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Characteristics of acid resisting bricks made from quarry residues and waste steel slag
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Construction and Building
MATERIALS
Construction and Building Materials 22 (2008) 1887–1896
www.elsevier.com/locate/conbuildmat
Characteristics of acid resisting bricks made from quarry residues and waste steel slag Medhat S. El-Mahllawy
*
Raw Building Materials Technology and Processing Research Institute, Housing and Building National Research Center, 87 El-Tahreer Street, Dokki, Giza, P.O. Box 1770, Cairo, Egypt Received 3 March 2007; received in revised form 24 March 2007; accepted 6 April 2007 Available online 11 June 2007
Abstract The present work focuses on the recycling feasibility of kaolin fine quarry residue (KFQR) combined with granulated blast-furnace slag (GBFS) and granite–basalt fine quarry residue (GBFQR) to make a brick resistible to chemical actions, particularly sewage waters, and possesses better properties than the conventional one. The conventional brick is composed of clay, feldspar (precious material) and sand with different percentages. Chemical and mineralogical analyses were carried out using X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques, respectively. Also, scanning electron microscopy (SEM) as well as energy dispersive X-ray (EDX) analyses was used to study the microstructures of some selected fired specimens. Solid briquettes were made from five suggested batches. These batches contained 50% of KFQR as a constant percentage, while the percentage of GBFS was increased from 10 to 40% on the expense of GBFQR percentage which was decreased from 40 to 10% (by weight). Firing was performed from 1100 C to 1175 C at an interval of 25 C with 5 C/m (firing rate) and 4 h as the soaking time. In order to evaluate the possibility of making acid resisting brick (ARB), the fired specimens were characterized with respect to the Egyptian standard specification (ESS 41-1986) as well as bulk density, volume changes and firing weight loss. The study shows that the batch S2 containing 50% KFQR, 20% GBFQR and 30% GBFS fired at 1125 C exhibits the most satisfying ceramic properties that meet the ESS requirements for making acid resistant brick. The study also indicates that the addition of more than 25% of GBFQR is not recommended, as it is significantly deleterious to the ceramic properties. 2007 Elsevier Ltd. All rights reserved. Keywords: Kaolin fine quarry residue; Granulated blast-furnace slag; Granite–basalt fine quarry residue; Acid resisting brick; Processing; Sintering
1. Introduction It is well known that the disposing of industrial wastes is one of the major worldwide environmental problems. In Egypt, for example, there are a limited number of dumping landfill sites and generally the disposal methods are considered to be environmentally unfriendly. Furthermore, as a consequence of environmental and financial considerations, there is a growing demand for wastes to be re-used or recycled. At present, the utilization of blast-furnace slags, basalt–granite and kaolin fine quarry residues is an urgent environmental and ecological demand, especially *
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after the increase of the annual accumulation of these pollutants. Blast furnace slag is a nonmetallic by-product from iron and steel industry. It is generated during the conversion of iron ore or scarp iron to steel, along with coke for fuel. Production of one tonne of steel leads to the manufacturing of 500–700 kg of slags [1]. The molten slag comprises about 20% by mass of iron production. Some steel slags may contain hazardous elements such as Pb, Cd, Ni and Cr [2]. Different forms of slag products are produced depending on the method used to cool the molten slag. These products include air-cooled blast furnace slag, expanded or foamed slag, palletized slag, and granulated blast furnace slag. In this study granulated blast furnace slag is considered, which is cooled and solidified by rapid water quenching
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to a glassy state with little or no crystallization. Many solutions have been proposed for the technical treatment of the blast furnace slag in variable fields and industries such as concrete works [3], steel corrosion prevention [4], reduction of alkali silica reactivity [5], cement industry [6], road constructions [7], clay brick production [8] and ceramic field [9]. On the other hand, the quarrying of crushed kaolin and basalt–granite aggregates generates a considerable volume of quarry fines, often termed ‘quarry dust’ and ‘filler grade’. The fine fraction of aggregate products (the quarry dust) is usually smaller than 5 mm in size. When the quarry fines consist of a grade mix of coarse, medium and fine sand sized particles, plus a clay/silt fraction of less than 0.075 mm, they can be described as the ‘filler grade’ residue [10]. The investigated residues have been used before in many useful applications, such as fertilizer for acid soils [11], production of ceramic bricks and tiles [12,13] and making of building clay bricks [14]. The present study focuses on the recycling feasibility of kaolin fine quarry residue (KFQR) combined with granulated blast furnace slag (GBFS) and basalt–granite fine quarry residue (GBFQR) to make acid resisting brick, at relatively low cost, and with good physical, chemical and mechanical properties. Furthermore, this study will maximize the industrial profitability and abate both wastes and environmental impacts. 2. Materials, methods and processes 2.1. Materials In this study, two fine quarry residues and one industrial waste were used. The kaolin fine quarry residue (KFQR) was acquired from Abu-Zenima crusher (South Sinai, Egypt). Granite–basalt fine quarry residue (GBFQR) was collected from a crusher site near Hurghada (Egypt), while the granulated blast furnace slag (GBFS) was taken from the stock piles of the Egyptian Iron and Steel Co. which is located in Abu-Za’bal area (Egypt). 2.2. Methods and techniques The chemical composition of the studied starting materials was determined via a computerized X-ray fluorescence (Philips, PW 1400 Spectrometer, Holland). The mineralogical composition was obtained by using X-ray diffraction technique (Philips, PW 1730 Vertical Diffractometer, Holland). This analysis was run at 40 kV and 25 mA using Cu Ka radiation. The used 2h was from 15 until about 50. The identification of the resultant minerals was achieved by using Traces software Version 6 (Microsoft Co., USA). The microstructure of some selected fired specimens was investigated through the scanning electron microscopy (Leica Steroscan 440, UK). The fired specimens were dried for 24 h and then coated by carbon using the SPI-Module
Table 1 Suggested mixtures from the materials used Batch no.
