A study of pressure influences of phosphogypsum based bricks

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A study of pressure influences of phosphogypsum based bricks

  1. 1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME 143 A STUDY OF PRESSURE INFLUENCES OF PHOSPHOGYPSUM- BASED BRICKS Lamia Bouchhima(1), Mohamed Jamel Rouis (2), Mohamed Choura (3) Unit of research environmental geotechnique and civil materials, Institute of the engineers of Sfax, Tunisia ABSTRACT Housing is a great problem in today’s world. The most basic building material for construction of houses is the usual burnt clay brick. A significant quantity of fuel is utilized in making these bricks. Also, continuous removal of topsoil, in producing conventional bricks, creates environmental problems. A feasibility study was undertaken on the production of phosphogypsum-wade sand based bricks to build houses economically by utilizing industrial wastes. All full bricks were made on a bench model, semiautomatic press, to produce bricks under a static compaction of 15 and 20 MPa. The compressive strength, flexural strength water absorption and density of these bricks are investigated. It is observed that these bricks have sufficient strength for their use in housing development. Tests were also conducted to study the pressure influences of bricks. The results suggest that compressive and flexural strength increase with pressure. Tests were also conducted to study behavior immersion of phosphogypsum- wade sand based bricks. The results suggest that behavior immersion of bricks improves with increasing pressure. Keywords: phosphogypsum-wade sand based bricks; strength; pressure. 1. INTRODUCTION Phosphogypsum (calcium sulfate) is a naturally occurring part of the process of creating phosphoric acid (H3PO4), an essential component of many modern fertilizers. For every tonne of phosphoric acid made, from the reaction of phosphate rock with acid, commonly sulfuric acid, about 3 t of phosphogypsum are created. There are three options for managing phosphogypsum: (i) disposal or dumping, (ii) stacking, (iii) use-in, for example, agriculture, construction, or landfill.The need to reduce solid waste volume has caused scientists to invent new construction materials produced using waste materials. INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (IJCIET) ISSN 0976 – 6308 (Print) ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), pp. 143-154 © IAEME: www.iaeme.com/ijciet.asp Journal Impact Factor (2013): 5.3277 (Calculated by GISI) www.jifactor.com IJCIET © IAEME
  2. 2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME 144 In Tunisia, for several years, a set of phosphoric acid production factories have produced PG in large great quantities (approximately 10 million tons per year [1]. Currently, the PG is stored into piles in the vicinity of the factory, by dry or wet process. The storage of PG causes the pollution of the water table and the soils by acid and heavy metals infiltrations. Its valorization leads to environmental protection and to minimization of the storage costs. Several researchers had studied the use of PG in various fields. The PG was treated to be used in the plaster manufacture. It has been found that the PG is suitable for making good quality plaster showing similar proprieties to natural gypsum plaster [2-4]. This field is advantageous for the countries which do not have natural quarries such as Japan and India. The PG has been sought also to be used in agriculture [5]. It is as effective as the crushed natural gypsum. However, the quantities used are limited and moreover the health standards became increasingly restrictive. But the most interesting use of the PG is for the cement manufacturing: either by natural gypsum substitution (about 5%), which will play the role of a set retarder [6-7], or to reduce the clinkerization temperature [8]. The PG was also used in soil stabilization [9]. Finally phosphogypsum PG has been studied to be used in hollow blocks [10] and light brick [11]. In Tunisia, the PG was studied to be used in similar fields. The most successful application so far is in the manufacture of cement; by substitution of the gypsum. The obtained product is known under the name of cement ultimo. It showed good performances but the used quantity is low [12-13]. Moussa et al [14] had studied the possibility of the use of the PG in the embankments. The PG is studied in order to use it like a fill. This study showed a behavior to the compaction not similar to that of a soil. Furthermore, the fill showed also a continuous settlement because of the PG solubility. Moreover, Kuryatnyk and Angulski- Ambroise- Pera [15] have employed the Gabes and Skhira PG to be used as a hydraulic binder. But formation of ettringite led to cracking and strength loss. Finally, Sfar [16] has explored the PG for a road use. The study proposed the following formulation: 46.5% of PG, 46.5% of sand and 7% of cement. But this study was conducted in the Tunisian south region, where the rainfall is low. In this paper compressive strength, flexural strength water absorption, density and behavior immersion of phosphogypsum- wade sand-lime-cement bricks are investigated. The influences of pressure on these characteristics are studied. 2. EXPERIMENTAL PROGRAM. 2.1. Chemical composition The chemical analyses, considered most relevant to the prospect use in commercial brick making, were undertaken on the PG. The results of these analyses are presented in Table 1. The PG is primarily (about 77%) made up of calcium sulfate (CaSO4). The remaining components are present at low percentage. It should be noted that the pH of PG samples has been found to be around 2.9, indicating a high acidity of the PG. Table1. Chemical composition of phosphogypsum Elements (%) CaO SO3 P2O5 F SiO2 Fe2O3 Al2O3 MgO Ignition loss at 1000°C 32.8 44.4 1.69 0.55 1.37 0.03 0.11 0.007 22.3
