at SciVerse ScienceDirect

Journal of Cleaner Production 59 (2013) 111e119

Contents lists available

Journal of Cleaner Production

journal homepage: www.elsevier .com/locate/ jc lepro

Properties of bricks with waste ferrochromium slag and zeolite

Osman Gencel a,*, Mucahit Sutcu b, Ertugrul Erdogmus c, Vahdettin Koc d, Vedat Veli Cay e,Mustafa Sabri Gok f

aDepartment of Civil Engineering, Faculty of Engineering, Bartin University, 74100 Bartin, TurkeybDepartment of Materials Science and Engineering, Izmir Katip Celebi University, 35620 Izmir, TurkeycDepartment of Environmental Engineering, Bartin University, 74100 Bartin, TurkeydDepartment of Metallurgy, Faculty of Technical Education, University of Adiyaman, Adiyaman, Turkeye School of Aviation, Dicle University, 21280 Diyarbakir, TurkeyfDepartment of Metallurgical and Materials Engineering, Bartin University, 74100 Bartin, Turkey

a r t i c l e i n f o

Article history:Received 15 March 2013Received in revised form30 June 2013Accepted 30 June 2013Available online 11 July 2013

Keywords:ClayBrickZeoliteFerrochromium slag

* Corresponding author. Tel.: þ90 378 223 5360; faE-mail address: osmangencel@gmail.com (O. Genc

0959-6526/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.jclepro.2013.06.055

a b s t r a c t

Effect of ferrochromium slag, zeolite and combinations on physical, mechanical, thermal conductivityand microstructure properties of bricks was investigated. They were substituted to brick raw material.Semi-dry mixtures were compressed with 20 MPa. Samples were fired at rate of 5 �C/min until 900 �C for2 h. Characterization of fired bricks, density, porosity, water absorption, weight loss, compressive andbending strength, thermal conductivity properties and microstructural and phase analysis of bricks weredetermined. Mechanical strengths of bricks were higher than 7 MPa. Thermal conductivity of samplesdecreases 42.3%. Results showed that bricks with zeolite and slag could be used as construction material.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Energy consumption of fossil origin and pollution due to thesame one, mainly CO2, represent a strategic, economic and envi-ronmental problem in a country. The Kyoto Protocol is an agree-ment made under the United Nations Framework Convention onClimate Change (del Coz Diaz et al., 2008a). Countries ratifying thisprotocol commit to reduce their emissions of carbon dioxide andother greenhouse gases, or engage in emissions trading if theymaintain or increase emissions of these gases. This protocol nowcovers more than 160 countries globally and over 55% of globalgreenhouse gas emissions (Lau et al., 2012; Viguier et al., 2003).These government organizations are working closely with theirmajor utility, energy, oil and gas and chemicals conglomerates inorder to decrease the global greenhouse gas emissions. At presenttime, energy consumption of buildings in Turkey and the countriesof the EU is a high-priority subject. Buildings sector has beenstudied as part of a broader examination in relation to a rationalfuel use and emissions in countries (del Coz Diaz et al., 2008b).Economic and environmental constraints are bound to increase in

x: þ90 378 223 5258.el).

All rights reserved.

coming years and one effect of this on construction industry will bethe need to obtainmore energy efficient buildings and constructionmaterials. Buildings are considered as open systems, and in thatsense they interact with the environment. Part of this interactionincludes thermal energy transmission carried out by the heattransfer mechanisms of conduction, convection and radiation. En-ergy use in buildings is a significant factor in world’s overall energyconsumption and a major contributor to greenhouse gases.Nowadays, approximately 25e30% of the total energy consumed inthe world is used in buildings (Wouter, 2004). An important way ofachieving better energy efficiency in buildings is to improve theirthermal insulation properties. Reduction of heat loss in buildingsdecreases consumption of energy and thus reduces the cost ofheating and cooling (EN 832, 1998). Energy saving can be obtainedby insulation since a significant part of heat losses or heat gainsoccurs through walls and ceilings (Wouter, 2004; EN 832, 1998;Koksal et al., 2012). European standard EN 832 states that,depending on the location and climate, walls should be made ofmaterial with a heat transfer coefficient of 0.4e0.7 W/m2K, thelower the better. Hence many brick manufacturers are seeking toproduce such materials (Sutcu and Akkurt, 2009).

Clay based bricks are the most widely used building materialsfor many purpose such as decorative, load carrier wall and isolation

Fig. 1. Ferrochromium slag before milling.

O. Gencel et al. / Journal of Cleaner Production 59 (2013) 111e119112

etc. Studies on brick materials produced with waste additive by aimof recycling have increased recently and their physical, mechanicaland thermal properties have been intensively investigated (Sutcuand Akkurt, 2009; Dondi et al., 1997; Junge, 2000; Ducman andKopar, 2007; Bilgin et al., 2012; Kohler, 2002; Demir et al., 2005;Rimpel, 1996; Ge et al., 2012; Jankovic et al., 2012; Xu et al.,2012). Radiation shielding properties of bricks have been investi-gated in some papers (Kharitonov, 2002; Fathivand et al., 2007; ElAbd et al., 2009; Asghar et al., 2010; Erdem et al., 2010;Wattanasiriwech et al., 2009).

