Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and                  Applications (IJERA) IS...
Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and                     Applications (IJERA)...
Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and                   Applications (IJERA) I...
Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and                  Applications (IJERA) IS...
Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and                  Applications (IJERA) IS...
Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and                   Applications (IJERA) I...
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  1. 1. Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.2142-2147 Effect Of Na2o/Al2o3, Sio2/Al2o3 And W/B Ratio On Setting Time And Workability Of Flyash Based Geopolymer Kushal Ghosh 1 and Dr. Partha Ghosh 2 1 Vocational Research student , Department of Construction Engineering, Jadavpur University, Kolkata, India 2 Asst. Professor, Department of Construction Engineering, Jadavpur University, Kolkata, India Keywords – Compressive strength, Geopolymer, Porosity, Microstructure, FlyashABSTRACT The objectives of the present research is Optimization of such a complex system requiresto appreciate the effect of synthesizing parameters systematic study of a number of synthesizingon setting time and workability of Fly ash based parameters as well as of their interactions. Secondly,geopolymer paste . Locally available low calcium fly ash from different sources show different level offly ash from a thermal power plant located near reactivity under specific geopolymer synthesisKolkata, India, was used . Fly ash used are lignite conditions and consequently affects the finalcoal based and falls under class F category. The properties. Hence , for manufacturing highbroad areas of present research include: performance geopolymer binder from fly ash, it isManufacturing of Geopolymer and a necessary to understand the effects of a variouscomprehensive study on the effect of synthesizing synthesis parameters and their relationship . Theparameters , Alkali content (Na2O/Al2O3), Silica Geopolymer mix composition is normally controlledcontent (SiO2/Al2O3) and Water to Geopolymer by adjusting alkali and silicate content of activatingbinder ratio on setting time of geopolymer paste solution. The SiO2/Al2O3 molar ratio is an extremelyand workability of geopolymer mortar and important parameter which has major influence onarrived at certain level of understanding which setting time and workability which in turn affectswill be useful to the researchers and physical and mechanical properties as well as on itsmanufacturers. microstructure. The properties of fly ash based geopolymer1. INTRODUCTION state depends on chemical composition and quantity Geopolymers is an inorganic polymeric materials of fly ash as well as activator solution. It may beformed by activating silica-aluminum rich minerals noted here that, percentage of Na2O (by weight of flywith alkaline or alkaline-silicate solution at ash) and SiO2/Na2O ratio of the mix significantlyambient or higher temperature level. Potential affect workability and setting time of geopolymer.applications includes: fire resistant materials, thermal The workability of the mix depends on its viscosity.insulating material, low energy tiles , waste The viscosity of gel increases with time due tocontainment, paver blocks etc. geopolymerisation process. A study on loss of flow Geopolymerisation is a very complex with time is necessary to determine handling time ofmultiphase exothermic process, involving a series of geopolymer mix. Moreover, these studies aredissolution-reorientation-solidification reaction important for locally available fly ash for wideanalogous to zeolite synthesis. High alkaline applications in the industry.solutions are used to induce the silicon andaluminium atoms in the source material to dissolve, 2. EXPERIMENTAL INVESTIGATIONforming three dimensional polymeric structure The experimental investigation has been conducted atconsisting of -Si-O-Al-O- bonds, represented as