  3. 3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME 145 2.2. Preparation of phosphogypsum, wade sand, lime-cement bricks The mix proportions of phosphogypsum, wade sand (WS), lime and cement (cement HRS 42.5) for bricks are given in table 2. The mix proportions are given in terms of dry weights of the ingredients. The water content of Phosphogypsum-wade sand-lime mixtures was fixed to 4 %. Bricks produced with more than 4 % showed cracks after fabrication due to excessive water. Table 2. Mix proportions of WS-NHL-C-PG full bricks Mix désignation Constituant materials (Weight %) Phosphogypsum Sand (WS) Cement Lime M-1 60 32 5 3 M-2 60 29.5 7.5 3 M-3 60 27 10 3 M-4 70 22 5 3 M-5 70 19.5 7.5 3 M-6 70 17 10 3 M-7 80 12 5 3 M-8 80 9.5 7.5 3 M-9 80 7 10 3 The dry phosphogypsum was sieved through 1 mm sieve. The weighed quantity of phosphogypsum, wade sand, lime and cement were first thoroughly mixed in dry state for a period of 10 minutes to uniform blending. The required water was then gradually added and the mixing continued for another 5 min. All solid bricks were made on a bench model, semiautomatic press having a capacity of 25 tons, to produce bricks of 51×95×203 mm in size under a static compaction of 15 and 20MPa. 2.3. Testing of bricks All bricks were dried to the free air for a period of 28, 56 and 90 days. Compressive strength, density, water absorption, and leaching tests of bricks from different mixes of phosphogypsum, wade sand, lime and cement with available mixing water content were determined. Compressive strength of the units was determined according ASTM C67 [17]. Test bricks consist of a half brick with full height and width. Flexural strength tests on the bricks were performed according to ASTM C 67 [17]. Test specimens were taken as full-size brick units. Rate of absorption is an important property of brick because it affects mortar and grout bond. If the rate of absorption is too high, brick will absorb moisture from the mortar or grout at a rapid rate, thus impairing the strength and extend of bend. Water absorption was determined according to ASTM C67 [17]. The test specimens were consisted of half bricks. Five specimens were tested. This test was determined on bricks tested after 28 days of casting. In order to determine the density of each brick, dry bricks were weighed accurately and their volumes were measured.
  4. 4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME 146 To simulate the action of the weather, the bricks are soaked in water for two days [18] after 90 days of treatment. The effect of immersion on compressive strength and flexural strength has been studied. The leaching tests had been performed according to the French norm NF EN 12457-3 [19] at an ambient temperature (20 ± 5°C). The specimens (three different samples for each mix-design) were crushed and an amount of 0.175 kg was taken to be analyzed. The distilled water was added to obtain a liquid/solid ratio of 10 l/kg. The leaching test was determined on bricks tested after 28 days of casting. 3. TEST RESULTS AND DISCUSSION 3.1. Dry density The densities of WS-NHL-C-PG full bricks are shown in table 3. These densities range from 1434.5 to 1760.5 kg/m3 . Therefore the WS-NHL-C-PG full bricks have high density. We note that the densities of bricks increases with the phosphogypsum and cement additions. Also densities of all full bricks increase with increasing pressure. Table 3. Dry densities (kg/m3 ) of WS-NHL-C-PG full bricks versus pressure Mix design Dry densities (kg/m3 ) 15MPa 20MPa 28 days 56 days 90 days 28 days 56 days 90 days M1 1434.5 1495 1526.5 1523 1575 1590 M2 1499 1545 1560.5 1562.5 1600 1618.5 M3 1559.5 1601 1620 1589.5 1635.5 1650 M4 1520.5 1538 1544 1550.5 1588 1600 M5 1560.5 1585 1593 1595 1620.5 1630 M6 1592 1620.5 1630 1620 1646 1660.5 M7 1587 1650 1691.5 1602 1675.5 1706 M8 1614.5 1690 1714.5 1625.5 1690.5 1724 M9 1667 1750 1783 1670 1760.5 1760.5 3.2. The 24-h cold water absorption of studied bricks The water absorption is a principal factor for the durability of the product and its behavior to natural environment. Table 4 presents the results of the water absorption for the selected percentages of the bricks. It was observed that the water absorption of bricks decreased with the increase of pressure. Also, it was observed that the values obtained were favorable when compared with those of clay bricks (0 to 30%) [20]. the addition of pressure produces a decrease in the internal pore size. Thus, the brick becomes less porous causing an increase in the water absorption.