Currently, since metallic ferrochrome production has increased,large quantities of their waste (ferrochromium slag) occur at theresult of the metallurgical processing. These wastes may be alter-natively used in the brick body in order to produce a radiationprotection material (Kharitonov, 2002; Gencel et al., 2012a; Korkutet al., 2013). Recently, a lot of industrial wastes have been widelyused in construction materials as an additive, and then convertedthe useful and environmental benign materials (Sutcu and Akkurt,2009; Dondi et al., 1997; Junge, 2000; Ducman and Kopar, 2007;Bilgin et al., 2012; Kohler, 2002; Demir et al., 2005; Rimpel, 1996;Marie and Quiasrawi, 2012; Coelho and de Brito, 2013; Ling andPoon, 2012; Turgut, 2012; Hodge et al., 2010). Mineralogical andcompositional content of industrial inorganic wastes are well-matched with that of brick structure.

The slag is waste material obtained in the manufacture of high-carbon ferrochromium. High-carbon FeCr metal with 65% Cr(minimum) content is produced in electric arc furnaces by a car-bothermal process from the oxide of chromium orewith coke as thereducing agent at the temperature of about 1700 �C. Both the liq-uids of the high-carbon ferrochromium metal and of the slag flowout into ladles. After stratification of the metal from the slag bymeans of their different specific gravities, the molten slag e slowlycooling in the air e forms a stable crystalline dense rock productwith mechanical properties similar to basalt (Zelic, 2005). A rela-tively small percentage of this material finds application, but thevast majority of material generated each year is held in dumps; asland disposing costs increase, new disposal options are needed in(Erdem et al., 2005). Waste recycling alternatives are gainingincreasing importance (Correia et al., 2009; Barrera-Díaz et al.,2011). Also, in developed countries, restricted laws in a form ofprohibitions or special taxes for creating waste areas have beenimplemented. Still stricter waste disposal regulations are expectedin the future. Recycling has the potential to reduce the amount ofwastes disposed of in landfills and to preserve natural resources.Recycling, one of the strategies in minimizing wastes, offers threebenefits: (i) reduces the demand for new resources; (ii) cuts downon transport and production energy costs; (iii) utilizes waste whichwould otherwise be gone into landfill sites. Construction materialssuch as brick and concrete containing wastes can support con-struction sustainability and contribute to the development of thecivil engineering area by using industrial waste, minimizing theconsumption of natural resources and producing more efficientmaterials (Pelisser et al., 2011; Gencel et al., 2012b).

Natural zeolite used in this study which is clinoptilolite type, iswidely found in Gördes region of Turkey. Zeolites belong to a familyof naturally occurring volcanic minerals such as vitreous pumiceand diatomaceous earths with unique physical and chemicalcharacteristics. Zeolite tuffs are the diagenetically altered counter-parts of vitreous pumice and occur in abundant quantities in areasof recent or ancient volcanism (Colella et al., 2001; Snellings et al.,2010). Zeolites belong to the tectosilicate mineral group and arebuilding up by a framework of corner-sharing (aluminoesilicatetetrahedral). The framework is arranged as such to form a micro-porous structure with large cages (diameters of less than 2 nm)connected into channels. They possess special properties, such as

ion exchange, molecular sieves, a large surface area, and catalyticactivity, which make them a preferable material for tremendousindustrial applications in industries such as domestic and com-mercial water purification, softening, petrochemical industry, nu-clear industry, biogas industry, heating and refrigeration,detergents, medical, agriculture (Breck, 1971). In the recent years,rather than the known application areas mentioned, many re-searches (De Gennaro et al., 2004) concerning the use of naturalzeolite, especially clinoptilolite in construction industry. It has beenused in concrete technology and applications, such as pozzolaniccement, light-weight aggregates and dimension stone (Karakurtand Topcu, 2011; Perraki et al., 2010, 2003; Canpolat et al., 2004;Caputo et al., 2008). Although the large number of papers isavailable in the literature on this subject, very limited study hasbeen made to date to investigate both the action mechanism ofzeolite addition to clay based bricks (Janke and Motel, 1997).

Literature survey above shows there was no study on utilizationof ferrochromium waste in fabrication of bricks. Also, usage ofzeolite is very limited in bricks production. Therefore, the purposeof this work was determination of feasibility of using ferrochro-mium, zeolite and combination of them in fabrication of bricks andthe effects of them on physical, mechanical and thermal propertiesof bricks so produced.

2. Materials and method

2.1. Characterization of the used brick raw materials

In this study, production of bricks from mixtures of brick clayand additives containing ferrochromium slag and natural zeolitewas accomplished. The ferrochromium slag (see Fig. 1) is a wastematerial that obtained from the manufacture of ferrochromiummetal in the Eti Krom Works, Elazı�g, Turkey. Ferrochromium slagremains as a waste among others in the production of ferrochro-mium metal. The slag was prepared as aggregate by crushing andgrinding it in a laboratory mill to particle size smaller than 100micron for brick production. The clay raw material was obtainedfrom a brick manufacturer (Üç Yıldız Tu�gla) in Bartin, Turkey.Another raw material is natural zeolite (clinoptilolite type) ob-tained from Rota Madencilik, Gördes, Turkey.

