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Mechanical properties of concrete in presence of Iron filings as complete replacement of fine aggregates
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 15 (2019) 536–545
www.materialstoday.com/proceedings
ICMAM-2018
Mechanical properties of concrete in presence of Iron filings as complete replacement of fine aggregates Satyaprakasha*, Pashtoon Helmandb and Shikha Sainia# a
Department of Civil Engineering, Sharda University, Greater Noida, UP. India b Department of Civil Engineering, Bost University, Afghanistan # Current Address: MJK Construction Inc., Mississauga, Ontario, Canada.
Abstract Depletion of natural resources and its effect on the environment is increasing with the need of more building materials for increased construction. To achieve a balance between the materials used and saving the planet from the hazards of using the materials, the authors have experimented with the suitability of iron filings (metal waste) as a complete replacement of sand in the production of concrete so as to reduce the effect of sand mining on the environment. It has been found that by completely replacing sand with iron filings in concrete there has been a substantial increase in the compressive and split-tensile strength. The experiments have also shown that there is a decrease in abrasion with increasing addition of iron filings which can be used in pavements and floors in factories.
© 2019 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL ADVANCED MATERIALS (ICMAM-2018).
Keywords: Iron filings, Concrete, Sand, Abrasion, Compressive Strength, Tensile Strength.
*Email address: [email protected]
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL ADVANCED MATERIALS (ICMAM-2018).
Satyaprakash et al. / Materials Today: Proceedings 15 (2019) 536–545
537
1.0 Introduction Waste or discarded materials produced commonly in industries, factories or mechanical plants are increasing daily thereby constituting increased pollution in the environment. Iron filing, composed of minute pieces of iron or galvanized iron (GI), is one such a waste product which is a by-product of the grinding, filing, or milling of finished iron products. They are either recycled, to be used in low quality iron products, or they end up as a waste in landfill sites. One of the disadvantages of the use of iron in different industries is the large quantity of waste iron resulting from the industrial sector which is deposited in domestic waste and in landfills. World-wide steel production stands at 1630 MT in 2016 [1] and its apparent use is 1515 MT and true steel usage is 1406 MT. Using an estimate of 10% wastage, there is wastage of 140 MT annually amounts to 12 MT per month. An article [2] suggests that global ferrous scrap availability stood at 750 MT in 2017, 630 MT of which was recycled. Even after recycling, around 120 MT (16% of total scrap generated) was disposed in the landfill. The scrap is expected to reach about 1 billion tonnes (BT) in 2030 and 1.3 BT in 2050. By then, the amount of scrap reaching the landfill would be 0.2 BT (0.2 trillion kg). Alternate use of the steel waste needs to be found out if we want to stop this from reaching the landfill sites. Sand (fine aggregate) is one of the basic materials used for production of concrete and is about 20-30% of the total volume of the concrete. Based upon the 2017 production of global cement at 4100 million MT [3] and assuming 90% is used for production of concrete, globally 12 billion m3 of concrete is produced, which needs 2.4 billion m3 (4 trillion kgs) of sand in 2017 which would be increasing with the increase in the consumption of cement. Demand of natural sand is increasing day by day due to rapid infrastructure growth. Sand deposits from the river beds are being used up rapidly and causing threat to environment. Due to less availability of sand from the river bed, stones are being crushed into fine powder and used as fine aggregate. Quarrying of stones from the mountains has led to the depletion of another natural resource and also is causing the loss of green covers in the mountains, not to mention the air pollution which it causes, when the stones are quarried and crushed to form sand. All these factors have led to the research for cheap and easily available alternative material to natural sand. Several studies have been carried out where sand has been replaced with materials such as fly-ash, limestone quarry dust and stone powder, marble sludge, copper slag etc. Iron filing is one such waste product which can replace the sand in concrete. And even if 5% (0.2 trillion kgs) of 4 trillion kg of sand can be replaced by waste iron filings, it would be a great help in saving the environment. The possibilities of application of iron containing waste materials in manufacturing of heavy concrete was explored for the first time in 2011 [4]. Further, the effect of adding iron filing in concrete was studied [5] and was reported that there is an increase in the compressive strength of 17% when 30% of iron filling added. However, there is a minor 13% increase in strength for 10% addition of iron filings on the tensile strength of concrete, if the percentage of iron filing added is more than 10%. The study fails to explain why the percentage of iron filing was not increased beyond 30% for compressive strength and 10% for tensile strength and how the formula proposed has validity beyond 30% and 10% respectively. The strength and the properties of concrete produced with Iron Filings as sand replacement was further studied [6]. The results obtained showed that the compressive strength of concrete increased for the 10% and 20% replacement levels of sand with iron filings by 3.5% and 13.5% respectively while there was a decrease of 8% for the 30% replacement level. The split-tensile strength of concrete for the 10% and 20% replacement levels increased by 12.7% and 1% respectively and decreased marginally by 1.7% for the 30% replacement level when compared to the control mix. It was concluded that a maximum of 20% of sand can be replaced by iron filings. However, it was not explained so as to why the compressive and flexural strength decreased after 20% of iron filings. Some authors [7] tested the iron waste till 30% and have shown that the maximum compressive strength and flexural strength of concrete can be achieved with iron filings at 12% and beyond which it starts decreasing. This is in contrast to the earlier studies [5] [6] where it was shown that the both compressive and flexural strength increases till 30% replacement of sand with iron filings.
