Metallurgical slag as a component in blended cement

Construction and Building Materials 16(2002)489–4940950-0618/02/$-see front matter ᮊ2002Elsevier Science Ltd.All rights reserved.PII:S0950-0618Ž02.00046-6Metallurgical slag as a component in blended cementAmit Rai *,J.Prabakar ,C.B.Raju ,R.K.Morchalle a ,b b bBuilding Materials and Technology Promotion Council,Core 5A,1st Floor,India Habitat Centre,Lodi Road,New Delhi-110003,IndiaaRegional Research Laboratory,Hoshangabad Road,Bhopal-462026IndiabReceived 21December 2000;received in revised form 27May 2002;accepted 31May 2002AbstractMetallurgical slags (granulated and air-cooled ),are disposed as waste from the ferro-manganese and ferro-manganese–silicon alloys manufacturing plants.They find little use unlike blast furnace slags from steel plants.Investigations were carried out to explore the possibility of using high MnO and low MnO metallurgical slags on samples obtained from an alloy plant in India.Low MnO granulated slag was used in making blended slag cement with ordinary Portland cement (OPC ).Addition of slag lowered the compressive strength of the blended cement as compared to that of OPC used.However,the composition of a 50:50blend,ground to 3000cm y g (Blaine ),was found to conform to IS 455:1989for Portland slag cements and also to IS 269:1989,233grade OPC,with respect to standard consistency,setting times,soundness and compressive strength (22MPa at 7days and 33MPa at 28days )tests carried out as per IS 4031:1988.X-Ray diffraction analysis showed that low MnO granulated slag was non-crystalline,whereas the air-cooled slags were crystalline containing mainly quartz,MnO and Mn O .Chemical analysis 23showed that the slag samples were low in CaO and Fe O contents and high in SiO ,Al O ,MnO,MgO,Na O and K O,thus 2322322indicating pozzolanic reactions contributing to a great extent in the strength development of blended slag cement compositions studied.High MnO ()15%)and MgO ()8%)containing slags were considered unsuitable for blended cements because of their deleterious effects.Air-cooled lumpy slag was evaluated for use as aggregates in concrete.All the tests were carried out as per IS 2386:1963,methods of test for aggregate for concrete and to conform to IS 383:1990,coarse and fine aggregates from natural resources.The material passed all the tests viz.crushing strength,impact value,abrasion,alkali aggregate soundness,except for deleterious materials content.This slag could be used,with slight modification,for non-structural concrete.The results of the investigations provide a direction for profitable plans for making blended slag cements.ᮊ2002Elsevier Science Ltd.All rights reserved.Keywords:Physical properties;Size effect;Building materials;Cement;Compressive strength1.IntroductionWith rapid growth of industrialization,there is pres-sure all over the world on available land,not only for housing and industrial complexes,but for land-filling as a means of disposing huge quantities of waste generated from industrial and mining-mineral processing opera-tions.The problem of waste disposal has reached a stage where it occupies large tracts of land for storage of wastes,which can be much larger than that of industry.These waste materials are a significant source of pollu-tion of air,water and streams.They also adversely affect*Corresponding author.Fax:q 91-11-464-2849.E-mail address:raiamit@ (A.Rai ).growth of plant and vegetation w 1x .Some of the wastes are also hazardous to health as they contain radioactive and heavy metals beyond permissible limits.All these problems suggest that there should be some broad-base action to use waste materials for production of value-added products.One such waste is metallurgical slags,which have not so far been given much attention for their utilization.These slags are different in chemical composition than the blast furnace slags obtained from integrated steel plants,and which are used worldwide for making slag cements and as concrete aggregates.Metallurgical slags,however,are obtained as waste y by-products in the manufacture of ferro-manganese,ferro-chrome and ferro-silicon alloys and in the smelting of non-ferrous metals such as lead,zinc and copper.India produces such slags in nearly 30major alloy-steel490 A.Rai et al./Construction and Building Materials16(2002)489–494plants besides those from foundries and mini-steel plants,and all that simply accumulate!In the past few decades,however,in other countries, considerable research and development on metallurgical slags has been carried out.In Canada,some steel alloy slags are being used as an additive in cement raw materials and the effects on cooling rate of structures in which the cements blended with those slags was used w2x.Plasma treatment has also been used on metallur-gical slag and is used to reduce copper,nickel and cobalt levels in the treated slag w3x.Microwave treatment of ferrous slag is reportedly used to control the heating rate of slag due to addition of carbon and magnetite, with potential