The raw materials were initially subjected to pretreatmentssuch as drying, milling and sieving. The chemical composition ofthe raw materials was determined by the X-ray fluorescenceelemental analysis (XRF) spectrometer. The crystalline phaseanalysis ormineral content of the rawmaterials wasmade by the X-ray powder diffraction (XRD). Their thermal behaviors were per-formed by thermo-gravimetric analysis (TGA). Also, their micro-structural images and elemental maps were investigated by

Table 1The brick mixtures prepared from the raw materials used (% by weight).

Mix code Brick clay Ferrochromium slag Natural zeolite

RF 100 0 0A1 90 10 0A2 80 20 0A3 70 30 0B1 90 0 10B2 80 0 20B3 70 0 30C1 90 5 5C2 80 10 10C3 70 15 15

Table 2Chemical composition of the raw materials used.

Oxides (wt.%) Brick clay The slag Zeolite

Al2O3 15.7 23.47 11.82SiO2 61.6 29.38 67.1Fe2O3 6.8 1.55 1.47MgO 2.3 38.5 1.15CaO 2.16 0.93 2.16K2O 2.36 0.06 3.43Na2O 0.82 0.15 0.37Cr2O3 0 5.17 0Loss on ignition 7.2 1.5 12.5

O. Gencel et al. / Journal of Cleaner Production 59 (2013) 111e119 113

scanning electron microscopy (SEM) analysis with energy disper-sive spectrometer (EDS).

2.2. Preparation of brick samples and firing procedure

The raw materials were initially dried at 100 �C in a dry-oven,and then ground by a laboratory mill. The mixtures containingbrick clay with ferrochromium slag and natural zeolite additionwere prepared in a mechanical mixer. Mixture proportions werepresented in Table 1.

Fig. 2 shows the experimental flowchart for the preparation ofbrick samples. The ground raw materials were mechanically mixedfor 30 min to get a uniform consistency. After dry mixing, the waterabout 15wt. % of total weight was sprayed to the powder mixturesfor the production of semi-dry molded brick samples.

A hydraulic press was used to make bricks with 100 � 50 �20 mm in size. Semi-dry mixtures were compressed with a pres-sure of 20 MPa. After shaping of bricks, they were left to dry inambient conditions for 24 h. Samples were dried in an ovenmaintained at 40 �C for 12 h and then at 100 �C for 24 h. The drysamples were then fired in a laboratory-type electrical furnace atthe rate of 5 �C/min until 900 �C, for 2 h to achieved strength.

2.3. Characterization of fired brick samples

The physical properties of the samples after firing were char-acterized. Bulk density, apparent porosity and water absorptionvalues of the fired samples were measured by Archimedes methodaccording to ASTM C20 standard (2005). The mechanical propertiesof brick samples such as compressive and bending strengths werecarried out according to ASTM C67 (2009). Their microstructuraland phase analysis was performed by SEM, EDS and XRD. In addi-tion, the thermal conductivities of the bricks were measured by C-Therm TCi Thermal Conductivity Analyzer with modified transientplane source.

3. Results and discussion

3.1. Properties of brick raw materials

The chemical composition of the raw materials is given inTable 2 in oxide form. According to the XRF analysis, the brick claycontains a large fraction of silica as well as the oxides of aluminum,

Fig. 2. Experimental flowchar

iron, calcium, magnesium and potassium. Loss on ignition of brickraw material upon heating at 1000 �C was measured as 7.2%. Theferrochromium slag includes large amounts of MgO, SiO2, Al2O3 andCr2O3. Natural zeolite raw material is a crystalline aluminoesilicatecontaining elements such as sodium, potassium, magnesium andcalcium. Chemical formulas of the zeolite is (Ca,K2,Na2,Mg)4Al8-Si40O96.24H2O and its mineral content mainly clinoptilolite. Thespecific gravities of clay, the slag and zeolite are 2.6, 3.17 and 1.85 g/cm3.

According to the X-ray diffraction analysis made for mineralphase contents of the raw materials, the brick clay includes mainlyquartz, illite and small amount of chlorite constituents (Sutcu andAkkurt, 2009). The main components of the ferrochromium slagare SiO2, MgO and Al2O3 as well as chromium and iron oxides andfewer amounts of calcium oxides (Gencel et al., 2012a). Commonphases in the slag are amorphous glass, forsterite ((Mg,Fe)2SiO4),FeeMgeCreAl-spinels (MgAl2O4) and enstatite (MgSiO3) that arehigh temperature phases. The structure of the slag includes partlycrystalline and partly amorphous glassy phases as shown in Fig. 3.The mineral content zeolite powder has mainly clinoptilolite aswell as presence of quartz and cristobalite.

