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Durability studies on high strength high performance concrete 2 Durability studies on high strength high performance concrete 2 Document Transcript

  • INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 1, January-(IJCIET) TECHNOLOGY February (2013), © IAEMEISSN 0976 – 6308 (Print)ISSN 0976 – 6316(Online)Volume 4, Issue 1, January- February (2013), pp. 16-25 IJCIET© IAEME: www.iaeme.com/ijciet.aspJournal Impact Factor (2012): 3.1861 (Calculated by GISI)www.jifactor.com © IAEME DURABILITY STUDIES ON HIGH STRENGTH HIGH PERFORMANCE CONCRETE Vinod P.a, LaluMangalb, Jeenu G.c* a Professor in Civil Engineering, College of Engineering Trivandrum- 695 016,India. Phone no.: 91 471 2515617, E-mail:dr_pvinod@rediffmail.com b Professor in Civil Engineering, T.K.M. College of Engineering, Kollam- 691 005, India. Phone no.: 91 474 2712022,E- mail: lalu_mangal@yahoo.com c* Corresponding author, Associate Professor in Civil Engineering, College of Engineering Trivandrum- 695 016, India. Phone no.: 91 471 2515617 E-mail: jeenu_shaj@yahoo.com ABSTRACT This paper focusses on the influence of aggregate gradation, cement content, micro silica and superplasticiser on durability of High Performance concrete (HPC). As the first step, an optimum aggregate gradation (for 20 mm size aggregates), derived from packing density test results, is proposed. HPC Specimens were tested for initial surface absorption, water absorption, sorptivity and chloride ion permeability. The results indicate that for given micro silica (MS), there exists a unique superplasticiser (SP) dosage that yields the best results and this value increases with increase in micro silica. Comparing mixes with same powder content,it is seen that the one having the higher cement content exhibitslesser absorption and permeability. The study emphasises the complex inter-relationship between the quantities of cement, MS and SP to be used to obtain a durable mix. Keywords: Durability, High Performance Concrete, Chloride ion permeability 1. INTRODUCTION The latest developments in the field of high performance concrete (HPC) attempt to make an ecological material with enhanced rheological, strength and durability characteristics, by utilizing the components to its full potential[1].Aggregate packing and the corresponding particle size distribution, andthe improvement in theproperties of cement paste and interfacial transition zone by the use of mineral and chemical admixtures have been found to play a paramount role in the behaviour of HPC [2-3]. However, most mix design methods for high strength and high performance concrete are not able to optimize the choice of mineral and chemical admixtures and their proportioning in the mixtures. 16
  • International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME The attacks of deleterious agents cause rapid deterioration of concrete structuresleading to prematurefailure[4-5]. The surface layer of concrete is the first line of defenceagainst the ingress of aggressive agents and hence, the characteristics of this layer of concretedetermine the rate of transport of the various aggressive substances into the concrete. Themoisture along with chlorides and dissolved oxygen will be absorbed into the concrete coverby capillary forces depending on the degree of saturation of the concrete, which initiates thechloride-induced corrosion of the reinforcing steel. Hence an assessment of the rate of ingressof chlorides has become very important for evaluating the long-term performance of concretestructures [6-7]. As the strength and behaviour of HPC is a function of the aggregate characteristicsand mineral as well as chemical admixture content, there is a need to reinvestigate the mosteffective particle size distribution and proportion of mineral and chemical admixtures thatwould result in optimised performance of HPC.The paper first elucidates the influence of theaggregate gradation characteristics on the packing density of all in aggregates, to