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With this background where others have not attempted adding iron filings beyond 30% in the production of concrete and the fact that use of iron filings can replace about 5% of the global sand usage, the authors attempted to address both the issues of reuse of the iron filings and the growing scarcity of river sand to find an alternate sustainable material in the current study by replacing 100% sand with iron filings. Also there is a discrepancy in the values of strength of the concrete obtained when iron filings are added beyond 12% [7] to that of others who have shown that the strength increases till 30% of iron filings [5] [6]. This study was carried out to study the discrepancy & ambiguity of the previous studies. 2.0 Materials and Methods Locally available materials were used for the investigations. The details are in the below sections. 2.1 Cement Ordinary Portland cement grade 43 was used for the present investigation. The cement used was of uniform colour (grey with a light greenish shade), free from any hard lumps. Table-1 summarises the results of tests conducted on cement in accordance with procedure laid down in IS 8112: 1989 [8] Table-1: Physical properties of Grade 43 Portland cement. S. No.
Properties
Obtained value Experimentally
Value specified by IS 8112:1989
1 2
Specific Gravity Standard Consistency Percentage
3.14 33%
-
3
Initial Stetting Time Minutes
47
> 30 minutes
4
Finally Setting Time Minutes
242
< 600 minutes
5
Fineness
4.7%
<10
2.2. Fine aggregate Locally procured fine aggregate, conforming to the Zone III was used in the investigation. The aggregate was passed through sieve size of 4.75mm so that all the aggregate falls under fine and then sieve analysis as per IS 383: 1970 [9] was carried out. The physical properties and the results of sieve analysis are listed in Table-2 and 3. Table-2: Physical properties of fine aggregate S. No. 1 2 3 4
Characteristics Specific gravity Fineness modulus Moisture content
Value 2.62 2.61 25%
Grading zone (Based on percentage passing) )
Zone 3 (see Table 3)
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Table-3: Sieve analysis of fine aggregate S. No.
Sieve (mm)
Mass retained (kg)
% retained
1
10
0.07
0.35
2
4.75
0.120
3
2.36
0.147
4
1.18
0.157
7.85
5
0.06
0.213
6
0.03
1.099
7
0.015
8
Pan
9
Cumulative frequency
% finer Obtained
Std Value for Zone-III 100
0.35
99.65
6.4
6.75
93.25
90-100
7.35
14.1
85.9
85-100
21.95
78.05
75-100
10.65
32.6
67.40
60-79
54.95
87.55
12.45
12-40
0.21
10.5
98.05
1.95
0-10
0.039
1.95
100
--
--
Fineness Modulus
2.61
2.78-1.71
2.3 Coarse Aggregate Locally available crushed stone aggregate of maximum size 20 mm were used throughout the investigation. Before use, they were washed of dust and dirt and are dried to surface dry condition. Table-4 summarises the results of tests conducted on coarse aggregates, as per IS 383: 1970 [9]. Table-4: Physical properties of coarse aggregate S. No.
Characteristics
Value
1
Type
Crushed
2
Specific Gravity
2.68
3
Water Absorption
1%
4
Impact Value
29.97%
5
Moisture Content
NIL
2.4 Iron Filing Iron filings were obtained from local mechanical workshop where filing, shaving and grinding of steel/ iron is done. Care was taken to collect only those filings which were generated through galvanised iron (GI) or steel so that it does not rust when used in concrete. Figure-1 shows the iron filings used for the investigation. Table-5 lists the physical properties and Table-6 summarises the results of sieve analysis performed. It was found that based upon the grading zone, the iron filings also was in Zone III, same as the fine aggregate as per IS 383: 1970 [9] and hence may replace fine aggregate in concrete.
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Fig-1: Iron filing used in the experiment Table-5: Physical properties of iron filing S. No. 1 2 3 4 5 6 7
Characteristics Colour Specific Gravity Density Melting/ Freezing point Reacting Solubility Grading zone
Value Greyish 3.66 2040 kg/m3 1535 0C (2795 0F) In free moisture Insoluble in cold and hot water Zone 3 (see Table #6). Same as fine aggregate
Table-6: Sieve analysis of iron filing S. No.
Sieve (mm)
Mass retained (kg)
% retained
Cumulative frequency
% finer Obtained
1
10
2
4.75
3
2.36
4
1.18
5
0.06
6
0.03
7
0.015
8
Pan
9
0
0
0
100
0.009
0.45
0.45
99.55
0.0069
0.345
0.795
99.205
0.362
18.1
18.895
81.105
0.297
14.85
33.745
66.255
0.562
28.1
61.845
38.155
0.472
23.45
85.43
14.57
14.55
100
--
0.291 Fineness Modulus
2.01
Std Value for Zone III 100 90-100 85-100 75-100 60-79 12-40 0-10 -2.78-1.71
2.5 Water Potable water with pH of 7 or less was used in this investigation for both mixing and curing. The amount of water in concrete controls fresh and hardened properties of concrete including workability, compressive strength, permeability, water tightness, durability & weathering, drying shrinkage and potential for cracking. For these reasons, limiting and controlling the amount of water in concrete in important for more constructability and service life.