The thermo-gravimetric analysis curves of the rawmaterials aregiven in Fig. 4. According to the TGA results, loss on ignition valuesof brick clay, the slag and zeolite powders for 1100 �C weremeasured as 7%, 0.7% and 14%. In Fig. 4a, total weight loss of thebrick clay of about 7%was observed at 1100 �C. The first 1% decreasein the mass occurred about 100 �C due to the evaporation ofphysical water. The second (1%) and third (2%) weight losses wereobserved between the 200e300 �C and the 350e550 �C rangeswhichmay be due to the burning of organic matter and the removalof chemical water. The largest weight loss (2.5%) was detected inbetween the 500e800 �C range which is related with the dehy-droxylation of illite and chlorites. Total weight loss of the slag(Fig. 4b) was almost absent. In Fig. 4c, total weight loss of the zeoliteof about 14% was observed at 1100 �C. Around 600 �C, the removalof chemical water was possibly observed.

Fig. 5 shows the SEM images of brick clay, FeCr slag and zeoliteraw material in powder form used in this study. The SEMmorphology of the clay and zeolite powders revealed that theirparticle sizes are smaller than 20 mm. The particle size of FeCr slag issmaller than 100 mm. The larger micrograph of a slag particle insetin Fig.5b is shown.

t for sample preparation.

0

200

400

600

800

1000

10 20 30 40 50

Inte

nsity

(co

unts

/s)

2theta (degree)

F

F

FF

F FF

F

F

F

F F

FF

S

S

S

F

E

FE

E E

Fig. 3. X-ray powder diffraction pattern of the ferrochromium slag used (F: forsterite,(Mg,Fe)2SiO4; S: spinel, MgAl2O4; E: enstatite, MgSiO3).

Fig. 4. TGA curves of the raw materials: (a) br

O. Gencel et al. / Journal of Cleaner Production 59 (2013) 111e119114

3.2. Properties of the fired brick samples

3.2.1. Unit weightThe fired densities of the produced bricks were presented in

Fig. 6. As seen From Fig. 6, the density values of the samples variedbetween 1679 and 1913 kg/m3. The densities of bricks with ferro-chromium slag are slightly higher than for bricks without additives.As the ferrochromium slag content increases, the fired density in-creases. By contrast, incorporating zeolite into the mixture de-creases the fired density. This is due to the difference of specificgravities of the ferrochromium slag and zeolite. Zeolite (1850 kg/m3) has lower specific gravity than that of ferrochromium slag(3170 kg/m3). The density of brick sample without addition that isreference brick (RF) was 1679 kg/m3. When the density of A1, A2and A3, which are containing ferrochromium slag, were comparedto that of RF, density of A1, A2 and A3 were higher 9.1%, %11.1 and %13.9. Zeolite addition decreases the density of bricks 1.8%, 7.1%,11.9% for 10%, 20% and 30% zeolite content. When looked at thecombined effect of ferrochromium slag and zeolite on density, thedifferences between RF, C1, C2 and C3 were negligible. The brickcontaining 30% ferrochromium slag had the highest fired densitycompared to the other bricks. The boundary value for unit weightwas not given in TS EN 771 (2012).

ick clay, (b) the FeCr slag and (c) zeolite.

Fig. 5. SEM images of the raw materials used.

Fig. 6. Fired density of the produced bricks.

O. Gencel et al. / Journal of Cleaner Production 59 (2013) 111e119 115

3.2.2. Weight loss after firingWeight losses of the produced bricks were presented in Fig. 7. As

seen from Fig. 7, the weight loss values were within in the range of4.7%e8.9%. Fig. 7 shows gradually decreasing weight loss of thesamples with increasing ferrochromium slag concentration. This isdue to the absence of weight loss of the slag. By contrast, incor-porating zeolite into the mixtures increases the weight loss due tothe water content of zeolite.

Firing process causes a small increase in total linear shrinkage ofbrick samples. Since a high firing temperature (especially above900 �C) increases the vitrification due to the alkali oxides in the clay

Fig. 7. Weight loss of the produced bricks after firing.

occurred melted phases in the structure, the shrinkage values in-creases (Gorhan and Simsek, 2013). Therefore, a firing temperatureof 900 �Cwas selected for firing step in this study. Increasing zeolitecontent in the mixtures especially results in rise of the total linearshrinkage of the fired bricks. However, the maximum value for thebrick sample with added 30% zeolite is around 2%. Therefore, thevalues obtained from samples with ferrochromium slag are negli-gibly lower than values obtained from reference sample and sam-ples with zeolite. The boundary value for total linear shrinkage wasnot given in TS 4790 (1986). The brick samples showed thedimensional stability during firing at 900 �C and their linear firingshrinkages were almost negligible.

3.2.3. PorosityApparent porosity values of the produced bricks were presented

in Fig. 8. As seen from Fig. 8, porosity varied between 32.1% and42.8%. The lowest porosity was obtained in A3. The highest porositywas seen in B3.While ferrochromium slag decreases the porosity ofbricks, zeolite has an effect to increase the porosity of bricks. Thiscan be attributed to the particle structure of the slag and zeolite rawmaterials. The calcareous or non-calcareous low refractive clayscontaining fluxing agents in oxidizing conditions widely go intovitrification around 900 �C (Musthafa et al., 2010). So firing tem-perature around 900 �C decreases the porosity. In this respect,although the examinations of obtained findings revealed that theporosity of samples with zeolite tends to increase due to themicroporous structure of zeolite, the changes in porosity of bricksamples were quite small. Difference between the highest and thelowest values was only 10.7% observed. It is possible that thestructure of zeolite is partially collapsed during firing due to its

Fig. 8. Porosities of the produced bricks.