arrive at themost effective gradation. The combined use of cement, micro silica (MS), andsuperplasticiser(SP) on durability of HPC is assessed by conducting initial surface absorption,water absorption, sorptivity and RCPT.The work reported herein also provides guidelines forobtaining a flowable HPC mix with slump greater than190 mm (for flowing concreteaccording to ASTM C1017-07[8]), having compressive strength greater than 75N/mm2andthat provides enhanced durability characteristics.2. MATERIALS AND METHODS2.1 Materials used Coarse aggregate: Crushed quartz aggregates of angular shape and rough texture (size<20 mm) were used. The specific gravity of coarse aggregate was 2.67.Fine aggregate: River sand passing through 4.75 mm sieve was used. Its specific gravity andfineness modulus were 2.55 and 2.64 respectively.Cement: The chemical composition of cement used (53 grade OPC) is given in Table1.MS: The chemical composition of MS used is given in Table 1.SP: Polycarboxylate ether based high range water-reducing admixture with solid content 42% and specific gravity 1.1 was used. Table 1 Chemical composition of cementitious materials (in percentage) Compounds Cement Micro silica Silica (SiO2) 18.10 98.12 Calcium Oxide (CaO) 60.30 0.053 Iron Oxide (Fe2O3) 4.90 0.52 Aluminium Oxide (Al2O3) 4.54 0.29 Titanium Dioxide (TiO2) 0.27 0.17 Magnesium Oxide (MgO) 0.68 0.15 Potassium Oxide (K2O) 0.57 - Sulphur Trioxide (SO3) 3.59 - Sodium Oxide (Na2O) 0.20 - 17
  • International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME2.2. Gradation of aggregates To achieve the most effective particle size distribution that would yield the densestgradation, packing densities of different aggregate combinations were determined byseparating the all in aggregates into different size fractions and by varying the percentage ofindividual fractions. The packing density of each aggregate combination was measured byweighing a one-litre container filled with aggregates consolidated on a vibrating table for twominutes [9]. The specific gravity of the aggregate fractions was determined according toASTM C127-12 [10]. From the weight of aggregate filling the container, bulk density as wellas solid density was determined using the known values of proportion and specific gravity ofeach individual fraction. The aggregate combination that exhibited the highest value ofpacking density (presented in Table 2) was used for all subsequent experiments in this study. Table 2 Optimal gradation pattern (for 20 mm aggregates) Particle fractions considered (mm) Packing density 20-12.5 12.5-10 10-4.75 4.75-2.36 2.36-1.18 1.18-0.6 0.6-0.15 10 10 30 10 10 20 10 0.79512.3 Mix proportion HPC mixes were proportioned by absolute volume method. To optimise the range ofcement content and water- cement ratio for the targeted compressive strength (75 N/mm2),trial mixes were made by varying the cement content between 400 and 750 kg/m3 and water-cement ratios between 0.21 and 0.27. Based on the preliminary results, three cement contents(450 kg/m3, 525 kg/m3 and 600 kg/m3) and two water-cement ratios (0.23 and 0.25) wereselected. For each cement content and water cement ratio, mixes were proportioned byvarying the MS content from 0% to 25% (in steps of 5%) by weight of cement and SP dosagefrom 0.0% to 3.5% (in steps of 0.5%). From these mixes, only those that exhibited slumphigher than 190 mm were considered for further investigation. The mixes are designated as Mfollowed by the cement content, water-cement ratio and the percentages of MS and SP (Table3).The concrete is mixed in a tilting concrete mixer of 200 l capacity for about 6 minutes. Theprepared HPC mixes were filled in three layers in steel moulds of standard sizes, each layerbeing compacted well using a table vibrator. The specimens were demoulded after 24 hoursand water cured until testing.2.4 Test procedure The rate of water absorption by the surface zone of concrete under a head of 200 mmbetween 10 minutes to 2 hours was measured and the multidimensional capillary absorptionof water into concrete was determined as per ASTM C642-06[11]. Sorptivity, whichrepresents the rate of penetration of water into the pores of concrete by capillary suction, wasmeasured as per ASTM C1585-11 [12]. The ability to resist chloride penetration was assessedby RCPT as per ASTM C1202-12 [13].The compressive strength at the age of 3, 7 and 28days was also determined (ASTM C39-12[14]). 18
