strengths of the blocks of lime – insoluble black ash residue Vs lime – sand mortars Surface area: 50cm2 Composition of Block
Approx. ratio
Compressive strength in kg/cm2 after 7 days
Residual wastes/Lime
3:1
Sand/Lime
3:1
3.86 broken even without application of load
after 30 days 7.50 3.90
Jyotsna Agarwal/ Materials Today: Proceedings 18 (2019) 4810–4815
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Table 2 reveals the compressive strength of the blocks of residual waste material - lime mortars and sand - lime mortars prepared as per the standard procedures. Results shown are average of three blocks (one set of 3 blocks was used after 7 days and one set of 3 blocks was used after 30 days respectively for both compositions). It is clear from Figure1 that water insoluble part of black ash shows excellent binding characteristics with lime. It is far better than sand - lime mortars with respect to its compressive strength taken either 7 or 30 days.
7.5 Compressive Strength in Kg/Cm2
8 7 6 5 4 3 2 1 0
3.9
3.86
0
After 7 days
After 30 days Sand/Lime Mortar(3:1)
Fig. 1 Compressive strength of mortars of residual waste black ash/lime and sand/lime in kg/cm2.
Probable cause for this fact may be, black ash formed due to prolonged (48 hrs) carbothermal reduction of barite and carbon in the pit furnace, resulting in the formation of water soluble barium sulphide on one hand and water insoluble or difficult soluble compositions like amorphous silica, silicates, sulphides, oxides etc. on the other. The latter materials react with lime in a faster and better way because of their amorphous character when compared to the weathered gravel which is of crystalline texture. At ordinary temperature, the latter materials react with lime to form calcium silicate, calcium aluminate, calcium aluminosilicate etc. These different types of lime bearing phases are subsequently hydrated with water which changes them into compounds with cementitious properties and is responsible for development of strength in the mortar. Thus higher compressive strength of the water insoluble black ash and lime mortar is expected. Sulphides also reacted with lime to form insoluble phases of calcium sulphide and hence their damaging effects towards the mechanical strength of the matrix is nullified. Proposed reactions are as follows: Silica Ca (OH) 2 → Calcium silicates --------- (1) (Insoluble) CaO
+
H2O
→
Ca (OH) 2
-------- (2)
(Sulphide) Ca (OH) 2 Ca (OH) 2 + CO2 (Unused)
→
CaS + H2O etc. (Insoluble) →
CaCO3 + H2O (Insoluble)
-------- (3) -------- (4)
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Jyotsna Agarwal/ Materials Today: Proceedings 18 (2019) 4810–4815
Earlier strength (recorded after 7 days) is mainly due to (3) reaction, but gradually other reactions also go on side by side and are responsible for higher ultimate strength (recorded after 30 days). Table 3. Compressive strengths of the blocks of cement – insoluble black ash residue Vs cement – sand mortars Surface area: 50cm2 Composition of Block
Compressive strength in kg/cm2
Approx. ratio
Residual wastes/Cement
3:1
Sand/Cement
3:1
after 7 days
after 30 days
18.0
39.0
25.0
48.0
Table 3 shows the average compressive strength of three blocks (one set of 3 blocks was used after 7 days and one set of 3 blocks was used after 30 days respectively) of residual waste material - cement mortars and sand - cement mortars prepared as per the standard procedures. Figure 2 is reflecting the comparative strength of above discussed mortars.
48 Compressive Strength in Kg/Cm2
50
39
40 30
25 18
20 10 0 After 7 days Sand/Cement Mortar(3:1)
After 30 days Residual Waste/Cement Mortar (3:1)
Fig. 2 Compressive strength of mortars of residual waste black ash Vs cement and sand Vs cement in kg/cm2.
Figure 2 patently specifies that along with cement, black ash residues do contribute to the compressive strength but to a less extent as compared to cement-gravel mortars. Probable cause for this fact appear to be the less percentage of sand in the black ash residue then that in the gravel. In addition available sulphide in the black ash residues (though in very small extent), pose adverse effect on the setting and binding behaviour of Portland cement. Thus decrease in strength of the blocks made up of black ash insoluble residues is expected. This phenomenon can be explained on the basis of formation of sulphoaluminate and sulphosilicate of calcium in the blocks made by cementblack ash residue mortars. However, smooth physical appearance of the cement-black ash residue blocks even after keeping the blocks in water for over one month is suggestive of their more water tightness as compared to cement-gravel blocks which are found to be more porous. This is also explicable on similar reasons as mentioned above.
Jyotsna Agarwal/ Materials Today: Proceedings 18 (2019) 4810–4815
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4. Conclusions Water insoluble black ash residue in powdered form is better substitute of gravel in mortars based on hydraulic lime. Within the experimental limitations water insoluble contents of black ash in powdered form, forms hydraulic mortar with lime of better strength than that formed by gravel (sand). Though compressive strength of cement-black ash residue blocks is less as compared to that of the cement-gravel blocks, water tightness of the former is more than that of the latter. Except for heavy duty purposes water insoluble residue of the black ash is a very good substitute of the gravel. Cement-black ash insoluble residue mortars can be effectively used for plastering purpose for their smoothness, particularly in the buildings of dark rooms. References [1] Snapshot Waste Management in India, European Business and technology centre, www.ebtc.eu.pdf 2011. [2] CPCB, Inventorisation of hazardous waste generating units in Orissa, Hazardous Waste Management Series, 2003. [3] K.K. Wankhade., The dangers of hazardous waste, www.toxiclink.org. 2004. [4] J.P. Lehman, Hazardous Waste Disposal, Vol. 4. Plenum Press, New York, 1981. [5] IBM., 2011. Indian Mineral Year Book, fifty ed. Nagpur. [6] G. Clayton and F. Clayton. Patty’s industrial hygiene and toxicology, third ed. John Wiley & Sons, New York, 1981. [7] F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, fourth ed. John Wiley, New York, 1980. [8] IPCS, Barium and Barium Compounds, World Health Organization, Geneva, 2001. [9] NLM, The hazardous substances data bank: barium sulphate, Bethesda, MD: National Library of Medicine, 1991. [10] A.L. Reeves et al. (Eds.), Handbook on the Toxicology of Metals, second ed., Amsterdam, Elsevier, 1986. [11] US EPA, Health effects assessment for barium. Washington, DC, 1984. [12] U. Barbier, Industrial Italian. Laterizi, (1986) pp 40 - 53. [13] J.D. Watt, D.J. Thorne, J. App. Chem., 15, (1996) 585. [14] Ozlem Cizer., Koenraad Van Balen., Dionys Van Gemert., Jan Elsen., 2006. Carbonation reaction of lime hydrate and hydraulic binders at 20°C in ACEME. [15] MDA Thomas, Delayed ettringite formation in concrete. Recent developments and future directions, Department of civil engineering, University of Toronto 1998. [16] International Organization for Standardization, ISO 5877:1971 Barium sulphide, technical (black ash), New Delhi, 1971.