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3.0 Experimental Design Compressive strength test on M30 concrete cubes of size 150x150x150mm with varying proportions of iron filings replacing sand was carried out. The split-tensile strength was carried out on M30 concrete cylinder of size 150x300mm with different proportions of iron filing, same as that was used for cubes. The proportion of iron filings was varied in 7 steps between 10% to 100% (10, 20, 30, 50, 70, 80 and 100). One sample of control mix was also casted and tested for comparison. For each proportion, 3 samples (for testing after 7, 14 and 28 days of curing) were casted. A total of 72 cubes and 72 cylinders were casted and tested as per the IS 516:1959 [10]. Mix design for M30 concrete was done according to IS 456:2000 [11] & IS 10262:2009 [12] so as to achieve compressive strength of 30N/mm2 after 28days normal curing. The concrete mix proportion was used 1:0.93:2.27:0.4 (Cement:Sand:Aggregate:Water). Mixing was done by adding coarse aggregate and cement, followed by 25% of total water. Then sand was added with other 25% of water. After thoroughly mixing of cement, sand and aggregates, remaining 50% of water was added. This process was followed for all the samples. For each mix, slump test, Vee-Bee test, and compaction tests were conducted to measure workability. After mixing, the concrete was filled into moulds and compacted on vibration table. Demoulding of the samples was done after 24 hours of casting and samples were cured by following water immersion method, in curing tank for 7, 14 and 28 days. Compressive and split tensile strength tests were carried out on the hardened concrete using Compression Testing Machine (CTM) (Figures-2 & 3) by applying a constant load till the sample fails and converting the readings to the corresponding strength.
Figure-2: Compressive Strength Test on the cube; Figure-3: Split tensile strength testing of the specimen
Abrasion is the process of scuffing, scratching, wearing down, marring, or rubbing away and has an undesirable effect of exposure to normal use or exposure to the elements. It can also be intentionally imposed in controlled process using an abrasive. Three samples, of size (50x50x50) mm cubes after 7 days and 28 days of curing, were tested. One sample was of control mix, another with 50% iron filing and the last with 100% iron filing. The samples were tested in Los-Angeles machine (Figure-4) by the procedure laid down in IS 2386 (Part IV): 1963 [13]. Scanning Electron Microscope (SEM) tests were also performed on the samples in which sand was replaced with iron filings to see the internal structure of the concrete. For this, slides were prepared from the broken sample containing 50% and 100% iron filings and were tested under SEM.
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Figure-4: Los Angeles Abrasion Test Machine.
4.0 Results and Discussion 4.1 Compressive Strength with and without Iron Filing of Concrete: For control mix of M30 concrete, the strength obtained was 70% of the final strength after 7 days of cuing and was 90% after 14 days of curing. However, it attained more than the specified strength of 30N/mm2 by 7%. In the case of iron filings, there is a steady increase in the strength with increasing percentage of iron filings. The strength reaches to a maximum of 43N/mm2, after 28 days of curing, which is an increase of around 26% when all of the sand has been replaced by iron filings as compared with the control mix sample. There is an increase of approximately 25-30% between 14 days and 28 days of curing and same is the case with 7 days and 14 days till 30% of iron filing, beyond which the percentage starts decreasing and at 100% it is about only 3%. The results are tabulated in Table-7 and the strength is plotted in Figure-5 in the form of bar graph. Table 7: Compressive Strength (N/mm2) Days 7 14 28
0% 21 26.71 34.0
10% 21.1 27.03 35.0
Compressive Strength in N/mm2 obtained after adding iron filings 20% 30% 50% 70% 80% 22.0 22.4 24.14 27.0 28.5 27.88 27.99 28.03 28.61 30.67 36.2 36.80 37.4 38.0 38.9
100% 32.0 33.0 43.0
Figure-5: Compressive Strength Test results of cubes with and without iron filings
4.2 Split Tensile Strength with and without Iron Filing of Concrete The split tensile strength obtained is summarised in Table-8 for different values of iron filings and corresponding line chart is shown in Figure-6. As can be seen from the Tables-7 & 8 that the 28 days split tensile strength is about 9% of the compressive strength for all the samples, which is in agreement with the 10% for control mix. The trendline for all the three (7 days, 14 days and 28 days of curing) are almost parallel to each. However, there is again an increase in tensile strength of around 24%, similar to that of compressive strength when 100% iron filing sample has been compared with the control mix.