  • International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME3. RESULTS AND DISCUSSION3.1 Initial surface absorption After 10 minutes of immersion, initial surface absorption values greater than 0.50ml/m2/s is considered high and less than 0.25 ml/m2/s is considered low. After 120 min,initial surface absorption values greater than 0.15 ml/m2/s is considered high and less than0.07 ml/m2/s is considered low[15]. For the set of ingredients used in the present study, thevalues of initial surface absorption, after 10 minutes, ranged between 0.00 and 0.17 ml/m2/sand was zero after 120 minutes, for all except one series (MS=5% and SP=3.5%) of theinvestigated mixes. Typical results are given in Table 3. For the very low MS content, ahigher SP dosage would have caused unpacking of the system, resulting in more pore spacesand consequent higher initial surface absorption. It was also noticed that initial surfaceabsorption did not bear any relationship with the change in MS dosage or powder content.The negligibly low values of surface absorption shows that the highly dense aggregatepacking, which was further densified by the successive filling of pores with cement andmicro silica, is very effective in preventing the ingress of water into the cover zone. Table 3 Durability characteristics and compressive strength of typical investigated mixesMix designation ISAT ISAT Water Coefficient Sorptivity Charge 28 day at 10 at 120 absorption of passed Compressive 3 2 ( mm /mm min min (%) Absorption /√min) (C) strength (ml/m²/s) (ml/m²/s) (m²/s) (N/mm2)M-450-0.23-5-1.0 0.167 0.000 1.453 1.94E-09 0.0211 148.5 98.0M-450-0.23-5-1.5 0.167 0.000 1.000 1.67E-09 0.0252 111.6 95.0M-450-0.23-5-2.0 0.000 0.000 1.029 8.33E-10 0.0323 130.5 97.5M-450-0.23-5-2.5 0.167 0.000 1.074 8.33E-10 0.0398 100.8 95.0M-450-0.23-5-3.0 0.167 0.000 1.179 8.33E-10 0.0477 126.0 81.0M-450-0.23-5-3.5 0.167 0.167 1.302 1.39E-09 0.0497 125.1 80.5M-450-0.23-10-1.0 0.000 0.000 1.570 1.59E-09 0.0177 123.3 97.0M-450-0.23-10-1.5 0.000 0.000 1.300 1.11E-09 0.0202 21.6 101.0M-450-0.23-10-2.0 0.000 0.000 0.950 8.33E-10 0.0257 68.4 100.0M-450-0.23-10-2.5 0.167 0.000 0.956 8.33E-10 0.0167 47.7 97.0M-450-0.23-10-3.0 0.167 0.000 0.972 1.39E-09 0.0236 123.2 98.0M-450-0.23-10-3.5 0.167 0.000 1.099 1.11E-09 0.0240 125.3 88.5M-450-0.23-15-1.0 0.000 0.000 1.560 1.91E-09 0.0330 234.0 102.0M-450-0.23-15-1.5 0.000 0.000 1.284 1.67E-09 0.0391 198.0 102.0M-450-0.23-15-2.0 0.167 0.000 0.920 1.39E-09 0.0278 143.1 103.5M-450-0.23-15-2.5 0.000 0.000 0.932 1.11E-09 0.0278 92.0 108.0M-450-0.23-15-3.0 0.167 0.000 0.835 1.39E-09 0.0252 112.0 95.0M-450-0.23-15-3.5 0.167 0.000 0.859 1.11E-09 0.0292 178.3 83.0M-450-0.23-20-1.0 0.167 0.000 2.216 2.5E-09 0.0496 191.7 105.0M-450-0.23-20-1.5 0.000 0.000 1.008 1.94E-09 0.0430 171.1 107.5M-450-0.23-20-2.0 0.167 0.000 1.263 1.67E-09 0.0341 155.8 110.0M-450-0.23-20-2.5 0.167 0.000 1.109 1.67E-09 0.0427 121.6 112.0M-450-0.23-20-3.0 0.167 0.000 1.014 1.67E-09 0.0458 121.6 111.0M-450-0.23-20-3.5 0.167 0.000 1.974 1.67E-09 0.0552 174.7 93.5 19