Fig. 9. Water absorption values of the produced bricks.Fig. 11. Bending strength values of the produced bricks.

O. Gencel et al. / Journal of Cleaner Production 59 (2013) 111e119116

vitrification. Still, we got a high porosity over 30%. An increase inthe porosity of the bricks helps to improve their thermal insulatingproperties.

3.2.4. Water absorptionWater absorption values of the produced bricks were presented

in Fig. 9. As seen from Fig. 9, water absorption values varied be-tween 16.1% and 25.9%. The lowest value was obtained in A3. Thehighest one was seen in B3. Ferrochromium slag decreases waterabsorption. But, zeolite additive has an effect to increase the waterabsorption of bricks. This depends on the increasing of their po-rosities. The reason behind it is that the zeolite has a microporousstructure of interconnected framework. This structure of zeoliteabsorbs thewater. For good quality bricks, after immersing bricks incold water for 24 h, water absorption of bricks should not be morethan 20 percent by weight. While reference brick and bricks con-taining the slag are lower than this value, the bricks with zeolite (Bcoded samples) are higher than this value.

3.2.5. Compressive and bending strengthThere is no doubt that the compressive strength is the most

important property of construction materials applications. In manycountries, usage of building bricks is permitted up to three stairs. Soit is clear that the bricks must have a minimum compressivestrength that is 7 MPa according to the Turkish and correspondingEuropean Standards (TS EN 771-1). Compressive strengths of brickswere presented in Fig. 10.

As seen from Fig. 10, compressive strength of bricks decreasesdepending on concentrations of zeolite and ferrochromium slag.Although incorporating both admixtures to the mixture decreases

Fig. 10. Compressive strength values of the produced bricks.

the compressive strength of bricks, strength loss of bricks con-taining zeolite admixture is more than that of bricks with ferro-chromium slag. When compared to the strength of referencesbricks, strength losses were 8.3%, 14.6% and 21.2 for A1, A2 and A3.Strength losses were 36.1%, 44.4% and 59% for B1, B2 and B3. Andstrength losses were 20.6%, 24.6% and 50.1 for C1, C2 and C3.Although bricks loss strength, still all bricks have sufficient strengthaccording to code. According to Turkish and corresponding Euro-pean Standards (TS EN 771-1), bricks should have minimum 7 MPacompressive strength. The lowest brick strength obtained was14.3 MPa belong to B3. There was no strong bonding in the struc-ture of bricks containing zeolite, and these samples had lowercompressive strength among all sample groups. Also ferrochro-mium slag has a higher density and strength than those of zeolites.But, in compression, ferrochromium slag particles endure the stressthan that of zeolite particles. The reason behind the strength loss isrelated to porosity of bricks. Also, the bonding strength occurredafter sintering reaction at 900 �C of the slag together with clay orzeolite is not strong enough because the slag is a product of hightemperature reaction. Thus, the desired strong structure does notentirely provide. However, although the strengths of the bricksdecreased, the strength of produced bricks was still higher thanthat of the limit value.

Bending strength of bricks is presented in Fig. 11. Bendingstrengths of the samples showed the similar behavior in thecompressive strength. Bending strength decreases decreasedepending on admixtures incorporated into the clay brick mixture.The highest value was observed on reference brick whose bendingstrength was 14.1 MPa. The lowest value belonged to B3 with5.3 MPa bending strength.

Fig. 12. Thermal conductivities of the produced bricks.

Fig. 13. SEM images of the fired brick samples containing (a) 30% FeCr slag, (b) 30% zeolite and (c) 15% FeCr slagþ15% zeolite additives.In

tens

ity (

coun

t/s)

RF

A3

Q

Q QQ Q Q

QQ QH

SSF F FF F FF

NN

S FS

F

O. Gencel et al. / Journal of Cleaner Production 59 (2013) 111e119 117

3.2.6. Thermal conductivity of the bricksThermal conductivity results of the produced bricks are shown

in Fig. 12. The thermal conductivity value of reference brick (RF)was 1.196 W/mK. The thermal conductivity of the samples indi-cated a decrease depending on amount of zeolite admixtureincorporated into the clay brick mixture up to 0.69 W/mK (B3sample). However, addition of ferrochromium slag into brick mix-tures was slightly increased their thermal conductivities up to1.26 W/mK. The increment in thermal conductivity of brickincluding ferrochromium slag was up to %5.4. This can be attributedto the decreasing of brick porosity and also the crystalline andglassy phases come from the slag. As seen from Fig. 8, addition offerrochromium slag into the brick decreases porosity of brick.Consequently thermal conductivity of brick with ferrochromiumslag increase when compared to the RF. Thermal conductivityvalues of the brick samples produced with zeolite and combinationof zeolite and ferrochromium slag additives were lower than thereference sample. These results showed that the brick samplesproduced with zeolite addition can be used as a heat insulationconstruction material.