  5. 5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME 147 Table 4. Water absorption 24 h cold water of WS-NHL-C-PG full bricks Mix designation Water absorption after 24 hr cold water (%) (15MPa) Water absorption after 24 hr cold water (%) (20MPa) M1 28.9 26.97 M2 28.4 26.09 M3 27.4 24.29 M4 28 25.56 M5 27.3 24.05 M6 26 23.06 M7 27.5 24.5 M8 26 23.04 M9 25 22.33 3.3. Compressive strength of studied bricks The results, obtained as an average of measurements performed on three specimens, are shown in table 5. The BS6073-Part 1 [21] (require minimum compressive strengths of 7.0 MPa and 11.7 MPa after a 28-day curing period for load-bearing concrete masonry units. All mixtures described in this study satisfied the standard for compressive strength. For all the studied cases, the strength of the 90 days cured full bricks was higher than 10.3 MPa, which is the minimum strength indicated by the standards [22]. Cement and lime as a source of reactive silica and alumina are given to silicate and aluminate hydrates, which are responsible for the development of strength. These Figures show also increase in the strength with the pressure. The maximum of compressive strength is reached with 20 MPa. This result confirms the water absorption test outcome, where it has been indicated that the brick becomes less porous causing an increase in the mechanical strength. Table 5. Compressive strength (MPa) of WS-NHL-C-PG full bricks versus pressure Mix design Compressive strength (MPa) 15MPa 20MPa 28 days 56 days 90 days 28 days 56 days 90 days M1 9.04 10.526 10.78 11.24 12.028 12.316 M2 10.182 11.364 11.647 12 13.473 13.747 M3 11.278 12.1 12.366 13 13.955 14.247 M4 10 10.94 11.2 11.718 12.41 12.7 M5 10.406 11.547 11.811 12.45 13.35 13.805 M6 11.46 12.4 12.634 13.63 14.289 14.523 M7 10.441 11.25 11.42 12.179 12.9 13.2 M8 11.461 12 12.2 13.4 14.331 14.63 M9 11.964 12.69 12.874 14.21 14.765 15.01 3.4. Flexural strength of studied bricks The results, obtained as an average of measurements performed on three specimens, are shown in table 6. The code ASTM does not specify a requirement for flexural strength.
  6. 6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME 148 However the values obtained were favorable when compared with the minimum flexural strength required by BS6073-Part 1 (0.65 MPa) after a 28-day curing period wich was surpassed by all the samples. These Figures show also increase in the flexural strength with the pressure. The maximum of compressive strength is reached with 20 MPa. Table 6. Flexural strength (MPa) of WS-NHL-C-PG full bricks versus pressure Mix design Flexural strength (MPa) 15MPa 20MPa 28 days 56 days 90 days 28 days 56 days 90 days M1 5.59 5.915 6.015 7.65 7.9 8 M2 5.65 6.053 6.203 7.79 8.062 8.198 M3 5.8 6.118 6.319 7.93 8.24 8.342 M4 5.68 6 6.2 7.73 8.12 8.267 M5 5.79 6.19 6.323 7.85 8.27 8.36 M6 5.9 6.3 6.439 7.97 8.385 8.532 M7 5.79 6.115 6.316 7.82 8.175 8.386 M8 5.85 6.25 6.464 8.08 8.503 8.723 M9 5.98 6.356 6.57 8.18 8.606 8.846 3.5. Behavior immersion of bricks 3.5.1. Compressive strength of full bricks after 2 days immersion The results, obtained as an average of measurements performed on three specimens, are shown in table 7. The loss of compressive strength after 2 days of immersion in water is given in figs.1-3. It is observed that loss in compressive strength decrease with phosphogypsum and cement content. So bricks with more phosphogypsum and cement have better compressive strength after 2 days immersion. Also, we note a decreasing of loss in compressive strength with increasing pressure. So the behavior immersion of bricks becomes better with increasing pressure. Table 7 Compressive strength of WS-NHL-C-PG full bricks after 2 days of immersion in water Mix design Compressive strength after 2 days of immersion in water (MPa) 15MPa 20MPa M1 8,55 10,38 M2 9,58 11,98 M3 10,38 12,67 M4 9,02 10,79 M5 9,81 12,1 M6 10,68 13 M7 9,33 11,29 M8 10,22 12,84 M9 10,95 13,49