  • International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME3.2 Water absorption High water absorption implies higher pore volume. If pore volume is high and the pores areinterconnected, permeability of the concrete is high and this indicates poor durability. It has beenreported that good concretes have absorption values well below 10% by mass [7,15].Bharatkumar etal. (2001) [16] have reported water absorption values between 2.5% and 6.8% for fly ash concrete.Khatib and Clay (2004) [17]obtained values between 4.2% and 5.4% for concrete mixes withmetakaolin as mineral admixture. For the mixes used in the present study, water absorption valueswas found to lie in the range of 0.8 to 2.2% (Table 3). For all the cement contents considered in the study, mixes with MS dosage 10% exhibited theleast water absorption. Typical results are given in Fig.1. The relatively higher values of waterabsorption for the mixes with 20% MS can be due to the unpacking of the granular system as pointedout by Sobolev (2004)[18]. In addition, all the mixes with cement content 600 kg/m3 showedrelatively higher values of water absorption, possibly due to the higher powder content. It was alsonoticed that for a given MS content, there is an optimum value of SP that results in the least waterabsorption and this optimum value generally increases with increase in MS (Fig.2). Also, when mixeswith the same powder content was compared, the one with higher cement content exhibited lesserwater absorption. For instance, though the mixes M-450-0.23-20-1.0 and M-525-0.23-5-1.0 had thesame powder content, the one with higher cement content showed lesser water absorption (Fig.3).Coefficient of absorption, which is a measure of permeability to water for a hardened concrete, wasalso computed [16]. Very low values of coefficient of absorption of the mixes investigated in thepresent study (Table 3) are quite encouraging and comparable with those reported in the literature forHPC mixes with mineral admixtures[16]. The slightly adverse effect of larger quantities of fineparticles is evident from the comparatively higher values coefficient of absorption for mixes with 20%MS. The least values of absorption were generally observed for MS content of 10%, with SP dosageabout 2 to 2.5%.Noticeable increase in water absorption with time was observed in the experimentsfor about 90 minutes as illustrated in Fig.4. Thereafter, the absorption rate decreased significantly dueto the saturation of the outer zone of the concrete surface. Based on the present study, for developingflowable HPC mixes with negligible water absorption, cement content in the range of 450 to 525kg/m3 with MS content of about 10% and SP dosages of about 2% are recommended. Fig.1 Typical variation of water absorption with cement content (w/c = 0.23; SP=2.0%) 20
  • International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME Fig.2 Typical variation of water absorption with SP dosage (cement content=525 kg/m3; w/c=0.23) Fig. 3 Combined influence of cement and micro silica (powder content) on water absorption (w/c = 0.23; SP=2.0%) 21
  • International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME Fig. 4 Cumulative water absorption versus elapsed time relationship (cement=525 kg/m3; w/c=0.23; MS= 15%)3.3 Sorptivity Sorptivity is a function of porosity, pore diameter and continuity of pores within theconcrete matrix and can be correlated to permeability.It has been suggested that for lowpermeability concrete, the sorptivity values should be less than 0.1 mm3/mm2 /√min [6]. Forall the HPC mixes investigated in the study, sorptivity values less than 0.055 mm3/mm2 /√minwere observed (Table 3), indicating dense concrete with finer pores and lesser interconnectednetwork of capillary pores. One of the main reasons is the merit of the chosen aggregategradation. Also, the presence of micro silica acting as micro fillers would have helped toreduce the size of capillary pores of cement paste, causing the pore system to becomesegmented through partial blocking. Results from the study as shown in Table 3 also indicatethat the mixes with 10% MS content exhibited the least sorptivity.3.4 Chloride ion permeability The charge passed through the specimen was observed to be less than 450 C for all theinvestigated mixes (Table 3). Comparable values have been reported in the literature [19].The lower the total charge passed through the hardened cement matrix, the higher itsresistance to chloride penetration. The negligibly low values of chloride ion penetrability inthe investigated mixes indicate very high durability. As in the case of water absorption,comparison of mixes with the same powder content revealed that the mix with higher cementcontent exhibits lesser sorptivity and chloride ion penetration. The mixes with higher cementcontent (600 kg/m3) exhibited higher chloride ion permeability and this might be due to thehigher powder content. 22