3.2.7. Microstructural and phase analysis of the bricksFig. 13 shows the SEM images of the fired bricks containing 30%

ferrochromium slag, 30% natural zeolite and 15% slagþ15% zeolitemixtures. As shown from the micrograph (Fig.13a) of the samplewith FeCr slag, the slag particles appeared to exist in the brickstructure as an aggregate. The EDS oxide-analysis of the bricksamples with additives in the selected image is presented in

Table 3The EDS analysis of the brick samples with additives (wt%).

Samples Al2O3 SiO2 MgO CaO K2O Na2O Fe2O3 Cr2O3

RF 16.9 66.4 2.48 2.33 2.54 0.88 7.32 e

A3 23.99 50.53 8.07 1.12 5.22 0.85 10.21 1.34B3 17.64 68.54 1.23 2.24 2.73 1.60 6.02 e

C3 21.27 64.60 3.69 2.13 2.65 2.12 3.55 0.78

Table 3. It was observed that these particles together with brick claydid not react during firing process, since they are the high tem-perature product. This case was corrected by X-ray analysis of firedbrick samples (Fig.14), since after firing new phases occurred in thebrick structure was not observed. The micrograph (Fig.13b) of firedbricks with zeolite additives especially shows a porous structurewhich is helpful in reducing their fired densities and thermalconductivities. Also the images revealed that particle morphologyof zeolite was partially vitrified during firing. After firing, thecrystalline and amorphous structure formations in these samplesprovided to attain above the limit mechanical strength.

The XRD analysis of the brick samples with additives is given inFig. 14. According to the phase analysis, the fired samples obviouslyindicated that reference brick contain quartz (SiO2) on a large scale,and also hematite (Fe2O3) and sanidine (KAlSi3O8) crystallinephases. Ferrochromium slag containing-bricks consisted mainly of

10 20 30 40 50 60

2theta

B3

C3P

Fig. 14. XRD graphs of the fired brick samples (Q: quartz, N: sanidine, H: hematite, F:forsterite, S: spinel, P: potassiumeironemagnesiumealuminum silicate).

O. Gencel et al. / Journal of Cleaner Production 59 (2013) 111e119118

quartz and hematite as well as crystalline phases such as spinel(MgAl2O4) and forsterite ((Mg,Fe)2SiO4). These phases come fromthe slag in the brick structure showed a stable behavior at theelevated temperature. Due to the slag and clay did not react, frompoint of view the mechanical strength these mixtures have notenough strength to form bonding strength required. The zeolite andslag containing bricks (C3 coded mixture) included mainly quartzand hematite as well as potassiumesodiumeironemagnesiume

aluminum silicate phase and less amounts of the slag crystallinephases. A newcrystalline peak (signed by P) containing potassiume

sodiumeironemagnesiumealuminum silicate phase possiblyoccurred at the result of sintering reaction of clinoptilolite((Ca,K2,Na2,Mg)4Al8Si40O96.24H2O), slag and clay minerals. Ac-cording to XRD analysis, the main crystalline phases as well as lessamount of an amorphous phase were observed in these samplesfired at 900 �C. These phases occurred in the structure have animportant effect on the properties of the bricks.

4. Conclusions

The key findings of the using ferrochromium slag and naturalzeolite in fabrication of fired bricks are as follows;

While bulk density of bricks with the slag increased, that ofbricks with zeolite decreased. Bricks with the 10%, 20% and 30%addition of the slag to brick clay present a compressive strength of27.5e32 MPa which is slightly smaller than the reference brickwhich has 34.9 MPa. The bricks with 10%, 20% and 30% addition ofzeolite to brick clay show a compressive strength of 14.3e22.3 MPa.Compressive strengths of bricks including combination of the slagand zeolite ranged between 17.4 and 27.7 MPa. But, both of thebricks with ferrochromium slag and zeolite have sufficientstrengths over 14 MPa that satisfies the requirements in TS EN 771and disaster regulation for a building material to be used in thestructural applications. All bricks have high porosity that is desiredto survive under elevated temperature. The effect of zeolite onporosity of brick is dominant due to porous structure and loss onignition of zeolite. Brick sample with 30% zeolite additive gives thelowest thermal conductivity value with 0.69 W/mK. The highestthermal conductivity value was obtained as 1.26 W/mK whichbelong to brick sample including 30% slag additive. Thermal con-ductivity coefficients increased in samples added ferrochromiumslag while decreased in samples added zeolite. All results showedthat the brick samples produced with natural zeolite and ferro-chromium slag þ zeolite addition can be used as a heat insulationconstruction material.

Acknowledgments

Authors would like to thank to Prof. Dr. Juan Jose del Coz Diaz(GICONSIME Research Team of the High Polytechnical School of theUniversity of Oviedo) for their helps in thermal conductivitymeasurements.

References

Asghar, M., Tufail, M., Khan, K., Mahmood, A., 2010. Assessment of radiologicalhazards of clay bricks fabricated in the Punjab province of Pakistan. Radiat.Protec. Dosim. 142, 369e377.

ASTM C20, 2005. Standard Test Methods for Apparent Porosity, Water Absorption,Apparent Specific Gravity, and Bulk Density of Burned Refractory Brick andShapes by Boiling Water. ASTM International, West Conshohocken, PA, USA.