Jadavpur University, Kolkata, India. The humidityfollows and ambient temperature in the laboratory are rangingMn [-(SiO2) z–AlO2] n . wH2O from 75% to 90% and 25°C to 40°C respectively. Where: M = the alkaline element or cation The experimental methodology was divided in twosuch as potassium, sodium or calcium; the symbol – main parts: (1) Preparation of geopolymer mix (2)indicates the presence of a bond, n is the degree of Testing to obtain setting time of paste andpolycondensation or polymerisation; z is 1, 2, 3, or workability of geopolymer mortar. Flow table testhigher. The exact reaction mechanism which explains has been conducted for workability. The laboratorythe setting and hardening of geopolymers is not yet tests were conducted as per relevant Indian standardquite understood, although it is thought to be /ASTM codes.dependent on the aluminosilicate base material aswell as on the composition of alkaline activator. 2142 | P a g e
  2. 2. Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.2.1 Raw Materials of the sodium silicate solution were specific Typical locally available low calcium Class F gravity=1.48 g/cc. The activator solution wasfly ash from a thermal power station near Kolkata was prepared at least one day prior to its use .used throughout the research. The alkaline activatorsolutions were prepared by mixing sodium hydroxidein pellets form in sodium silicate solution and distilledwater. 2.2 MANUFACTURING PROCESS Following steps were followed during2.1.1 FLYASH manufacturing of Geopolymer The chemical compositions of the fly ash, as  Mixing of sodium silicate solution, sodiumdetermined by X-Ray Fluorescence (XRF) analysis, hydroxide pellets and water according toare given in Table 2.1. predefined proportion to make alkalineOxide SiO2 Al2O3 Fe2O3 TiO2 CaO activator, at least one day prior to its use .Mass (%) 55.1 30.85 3.15 1.85 2.45  Hobart mixer with rotating blades, was used for preparing geopolymer mix  Mixing of fly ash and alkaline activator in MgO K2 O Na2O the Hobart mixer for about five to six 0.35 0.8 0.65 minutes to get a homogeneous paste.  Setting time of paste was obtained using Vicat apparatus  Workability test was conducted using FlowTable 2.1: Chemical composition of the fly ash Table test(mass %) 2.3 SYTHESIZING PARAMETERS The total percentage of (SiO2+ Al2O3+ The proportion of geopolymer mix wasFe2O3) is greater than 70%. The calcium oxide varied by changing quantity and proportion ofcontent is less than 10%. Hence, as per ASTM C sodium silicate and sodium hydroxide in activating6128-03, it can be classified as class F fly ash (or solution. The effect of alkali content (Na2O/Al2O3),siliceous pulverised fuel ash conforming to IS silicate content (SiO2/Al2O3) and water to3812(Part-I)-2003 specifications). The colour of the geopolymer binder ratio on setting time andfly ash was dark gray. About 90% of the particles workability of geopolymer paste was studied. Loss ofwere smaller than 45m, and the Blain specific workability with time was also studied.surface area of fly ash was 395m2/kg. The ScanningElectron Microscopy (SEM) image of fly ash show 2.4 MIX COMPOSITIONthat the fly ash particle are generally spherical in The effect of water content expressed asshape of varying size. The mineral composition of fly water to geopolymer binder (geopolymer binder isash was obtained by XRD analysis and it was found sum total of mass of fly ash + mass of solids inthat the major crystalline constituents of fly ash activating solution). Water to Geopolymer binderincluded quartz (SiO2), mullite (Al2O3), and ratio was varied from 0.325 to 0.365 by changingmagnetite (Fe3O4). The fly ash is also constituted of quantity of water. The initial and final setting time ofan X-ray amorphous phases indicated by the broad Geopolymer paste was determined at roomhump registered between 2θ =20° and 30° temperature using Vicat apparatus. The Geopolymer paste were prepared by varying % Na2O from 4.25%2.1.2 ACTIVATOR SOLUTION to 10.25% and % SiO2 from 4.5% to 17% . The water The alkaline activator was a combination of to fly ash ratio of 0.325 was kept constant. Again,sodium silicate and sodium hydroxide solutions. The water to fly ash ratio was varied from 0.325 to 0.365,sodium hydroxide solids were laboratory grade in keeping % Na2O and % SiO2 constant. Sand to flypellets form, with a specific gravity of 2.15, 97% ash ratio was strictly maintained at 1.5.purity. To avoid effects of unknown contaminants,distilled water was used for preparing the activator 3. DISCUSSION ON TEST RESULTSsolutions. 