applications in the recovery of iron from slag as well as in the modification of slag in order to produce a more saleable by-product w4x.Vitrification of slag is also being carried out with electric arc furnace dust,using a sol–gel process w5x.Recovery of Nb,Mn and P from slag is reported by some researchers.In the process,it was found that P slag can be used directly as a fertilizer.Other types of metallurgical slag are used as construction materials.Cement–metallurgical slag blended cements give compressive strengths in the range of15–30MPa w6x.However,notwithstanding all the efforts mentioned above there is a big gap between the generation and use of metallurgical slags produced by various industries.Prompted from the above background,samples of metallurgical slags from a ferro-manganese alloy plant in India were taken to study their suitability as a building material.The slag samples were of two types,i.e. granulated and air-cooled(lumpy).On the basis of chemical composition,both samples were of low MnO and high MnO varieties.Whereas the low MnO granu-lated slag was studied as an additive to ordinary Portland cement to produce Portland-slag cements,the low and high MnO air-cooled slags were evaluated as aggregates for concrete w7–9x.Two Indian Standard Specifications, IS455:1989and IS383:1990,with the related IS test methods,were employed for characterization and eval-uation of the blended slag cements and aggregates, respectively.This paper presents the results of the above investigations.2.Raw materials usedMetallurgical slag samples were obtained from Maharashtra Electrosmelt Ltd.,Chandrapur,India.Two kinds of slag are being generated by this factory in the production of ferro-manganese and ferro-Mn-silicon alloys.During the production process,the molten slag, cooled in the air,is called‘lumpy’slag.When the molten slag is also cooled after passing thorough a Jet of water,the resultant material is called granulated slag. These two varieties are stacked separately from which a composite sample of each type was obtained.Approximately800–900kg of slag is generated per tonne of ferro-manganese alloy produced.Out of approx-imately200tonnes slags disposed per day,140tonnes is granulated slag and60tonnes is‘lumpy’slag.The annual quantity of the slags generated is approximately 50000tonnes for the corresponding60000tonnes of alloys produced.Although physically granulated and lumpy slags are quite discernable,the samples had to be further sub-divided on the basis of chemical composition,into low MnO and high MnO slags.Thus,four samples were selected for the present investigations,and were marked as follows:A.Low MnO granulated slagB.High MnO granulated slagC.Low MnO air-cooled‘lumpy’slagD.High MnO air-cooled‘lumpy’slagIn practice,however,considerable quality control and categorization may have to be adopted as for any waste material for its profitable application.3.Characterization of raw materials3.1.DensitySpecific gravity and bulk density of the slags were determined using the standard methods(IS4001Part 11:1998).The specific gravity of both types of slag was found to be3.20g y cm,whereas there was a variation3in the bulk density,with low MnO slag having1.73g y cm and high MnO slag having2.05g y cm.333.2.Chemical analysisWaste generated and its chemical analysis data,given in Tables1and2,were obtained by the methods described in IS4032:1985,hydraulic cement-chemical analysis.It is seen that the high MnO slag contains33% MnO and the low MnO slag has15%MnO.High silica (39%)in the low MnO slag indicates the possibility of its use as a partial replacement for cement w10x.The trace elements were determined using atomic absorption spectophotometer and the range of the ele-ments present was compared with those of IS7017:1973, and found within the permissible limits(Table3).3.3.X-Ray diffractionX-Ray diffractograms were obtained(Fig.1)using the Philips X-ray diffractometer of CuK a target with detector speed of58y min.The diffractograms of the samples(a)and(b)pertain to low and high MnO granulated slags in which there are hardly any peaks indicating any crystalline phase.Thus,because of their non-crystalline nature and the granulated nature,(a)and491A.Rai et al./Construction and Building Materials 16(2002)489–494Table 1Estimated quantities offerroalloy slags produced at Maharashtra Electrosmelt Alloys Ltd.,Chandrapur,India ProductRaw material other Slag (tonne )y tonne of alloy Slag y day than iron used for GranulatedLumpyTotalgenerated production of one (tonne )tonne alloy (tonnes )Ferro-Manganese ore 2.20manganese Coke0.550.700.30 1.00150alloy Dolomite and lime 0.35Ferro-Manganese ore 1.60silicon–Coke 0.60manganese Dolomite0.20 1.000.40 1.40100alloyHigh grade silica0.80Table 2Chemical composition of slags and cement used ConstituentHigh Low Cement Range of oxide MnO MnO used composition in slag slag (wt.%)standard OPC (wt.%)(wt.%)(wt.