  7. 7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May Fig.1 Loss in compressive strength of WS Fig.2 Loss in compressive strength of WS 0 5 10 15 20 25 5 lossincompressivestrength(%) 0 5 10 15 20 5 lossincompressivestrength(%) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 Online) Volume 4, Issue 3, May - June (2013), © IAEME 149 Loss in compressive strength of WS-NHL-C-PG full bricks (phosphogypsum=60%) Loss in compressive strength of WS-NHL-C-PG full bricks (phosphogypsum=70%) 7.5 10 cement (%) 15MPa 20MPa 7.5 10 cement (%) 15MPa 20MPa International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 June (2013), © IAEME PG full bricks (phosphogypsum=60%) (phosphogypsum=70%) 15MPa 20MPa 15MPa 20MPa
  8. 8. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May Fig.3 Loss in compressive strength of WS 3.5.2. Flexural strength of full bricks after 2 days immersion The results, obtained as an average of measurements performed on three specimens, are shown in table 8. The loss of compressive strength after 2 days of immersion in water is given in figs.4-6. It is observed that loss in and cement content. So bricks with more phosphogypsum and cement have bette strength after 2 days immersion. Also, we note a decreasing of loss in decreasing is rather significant than decreasing in loss of compressive strength with pressure. Table8. Flexural strength of WS Mix design M1 M2 M3 M4 M5 M6 M7 M8 M9 0 5 10 15 20 5 lossincompressivestrength(%) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 Online) Volume 4, Issue 3, May - June (2013), © IAEME 150 Loss in compressive strength of WS-NHL-C-PG full bricks (phosphogypsum=80%) . Flexural strength of full bricks after 2 days immersion The results, obtained as an average of measurements performed on three specimens, hown in table 8. The loss of compressive strength after 2 days of immersion in water is 6. It is observed that loss in flexural strength decrease with phosphogypsum and cement content. So bricks with more phosphogypsum and cement have bette Also, we note a decreasing of loss in flexural strength with increasing pressure. rather significant than decreasing in loss of compressive strength with pressure. WS-NHL-C-PG full bricks after 2 days of immersion in water Flexural strength after 2 days of immersion in water (MPa) 15MPa 20MPa 3,75 6,68 4 6,96 4,46 7,49 4 7,05 4,28 7,23 4,7 7,71 4,22 7,32 4,5 7,84 4,92 8,18 7.5 10 cement (%) 15MPa 20MPa International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 June (2013), © IAEME PG full bricks (phosphogypsum=80%) The results, obtained as an average of measurements performed on three specimens, hown in table 8. The loss of compressive strength after 2 days of immersion in water is strength decrease with phosphogypsum and cement content. So bricks with more phosphogypsum and cement have better flexural strength with increasing pressure. The rather significant than decreasing in loss of compressive strength with pressure. PG full bricks after 2 days of immersion in water Flexural strength after 2 days of immersion in 15MPa 20MPa
  9. 9. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May Fig.4 Loss in flexural strength of WS Fig.5 Loss in flexural strength of WS 0 5 10 15 20 25 30 35 40 5 lossinflexuralstrength(%) 0 5 10 15 20 25 30 35 40 5 lossinflexuralstrength(%) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 Online) Volume 4, Issue 3, May - June (2013), © IAEME 151 Loss in flexural strength of WS-NHL-C-PG full bricks (phosphogypsum=60%) Loss in flexural strength of WS-NHL-C-PG full bricks (phosphogypsum=70%) 7.5 10 cement (%) 15MPa 20MPa 7.5 10 cement (%) 15MPa 20MPa International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 June (2013), © IAEME PG full bricks (phosphogypsum=60%) PG full bricks (phosphogypsum=70%) 15MPa 20MPa 15MPa 20MPa
