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Sand For Concrete From Steel Mills Induction Furnace WasteSlag

ByKaushal KishoreMaterials Engineer, Roorkee

INTRODUCTION:For the last 20 years, the use of by products of various origins in the production of concrete has becomean increasingly widespread practice in the world. The main advantages are all the elimination of scraps anda reduction in the over exploitation of quarries.

Blast f urnace slag is used in blended cement. Although many studies have been conducted on theevaluation of the electric arc f urnace slag to be use in concrete as aggregates replacing naturalaggregates, no studies have been perf ormed regarding the use of induction f urnace slag in concrete asaggregates replacing natural aggregates.

In making mild steel ingot scrap to sponge iron is f ed into the induction f urnace which produces largequantity of slag. For example Kotdwar a small town of Uttarakhand Steel Mills induction f urnances alonegenerates 15,000 tonnes of slag per year and about 1,50,000 tonnes of slag is lying as dump around thiscity posing an environmental problem. If about 20 steel f actories of Kotdwar generate such quantity of slagit can be calculated how much slag is being generated by about 600 induction f urnace units of India.

The purpose of this study is to utilized this waste as usef ul building material, save the steel mills f romtransport and disposal problems. In place of river sand, alternate sand may be available to builders oncheaper rates. This will prevent over exploitation of quarries and save our environment.

The slag while making mild steel contains iron oxides, silica, alumina, Manganese oxide and MagnesiumOxide. Pollution Control Board of various state has considered slag while making mild steel in inductionf urnaces as hazardous. The emission f rom induction f urnace include suspended particulate matter, oxidesof sulphur, oxides of nitrogen, and CO2 emissions will be more during charging of material to f urnace. Itcould be recommended that slag could be ef f ectively utilized as aggregates in all concrete application. Theconsumption of slag which is waste generated by steel industry, in concrete not only helps in reducinggreen house gases but also help in making environmently f riendly material.

ELECTRIC FURNACE1. Electric Arc Furnace – The heat in the arc f urnace is generated by an electric arc between two or moreelectrodes which are usually graphite or carbon between the electrodes and f urnace charge or between twoor more electrodes. When the scrap is melted down completely and melted slag has come over the top, theslag is tapped of f completely by tilt ing the f urnace. Af ter removal of impurit ies f rom molten steel, it is runinto the ladle f rom which it is poured into ingots or castings.

2. Induction Furnace – is an electric f urnace in which metal is heated using induction. The heat needed tomelt the raw materials is generated using electricity and its electromagnetic ef f ect. The raw material whichmay range f rom scrap to sponge iron is f ed into the f urnace. The capacities of an induction f urnace rangef rom about a kg to a 100 tonnes but the popular capacity range is 1 – 5 tonnes.

All the f actories of Kotdwar and near by towns using coreless induction f urnaces. This kind of inductionf urnace has copper coils through which electricity is supplied to create the desired amount of heat. Thecoils are covered by a material that has a high melting point which is in turn covered by a pot of a heatresistant material. The raw material is f ed into the pot and the heat f rom copper coils melts it. Af ter meltingthe metal is poured into mould. The tilt ing type f urnace is t ilted on a one side hinge to pour the moltenmetal. The selection of a proper power rating f or the f urnace is very important f or achieving the propermelting temperature. Specif ic power consumption norm in induction f urnace is 620 kwh/tonne of liquid metal.The induction melting f urnace industry is in operation in India f or three decades.

SAMPLE COLLECTIONIn making M.S. ingot steel scrap, sponge iron is melt in induction f urnace. For producing f our tones ofproduct, f ive tones of raw material is f ed in. About 200 kg of slag is generated in the production of onetonne iron. Samples of slag was collected f rom Uttarakhand Steel Mills waste slag. These mills grind theslag and recover iron content in it through magnetic separation. The slag contains about 10% of iron, upto7% of iron is recovered by magnetic separation. Slag boulders are crushed in primary crusher, then it iscrushed into f iner crusher. Iron is recovered f rom the product of f iner crusher by magnetic separator. Theremaining material is discarded as waste. The sample is taken f rom this waste slag. Testing carried outf rom this sample as obtained without any crushing, sieving or any other treatment.

MATERIALS 1. Cement – OPC-53 grade was used in this study. The physical properties are given in Tables 1. Thecement conf orms to IS: 12269-1987.

2. River sand – Sand f rom local river used in this study. The test results are given in Table 2. The sand isof zone-II as per IS: 383-1970.

3. Slag sand – The sample used in the study as obtained f rom local steel mills, no crushing, sieving are anyother process/treatment done in it. Its physical composition given in Tables 2.

The grading of slag sand f ound to be of Zone-II as per IS: 383-1970.

4. Aggregate – 20 mm graded crushed aggregate f rom local crushes was used in this study. The gradingof aggregate f ound to be as per IS: 383-1970. The properties are given in Table 2.

5. Water – City supply potable tape water was used in making concrete.

MIX DESIGN As per IS: 456-2000 and Ref . No. 8 mix design was carried out as per details given below.1. Grade of concrete – M-402. Target mean design strength – 40 + 1.65 x 5 = 48.3 N/mm2 at 28 – day age3. Slump – 100 + 10 mm at pour af ter one hour. Expected day temperature between 30 to 35oC.4. Placing – The mix should be designed f or pumped concrete.5. Retarder superplasticizer conf orming to IS: 9103-1999 based on Modif ied Sulphonate NaphthalaneCondensate.6. Materials – The physical properties of OPC is given in Table 1. The physical properties of river sand slagsand and 20 mm crushed aggregate are given in Table 2.