%)SiO 228.3239.0020.0016–26CaO 11.0014.0062.0058–67Al O 2310.509.63 3.008–13MnO 26.0015.00NP 0–3MgO 14.9011.50 1.801–6Na O 2 2.65 2.540.290–1K O 2 5.06 4.120.870–1Fe O 230.310.233.505–11NP s not present.Table 3Trace elements in slags (expressed in ppm )S.ElementsHigh Low Permissible no.MnO MnO limitslag slag (IS 7017:1973)1Ca 1.10 2.30752Cr 0.10.200.053Fe 7.0 5.800.304Co 0.030.03NI 5Ni 0.300.40NI 6Cu 0.560.130.057Zn 0.200.15 5.008Pb0.270.200.10NI s not indicated.Fig.1.(a )Low MnO granulated slag,(b )High MnO granulated slag.(c )Low MnO air-cooled ‘lump’slag,(d )High MnO air-cooled ‘lump’slag.(b )could be considered for making Portland-slag blend-ed cement.However,only sample (a ),i.e.low MnO granulated slag was used for making blended cement compositions for further tests.High MnO slags,both granulated and ‘lumpy’slags,as well as low MnO crystalline ‘lumpy’slag w (b ),(c )and (d )x were consid-ered unsuitable for blended cement because of known deleterious effects of high MnO contents in cement and y492 A.Rai et al./Construction and Building Materials 16(2002)489–494Table 4Physical properties of blended cements S.Portland Standard Setting time Soundness no.cement:low consistency (min )(mm )(Le MnO slag (%water )Initial Final Chatelier method )1100:00211053251280:20271804001370:30261753301460:40261954001550:50272354301Note:IS 269:198933grade ordinary Portland cement and IS 455:1989Portland slag cement provide values of setting times (vicat needle test )as initial setting time 30min (minimum )and final setting time of 600min (maximum ).Both these standard specifications also provide the value of soundness (Le Chatelier test )as 10mm (maxi-mum ).Hence,all the above compositions,SI.no.s 1–5,conform to both IS standard specifications with respect to setting times and soundness.Table 5Compressive strength of blended cementsS.Portland Compressive strength no.cement:(MPa )y wet curing low MnO 3days 7days 28days slag 1100:0030.633.061.0280:2018.029.046.8370:3016.625.835.6460:4015.524.033.5550:5015.222.533.3640:606.812.820.6Note:IS 269:1989,33grade ordinary Portland cement and IS 455:1989Portland slag cement provide compressive strength values of 22and 33MPa at 7and 28days,respectively,on wet covering.Three day strengths are not specified.Hence,the compositions up to S.no.5,with 50:50Portland cement and slag,conform to the com-pressive strength values provided in the above two Indian standard specifications.Table 6Engineering properties of air-cooled slay (lumpy slag )S.TestResult Remarkno.1Estimation of deleterious 5.5%Does not pass the IS 2386materials and organic matter (part 2)methods of test for aggregates for concrete 2Mechanical properties 18.34%Passes as IS 2386(part 4)(i )Aggregate crushing test as it provides 45%value and 10%fine value maximum fines (ii )Impact strengthSame3Abrasion test (Los angles test )45.67%Passes IS 2386(part 5)test 4Alkali aggregate reactivityPasses the testPasses IS 2386(part 7)testNote:In all the test results shown above,the slag samples conform to IS 383:1990for coarse and fine aggregates from natural resources,except for deleterious materials and organic matter (5%max ).or poor hydraulicity.The crystalline air-cooled slags could be used mainly as an aggregate for concrete.3.4.Air-cooled lumpy slag as aggregateThe lumpy slag samples,i.e.(c )and (d )were in stone form of light greenish and blackish in color.The material was reduced in size to 10–15mm for conduct-ing engineering properties,tests.The results are given in Table 6.The tests were carried out to know if they conformed to IS 383:1990,coarse and fine aggregates from natural resources.The methods of tests were those described in IS 2386:1963,methods of test for aggre-gates in concrete,in which Part 2deals with estimation of deleterious materials and organic impurities.Part 4with mechanical properties.Part 5with soundness test and Part 7with alkali-aggregate reactivity test.The results (Table 6)show that the lumpy slag passesall the IS tests except in deleterious materials,indicating the need for some beneficiation such as by washing,for upgrade.Yet,it is encouraging that this type of slag could be recommended for all non-structural concrete work.4.Results and discussions4.1.Portland slag cement using low MnO slag Different compositions,having 20–60%of low MnO granulated slag with ordinary Portland cement,were prepared by grinding in a ball mill to a fineness of 3000cm y g (Blaine’s air permeability test IS 5516:1969).2The results of the physical properties on the composi-tions (Tables 4–6)were compared with those specified in IS 455:1989for Portland slag cements.The standard consistency,setting times (Vicat ),soundness and com-493 A.Rai et al./Construction and Building Materials16(2002)489–494pressive strength tests were carried out according to IS 4031:1988(Part4,5,3and6,respectively)for hydraulic cements.All the results,up to those of50:50composi-tion(SI.no.1–5)conform to IS455:1989for Portland slag cements.The results clearly show that by increasing the slag content,there is a fall in compressive strength,yet the 50:50composition shows22MPa and33MPa at7and 28days,respectively,of wet curing