  10. 10. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May Fig.6 Loss in flexural strength of WS 3.5. Leaching tests The average values of the leachi concentrations of the selected metal species, i.e., Cd, Cu, Zn, Ni, Pb, and Cr, for design, were well below the regulatory limits. Thus, this result brick specimens can be considered as non hazardous materials. Table 9. Leaching test results, in mg/kg for L/S = 10 l/kg (15MPa) Eléments M1 M2 M3 M4 Cr 0.09 0.087 0.86 0.08 Ni 0.088 0.083 0.073 0.079 Zn 0.068 0.066 0.064 0.064 Pb 0.12 0.098 0.093 0.1 Cu 0.15 0.1 0.098 0.12 Cd 0.08 0.077 0.072 0.07 0 5 10 15 20 25 30 35 5 lossinflexuralstrength(%) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 Online) Volume 4, Issue 3, May - June (2013), © IAEME 152 Loss in flexural strength of WS-NHL-C-PG full bricks (phosphogypsum=80%) The average values of the leaching test are presented in Table 9 and 10 concentrations of the selected metal species, i.e., Cd, Cu, Zn, Ni, Pb, and Cr, for the regulatory limits. Thus, this result indicates that PG amended brick specimens can be considered as non hazardous materials. Leaching test results, in mg/kg for L/S = 10 l/kg (15MPa) M4 M5 M6 M7 M8 M9 Limit values acceptable as inert 0.08 0.078 0.08 0.068 0.069 0.063 4 0.079 0.074 0.066 0.074 0.07 0.068 0.4 0.064 0.062 0.06 0.06 0.058 0.06 4 0.1 0.095 0.09 0.095 0.093 0.09 0.5 0.12 0.098 0.096 0.099 0.096 0.094 2 0.07 0.05 0.045 0.055 0.041 0.04 0.04 7.5 10 cement (%) 15MPa 20MPa International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 June (2013), © IAEME PG full bricks (phosphogypsum=80%) 9 and 10. The concentrations of the selected metal species, i.e., Cd, Cu, Zn, Ni, Pb, and Cr, for all mix- indicates that PG amended Leaching test results, in mg/kg for L/S = 10 l/kg (15MPa) Limit values acceptable as inert Limit values acceptable as non hazardous 50 10 50 10 50 1 15MPa 20MPa
  11. 11. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME 153 Table 10. Leaching test results, in mg/kg for L/S = 10 l/kg (20MPa) Eléments M1 M2 M3 M4 M5 M6 M7 M8 M9 Limit values acceptable as inert Limit values acceptable as non hazardous Cr 0.069 0.066 0.65 0.059 0.056 0.048 0.046 0.037 0.031 4 50 Ni 0.066 0.061 0.051 0.057 0.052 0.044 0.052 0.049 0.046 0.4 10 Zn 0.046 0.044 0.042 0.042 0.04 0.039 0.038 0.036 0.034 4 50 Pb 0.095 0.09 0.088 0.091 0.089 0.087 0.088 0.087 0.085 0.5 10 Cu 0.1 0.095 0.093 0.09 0.092 0.089 0.088 0.086 0.079 2 50 Cd 0.06 0.057 0.052 0.05 0.03 0.02 0.035 0.02 0.02 0.04 1 4. CONCLUSION Based on the experimental investigation reported in this paper, following conclusions are drawn: (1) The WS-NHL-C-PG bricks manufacturing a static compaction of 15 and 20 MPa have sufficient strength and have potential as a replacement for load-bearing concrete masonry units and conventional full clay bricks grade NW. (2) Phosphogypsum has more pronounced binding action than wade sand. (3) The increase of the pressure resulted in increase in the mechanical strengths of bricks. (4) The increase of the pressure resulted in decrease in water absorption of bricks. (5) The increase of the percentages of PG and cement resulted in increase in the compressive and flexural strength of full bricks after 2 days of immersion in water. (6) The increase of pressure resulted in increase in the compressive and flexural strength of full bricks after 2 days of immersion in water. REFERENCES [1] Sfar Felfoul H, Clastres P, Carles GA, Ben Ouezdou M. (2002) Amelioration des caracteristiques du phosphogypse en vue de son utilisation en technique routiere. Dechets Sci Tech; vol. 28, pp. 21–5 [in French]. [2] Singh M. (2002) Treating waste phosphogypsum for cement and plaster manufacture. Cem Concr Res; vol. 32; No. 7, pp. 1033–8. [3] Singh M. (2003) Effect of phosphatic and fluoride impurities of phosphogypsum on the properties of selenite plaster. Cem Concr Res; vol. 33; No. 9, pp. 1363–9. [4] Singh M. (2005) Role of phosphogypsum impurities on strength and microstructure of serenity plaster. Constr Build Mater; vol. 19; No. 6, pp. 480–6. [5] Mullins GL, Mitchell CC. (1990) Wheat forage response to tillage and sulfur applied as PG. In: Proceedings of the third international symposium on PG, Orlando, USA, vol. I. Publication FIPR no. 01-060-083; pp. 362–75.