Composition (% by weight) Kaolin fine quarry residue (KFQR)
Granite–basalt fine quarry residue (GBFQR)
Granulated-blast furnace slag (GBFS)
S1 S2 S3 S4 S5
50 50 50 50 50
10 20 25 30 40
40 30 25 20 10
Carbon Fiber Coater. The magnification power was 2000· with an accelerating voltage of 20 kV.The obtained results were analyzed and normalized using energy dispersive Xray (EDX) attached unit, which also helped in phase identifications and microstructure observations. 2.3. Batch preparation and specimen process In order to investigate the feasibility of manufacturing the acid resisting brick (ARB), five suggested batches, namely S1, S2, S3, S4 and S5, were designed for the current study. These mixtures composed of 50% of KFQR and 10– 40% of GBFQR and GBFS, as given in Table 1. These starting materials were crushed, separately ground in a laboratory ball mill, and screened to pass 90 lm sieve. Every batch was first homogenized in a blender, then molded in 5 cm-side length cube by pressing under 225 kg/cm2. Mixing the batches components was implemented on a dry basis with spraying 5% water before molding. After forming, the green briquettes were dried out in an electrical dryer at 80 C for 24 h, and then fired at different firing temperatures (Tf) of 1100 C, 1125 C, 1150 C and 1175 C at 5 C/m firing rate and 4 h soaking time in a muffle furnace under oxidizing condition. Finally, the specimens were cooled inside the furnace until room temperature. In order to assess the physical, chemical and mechanical characteristics of the fired specimens, each batch composition is examined against the requirements of the Egyptian standard specification [15]. In addition, the volumetric changes, firing weight loss and bulk density were calculated. Accordingly, the successful and promising batches were identified and suggested for making acid resisting brick. 3. Results and discussion 3.1. Characteristics of raw material The chemical composition of the materials used is depicted in Table 2. It is clear that both the KFQR and GBFQR are composed essentially of SiO2 and CaO. The GBFS is composed mainly of SiO2, CaO, Al2O3 and BaO in descending order of abundance rather that other oxides content. From the chemical composition of the original
M.S. El-Mahllawy / Construction and Building Materials 22 (2008) 1887–1896 Table 2 Chemical composition of the materials used Oxide content (%)
Kaolin fine quarry residue (KFQR)
Granite–basalt fine quarry residue (GBFQR)
Granulated-blast furnace slag (GBFS)
SiO2 Al2O3 Fe2O3 CaO MgO MnO Na2O K2O SO3 BaO TiO2 L.O.I
53.92 26.76 1.37 1.75 0.32 – 0.16 0.04 1.49 – 2.09 11.95
80.01 8.88 2.29 3.78 1.58 – 0.29 0.32 0.05 – – 2.80
41.46 11.36 0.85 29.83 1.35 4.95 0.61 0.33 2.13 6.35 0.48 0.30
materials, it is expected that the formed ARB may give constituents within the equilibrium diagram of ternary phases SiO2–Al2O3–CaO. The X-ray diffraction pattern of the original materials (Fig. 1) manifests that the KFQR constitutes quartz and kaolinite minerals. The GBFQR consists predominately of quartz and the subsidiary of anorthite mineral. The GBFS is an amorphous material (glassy state) and this is due to the rapid water quenching process of the molten slag. 3.2. Mineralogy of the fired specimens Table 3 clarifies the withstood and melted specimens of different batches during firing progress. So, only ARB that may be used for industrial application will possess X-ray pattern. Figs. 2–6 demonstrate the XRD patterns of the withstood ARB of diverse batches in a function with firing temperature. From the represented patterns, it is found that
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Table 3 p Withstood ( ) and partially melted (X) specimens as a function of firing temperature Firing temperature (C)
1100 1125 1150 1175
Batch no. S1 p p
S2 p p
X X
X X
S3 p p p
S4 p p p
X
X
S5 p p p p
the crystalline phases are anorthite [(Ca,Na) (Si,Al)4O8], augite [Ca(Fe,Mg)Si2O6], diopside [CaMg(SiO3)2], wollastonite [CaSiO3] and quartz [SiO2]. As reported by Yilmaz et al. [16], the augite and diopside phases (pyroxene group) are usually referred to as one phase named diopsidic-augite. It is evident from the XRD patterns that the higher the crystallization temperature as well as the content of the GBFQR, the higher the intensity of the anorthite phase would be. On the contrary, quartz mineral decreases with the increase of firing temperature and increases with the increase of GBFQR. Also, the anorthite phase of S2 specimens fired at 1125 C has the highest sharp intensity, i.e. the highest crystallinity. The formation of anorthite may be due to the interaction between the silica of GBFQR and aluminum of Kaolin to form calcium aluminum silicate phase. The decrease of quartz can be attributed to the fat that the quartz mineral dissolutes in the liquid phase formed from the impurities (Na2O, K2O, Fe2O3 and CaO) present in the mixture composition [17] as well as its sharing in anorthite formation which increases with the increase of firing temperatures. It is observed that the wollastonite phase decreases, with appreciable percentage, in the fired specimens of mixtures S3–S5. This decrease is simultaneously associated with the decreasing of GBFS, the source of CaO. On the other hand, the cristobalite phase is not detected in
Fig. 1. XRD patterns of the fine quarry residues (KFQR and GBFQR) and industrial waste (GBFS) of starting materials.
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Fig. 2. XRD patterns of the fired specimens of S1 mixture in a function of firing temperature.
Fig. 3. XRD patterns of the fired specimens of S2 mixture in a function of firing temperature.
all the examined specimens and this is because they need more (>1175 C) than the suggested maximum temperature, as proposed by dos Santos et al. [18]. The presence of anorthite in the XRD patterns of the fired specimens demonstrates that the firing process reaches the equilibrium state giving evidences that the reaction is complete, as suggested by Gonzalez-Garcia et al. [19]. As regards the mineralogical analysis, there are no new phases formed after 1100 C as a result of the function of both mixture composition and firing temperature and the differences are only in mineral intensity. Needless to say, the slag is a product obtained from a high temperature process, so it is inert to sintering process if the temperature is not high enough.
3.3. Scanning electron microscope (SEM) analysis Some fired specimens were chosen for this analysis and their images are represented in Figs. 7 and 8. It is observed from the images of fired specimens at 1125 C of mixtures S1–S4 that are composed primarily of crystalline microstructure of anorthite (marked as A) and traces of augite (marked as U) and both as a ground mass in a crystalline form. Also, the diopside phase (marked as D) appears as a prismatic euhedral crystalline form and it is detected in the mixtures of S2 and S3. Moreover, some traces of barium and iron oxides are noticed in the specimen of S2 as free unreacted elements. It is worthy to mention that, may be based on the crystallinity of anorthite and presence
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Fig. 4. XRD patterns of the fired specimens of S3 mixture in a function a function of firing temperature.
Fig. 5. XRD patterns of the fired specimens of S4 mixture in a function of firing temperature.
of diopside and augite phases, in appreciable amount, the positive properties of the fired specimens of batches S2– S4 can be accredited. This opinion is also proved by Toya et al. [20]. Also, as appeared from the mentioned SEM microphotographs and XRD patterns, the high crystallinity of anorthite is always connected with specimens that have the highest compressive strength values, especially this is shown in the specimens of batch S2. This observation is supported by Taskiran et al. [21]. They reported that the high compressive strength is associated with the high crystallinity of anorthite phase to glassy ratio. On the other hand, as revealed from Fig. 8 that the examined fired specimens, batches S3, S4 and S5 fired at
1150 C, 1150 C and 1175 C, respectively, are composed of very minute crystals of anorthite. This is due to the presence of inadequate content of GBFS to form a crystalline phase of anorthite. Also, a crystalline form of freeunreacted CaO, and some particles of fused silica in addition to some open holes are observed. Consequently, the worst characteristics that are shown with these fired specimens, from SEM point of view, may be due to the lack of diopside and augite content and the presence of minute crystals of anorthite phase. The minute crystallinity of anorthite can be attributed to the occurrence of unfavorable fully formed conditions such as the scarcity of CaO content and higher crystallization temperature than neces-
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Fig. 6. XRD patterns of the fired specimens of S5 mixture in a function of firing temperature.