Satyaprakash et al. / Materials Today: Proceedings 15 (2019) 536–545
Days 7 14 28
0% 2.2 2.432 3.023
543
Table 8: Split Tensile Strength (N/mm2) Split-Tensile Strength in N/mm2 obtained after adding iron filings 10% 20% 30% 50% 70% 80% 2.130 2.43 2.51 2.66 2.71 2.79 2.685 2.79 2.95 2.987 3.01 3.067 3.089 3.14 3.178 3.24 3.42 3.66
100% 2.85 3.098 3.76
Figure-6: Split Tensile strength Test results of cylinder with and without iron filings
4.3 Abrasion Test of concrete with Iron Filings The percentage of residue retained on the sieve decreased as the percentage of iron filings were increased in the concrete. The abrasion reduced by approximately 20% (Table-9 (a-c) and Figure-7) when the entire fine aggregate has been replaced by iron filings, samples cured for 28 days. This result was expected as the presence of ion filing would make the surface tough and hence less of abrasion. Such slabs can be used in those places where the floor is subjected to severe abuse, such as parking lots and factories. Table-9Abrasion Test Comparison of concrete (a) Days 7 28
Original wt. (kg) 0.327 0.327
7 28
0.352 0.352
7 28
0.396 0.396
Conventional Concrete Passing Retained wt. (kg) wt. (kg) 0.243 0.084 0.235 0.092 9(b) 50% sand replaced 0.221 0.131 0.205 0.147 9(c) 100% sand replaced 0.236 0.160 0.212 0.184
Figure-7: Result of abrasion test for concrete with and without iron filings
Loss (%) 74.31 71.86
62.7 58.23
59.5 53.53
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4.4 Microstructure of the resultant concrete In the study, SEM was used to study the microstructure of the surface of fractured concrete when sand has been replaced by 50% (Figure-8) and 100% (Figure-9) iron filings, both after 28 days of curing. The SEM was performed at the Moser Baer India factory at Greater Noida, UP, India. The concrete microstructure is seen at 3000x. It can be seen in Figure-8 that CSH gel, foam like structure, acting as fillers, has formed and occupied most of the space in the concrete. The tubular structure could be the iron filings. Voids can be seen clearly, which are occupying around 20% of the total space. Size of most of the particles is smaller than 1µm. However, grain of bigger size (>10 µm) with smooth surface could be seen, which may be iron filings. Voids are observed near the CSH gel. These voids are attached with the bulk of the sample. As a composite material, multiphase of the sample could also be seen. The fillers coming out of the regular cement can also be clearly seen. When 100% sand has been replaced by iron filings (Figure-9), there seems to be no voids present and all the space in the concrete is occupied by CSH gel resulting in an increased surface area for fillers. The increased surface area leads to an increase in the interface area giving better bonding and improved material strength. This explains the maximum strength achieved when complete sand has been replaced by iron filings.
CSH gel CSH gel
Void
Figure-8: Microstructure at 50% iron filings
Figure-9: Microstructure at 100% iron filings
5.0 Conclusions Based upon the experiments carried out under the present investigation, it can be concluded that the iron filings may be an alternative to sand in the production of concrete. This would result in an increase in the compressive as well as split tensile strength to the order of 25% when compared with the control mix concrete. There is also a decrease in the surface abrasion of the order of 20%. These results have also been verified in the microstructure of the sample, as seen under SEM. However, the durability of the resulting concrete was not tested, which may be a concern arising out of the corrosion of the iron filings used in the concrete and its reaction with water during mixing and curing. Some more tests such as Water Permeability, Rapid Chloride Ion Penetration, Water Absorption, Initial Surface Absorption tests need to be performed so that the durability can be ascertained. Flexural test also need to be performed for testing its suitability in the beams, Drop weight Impact test to check the feasibility of the slabs to be used on floors. References [1] www.worldsteel.org [2] Çiftçi, B.B., 2018. Blog: The future of global scrap availability https://www.worldsteel.org/media-centre/blog/2018/future-of-global-scrapavailability.html [3] https://www.statista.com/statistics/219343/cement-production-worldwide/ [4] Mironovs, V., Bronka, J., Korjakins, A. and Kazjonovs, J., 2011. Possibilities of application iron containing waste materials in manufacturing of heavy concrete, 3rd Int’l Conferenece CIVIL ENGINEERING’11 Proceedings #1, Building Materials. [5] Alzaed, A.N., 2014. Effect of Iron Filings in Concrete Compression and Tensile Strength. International Journal of Recent Development in Engineering and Technology, 3(4), 121-125. [6] Olutoge, F., Onugba, M., & Ocholi, A., 2017. Strength Properties of Concrete Produced With Iron Filings as Sand Replacement. British Journal of Applied Science & Technology, 18, 1-6.
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[7] Noori, Krikar M-Gharrib, and Ibrahim, Hawkar Hashim., 2018. Mechanical Properties of Concrete Using Iron Waste As A Partial Replacement of Sand. 4th International Engineering Conference on Developments in Civil & Computer Engineering Applications, 2018, 204215. [8] IS 8112: 1989. Scheme of testing and inspection for certification of 43 grade ordinary portland cement. May 2005. [9] IS 383: 1970. Specification for coarse and fine aggregates from natural sources for concrete. Second revision, reaffirmed 2002. Bureau of Indian Standards, New Delhi [10] IS 516: 1959. Methods of tests for strength of concrete. Reaffirmed 2004. Bureau of Indian Standards, New Delhi [11] IS 456: 2000. Plain and Reinforced concrete – code of practice. Reaffirmed 2005. Bureau of Indian Standards, New Delhi [12] IS 10262: 2009. Concrete mix proportioning – Guidelines. Bureau of Indian Standards, New Delhi [13] IS 2386 (Part-IV): 1963. Methods of tests for aggregates for concrete. Reaffirmed 2002. Bureau of Indian Standards, New Delhi
ScienceDirect Materials Today: Proceedings 15 (2019) 536–545
www.materialstoday.com/proceedings
ICMAM-2018
Mechanical properties of concrete in presence of Iron filings as complete replacement of fine aggregates Satyaprakasha*, Pashtoon Helmandb and Shikha Sainia# a
Department of Civil Engineering, Sharda University, Greater Noida, UP. India b Department of Civil Engineering, Bost University, Afghanistan # Current Address: MJK Construction Inc., Mississauga, Ontario, Canada.