ASTM C67-12, 2009. Standard Test Methods for Sampling and Testing Brick andStructural Clay Tile. ASTM International, West Conshohocken, PA, USA.

Barrera-Díaz, C., Martínez-Barrera, G., Gencel, O., Brostow, W., Bernal-Martínez, L.A.,2011. Processed wastewater sludge recycled for improvement of mechanicalproperties of concretes. J. Hazard. Mater. 192, 108e115.

Bilgin, N., Yeprem, H.A., Arslan, S., Bilgin, A., Gunay, E., Marsoglu, M., 2012. Use ofwaste marble powder in brick industry. Constr. Build. Mater. 29, 449e457.

Breck, D.W., 1971. Zeolite Molecular Sieves: Structure. Wiley, New York.Canpolat, F., Yılmaz, K., Kose, M.M., Sumer, M., Yurdusev, M.A., 2004. Use of zeolite,

coal bottom ash and fly ash as replacement materials in cement production.Cem. Concr. Res. 34, 731e735.

Caputo, D., Liguori, B., Colella, C., 2008. Some advances in understanding thepozzolanic activity of zeolites: the effect of zeolite structure. Cem. Concr.Compos. 30, 455e462.

Coelho, A., de Brito, J., 2013. Economic viability analysis of a construction and de-molition waste recycling plant in Portugal e part I: location, materials, tech-nology and economic analysis. J. Clean. Prod. 39, 338e352.

Colella, C., de’ Gennaro, M., Aiello, R., 2001. Use of zeolitic tuff in the building in-dustry. In: Bish, D.L., Ming, D.W. (Eds.), Natural Zeolites: Occurrence, Properties,Applications, Reviews in Mineralogy and Geochemistry vol. 45. MineralogicalSociety of America, Washington, USA, ISBN 0-939950-57-X, pp. 551e588Chapter 16.

Correia, S.L., Souza, F.L., Dienstmann, G., Segadaes, A.M., 2009. Assessment of therecycling potential of fresh concrete waste using a factorial design of experi-ments. Waste Manage. 29, 2886e2891.

De Gennaro, R., Cappelletti, P., Cerri, G., de’ Gennaro, M., Dondi, M., Langella, A.,2004. Zeolitic tuff as raw material for lightweight aggregates. Appl. Clay. Sci. 25,71e81.

del Coz Diaz, J.J., Garcia-Nieto, P.J., Suarez-Sierra, J.L., Betegon-Biempica, C.,2008a. Nonlinear thermal optimization of external light concrete multi-holedbrick walls by the finite element method. Inter. J. Heat Mass Trans. 51, 1530e1541.

del Coz Diaz, J.J., Garci-Nieto, P.J., Suarez-Sierra, J.L., Penuelas-Sanchez, I., 2008b.Non-linear thermal optimization and design improvement of a new internallight concrete multi-holed brick walls by FEM. Appl. Therm. Eng. 28, 1090e1100.

Demir, I., Baspınar, M.S., Orhan, M., 2005. Utilization of kraft pulp production res-idues in clay brick production. Build. Environ. 40, 1533e1537.

Dondi, M., Marsigli, M., Fabbri, B., 1997. Recycling of industrial and urban wastes inbrick production. Tile Brick Intern. 13, 218e225.

Ducman, V., Kopar, T., 2007. The influence of different waste additions to clay-product mixtures. Mater. Tech. 41, 289e293.

El Abd, A., Czachor, A., Milczarek, J., 2009. Neutron radiography determination ofwater diffusivity in fired clay brick. Appl. Radiat. Isotope. 67, 556e559.

EN 832, 1998. Thermal Performance of Buildings. In: Calculation of Energy Use forHeating. Residential Buildings, CEN, Brussels, Belgium.

Erdem, M., Altundogan, H.S., Turan, M.D., Tumen, F., 2005. Hexavalent chromiumremoval by ferrochromium slag. J. Hazard. Mater. 126, 176e182.

Erdem, M., Baykara, O., Do�gru, M., Kuluöztürk, F., 2010. A novel shielding materialprepared from solid waste containing lead for gamma ray. Radiat. Phys. Chem.79, 917e922.

Fathivand, A.A., Amidi, J., Najafi, A., 2007. The natural radioactivity in the bricks usedfor the construction of the dwelling in Tehran areas of Iran. Radiat. Protec.Dosim. 123, 391e393.

Ge, Z., Gao, Z.L., Sun, R.J., Zheng, L., 2012. Mix design of concrete with recycled clay-brick-powder using the orthogonal design method. Constr. Build. Mater. 31,289e293.

Gencel, O., Koksal, F., Ozel, C., Brostow, W., 2012a. Combined effect of fly ashand waste ferrochromium on properties of concrete. Constr. Build. Mater. 29,633e640.

Gencel, O., Ozel, C., Koksal, F., Erdogmus, E., Martínez-Barrera, G., Brostow, W.,2012b. Properties of concrete paving blocks made with waste marble. J. Clean.Prod. 21, 62e70.

Gorhan, G., Simsek, O., 2013. Porous clay bricks manufactured with rice husks.Constr. Build. Mater. 40, 390e396.