Fig. 7. The SEM images of the sintered specimens at 1125 C of mixtures S1–S4.
sary. These are regarded as well crystalline phase formation. 3.4. Ceramic properties The withstood fired specimens with their ceramic properties according to ESS [15] are listed in Table 4. Also, the bulk density, volume changes and firing weight loss properties in a function of firing temperature with different batches are tabulated in Table 5. These physical, chemical and mechanical parameters are not only important to judge the quality of the product, but are also important to monitor the sintered body properties.
As shown in Table 4, all the fired specimens after 1125 C firmly suffer from a deleterious action in their properties. This deleterious action increases with increasing both the firing temperature and the GBFQR content. As reported by dos Santos [18], the impure SiO2 polymorphism is prone to form b-quartz at 573 C, b-cristobalite at more than 1000 C or b-tridymite at more than 1470 C, and these phases are associated with a volumetric expansion change (DV) of 1%, 14% and 16%, respectively. In laboratory experiments, cristobalite commonly forms before tridymite in the stability range of tridymite. Also, upon heating at a temperature higher than the respective cristobalite a M b transitions microcracking inside the
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Fig. 8. The SEM images of the sintered specimens at 1150 C, 1175 C and 1150 C of mixtures S4, S5 and S3, respectively.
grains is induced by the negative effect of thermal expansion. Later, these microcracks, during cooling, will be healed. Therefore, it is not possible to detect these microcracks for the specimens after firing by SEM. The polymorphism phenomena will affect all important ceramic properties. This interpretation can be supported with occurrence of voids and holes inside some fired specimens and that can be easily detected by the visual inspection of some broken parts with a normal hummer. These voids and holes increase in the same trend of the increase of firing temperature, after 1125 C, as well as GBFQR content. The maximum percentage of these holes is
Table 4 The average properties of withstanding ARB corresponding to ESS 41-1986 Batch no. S1
Firing temperature (C)
1100 1125 S2 1100 1125 S3 1100 1125 1150 S4 1100 1125 1150 S5 1100 1125 1150 1175 ESS 41:1986
Water absorption (%)
Acid weight loss (%)
Compressive strength (kg/cm2)
0.95 0.50 1.32 0.02 1.93 0.52 3.89 4.28 0.91 9.15 6.74 5.78 7.24 10.23 <6.0
0.25 0.15 0.35 0.06 0.38 0.18 0.45 0.42 0.25 0.49 0.50 0.48 0.52 0.53 <3.5
517 660 567 710 520 675 423 415 655 375 360 473 393 310 >300
observed clearly in the specimens of mixture S5 (40% GBFQR), especially at 1175 C. 3.4.1. Water absorption Water absorption property is an important factor affecting the durability of bricks. The less water that infiltrates the brick, the more durable and resistant it is to environmental damage. So, the water absorption is measured to investigate the extent of densification in the fired body and also used as an expression to open pores. Water absorption as a function of firing temperatures is shown in Fig. 9a. It is clearly shown from this figure that
Table 5 The volume changes, bulk density and firing weight loss properties as a function of firing temperature for variable batches specimens Batch no.
Firing temperature (C)
Volume changes (%)
Bulk density (gm/cm3)
Firing weight loss (%)
S1
1100 1125 1100 1125 1100 1125 1150 1100 1125 1150 1100 1125 1150 1175
2.62 3.59 2.02 4.53 5.23 3.03 6.71 3.84 2.11 10.01 4.45 3.66 13.30 16.72
6.43 4.99 6.77 5.38 6.81 6.55 4.96 6.71 6.35 5.78 6.68 6.25 5.35 4.25
5.85 6.40 7.14 7.96 7.35 7.51 8.23 7.55 7.91 9.25 7.78 7.95 9.97 10.12
S2 S3
S4
S5
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Fig. 9. The variation of different physico-mechanical properties of the batches specimen in a function of firing temperature.
after 1125 C the fired specimens suffer from the silica polymorphous transformation, negative expansion of silica, and this increases water absorption property after 1125 C (transition point). Also, increasing the content of GBFQR, the main source of silica, leads to the increase of water absorption. The water absorption of the fired specimens of S1-S3 at all firing temperatures achieves the limits of ESS [15]. The fired specimens of the S4 mixture fired up to 1125 C verify the stated Egyptian specification limits. The fired specimens of the S4 mixture, fired at 1150 C, and all the fired specimens of the S5 mixture are out of the pre-mentioned specification.
ported with the increase in water absorption values at the same trend. Also the narrow range of the acid weight loss increase (0.06–0.53%) is probably because there is no new phases formed that encourage acid weight loss i.e. the same mineralogical phases, which are formed within all firing temperatures at different mixture compositions. Also, water absorption is a good parameter that influences strength, durability, shrinkage and creep properties of materials [22]. The highest resistance of specimens toward acid attack (0.06%) always couples with the lowest water absorption value (0.02%), as both properties are a result of vitrification process of the specimens of the different batches.
3.4.2. Acid weight loss The results of the weight loss due to acid attack of the specimens of the different batches at different firing temperatures are illustrated in Fig. 9b. As percepted from this figure and Fig. 9a, the acid weight loss has a relationship not only with firing temperature but also with water absorption property. Acid weight loss values slightly increase with the increase of firing temperature after 1125 C. This is presumably due to the increase of open pores which is sup-
3.4.3. Compressive strength The compression test is the most important test that can be used to assure the engineering quality in the application of building materials. The compressive strength of different fired specimens is represented in Fig. 9c. The result of this figure indicates that the compressive strength values increase with the increase of firing temperature until 1125 C, and then decrease. At 1125 C, the polymorphism phenomenon of SiO2 plays its negative role in forming a
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spongy structure which weakens the body strength [23]. The spongy structure can be seen by the nacked eye for the broken parts of the specimens. On the other hand, the increase of GBFS from batches S1–S5 is reflected on the increase in compressive strength and vice versa in the case of the increase in GBFQR content, due to the negative effect of impure SiO2 polymorphism. In spite of the fact that the compressive strength of the fired specimens of all mixtures meets the limits of ESS [15]. It is worthy to say that the contradiction between the obtained ceramic results with Shih et al. [8] can be attributed to the fact that they used a different mixture design and a different slag type. That slag is characterized by its high content of Fe2O3, CaO and LOI. This is reflected on the physico-mechanical properties of fired specimens and intensity of the formed phases. They reported that both of the water absorption values of fired specimens increase and compressive strength values decrease with increase in slag content which is contradicted with the results of the present study. 3.4.4. Firing volume changes The volume changes are determined using the relation (Vd–Vf)/(Vd), where Vd is the specimen volume before firing and Vf is the specimen volume after firing at a temperature Tf. The firing volume changes of the fired specimens of assorted mixtures in a function of firing temperatures are depicted in Fig. 9d. It is noticeable that the fired specimens of all mixtures shrinked until 1125 C. After 1125 C, the specimens expanded with a corresponding increase of water absorption and decrease of compressive strength. This expansion perhaps is attributed to the negative role of silica as mentioned before. This expansion effect is supported with the increase of GBFQR content (the primary source of silica) from batch S1 until S5. Also, the expansion increases with the increase of firing temperature. This may be due to the increase of melting materials causing internal stress and cracks. Also, the expansion of the fired specimens decreases and the shrinkage increases with the increase of the GBFS content. 3.4.5. Bulk density The bulk density of the fired specimens is determined by dividing the volume over mass of fired briquettes. The relationship between the bulk density of the fired specimens and firing temperature can be shown in Fig. 9e. The bulk density within the range between 1100 C and 1125 C has gently decreasing values and then the decreasing increases briskly up to 1175 C. The primary reason for this decreasing trend is due to the quartz polymorphism effect. Also, the decreasing of bulk density may be construed to the bloating of specimens (i.e. pore volume expansion), which arises from the high pressure of gases such as carbon monoxide and carbon dioxide entrapped in closed pores [21].