Abstract Depletion of natural resources and its effect on the environment is increasing with the need of more building materials for increased construction. To achieve a balance between the materials used and saving the planet from the hazards of using the materials, the authors have experimented with the suitability of iron filings (metal waste) as a complete replacement of sand in the production of concrete so as to reduce the effect of sand mining on the environment. It has been found that by completely replacing sand with iron filings in concrete there has been a substantial increase in the compressive and split-tensile strength. The experiments have also shown that there is a decrease in abrasion with increasing addition of iron filings which can be used in pavements and floors in factories.
© 2019 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL ADVANCED MATERIALS (ICMAM-2018).
Keywords: Iron filings, Concrete, Sand, Abrasion, Compressive Strength, Tensile Strength.
*Email address: [email protected]
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL ADVANCED MATERIALS (ICMAM-2018).
Satyaprakash et al. / Materials Today: Proceedings 15 (2019) 536–545
537
1.0 Introduction Waste or discarded materials produced commonly in industries, factories or mechanical plants are increasing daily thereby constituting increased pollution in the environment. Iron filing, composed of minute pieces of iron or galvanized iron (GI), is one such a waste product which is a by-product of the grinding, filing, or milling of finished iron products. They are either recycled, to be used in low quality iron products, or they end up as a waste in landfill sites. One of the disadvantages of the use of iron in different industries is the large quantity of waste iron resulting from the industrial sector which is deposited in domestic waste and in landfills. World-wide steel production stands at 1630 MT in 2016 [1] and its apparent use is 1515 MT and true steel usage is 1406 MT. Using an estimate of 10% wastage, there is wastage of 140 MT annually amounts to 12 MT per month. An article [2] suggests that global ferrous scrap availability stood at 750 MT in 2017, 630 MT of which was recycled. Even after recycling, around 120 MT (16% of total scrap generated) was disposed in the landfill. The scrap is expected to reach about 1 billion tonnes (BT) in 2030 and 1.3 BT in 2050. By then, the amount of scrap reaching the landfill would be 0.2 BT (0.2 trillion kg). Alternate use of the steel waste needs to be found out if we want to stop this from reaching the landfill sites. Sand (fine aggregate) is one of the basic materials used for production of concrete and is about 20-30% of the total volume of the concrete. Based upon the 2017 production of global cement at 4100 million MT [3] and assuming 90% is used for production of concrete, globally 12 billion m3 of concrete is produced, which needs 2.4 billion m3 (4 trillion kgs) of sand in 2017 which would be increasing with the increase in the consumption of cement. Demand of natural sand is increasing day by day due to rapid infrastructure growth. Sand deposits from the river beds are being used up rapidly and causing threat to environment. Due to less availability of sand from the river bed, stones are being crushed into fine powder and used as fine aggregate. Quarrying of stones from the mountains has led to the depletion of another natural resource and also is causing the loss of green covers in the mountains, not to mention the air pollution which it causes, when the stones are quarried and crushed to form sand. All these factors have led to the research for cheap and easily available alternative material to natural sand. Several studies have been carried out where sand has been replaced with materials such as fly-ash, limestone quarry dust and stone powder, marble sludge, copper slag etc. Iron filing is one such waste product which can replace the sand in concrete. And even if 5% (0.2 trillion kgs) of 4 trillion kg of sand can be replaced by waste iron filings, it would be a great help in saving the environment. The possibilities of application of iron containing waste materials in manufacturing of heavy concrete was explored for the first time in 2011 [4]. Further, the effect of adding iron filing in concrete was studied [5] and was reported that there is an increase in the compressive strength of 17% when 30% of iron filling added. However, there is a minor 13% increase in strength for 10% addition of iron filings on the tensile strength of concrete, if the percentage of iron filing added is more than 10%. The study fails to explain why the percentage of iron filing was not increased beyond 30% for compressive strength and 10% for tensile strength and how the formula proposed has validity beyond 30% and 10% respectively. The strength and the properties of concrete produced with Iron Filings as sand replacement was further studied [6]. The results obtained showed that the compressive strength of concrete increased for the 10% and 20% replacement levels of sand with iron filings by 3.5% and 13.5% respectively while there was a decrease of 8% for the 30% replacement level. The split-tensile strength of concrete for the 10% and 20% replacement levels increased by 12.7% and 1% respectively and decreased marginally by 1.7% for the 30% replacement level when compared to the control mix. It was concluded that a maximum of 20% of sand can be replaced by iron filings. However, it was not explained so as to why the compressive and flexural strength decreased after 20% of iron filings. Some authors [7] tested the iron waste till 30% and have shown that the maximum compressive strength and flexural strength of concrete can be achieved with iron filings at 12% and beyond which it starts decreasing. This is in contrast to the earlier studies [5] [6] where it was shown that the both compressive and flexural strength increases till 30% replacement of sand with iron filings.