  12. 12. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME 154 [6] Potgieter JH, Potgieter SS, McCrindle RI, Strydom CA. (2003) An investigation into the effect of various chemical and physical treatments of a South African phosphogypsum to render it suitable as a set retarder for cement. Cem Concr Res. 33, pp. 1223–7. [7] Altun IA, Sert Y. (2004) Utilization of weathered phosphogypsum as set retarder in Portland cement. Cem Concr Res; vol.34, pp. 677–80. [8] Kacimi L, Simon-Masseron A, Ghomari A, Derriche Z. (2006) Reduction of clinkerization temperature by using phosphogypsum. J Hazard Mater; vol. B137, pp. 129–37. [9] Degirmenci N, Okucu A, Turabi A. (2007) Application of phosphogypsum in soil stabilization. Build Environ; vol. 42, pp. 3393-8. [10] Sunil K. (2003) Fly ash-lime-phosphogypsum hollow blocks for walls and partitions. Building and Environment; vol. 38, pp.291-295. [11] Abalı YK, Yurdusev MA, Zeybek MS, Kumanlıog˘lu AA. (2007) Using PG and boron concentrator wastes in light brick production. Constr Build Mater ; vol. 21, pp. 52–6. [12] Karray MA, Mensi R. (2000) Etude de la Deformabilite des Poutrelles en Beton Arme a base du Ciment Ultimax. Ann Batiment Travaux Publics;2, pp. 5–14 [in french]. [13] Charfi FF, Bouaziz J, Belayouni H. (2000) Valorisation du phosphogypse de Tunisie en vue de son utilisation comme substituant au gypse naturel dans la fabrication du ciment. [14] Moussa D, Crispel JJ, Legrand CL, Thenoz B. (1984) Laboratory study of the structure and compactibility of Tunisian phosphogypsum (Sfax) for use in embankment construction. Resour Conserv; vol. 11; No. 2, pp. 95–116 [in French]. [15] Kuryatnyk T, Angulski da Luz C, Ambroise J, Pera J. (2008) Valorization of phosphogypsum as hydraulic binder. J Hazard Mater; vol. 160, No. 2–3, pp. 681–7. [16] Sfar Felfoul H. (2004) Etude du phosphogypse de Sfax (Tunisie) en vue d’une valorisation en technique routiere. PhD thesis, Department of Civil Engineering, National Engineering School of Tunis/INSA Toulouse. [17] Ahmadi BH. (1989) Use of high strength by product gypsum bricks in masonry construction. PhD dissertation, University of Miami, Coral Gables, Florida, USA. 245p. ASTM international: C62-08, Standard specification for building brick: Solid Masonry Units Made from Clay. [18] FEKI N., (1991) : Utilisation du phosphogypse en assises de chaussées. Projet de fin d’études de la filière longue, Génie Géologique, ENIS, 93 p. [19] AFNOR. Lixiviation (2002) – Essai de conformite pour Lixiviation des dechets fragmentes et des boues. NF EN 12457-3; [in French]. [20] Deboucha S, Hashim R, Aziz AA. (2011) Engineering properties of cemented peat bricks Scientific Research and Essays Vol. 6. No. 8, pp. 1732-1739. [21] BS 6073: Part 1: precast concrete masonry units, Part 1. Specification for precast concrete masonry units. British Standards Institution, 1981. [22] ASTM international: C62-08, Standard specification for building brick: Solid Masonry Units Made from Clay (2008) 4p. [23] Lamia Bouchhima, Mohamed Jamel Rouis and Mohamed Choura, “Behavior Immersion of Phosphogypsum- Crushing Sand Based Bricks”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 4, 2013, pp. 96 - 106, ISSN Print: 0976-6480, ISSN Online: 0976-6499.

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