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3.4.6. Firing weight loss The firing weight loss of the acid resisting brick (ARB) is calculated by using the relationship (Wd–Wf)/(Wd), where Wd is the specimen weight before firing and Wf is the specimen weight after firing at a temperature Tf. The firing weight loss of the fired ARB of different batches versus firing temperature is demonstrated in Fig. 9f. The results indicate that there is a little increase in the weight loss up to 1125 C. After 1125 C, the weight loss increases with firing temperature with a moderate high rate up to 1175 C. This can be attributed to the increase of pore volume expansion as a function of increasing temperature; this gives the fired specimens a spongy structure which facilitates gas escaping. The maximum value of firing weight loss (10.12%) is accompanied with the highest volume expansion (16.72%). Also, the rising of the weight loss may be caused by the constructive role of quartz polymorphism. This role is maximized with the entrapment of solid samples for gases, such as H2O, CO2, and CO, by the pore system and these gases are released at higher temperatures as the pore system varies [24]. From the aforementioned parameters, it is evident that the real maximum densification of the reported specimens is achieved at 1100 C up to 1125 C. Within this range, the highest shrinkage, compressive strength and density, accompanied by the lowest water absorption and firing weight loss, are obtained. 4. Visual inspection The visual inspection of the successful fired specimens indicates that the ARB have a dark brown color, have smooth surfaces, sharp edges and are free from any type of cracks either in the external faces or internal parts. 5. Conclusions The characteristics of acid resisting brick made from kaolin fine quarry residue combined with granulated blast furnace slag and granite–basalt fine quarry residue were investigated in this research. From the obtained findings, the following conclusions are derived: (1) The fired formulated batches from S1 to S4 fired until 1125 C can be utilized for making acid resistance brick. (2) The most distinctive specimen achieving the limits of ESS (41-1986) was fabricated from batch S2 (50% KFQR, 20% GBFQR and 30% GBFS) and fired at 1125 C. (3) The polymorphous transformation of quartz phase during firing is the main cause for the negative abrupt changes as well as the deleterious action in ceramic properties, especially after 1125 C. (4) There are no new crystalline phases formed during the sintering process after 1100 C.
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(5) Addition of more than 25%wt of GBFQR is not recommended because it induced intolerable changes of the physical, chemical and mechanical properties. (6) Based on this work an environmentally inert brick, with good commercial characteristics, was made using recycling technology in a safe disposal manner for the studied pollutants. Overall, the most superior ceramic properties were for specimen that was prepared from the mixture S2 (50% KFQR, 20% GBFQR and 30% GBFS) and fired at 1125 C. For this reason, the S2 batch is selected to be the most promising mixture for acid resistant brick industry. Acknowledgements This research was conducted while the author was a Visiting Research Fellow at the University of Wollongong, Australia. The author would like to thank his coordinator Prof. Muhammad N. Hadi, Faculty of Engineering, the University of Wollongong, for his generous hospitality and help. My gratitude is due to Dr. David Wexler (Lecturer in Material Engineering, the University of Wollongong) for providing the facilities needed for the experimental work. Also, the author would indeed like to express his appreciation to Dr. Mohamed A. Shahin (Lecturer in Geotechnical and Construction Engineering, Curtin University of Technology) for his friendship and fruitful discussion. The financial support from the Egyptian Educational Missions is gratefully acknowledged. References [1] Galkin MP, Larionov VS, Stepanov AV, Nebol’sin VA, Milovanov IF, Nikitin GS. Utilization of the steelmaking slags. J Metallurg 1998;9:22–36. [2] Dominguez EA, Ullmann R. Ecological bricks made with clays and steel dust pollutants. Appl Clay Sci 1996;11:237–49. [3] Demirbog˘a R, Gu¨l R. Production of high strength concrete by use of industrial by-products. J Build Environ 2006;41(8):1124–7. [4] Holloway M, Sykes JM. Studies of the corrosion of mild steel in alkali-activated slag cement mortars with sodium chloride admixtures by a galvanostatic pulse method. J Corros Sci 2005;47(12):3097–110. [5] Hester D, McNally C, Richardson MA. Study of the influence of slag alkali level on the alkali–silica reactivity of slag concrete. J Constr Build Mater 2005;19(9):661–5.