538
Satyaprakash et al. / Materials Today: Proceedings 15 (2019) 536–545
With this background where others have not attempted adding iron filings beyond 30% in the production of concrete and the fact that use of iron filings can replace about 5% of the global sand usage, the authors attempted to address both the issues of reuse of the iron filings and the growing scarcity of river sand to find an alternate sustainable material in the current study by replacing 100% sand with iron filings. Also there is a discrepancy in the values of strength of the concrete obtained when iron filings are added beyond 12% [7] to that of others who have shown that the strength increases till 30% of iron filings [5] [6]. This study was carried out to study the discrepancy & ambiguity of the previous studies. 2.0 Materials and Methods Locally available materials were used for the investigations. The details are in the below sections. 2.1 Cement Ordinary Portland cement grade 43 was used for the present investigation. The cement used was of uniform colour (grey with a light greenish shade), free from any hard lumps. Table-1 summarises the results of tests conducted on cement in accordance with procedure laid down in IS 8112: 1989 [8] Table-1: Physical properties of Grade 43 Portland cement. S. No.
Properties
Obtained value Experimentally
Value specified by IS 8112:1989
1 2
Specific Gravity Standard Consistency Percentage
3.14 33%
-
3
Initial Stetting Time Minutes
47
> 30 minutes
4
Finally Setting Time Minutes
242
< 600 minutes
5
Fineness
4.7%
<10
2.2. Fine aggregate Locally procured fine aggregate, conforming to the Zone III was used in the investigation. The aggregate was passed through sieve size of 4.75mm so that all the aggregate falls under fine and then sieve analysis as per IS 383: 1970 [9] was carried out. The physical properties and the results of sieve analysis are listed in Table-2 and 3. Table-2: Physical properties of fine aggregate S. No. 1 2 3 4
Characteristics Specific gravity Fineness modulus Moisture content
Value 2.62 2.61 25%
Grading zone (Based on percentage passing) )
Zone 3 (see Table 3)
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Table-3: Sieve analysis of fine aggregate S. No.
Sieve (mm)
Mass retained (kg)
% retained
1
10
0.07
0.35
2
4.75
0.120
3
2.36
0.147
4
1.18
0.157
7.85
5
0.06
0.213
6
0.03
1.099
7
0.015
8
Pan
9
Cumulative frequency
% finer Obtained
Std Value for Zone-III 100
0.35
99.65
6.4
6.75
93.25
90-100
7.35
14.1
85.9
85-100
21.95
78.05
75-100
10.65
32.6
67.40
60-79
54.95
87.55
12.45
12-40
0.21
10.5
98.05
1.95
0-10
0.039
1.95
100
--
--
Fineness Modulus
2.61
2.78-1.71
2.3 Coarse Aggregate Locally available crushed stone aggregate of maximum size 20 mm were used throughout the investigation. Before use, they were washed of dust and dirt and are dried to surface dry condition. Table-4 summarises the results of tests conducted on coarse aggregates, as per IS 383: 1970 [9]. Table-4: Physical properties of coarse aggregate S. No.
Characteristics
Value
1
Type
Crushed
2
Specific Gravity
2.68
3
Water Absorption
1%
4
Impact Value
29.97%
5
Moisture Content
NIL
2.4 Iron Filing Iron filings were obtained from local mechanical workshop where filing, shaving and grinding of steel/ iron is done. Care was taken to collect only those filings which were generated through galvanised iron (GI) or steel so that it does not rust when used in concrete. Figure-1 shows the iron filings used for the investigation. Table-5 lists the physical properties and Table-6 summarises the results of sieve analysis performed. It was found that based upon the grading zone, the iron filings also was in Zone III, same as the fine aggregate as per IS 383: 1970 [9] and hence may replace fine aggregate in concrete.
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Fig-1: Iron filing used in the experiment Table-5: Physical properties of iron filing S. No. 1 2 3 4 5 6 7
Characteristics Colour Specific Gravity Density Melting/ Freezing point Reacting Solubility Grading zone
Value Greyish 3.66 2040 kg/m3 1535 0C (2795 0F) In free moisture Insoluble in cold and hot water Zone 3 (see Table #6). Same as fine aggregate
Table-6: Sieve analysis of iron filing S. No.
Sieve (mm)
Mass retained (kg)
% retained
Cumulative frequency
% finer Obtained
1
10
2
4.75
3
2.36
4
1.18
5
0.06
6
0.03
7
0.015
8
Pan
9
0
0
0
100
0.009
0.45
0.45
99.55
0.0069
0.345
0.795
99.205
0.362
18.1
18.895
81.105
0.297
14.85
33.745
66.255
0.562
28.1
61.845
38.155
0.472
23.45
85.43
14.57
14.55
100
--
0.291 Fineness Modulus
2.01
Std Value for Zone III 100 90-100 85-100 75-100 60-79 12-40 0-10 -2.78-1.71
2.5 Water Potable water with pH of 7 or less was used in this investigation for both mixing and curing. The amount of water in concrete controls fresh and hardened properties of concrete including workability, compressive strength, permeability, water tightness, durability & weathering, drying shrinkage and potential for cracking. For these reasons, limiting and controlling the amount of water in concrete in important for more constructability and service life.