to conform to IS 455:1989.It is known that while using granulated blast furnace slag in slag cements a pseudomorphic layer of low penetration is formed.To reduce this effect it is usual to grind finer and work hard the slag cements when lime released from the OPC part acts as an activator for slag hydration and strength development.Unlike blast furnace slag,metallurgical slag is rather acidic and it is likely that its higher SiO and Al O contents contribute223to pozzolanic reactions in strength development.Ahigher percentage of Na O and K O,as well as an MgO22content more than8%may also adversely affect strength development if the metallurgical slag content is increased beyond50%in slag cements.The hydraulicindex(F),as calculated by(CaC q MgO q Al O)y23 SiO or(CaO q CaSO q0.5MgO q Al O)y(SiO q 24232 MnO)for these slags works out as less than1against the specified value of1–2,and therefore such formulae, generally applicable for blast furnace slag,do not work with metallurgical slags as they are considerably less basic.The hardened blended cement paste of50:50com-position was ground and tested for free lime.Since no evidence of free lime was found the set cement is unlikely to have a chance to chemically deteriorate, expand and crack for a long duration as a result ofreactions with Ca(OH).2Free lime was determined by the modified Franke’s method w11x,using acetoacetic ester and isobutyl alcohol as the extracting medium.The filtrate in isobutyl alcohol was diluted with methyl alcohol and titrated with stan-dard hydrochloric acid solution using bromothymol blue as indicator.The chemical and mineralogical compositions of met-allurgical slags are the interesting factors requiring in-depth investigations on the role of MgO and MnO and the mineralogical make-up containing these constituents, to explain their hydraulicity,reaction products and over-all long-range durability of cements using such slags.5.ConclusionsThe above investigations showed that low MnO gran-ulated metallurgical slag,like that coming out from the ferro-manganese alloy manufacturing plant of Maharash-tra Electrosmelt Ltd.,Chandrapur,India,could be used as a partial replacement for ordinary Portland cement to make Portland slag cements.The50:50composition meets all the requirements of IS455:1989for such cements.Increasing the slag content beyond50%causes lowering of the minimum compressive strength specified in the Indian standard specification.High MnO slags could not be recommended for use in slag cements because of the deleterious effects of high MnO content.The crystalline and non-hydraulic nature of air-cooled‘lumpy’slag also restricts its use for slag cements.However,the role of MnO and MgO containing minerals in these slags needs further in-depth investigations.The air-cooled lumpy slag,however,meets all the requirements of IS383:1990for coarse and fine aggre-gates,except for deleterious materials content.Hence, this type of slag may require some beneficiation for upgrading.The air-cooled slag can be recommended for use in non-structural y unreinforced concrete work in foundation and flooring.The investigations reported in this paper are explora-tory,drawing attention for further research and devel-opment in the use of metallurgical slags for manufacturing blended slag cements,and as a concrete aggregate like the use of blast furnace slags in integrated steel plants.AcknowledgmentsThe authors are grateful to the Executive Director, Building Materials and Technology Promotion Council, New Delhi for providing financial support,and to the Director,Regional Research Laboratory,Bhopal,India for providing laboratory facilities and encouragement in carrying out the investigations.Referencesw1x Ramachandran V.The treatment and minimization of waste.J Met1995;February:50–51.w2x Murphy N,Ban PV,Meadoweraft TR.Waste processing and recycling in mineral and metallurgical industries II.Conference Proceedings.Vancouver(British Columbia,Canada):20–24th August,1995.w3x Pickels CA.Proceedings of the Eleventh International Sym-posium on Plasma Chemistry,vol.4.Loughborough(Leices-tershire,UK):22–27th August1993.w4x Hatton BD,Pickless CA.Proceedings of the Steel-Making Conference,vol.77.Chicago(IL,USA):20–23rd March 1994.w5x Sainz E,Femandez JM,Pascual L,Alonso M,Lopez FA.Second International Conference on the Recycling of Metals.Amsterdam(The Netherlands):19–21st October1994.494 A.Rai et al./Construction and Building Materials16(2002)489–494w6x Rong H.Extraction and Processing for Treatment and Mini-mization of Wastes.San Francisco(CA,USA)27th February–3rd March,1994.w7x Rai A.Proceedings of the Conference on Utilization of Blast Furnace Slag in Cement Industry.CE&E,August2000:25–27.w8x Taylor HFW.The Chemistry of Cements,2nd ed.London: Academic Press limited,1997.w9x Taylor HFW.The Chemistry of Cements,1st ed.London: Academic Press limited,1990.w10x Paul A.Chemistry of Glasses.London,New Y ork:Chapman and Hall,1982.w11x Lea FM.The Chemistry of Cement and :Edward Arnold Publishers Ltd,1970.p.25–6.。