[6] Al-Jabri KS, Taha RA, Al-Hashmi A, Al-Harthy AS. Effect of copper slag and cement by-pass dust addition on mechanical properties of concrete. J Constr Build Mater 2006;20(5):322–31. [7] Chaurand P, Rose J, Domas J, Bottero JY. Speciation of Cr and V within BOF steel slag reused in road constructions. J Geochem Explor 2006;88(1–3):10–4. [8] Shih PH, Wu ZZ, Chiang HL. Characteristics of bricks made from waste steel slag. J Waste Manage 2004;24(10):1043–7. [9] Youssef NF, El-Sokkary TM, El-Mahllawy MS. Simultaneous utilization of cement kiln dust and blast furnace slag in ceramic floor tile mixtures. In: Proceedings of the International Conference in Future Vision and Challenges for Urban Development, Egypt, 2005. p. 350–62. [10] Williams PT. Waste treatment and disposal. second ed. England: John Wiley & Sons Ltd.; 2005. p. 20–2. [11] Silva BM, Hermo SB, Rodeja GE, Freire VN. Reutilization of granite powder as an amendment and fertilizer for acid soils. J Chemosphere 2005;61(7):993–1002. [12] Menezes R, Ferreira HS, Neves G, Lira H, Ferreira HC. Use of granite sawing wastes in the production of ceramic bricks and tiles. J Eur Ceram Soc 2005;25(7):1149–58. [13] Youssef NF, Osman TA, El-Shimy E. Utilization of granite–basalt fine quarry waste in a ceramic floor tile mixture. J Silicate Industries 2004;69(1–2):7–13. [14] El-Alfi EA, Radwan AM, Ali MH. Physico-mechanical properties of basalt bricks. J Int Ceram 2004;53(3):178–81. [15] Egyptian standard specification (ESS). Acid-resisting bricks for lining sewerages tunnels.1986;41:1–5. [16] Yilmaz S, Ozkan OT, Gunay V. Crystallization kinetics of basalt glass. Ceram Int 1996;22:477–81. [17] Baldo JB, dos Santos WN. Phase transition and their effects on the thermal diffusivity behavior of some SiO2 polymorphs. Ceramica 2002;48:307–20. [18] dos Santos WN, Baldo JB, Baptista J, Taylor R. Effect of SiC on the thermal diffusivity of silica-based materials. Bull Mater Res 2000;35:2091–100. [19] Gonzalez-Garcia F, Romero-Acosta V, Garcia-Ramos G, GonzalezRodriguez M. Firing transformation of mixtures of clays containing illite, kaolinite and calcium carbonate used by ornamental tile industries. Appl Clay Sci 1990;5(4):361–75. [20] Toya T, Tamura Y, Kameshima Y, Okada K. Preparation and properties of CaO–MgO–Al2O3–SiO2 glass–ceramics from kaolin clay refining waste (Kira) and dolomite. J Ceramics 2004;30(6):983–9. [21] Taskiran MU, Demirkol N, Capoglu A. A new porcelainised stoneware material based on anorthite. J Eur Ceram Soc 2005;25(4):293–300. [22] O’Farrell M, Wild S, Sabir BB. Pore size distribution and compressive strength of waste clay mortar. Cement Concrete Comp 2004;23:81–91. [23] El-Mahllawy MS. The composition and ceramic properties of some Egyptian shale deposits and their possible utilization as building materials, Ph.D. Thesis, Department of Geology, Fac. Sci. Zagazig Univ. Egypt, 2004. [24] Toledo R, dos Santos DR, Faria RT, Carrio JG, Auler LT, Vargas H. Gas release during clay firing and evolution of ceramic properties. Appl Clay Sci 2004;27:151–7.
Construction and Building
MATERIALS
Construction and Building Materials 22 (2008) 1887–1896
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Characteristics of acid resisting bricks made from quarry residues and waste steel slag Medhat S. El-Mahllawy
*
Raw Building Materials Technology and Processing Research Institute, Housing and Building National Research Center, 87 El-Tahreer Street, Dokki, Giza, P.O. Box 1770, Cairo, Egypt Received 3 March 2007; received in revised form 24 March 2007; accepted 6 April 2007 Available online 11 June 2007
Abstract The present work focuses on the recycling feasibility of kaolin fine quarry residue (KFQR) combined with granulated blast-furnace slag (GBFS) and granite–basalt fine quarry residue (GBFQR) to make a brick resistible to chemical actions, particularly sewage waters, and possesses better properties than the conventional one. The conventional brick is composed of clay, feldspar (precious material) and sand with different percentages. Chemical and mineralogical analyses were carried out using X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques, respectively. Also, scanning electron microscopy (SEM) as well as energy dispersive X-ray (EDX) analyses was used to study the microstructures of some selected fired specimens. Solid briquettes were made from five suggested batches. These batches contained 50% of KFQR as a constant percentage, while the percentage of GBFS was increased from 10 to 40% on the expense of GBFQR percentage which was decreased from 40 to 10% (by weight). Firing was performed from 1100 C to 1175 C at an interval of 25 C with 5 C/m (firing rate) and 4 h as the soaking time. In order to evaluate the possibility of making acid resisting brick (ARB), the fired specimens were characterized with respect to the Egyptian standard specification (ESS 41-1986) as well as bulk density, volume changes and firing weight loss. The study shows that the batch S2 containing 50% KFQR, 20% GBFQR and 30% GBFS fired at 1125 C exhibits the most satisfying ceramic properties that meet the ESS requirements for making acid resistant brick. The study also indicates that the addition of more than 25% of GBFQR is not recommended, as it is significantly deleterious to the ceramic properties. 2007 Elsevier Ltd. All rights reserved. Keywords: Kaolin fine quarry residue; Granulated blast-furnace slag; Granite–basalt fine quarry residue; Acid resisting brick; Processing; Sintering
1. Introduction It is well known that the disposing of industrial wastes is one of the major worldwide environmental problems. In Egypt, for example, there are a limited number of dumping landfill sites and generally the disposal methods are considered to be environmentally unfriendly. Furthermore, as a consequence of environmental and financial considerations, there is a growing demand for wastes to be re-used or recycled. At present, the utilization of blast-furnace slags, basalt–granite and kaolin fine quarry residues is an urgent environmental and ecological demand, especially *
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after the increase of the annual accumulation of these pollutants. Blast furnace slag is a nonmetallic by-product from iron and steel industry. It is generated during the conversion of iron ore or scarp iron to steel, along with coke for fuel. Production of one tonne of steel leads to the manufacturing of 500–700 kg of slags [1]. The molten slag comprises about 20% by mass of iron production. Some steel slags may contain hazardous elements such as Pb, Cd, Ni and Cr [2]. Different forms of slag products are produced depending on the method used to cool the molten slag. These products include air-cooled blast furnace slag, expanded or foamed slag, palletized slag, and granulated blast furnace slag. In this study granulated blast furnace slag is considered, which is cooled and solidified by rapid water quenching
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to a glassy state with little or no crystallization. Many solutions have been proposed for the technical treatment of the blast furnace slag in variable fields and industries such as concrete works [3], steel corrosion prevention [4], reduction of alkali silica reactivity [5], cement industry [6], road constructions [7], clay brick production [8] and ceramic field [9]. On the other hand, the quarrying of crushed kaolin and basalt–granite aggregates generates a considerable volume of quarry fines, often termed ‘quarry dust’ and ‘filler grade’. The fine fraction of aggregate products (the quarry dust) is usually smaller than 5 mm in size. When the quarry fines consist of a grade mix of coarse, medium and fine sand sized particles, plus a clay/silt fraction of less than 0.075 mm, they can be described as the ‘filler grade’ residue [10]. The investigated residues have been used before in many useful applications, such as fertilizer for acid soils [11], production of ceramic bricks and tiles [12,13] and making of building clay bricks [14]. The present study focuses on the recycling feasibility of kaolin fine quarry residue (KFQR) combined with granulated blast furnace slag (GBFS) and basalt–granite fine quarry residue (GBFQR) to make acid resisting brick, at relatively low cost, and with good physical, chemical and mechanical properties. Furthermore, this study will maximize the industrial profitability and abate both wastes and environmental impacts. 2. Materials, methods and processes 2.1. Materials In this study, two fine quarry residues and one industrial waste were used. The kaolin fine quarry residue (KFQR) was acquired from Abu-Zenima crusher (South Sinai, Egypt). Granite–basalt fine quarry residue (GBFQR) was collected from a crusher site near Hurghada (Egypt), while the granulated blast furnace slag (GBFS) was taken from the stock piles of the Egyptian Iron and Steel Co. which is located in Abu-Za’bal area (Egypt). 2.2. Methods and techniques The chemical composition of the studied starting materials was determined via a computerized X-ray fluorescence (Philips, PW 1400 Spectrometer, Holland). The mineralogical composition was obtained by using X-ray diffraction technique (Philips, PW 1730 Vertical Diffractometer, Holland). This analysis was run at 40 kV and 25 mA using Cu Ka radiation. The used 2h was from 15 until about 50. The identification of the resultant minerals was achieved by using Traces software Version 6 (Microsoft Co., USA). The microstructure of some selected fired specimens was investigated through the scanning electron microscopy (Leica Steroscan 440, UK). The fired specimens were dried for 24 h and then coated by carbon using the SPI-Module
Table 1 Suggested mixtures from the materials used Batch no.