  • International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME3.5 Compressive strength The 3-day compressive strength of all the mixes considered in the present study washigher than 50 N/mm2 while the 28-day compressive strength varied between 76 N/mm2and125 N/mm2. About 88% of the 28-day compressive strength was attained within seven days.Most of the calcium hydroxide released during the hydration of Portland cement wouldprobably have reacted with the highly reactive micro silica (silicon dioxide content >98%)within seven days and would have contributed to the development of high 7-day compressivestrength. It was also noticed that though very low water absorption values were observed forhigh strength mixes, there was no direct correlation between water absorption andcompressive strength. A similar observation has been reported elsewhere [17].4. CONCLUSIONSThe following conclusions are drawn based on the results of the present study: • A new gradation characteristics (for 20 mm size aggregates), which is derived from the packing density test results, is proposed to obtain concrete that yields acceptable level of performance, from workability, strength and durability points of view. • The measured initial surface absorption, multi-dimensional water absorption, sorptivity and chloride ion permeability values for the HPC specimens, (regardless of cement content (450, 525 and 600 kg/m3), water cement ratios (0.23 and 0.25), MS content (5 to 20%) and SP dosage (1 to 3.5%)) were significantly lower than the values reported in the literature as well as the recommended ones. • For the set of ingredients used in the present study and for the ranges of values of variables considered, MS should be kept to about 10% and SP to about 2% of the cement content to yield the best results. • There exists a unique SP dosage that yields the best results, for a given MS content and this value increases with increase in MS content. • Comparing the HPC mixes with the same powder content has revealed that the specimen with higher cement content exhibits lesser water absorption, sorptivity and chloride ion permeability. • There is a noticeable increase in water absorption with time up to about 90 minutes. Thereafter, the rate of absorption decreases significantly. • The strength and durability properties were found to be poorly correlated, though high strength mixes exhibited extremely low absorption and permeability characteristics.The study emphasises that there is a complex inter-relationship between the quantities ofcement, MS and SP to be used to obtain a densified mix. It may be noted that findingsobtained in the present study, to a certain extent, are material specific. Also, it isrecommended to perform more studies related to electrical conductivity of concrete,considering the uncertainties associated with the RCPT.ACKNOWLEDGEMENT Authors express their gratitude to the Kerala State Council for Science, Technologyand Environment (KSCSTE), Government of Kerala, India, for funding this study, which ispart of the sponsored research project on “Investigations on Ultra High PerformanceCementitious Composites”. 23