Hodge, M., Ochsendorf, J., Fernandez, J., 2010. Quantifying potential profit frommaterial recycling: a case study in brick manufacturing. J. Clean. Prod. 18, 1190e1199.

Janke, N., Motel, H., 1997. Used zeolite catalysts show promise as a brick additive.Ceram. Indust. 147, 1e8.

Jankovic, K., Nikolic, D., Bojovic, D., 2012. Concrete paving blocks and flags madewith crushed brick as aggregate. Constr. Build. Mater. 28, 659e663.

Junge, K., 2000. Additives in the brick and tile industry. Brick and Tile Indust. Intern.12, 25e39.

Karakurt, C., Topcu, I.B., 2011. Effect of blended cements produced with naturalzeolite and industrial by-products on alkali-silica reaction and sulfate resistanceof concrete. Constr. Build. Mater. 25, 1789e1795.

Kharitonov, V.I., 2002. Radiation shielding bricks from metallurgical products.Indust. Ceram. 22, 169e174.

Kohler, R., 2002. Use of leather residues as pore-forming agents for masonry bricks.Ziegelindustrie Intern. 58, 30e38.

Koksal, F., Gencel, O., Lobland, H.E.H., Brostow, W., 2012. Effect of high temperatureon mechanical and physical properties of lightweight cement based refractoryincluding expanded vermiculite. Mater. Res. Innov. 16, 7e13.

Korkut, T., Gencel, O., Kam, E., Brostow, W., 2013. X ray, gamma and neutron radi-ation tests on Epoxy-Ferrochromium slag composites. Intern. J. Polym. Analy.Charact. 18, 224e231.

Lau, L.C., Lee, K.T., Mohamed, A.R., 2012. Global warming mitigation and renewableenergy policy development from the Kyoto protocol to the Copenhagen accorde a comment. Renew. & Sustain. Energy Rev. 16, 5280e5284.

Ling, T.C., Poon, C.S., 2012. Feasible use of recycled CRT funnel glass as heavyweightfine aggregate in barite concrete. J. Clean. Prod. 33, 42e49.

O. Gencel et al. / Journal of Cleaner Production 59 (2013) 111e119 119

Marie, I., Quiasrawi, H., 2012. Closed-loop recycling of recycled concrete aggregates.J. Clean. Prod. 37, 243e248.

Musthafa, A.M., Janaki, K., Velraj, G., 2010. Microscopy, porosimetry and chemicalanalysis to estimate the firing temperature of some archaeological potteryshreds from India. Microchem. J. 95, 311e314.

Pelisser, F., Zavarise, N., Longo, T.A., Bernardin, A.M., 2011. Concrete made withrecycled tire rubber: effect of alkaline activation and silica fume addition.J. Clean. Prod. 19, 757e763.

Perraki, T.H., Kakali, G., Kontoleon, F., 2003. The effect of natural zeolites on theearly hydration of Portland cement. Micropor. Mesopor. Mater. 61, 205e212.

Perraki, T., Kontori, E., Tsivilis, S., Kakali, G., 2010. The effect of zeolite onthe properties and hydration of blended cements. Cem. Concr. Compos. 32,128e133.

Rimpel, E., 1996. Industrial production of high-porosity brick materials. Ziege-lindustrie Intern. Annu., 174e207.

Snellings, R., Mertens, G., Cizer, O., Elsen, J., 2010. Early age hydration and pozzo-lanic reaction in natural zeolite blended cements: reaction kinetics and prod-ucts by in situ synchrotron X-ray powder diffraction. Cem. Concr. Res. 40, 1704e1713.

Sutcu, M., Akkurt, S., 2009. The use of recycled paper processing residues in makingporous brick with reduced thermal conductivity. Ceram. Intern. 35, 2625e2631.

TS 4790, 1986. Tugla ve Kiremit Topraklarinin Deney Metodu (Test Method forCommon Bricks and Roofing Tile Clays). (Ankara e Turkey).

TS EN771-1, 2012. Turkish Standard Institution (TSEN771-1), Specification for Ma-sonry Units e Part 1: Clay Masonry Units. (Ankara, Turkey).

Turgut, P., 2012. Manufacturing of building bricks without Portland cement. J. Clean.Prod. 37, 361e367.

Viguier, L.L., Babiker, M.H., Reilly, J.M., 2003. The costs of the Kyoto protocol in theEuropa Union. Energ. Polic. 31, 459e481.

Wattanasiriwech, D., Saiton, A., Wattanasiriwech, S., 2009. Paving blocks fromceramic tile production waste. J. Clean. Prod. 17, 1663e1668.

Wouter, P., 2004. Energy Performance of Building: Assessment of InnovativeTechnologies. ENPER-TEBUC, Brussels, Belgium. Final Report.

Xu, Y., Jiang, L.H., Xu, J.X., Li, Y., 2012. Mechanical properties of expandedpolystyrene lightweight aggregate concrete and brick. Constr. Build. Mater. 27,32e38.

Zelic, J., 2005. Properties of concrete pavements prepared with ferrochromium slagas concrete aggregate. Cem. Concr. Res. 35, 2340e2349.