Composition (% by weight) Kaolin fine quarry residue (KFQR)
Granite–basalt fine quarry residue (GBFQR)
Granulated-blast furnace slag (GBFS)
S1 S2 S3 S4 S5
50 50 50 50 50
10 20 25 30 40
40 30 25 20 10
Carbon Fiber Coater. The magnification power was 2000· with an accelerating voltage of 20 kV.The obtained results were analyzed and normalized using energy dispersive Xray (EDX) attached unit, which also helped in phase identifications and microstructure observations. 2.3. Batch preparation and specimen process In order to investigate the feasibility of manufacturing the acid resisting brick (ARB), five suggested batches, namely S1, S2, S3, S4 and S5, were designed for the current study. These mixtures composed of 50% of KFQR and 10– 40% of GBFQR and GBFS, as given in Table 1. These starting materials were crushed, separately ground in a laboratory ball mill, and screened to pass 90 lm sieve. Every batch was first homogenized in a blender, then molded in 5 cm-side length cube by pressing under 225 kg/cm2. Mixing the batches components was implemented on a dry basis with spraying 5% water before molding. After forming, the green briquettes were dried out in an electrical dryer at 80 C for 24 h, and then fired at different firing temperatures (Tf) of 1100 C, 1125 C, 1150 C and 1175 C at 5 C/m firing rate and 4 h soaking time in a muffle furnace under oxidizing condition. Finally, the specimens were cooled inside the furnace until room temperature. In order to assess the physical, chemical and mechanical characteristics of the fired specimens, each batch composition is examined against the requirements of the Egyptian standard specification [15]. In addition, the volumetric changes, firing weight loss and bulk density were calculated. Accordingly, the successful and promising batches were identified and suggested for making acid resisting brick. 3. Results and discussion 3.1. Characteristics of raw material The chemical composition of the materials used is depicted in Table 2. It is clear that both the KFQR and GBFQR are composed essentially of SiO2 and CaO. The GBFS is composed mainly of SiO2, CaO, Al2O3 and BaO in descending order of abundance rather that other oxides content. From the chemical composition of the original
M.S. El-Mahllawy / Construction and Building Materials 22 (2008) 1887–1896 Table 2 Chemical composition of the materials used Oxide content (%)
Kaolin fine quarry residue (KFQR)
Granite–basalt fine quarry residue (GBFQR)
Granulated-blast furnace slag (GBFS)
SiO2 Al2O3 Fe2O3 CaO MgO MnO Na2O K2O SO3 BaO TiO2 L.O.I
53.92 26.76 1.37 1.75 0.32 – 0.16 0.04 1.49 – 2.09 11.95
80.01 8.88 2.29 3.78 1.58 – 0.29 0.32 0.05 – – 2.80
41.46 11.36 0.85 29.83 1.35 4.95 0.61 0.33 2.13 6.35 0.48 0.30
materials, it is expected that the formed ARB may give constituents within the equilibrium diagram of ternary phases SiO2–Al2O3–CaO. The X-ray diffraction pattern of the original materials (Fig. 1) manifests that the KFQR constitutes quartz and kaolinite minerals. The GBFQR consists predominately of quartz and the subsidiary of anorthite mineral. The GBFS is an amorphous material (glassy state) and this is due to the rapid water quenching process of the molten slag. 3.2. Mineralogy of the fired specimens Table 3 clarifies the withstood and melted specimens of different batches during firing progress. So, only ARB that may be used for industrial application will possess X-ray pattern. Figs. 2–6 demonstrate the XRD patterns of the withstood ARB of diverse batches in a function with firing temperature. From the represented patterns, it is found that
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Table 3 p Withstood ( ) and partially melted (X) specimens as a function of firing temperature Firing temperature (C)
1100 1125 1150 1175
Batch no. S1 p p
S2 p p
X X
X X
S3 p p p
S4 p p p
X
X
S5 p p p p
the crystalline phases are anorthite [(Ca,Na) (Si,Al)4O8], augite [Ca(Fe,Mg)Si2O6], diopside [CaMg(SiO3)2], wollastonite [CaSiO3] and quartz [SiO2]. As reported by Yilmaz et al. [16], the augite and diopside phases (pyroxene group) are usually referred to as one phase named diopsidic-augite. It is evident from the XRD patterns that the higher the crystallization temperature as well as the content of the GBFQR, the higher the intensity of the anorthite phase would be. On the contrary, quartz mineral decreases with the increase of firing temperature and increases with the increase of GBFQR. Also, the anorthite phase of S2 specimens fired at 1125 C has the highest sharp intensity, i.e. the highest crystallinity. The formation of anorthite may be due to the interaction between the silica of GBFQR and aluminum of Kaolin to form calcium aluminum silicate phase. The decrease of quartz can be attributed to the fat that the quartz mineral dissolutes in the liquid phase formed from the impurities (Na2O, K2O, Fe2O3 and CaO) present in the mixture composition [17] as well as its sharing in anorthite formation which increases with the increase of firing temperatures. It is observed that the wollastonite phase decreases, with appreciable percentage, in the fired specimens of mixtures S3–S5. This decrease is simultaneously associated with the decreasing of GBFS, the source of CaO. On the other hand, the cristobalite phase is not detected in
Fig. 1. XRD patterns of the fine quarry residues (KFQR and GBFQR) and industrial waste (GBFS) of starting materials.
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Fig. 2. XRD patterns of the fired specimens of S1 mixture in a function of firing temperature.
Fig. 3. XRD patterns of the fired specimens of S2 mixture in a function of firing temperature.
all the examined specimens and this is because they need more (>1175 C) than the suggested maximum temperature, as proposed by dos Santos et al. [18]. The presence of anorthite in the XRD patterns of the fired specimens demonstrates that the firing process reaches the equilibrium state giving evidences that the reaction is complete, as suggested by Gonzalez-Garcia et al. [19]. As regards the mineralogical analysis, there are no new phases formed after 1100 C as a result of the function of both mixture composition and firing temperature and the differences are only in mineral intensity. Needless to say, the slag is a product obtained from a high temperature process, so it is inert to sintering process if the temperature is not high enough.