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3.0 Experimental Design Compressive strength test on M30 concrete cubes of size 150x150x150mm with varying proportions of iron filings replacing sand was carried out. The split-tensile strength was carried out on M30 concrete cylinder of size 150x300mm with different proportions of iron filing, same as that was used for cubes. The proportion of iron filings was varied in 7 steps between 10% to 100% (10, 20, 30, 50, 70, 80 and 100). One sample of control mix was also casted and tested for comparison. For each proportion, 3 samples (for testing after 7, 14 and 28 days of curing) were casted. A total of 72 cubes and 72 cylinders were casted and tested as per the IS 516:1959 [10]. Mix design for M30 concrete was done according to IS 456:2000 [11] & IS 10262:2009 [12] so as to achieve compressive strength of 30N/mm2 after 28days normal curing. The concrete mix proportion was used 1:0.93:2.27:0.4 (Cement:Sand:Aggregate:Water). Mixing was done by adding coarse aggregate and cement, followed by 25% of total water. Then sand was added with other 25% of water. After thoroughly mixing of cement, sand and aggregates, remaining 50% of water was added. This process was followed for all the samples. For each mix, slump test, Vee-Bee test, and compaction tests were conducted to measure workability. After mixing, the concrete was filled into moulds and compacted on vibration table. Demoulding of the samples was done after 24 hours of casting and samples were cured by following water immersion method, in curing tank for 7, 14 and 28 days. Compressive and split tensile strength tests were carried out on the hardened concrete using Compression Testing Machine (CTM) (Figures-2 & 3) by applying a constant load till the sample fails and converting the readings to the corresponding strength.
Figure-2: Compressive Strength Test on the cube; Figure-3: Split tensile strength testing of the specimen
Abrasion is the process of scuffing, scratching, wearing down, marring, or rubbing away and has an undesirable effect of exposure to normal use or exposure to the elements. It can also be intentionally imposed in controlled process using an abrasive. Three samples, of size (50x50x50) mm cubes after 7 days and 28 days of curing, were tested. One sample was of control mix, another with 50% iron filing and the last with 100% iron filing. The samples were tested in Los-Angeles machine (Figure-4) by the procedure laid down in IS 2386 (Part IV): 1963 [13]. Scanning Electron Microscope (SEM) tests were also performed on the samples in which sand was replaced with iron filings to see the internal structure of the concrete. For this, slides were prepared from the broken sample containing 50% and 100% iron filings and were tested under SEM.
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Figure-4: Los Angeles Abrasion Test Machine.
4.0 Results and Discussion 4.1 Compressive Strength with and without Iron Filing of Concrete: For control mix of M30 concrete, the strength obtained was 70% of the final strength after 7 days of cuing and was 90% after 14 days of curing. However, it attained more than the specified strength of 30N/mm2 by 7%. In the case of iron filings, there is a steady increase in the strength with increasing percentage of iron filings. The strength reaches to a maximum of 43N/mm2, after 28 days of curing, which is an increase of around 26% when all of the sand has been replaced by iron filings as compared with the control mix sample. There is an increase of approximately 25-30% between 14 days and 28 days of curing and same is the case with 7 days and 14 days till 30% of iron filing, beyond which the percentage starts decreasing and at 100% it is about only 3%. The results are tabulated in Table-7 and the strength is plotted in Figure-5 in the form of bar graph. Table 7: Compressive Strength (N/mm2) Days 7 14 28
0% 21 26.71 34.0
10% 21.1 27.03 35.0
Compressive Strength in N/mm2 obtained after adding iron filings 20% 30% 50% 70% 80% 22.0 22.4 24.14 27.0 28.5 27.88 27.99 28.03 28.61 30.67 36.2 36.80 37.4 38.0 38.9
100% 32.0 33.0 43.0
Figure-5: Compressive Strength Test results of cubes with and without iron filings
4.2 Split Tensile Strength with and without Iron Filing of Concrete The split tensile strength obtained is summarised in Table-8 for different values of iron filings and corresponding line chart is shown in Figure-6. As can be seen from the Tables-7 & 8 that the 28 days split tensile strength is about 9% of the compressive strength for all the samples, which is in agreement with the 10% for control mix. The trendline for all the three (7 days, 14 days and 28 days of curing) are almost parallel to each. However, there is again an increase in tensile strength of around 24%, similar to that of compressive strength when 100% iron filing sample has been compared with the control mix.