  • International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEREFERENCES1. Aitcin, P.C. (2003).The durability characteristics of high performane concrete: a review.Cement and Concrete Composites, Vol. 25, No. 4, 409-420.2. Meddah, M.S., Zitouni, S. andBelâabes, S. (2010). Effect of content and particle size distribution of coarse aggregate on compressive strength of concrete.Construction and Building material, Vol. 24, No. 4, 505-512.3. MegatJohari, M. A., Brooks, J. J., Kabir, S. andRivard, P. (2011). Influence of supplementary cementitious materials on engineering properties of high strength concrete. Construction and Building Materials, Vol. 25, No.5, 2639–26484. Wee, T. H., Suryavanshi, A. Kand Tin, S. S. (1999). Influence of aggregate fraction in the mix on the reliability of the rapid chloride permeability test. Cement and Concrete Composites, Vol. 21, No.1,59-72.5. Rahmani, H.andRamazanianpour, A.A. (2008). Effect of binary cement replacement materials on sulphuric acid resistance of dense concretes.Magazine of Concrete Research, Vol. 60, No.2, 145-155.6. Razak, H. A., Chai, H. K. and Wong, H. S. (2004). Near surface characteristics of concrete containing supplementary cementitious materials. Cement and concrete composites, Vol. 26, No.7, 883-889.7. Siddique, R. andKadri , E. (2011). Effect of metakaolin and foundry sand on the near surface characteristics of concrete, Construction and Building Materials, Vol. 25, No.8, 3257–3266.8. ASTM C1017- 07.Standard Specification for Chemical Admixtures for Use in Producing Flowing Concrete..9. deLarrard, F. and Sedran, T. (1994).Optimisation of ultra high performance concrete by the use of a packing model. Cement and Concrete Research, Vol. 24, No. 6, 997-1009.10. ASTM C127 – 12.Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Coarse Aggregate11. ASTM C642-06.Standard Test Method for Density, Absorption, and Voids in Hardened Concrete.12. ASTM C1585-11.Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic-Cement Concretes.13. ASTM C1202-12.Standard Test Method for Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration. ,14. ASTM C39/C39M -12Standard Test Method for CompressiveStrengthof Cylindrical Concrete Specimens. .15. Neville, A.M. Properties of concrete.4th ed. Pearson, India, 2010.16. Bharatkumar, B.H., Narayanan, R., Raghuprasad, B.K. andRamachandramurthy, D.S. (2001). Mix proportioning of high performance concrete. Cement and Concrete Composites, Vol. 23, No. 1, 71-80.17. Khatib, J. M.and Clay, R.M. (2004). Absorption characteristics of metakaolin concrete.Cementand Concrete Composites,Vol.34, No.1, 19-29.18. Sobolev K. (2004). The development of a new method for the proportioning of high- performance concrete mixtures. Cement Concrete Composites,Vol. 26, No.7, 901-907.19. Julio-Betancourt, G.A. and Hooton, R.D. (2004). Study of the Joule effect on rapid chloride permeability values and evaluation of related electrical properties of concretes. Cement and Concrete Research, Vol. 34, No.6, 1007–1015. 24
  • International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME20. V.S.Tamilarasan, Dr.P.Perumal and Dr.J.Maheswaran, “Experimental Study On Water Permeability And Chloride Permeability Of Concrete With Ggbs As A Replacement Material For Cement” International Journal of Civil Engineering & Technology (IJCIET), Volume 3, Issue 2, 2012, pp. 25 - 40, Published by IAEME21. Prof. P. M.Mohite, Prof. D. B. Kulkarni and Prof Mrs S N Patil, “Effect Of Controlled Temperature (27°C- 42°C)On Strength Of M20 Grade Of Concrete”, International Journal of Civil Engineering Research and Development (IJCERD), Volume 1, Number 2, 2011, pp. 30 - 40, Published by PRJpublication.22. M.N.Bajad, C.D.Modhera and A.K.Desai “Influence Of A Fine Glass Powder On Strength Of Concrete Subjected To Chloride Attack” International Journal of Civil Engineering & Technology (IJCIET), Volume 2, Issue 2, 2011, pp. 1 - 12, Published by IAEME23. M. Vijaya Sekhar Reddy, Dr.I.V. Ramana Reddy and N.Krishna Murthy “Durability Of Standard Concrete Incorporating Supplementary Cementing Materials Using Rapid Chloride Permeability Test” International Journal of Civil Engineering & Technology (IJCIET), Volume 3, Issue 2, 2012, pp. 373 - 379, Published by IAEME24. A.S Jeyabharathy, Dr.S.Robert Ravi and Dr.G.Prince Arulraj “Finite Element Modeling Of Reinforced Concrete Beam Column Joints Retrofitted With Gfrp Wrapping” International Journal of Civil Engineering & Technology (IJCIET), Volume 2, Issue 1, 2011, pp. 35 - 39, Published by IAEME 25