3.3. Scanning electron microscope (SEM) analysis Some fired specimens were chosen for this analysis and their images are represented in Figs. 7 and 8. It is observed from the images of fired specimens at 1125 C of mixtures S1–S4 that are composed primarily of crystalline microstructure of anorthite (marked as A) and traces of augite (marked as U) and both as a ground mass in a crystalline form. Also, the diopside phase (marked as D) appears as a prismatic euhedral crystalline form and it is detected in the mixtures of S2 and S3. Moreover, some traces of barium and iron oxides are noticed in the specimen of S2 as free unreacted elements. It is worthy to mention that, may be based on the crystallinity of anorthite and presence
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Fig. 4. XRD patterns of the fired specimens of S3 mixture in a function a function of firing temperature.
Fig. 5. XRD patterns of the fired specimens of S4 mixture in a function of firing temperature.
of diopside and augite phases, in appreciable amount, the positive properties of the fired specimens of batches S2– S4 can be accredited. This opinion is also proved by Toya et al. [20]. Also, as appeared from the mentioned SEM microphotographs and XRD patterns, the high crystallinity of anorthite is always connected with specimens that have the highest compressive strength values, especially this is shown in the specimens of batch S2. This observation is supported by Taskiran et al. [21]. They reported that the high compressive strength is associated with the high crystallinity of anorthite phase to glassy ratio. On the other hand, as revealed from Fig. 8 that the examined fired specimens, batches S3, S4 and S5 fired at
1150 C, 1150 C and 1175 C, respectively, are composed of very minute crystals of anorthite. This is due to the presence of inadequate content of GBFS to form a crystalline phase of anorthite. Also, a crystalline form of freeunreacted CaO, and some particles of fused silica in addition to some open holes are observed. Consequently, the worst characteristics that are shown with these fired specimens, from SEM point of view, may be due to the lack of diopside and augite content and the presence of minute crystals of anorthite phase. The minute crystallinity of anorthite can be attributed to the occurrence of unfavorable fully formed conditions such as the scarcity of CaO content and higher crystallization temperature than neces-
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Fig. 6. XRD patterns of the fired specimens of S5 mixture in a function of firing temperature.
Fig. 7. The SEM images of the sintered specimens at 1125 C of mixtures S1–S4.
sary. These are regarded as well crystalline phase formation. 3.4. Ceramic properties The withstood fired specimens with their ceramic properties according to ESS [15] are listed in Table 4. Also, the bulk density, volume changes and firing weight loss properties in a function of firing temperature with different batches are tabulated in Table 5. These physical, chemical and mechanical parameters are not only important to judge the quality of the product, but are also important to monitor the sintered body properties.
As shown in Table 4, all the fired specimens after 1125 C firmly suffer from a deleterious action in their properties. This deleterious action increases with increasing both the firing temperature and the GBFQR content. As reported by dos Santos [18], the impure SiO2 polymorphism is prone to form b-quartz at 573 C, b-cristobalite at more than 1000 C or b-tridymite at more than 1470 C, and these phases are associated with a volumetric expansion change (DV) of 1%, 14% and 16%, respectively. In laboratory experiments, cristobalite commonly forms before tridymite in the stability range of tridymite. Also, upon heating at a temperature higher than the respective cristobalite a M b transitions microcracking inside the
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Fig. 8. The SEM images of the sintered specimens at 1150 C, 1175 C and 1150 C of mixtures S4, S5 and S3, respectively.
grains is induced by the negative effect of thermal expansion. Later, these microcracks, during cooling, will be healed. Therefore, it is not possible to detect these microcracks for the specimens after firing by SEM. The polymorphism phenomena will affect all important ceramic properties. This interpretation can be supported with occurrence of voids and holes inside some fired specimens and that can be easily detected by the visual inspection of some broken parts with a normal hummer. These voids and holes increase in the same trend of the increase of firing temperature, after 1125 C, as well as GBFQR content. The maximum percentage of these holes is
Table 4 The average properties of withstanding ARB corresponding to ESS 41-1986 Batch no. S1
Firing temperature (C)
1100 1125 S2 1100 1125 S3 1100 1125 1150 S4 1100 1125 1150 S5 1100 1125 1150 1175 ESS 41:1986
Water absorption (%)
Acid weight loss (%)
Compressive strength (kg/cm2)
0.95 0.50 1.32 0.02 1.93 0.52 3.89 4.28 0.91 9.15 6.74 5.78 7.24 10.23 <6.0
0.25 0.15 0.35 0.06 0.38 0.18 0.45 0.42 0.25 0.49 0.50 0.48 0.52 0.53 <3.5
517 660 567 710 520 675 423 415 655 375 360 473 393 310 >300
observed clearly in the specimens of mixture S5 (40% GBFQR), especially at 1175 C. 3.4.1. Water absorption Water absorption property is an important factor affecting the durability of bricks. The less water that infiltrates the brick, the more durable and resistant it is to environmental damage. So, the water absorption is measured to investigate the extent of densification in the fired body and also used as an expression to open pores. Water absorption as a function of firing temperatures is shown in Fig. 9a. It is clearly shown from this figure that
Table 5 The volume changes, bulk density and firing weight loss properties as a function of firing temperature for variable batches specimens Batch no.
Firing temperature (C)
Volume changes (%)
Bulk density (gm/cm3)
Firing weight loss (%)
S1
1100 1125 1100 1125 1100 1125 1150 1100 1125 1150 1100 1125 1150 1175
2.62 3.59 2.02 4.53 5.23 3.03 6.71 3.84 2.11 10.01 4.45 3.66 13.30 16.72
6.43 4.99 6.77 5.38 6.81 6.55 4.96 6.71 6.35 5.78 6.68 6.25 5.35 4.25
5.85 6.40 7.14 7.96 7.35 7.51 8.23 7.55 7.91 9.25 7.78 7.95 9.97 10.12
S2 S3
S4
S5
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Fig. 9. The variation of different physico-mechanical properties of the batches specimen in a function of firing temperature.
after 1125 C the fired specimens suffer from the silica polymorphous transformation, negative expansion of silica, and this increases water absorption property after 1125 C (transition point). Also, increasing the content of GBFQR, the main source of silica, leads to the increase of water absorption. The water absorption of the fired specimens of S1-S3 at all firing temperatures achieves the limits of ESS [15]. The fired specimens of the S4 mixture fired up to 1125 C verify the stated Egyptian specification limits. The fired specimens of the S4 mixture, fired at 1150 C, and all the fired specimens of the S5 mixture are out of the pre-mentioned specification.
ported with the increase in water absorption values at the same trend. Also the narrow range of the acid weight loss increase (0.06–0.53%) is probably because there is no new phases formed that encourage acid weight loss i.e. the same mineralogical phases, which are formed within all firing temperatures at different mixture compositions. Also, water absorption is a good parameter that influences strength, durability, shrinkage and creep properties of materials [22]. The highest resistance of specimens toward acid attack (0.06%) always couples with the lowest water absorption value (0.02%), as both properties are a result of vitrification process of the specimens of the different batches.