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Days 7 14 28
0% 2.2 2.432 3.023
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Table 8: Split Tensile Strength (N/mm2) Split-Tensile Strength in N/mm2 obtained after adding iron filings 10% 20% 30% 50% 70% 80% 2.130 2.43 2.51 2.66 2.71 2.79 2.685 2.79 2.95 2.987 3.01 3.067 3.089 3.14 3.178 3.24 3.42 3.66
100% 2.85 3.098 3.76
Figure-6: Split Tensile strength Test results of cylinder with and without iron filings
4.3 Abrasion Test of concrete with Iron Filings The percentage of residue retained on the sieve decreased as the percentage of iron filings were increased in the concrete. The abrasion reduced by approximately 20% (Table-9 (a-c) and Figure-7) when the entire fine aggregate has been replaced by iron filings, samples cured for 28 days. This result was expected as the presence of ion filing would make the surface tough and hence less of abrasion. Such slabs can be used in those places where the floor is subjected to severe abuse, such as parking lots and factories. Table-9Abrasion Test Comparison of concrete (a) Days 7 28
Original wt. (kg) 0.327 0.327
7 28
0.352 0.352
7 28
0.396 0.396
Conventional Concrete Passing Retained wt. (kg) wt. (kg) 0.243 0.084 0.235 0.092 9(b) 50% sand replaced 0.221 0.131 0.205 0.147 9(c) 100% sand replaced 0.236 0.160 0.212 0.184
Figure-7: Result of abrasion test for concrete with and without iron filings
Loss (%) 74.31 71.86
62.7 58.23
59.5 53.53
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4.4 Microstructure of the resultant concrete In the study, SEM was used to study the microstructure of the surface of fractured concrete when sand has been replaced by 50% (Figure-8) and 100% (Figure-9) iron filings, both after 28 days of curing. The SEM was performed at the Moser Baer India factory at Greater Noida, UP, India. The concrete microstructure is seen at 3000x. It can be seen in Figure-8 that CSH gel, foam like structure, acting as fillers, has formed and occupied most of the space in the concrete. The tubular structure could be the iron filings. Voids can be seen clearly, which are occupying around 20% of the total space. Size of most of the particles is smaller than 1µm. However, grain of bigger size (>10 µm) with smooth surface could be seen, which may be iron filings. Voids are observed near the CSH gel. These voids are attached with the bulk of the sample. As a composite material, multiphase of the sample could also be seen. The fillers coming out of the regular cement can also be clearly seen. When 100% sand has been replaced by iron filings (Figure-9), there seems to be no voids present and all the space in the concrete is occupied by CSH gel resulting in an increased surface area for fillers. The increased surface area leads to an increase in the interface area giving better bonding and improved material strength. This explains the maximum strength achieved when complete sand has been replaced by iron filings.
CSH gel CSH gel
Void
Figure-8: Microstructure at 50% iron filings
Figure-9: Microstructure at 100% iron filings
5.0 Conclusions Based upon the experiments carried out under the present investigation, it can be concluded that the iron filings may be an alternative to sand in the production of concrete. This would result in an increase in the compressive as well as split tensile strength to the order of 25% when compared with the control mix concrete. There is also a decrease in the surface abrasion of the order of 20%. These results have also been verified in the microstructure of the sample, as seen under SEM. However, the durability of the resulting concrete was not tested, which may be a concern arising out of the corrosion of the iron filings used in the concrete and its reaction with water during mixing and curing. Some more tests such as Water Permeability, Rapid Chloride Ion Penetration, Water Absorption, Initial Surface Absorption tests need to be performed so that the durability can be ascertained. Flexural test also need to be performed for testing its suitability in the beams, Drop weight Impact test to check the feasibility of the slabs to be used on floors. References [1] www.worldsteel.org [2] Çiftçi, B.B., 2018. Blog: The future of global scrap availability https://www.worldsteel.org/media-centre/blog/2018/future-of-global-scrapavailability.html [3] https://www.statista.com/statistics/219343/cement-production-worldwide/ [4] Mironovs, V., Bronka, J., Korjakins, A. and Kazjonovs, J., 2011. Possibilities of application iron containing waste materials in manufacturing of heavy concrete, 3rd Int’l Conferenece CIVIL ENGINEERING’11 Proceedings #1, Building Materials. [5] Alzaed, A.N., 2014. Effect of Iron Filings in Concrete Compression and Tensile Strength. International Journal of Recent Development in Engineering and Technology, 3(4), 121-125. [6] Olutoge, F., Onugba, M., & Ocholi, A., 2017. Strength Properties of Concrete Produced With Iron Filings as Sand Replacement. British Journal of Applied Science & Technology, 18, 1-6.
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[7] Noori, Krikar M-Gharrib, and Ibrahim, Hawkar Hashim., 2018. Mechanical Properties of Concrete Using Iron Waste As A Partial Replacement of Sand. 4th International Engineering Conference on Developments in Civil & Computer Engineering Applications, 2018, 204215. [8] IS 8112: 1989. Scheme of testing and inspection for certification of 43 grade ordinary portland cement. May 2005. [9] IS 383: 1970. Specification for coarse and fine aggregates from natural sources for concrete. Second revision, reaffirmed 2002. Bureau of Indian Standards, New Delhi [10] IS 516: 1959. Methods of tests for strength of concrete. Reaffirmed 2004. Bureau of Indian Standards, New Delhi [11] IS 456: 2000. Plain and Reinforced concrete – code of practice. Reaffirmed 2005. Bureau of Indian Standards, New Delhi [12] IS 10262: 2009. Concrete mix proportioning – Guidelines. Bureau of Indian Standards, New Delhi [13] IS 2386 (Part-IV): 1963. Methods of tests for aggregates for concrete. Reaffirmed 2002. Bureau of Indian Standards, New Delhi