DISCUSSION OF TEST RESULTSConcrete specimens were cast f rom the mixes as given in Table 3, covered with moist gunny bags f or 24hours, demoulded and immersed in water upto the specif ied testing age, cubes, beam and 24 hours waterabsorption tests have shown overall better perf ormance of slag sand mixes than river sand mixes.

CONCLUSIONS(1) In this limited study it is f ound that river sand can be replace f ully with slag sand.(2) The research scholar should take interest in its detail study particularly long term durability of concretemade with slag sand.(3) The builder should use slag sand in their construction on trial basis.(4) Huge quantity of induction f urnace slag is dump and being generated daily, posing not onlyenvironmental but also transport and disposal problems.(5) Af ter detail study a of f icial code should be published, so that those engage in construction should useit as replacement of natural sand without any hesitation.(6) The management of steel mills should also take interest and cooperate in the utilization of slag asbuilding material rather than discarding it as waste material of no use.(7) To start with the builders of Kotdwar where huge quantity of slag is available on regular basis shoulduse it in their construction on trial basis. They should know how cheap it will in comparison to river sand.Further the availability of good quality river sand is being diminishing day by day.(8) Cubes, beam and 24 hours water absorption test have shown overall better perf ormance of slag sandmixes than river sand mixes.

REFERENCES1. IS: 383-1970, Specif ications f or coarse and f ine aggregates f rom natural sources f or concrete (secondrevision), BIS New Delhi.2. IS: 456-2000, Plain and reinf orced concrete – code of Practice (Fourth Revision), BIS, New Delhi.3. IS: 516-1959, Method of test f or strength of concrete, BIS New Delhi.4. IS: 9103-1999, Specif ication f or admixture f or concrete (First revision), BIS, New Delhi.5. IS: 12269-1987, Specif ication f or 53 Grade ordinary Portland cement, BIS, New Delhi.6. Centre f or Science and Environment New Delhi – Environmental Assessment Jasodharpur Industrial Area,Kotdwar, Uttarkhand.7. Rajasthan State Pollution Central Board – Guidelines f or Abatement of Pollution in Steel Re-rolling Mills.8. Kishore Kaushal – Mix Design f or Pumped Concrete with, PPC, OPC, OPC + Flyash, NBM & CW,September 2010, pp. 204-216.

Table 1 – Physical properties of OPC 53 Grade

Properties Requirements as per IS: 12269-1987

Fineness (m2/kg) = 294 225 minimum

Soundness (mm) = 2.0 10 maximum

Setting time (minutes)a) Init ial = 122b) Final = 193

30 minimum

600 maximum

Compressive strength (N/mm2)a) 3 day = 35.5b) 7 days = 43.3c) 28 days = 58.9

27 minimum

37 minimum

53 minimum

Specif ic gravity = 3.15 -

Table 2 – Physical properties of sand, slag and crushed aggregate

I.S. sieve size Percentage passing by mass

Riversand

Slagsand

20 mmcrushedaggregate

IS: 383-1970 Zone-IIrequirements ofsand

IS: 383-1970 20 mm gradedaggregate requirements

40 mm X X 100 X 100

20 mm X X 100 X 95 – 100

10 mm 100 100 47 100 25 – 55

4.75 mm 94 95 7 90 – 100 0 – 10

2.36 mm 83 90 0 75 – 100 -

1.18 mm 68 72 55 – 90

600 micron 47 54 35 – 59

300 micron 25 27 8 – 30

150 micron 6 12 0 – 10

Specif ic gravity 2.65 2.90 2.65 - -

Waterabsorption %

0.8 0.36 0.5 - -

Bulk densityloose room drykg/lit.

1.64 1.71 1.39 - -

Table 3 – M-40 Grade of concrete quantity of materials per cu.m. of concrete on the basis ofsaturated and surface dry river sand, slag sand and 20 mm aggregate

Sl. No. Materials I Mix II Mix

1. Water (kg/m3) 160 160

2. OPC (kg/m3) 400 400

3. River sand (kg/m3) 740 -

4. Slag sand (kg/m3) - 775

5. 20 mm Agg. (kg/m3) 1110 1160

6. Retarder SP (kg/m3) 4.0 4.5

7. Slump af ter one hour (mm) 95 105

8. Volume of Air (%) 1.4 1.5

9. Cubes compressive strength (N/mm2)a) 7 dayb) 28 day

33.5

49.5

34.7

52.7

10. Flexural strength 28 day (N/mm2) 5.2 5.4

11. Water absorption of 28 day matured cubes (%) 4.8 4.2

FIG. 1 INDUCTION FURNACE SLAG

FIG. 2 – SLAG IS BEING CRUSHED IN FIRST CRUSHER

FIG. 3 – SLAG IS BEING CRUSHED IN THE 2ND CRUSHER

FIG. 4 – FINE SLAG

FIG. 5 – IRON RECOVERY BY MAGNET SEPARATOR

FIG. 6 – WASTE SLAG BEING REMOVED

FIG. 7 – SLAG SAND

FIG. 8 – SLAG SAND

We at engineeringcivil.com are thankful to Sir Kaushal Kishore for submitting his research paper on “SandFor Concrete From Steel Mills Induction Furnace Waste Slag” to us. This will not only be a great help to all civilengineers seeking information on use of other materials in concrete but will also be very helpful in protectingour environmental .