3.4.2. Acid weight loss The results of the weight loss due to acid attack of the specimens of the different batches at different firing temperatures are illustrated in Fig. 9b. As percepted from this figure and Fig. 9a, the acid weight loss has a relationship not only with firing temperature but also with water absorption property. Acid weight loss values slightly increase with the increase of firing temperature after 1125 C. This is presumably due to the increase of open pores which is sup-
3.4.3. Compressive strength The compression test is the most important test that can be used to assure the engineering quality in the application of building materials. The compressive strength of different fired specimens is represented in Fig. 9c. The result of this figure indicates that the compressive strength values increase with the increase of firing temperature until 1125 C, and then decrease. At 1125 C, the polymorphism phenomenon of SiO2 plays its negative role in forming a
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spongy structure which weakens the body strength [23]. The spongy structure can be seen by the nacked eye for the broken parts of the specimens. On the other hand, the increase of GBFS from batches S1–S5 is reflected on the increase in compressive strength and vice versa in the case of the increase in GBFQR content, due to the negative effect of impure SiO2 polymorphism. In spite of the fact that the compressive strength of the fired specimens of all mixtures meets the limits of ESS [15]. It is worthy to say that the contradiction between the obtained ceramic results with Shih et al. [8] can be attributed to the fact that they used a different mixture design and a different slag type. That slag is characterized by its high content of Fe2O3, CaO and LOI. This is reflected on the physico-mechanical properties of fired specimens and intensity of the formed phases. They reported that both of the water absorption values of fired specimens increase and compressive strength values decrease with increase in slag content which is contradicted with the results of the present study. 3.4.4. Firing volume changes The volume changes are determined using the relation (Vd–Vf)/(Vd), where Vd is the specimen volume before firing and Vf is the specimen volume after firing at a temperature Tf. The firing volume changes of the fired specimens of assorted mixtures in a function of firing temperatures are depicted in Fig. 9d. It is noticeable that the fired specimens of all mixtures shrinked until 1125 C. After 1125 C, the specimens expanded with a corresponding increase of water absorption and decrease of compressive strength. This expansion perhaps is attributed to the negative role of silica as mentioned before. This expansion effect is supported with the increase of GBFQR content (the primary source of silica) from batch S1 until S5. Also, the expansion increases with the increase of firing temperature. This may be due to the increase of melting materials causing internal stress and cracks. Also, the expansion of the fired specimens decreases and the shrinkage increases with the increase of the GBFS content. 3.4.5. Bulk density The bulk density of the fired specimens is determined by dividing the volume over mass of fired briquettes. The relationship between the bulk density of the fired specimens and firing temperature can be shown in Fig. 9e. The bulk density within the range between 1100 C and 1125 C has gently decreasing values and then the decreasing increases briskly up to 1175 C. The primary reason for this decreasing trend is due to the quartz polymorphism effect. Also, the decreasing of bulk density may be construed to the bloating of specimens (i.e. pore volume expansion), which arises from the high pressure of gases such as carbon monoxide and carbon dioxide entrapped in closed pores [21].
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3.4.6. Firing weight loss The firing weight loss of the acid resisting brick (ARB) is calculated by using the relationship (Wd–Wf)/(Wd), where Wd is the specimen weight before firing and Wf is the specimen weight after firing at a temperature Tf. The firing weight loss of the fired ARB of different batches versus firing temperature is demonstrated in Fig. 9f. The results indicate that there is a little increase in the weight loss up to 1125 C. After 1125 C, the weight loss increases with firing temperature with a moderate high rate up to 1175 C. This can be attributed to the increase of pore volume expansion as a function of increasing temperature; this gives the fired specimens a spongy structure which facilitates gas escaping. The maximum value of firing weight loss (10.12%) is accompanied with the highest volume expansion (16.72%). Also, the rising of the weight loss may be caused by the constructive role of quartz polymorphism. This role is maximized with the entrapment of solid samples for gases, such as H2O, CO2, and CO, by the pore system and these gases are released at higher temperatures as the pore system varies [24]. From the aforementioned parameters, it is evident that the real maximum densification of the reported specimens is achieved at 1100 C up to 1125 C. Within this range, the highest shrinkage, compressive strength and density, accompanied by the lowest water absorption and firing weight loss, are obtained. 4. Visual inspection The visual inspection of the successful fired specimens indicates that the ARB have a dark brown color, have smooth surfaces, sharp edges and are free from any type of cracks either in the external faces or internal parts. 5. Conclusions The characteristics of acid resisting brick made from kaolin fine quarry residue combined with granulated blast furnace slag and granite–basalt fine quarry residue were investigated in this research. From the obtained findings, the following conclusions are derived: (1) The fired formulated batches from S1 to S4 fired until 1125 C can be utilized for making acid resistance brick. (2) The most distinctive specimen achieving the limits of ESS (41-1986) was fabricated from batch S2 (50% KFQR, 20% GBFQR and 30% GBFS) and fired at 1125 C. (3) The polymorphous transformation of quartz phase during firing is the main cause for the negative abrupt changes as well as the deleterious action in ceramic properties, especially after 1125 C. (4) There are no new crystalline phases formed during the sintering process after 1100 C.
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(5) Addition of more than 25%wt of GBFQR is not recommended because it induced intolerable changes of the physical, chemical and mechanical properties. (6) Based on this work an environmentally inert brick, with good commercial characteristics, was made using recycling technology in a safe disposal manner for the studied pollutants. Overall, the most superior ceramic properties were for specimen that was prepared from the mixture S2 (50% KFQR, 20% GBFQR and 30% GBFS) and fired at 1125 C. For this reason, the S2 batch is selected to be the most promising mixture for acid resistant brick industry. Acknowledgements This research was conducted while the author was a Visiting Research Fellow at the University of Wollongong, Australia. The author would like to thank his coordinator Prof. Muhammad N. Hadi, Faculty of Engineering, the University of Wollongong, for his generous hospitality and help. My gratitude is due to Dr. David Wexler (Lecturer in Material Engineering, the University of Wollongong) for providing the facilities needed for the experimental work. Also, the author would indeed like to express his appreciation to Dr. Mohamed A. Shahin (Lecturer in Geotechnical and Construction Engineering, Curtin University of Technology) for his friendship and fruitful discussion. The financial support from the Egyptian Educational Missions is gratefully acknowledged. References [1] Galkin MP, Larionov VS, Stepanov AV, Nebol’sin VA, Milovanov IF, Nikitin GS. Utilization of the steelmaking slags. J Metallurg 1998;9:22–36. [2] Dominguez EA, Ullmann R. Ecological bricks made with clays and steel dust pollutants. Appl Clay Sci 1996;11:237–49. [3] Demirbog˘a R, Gu¨l R. Production of high strength concrete by use of industrial by-products. J Build Environ 2006;41(8):1124–7. [4] Holloway M, Sykes JM. Studies of the corrosion of mild steel in alkali-activated slag cement mortars with sodium chloride admixtures by a galvanostatic pulse method. J Corros Sci 2005;47(12):3097–110. [5] Hester D, McNally C, Richardson MA. Study of the influence of slag alkali level on the alkali–silica reactivity of slag concrete. J Constr Build Mater 2005;19(9):661–5.
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