3.1 Effect of alkali content on setting timeThe sodium hydroxide (NaOH) solution was Geopolymers pastes prepared by varying %prepared by dissolving NaOH pellets in water. The Na2O from 4.25% to 10.25%. The %SiO2 and watermass of NaOH solids in a solution was varied to fly ash ratio was 8 % and 0.325 respectively. It isdepending on the required concentration of the observed that both initial and final setting time ofsolution. The chemical composition of the sodium Geopolymer paste decreases with increase in alkalisilicate solution was Na2O=14.7%, SiO2=29.4%, content i.e. % Na2O. ( Ref. to Table 3.1 )and water 55.9% by mass. The other characteristics 2143 | P a g e
  3. 3. Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp. Table:- 3.1 - Effect of % Na2O on initial and final mortar flow on flow table in two perpendicularsetting time directions. The following test were designed to study MIX %Na2O %SiO2 Water/ Initial Final the effect of various synthesizing parameters on ID Fly Setting setting workability of Geopolymer mix. ash Time time a) The effect of alkali content (% Na2O) (min.) (min.) b) The effect of silicate ratio (SiO2/Na2O) SW1 4.25 8 0.325 250 300 c) The effect of water content SW2 6.25 8 0.325 200 245 d) Effect of dosage of plasticizer The minimum flow diameter of 150± 10 mm was SW3 8.25 8 0.325 182 208 considered as desirable as the mortar could be easily SW4 10.25 8 0.325 128 145 placed in the mould for casting the Geopolymer specimens. However, based on the flow diameter the workability of mix may be classified as shown in the However, the difference in initial and final Table 3.3.setting time reduces with the increase in alkali Table 3.3 Workability criteria of Geopolymercontent. Geopolymerisation get accelerated at high mortaralkali content and as a result setting time is reduced. Sl. No. Flow Diameter WorkabilityThe faster rate of reaction also resulted in reducingdifference in initial and final setting time at higher 1. Above 250 Very Highalkali content . 2. 180 to 250 mm High3.2 Effect of %SiO2 on setting time 3. 150 to 180 mm Moderate Geopolymers paste has been prepared by 4. 150 to 120 mm Stiffvarying %SiO2. The %Na2O and water to fly ashratio of the mix was kept constant to 8% and 0.325 5. Below 120 mm Very Stiffrespectively.Table 3.2 Effect of %SiO2 on initial and final The loss of flow with time was also studied .setting timeMIX % %SiO2 Water/ Initial Final 3.3.1 Effect of % Na2O on WorkabilityID Na2O Fly Setting Setting Geopolymers mortar prepared by varying % Na 2O ash Time Time from 4.25% to 10.25%. The silica content and water ratio (Minutes) (Minutes) to binder ratio of the mix wad kept constant to 8%SW5 8 0.00 0.325 160 183 and 0.325 respectively.SW6 Table 3.3.1 Effect of % Na2O on Workability 8 4.5 0.325 115 130 MIX ID % Na2O %SiO2 Water/ FLOWSW7 8 8.75 0.325 177 206 Fly DIAMETER ashSW8 8 13 0.325 212 248 SWM1 4.25 8 0.325 270± 12mmSW9 8 17.00 0.325 232 289 SWM2 6.25 8 0.325 194± 10mm It can be seen that, the setting time of paste SWM3 8.25 8 0.325 159± 8mmsuddenly reduced after addition of silicate. At lower SWM4 10.25 8 0.325 131± 7mmsilicate modulus and higher alkali content , rate ofpolycondensation was very high due to large quantityof Si and Al dissolved in the initial process of It has been observed that, the flow diameter decreases almost linearly with the increase in % ofdissolution. The dissolves species coagulate very fast Na2O. Since the water content of the all mixes waswith limited quantity of soluble silicate available in 0.325, increase in % Na2O increases viscosity of thethe mix which resulted in faster rate of setting. mix and resulted in reduction of flow diameter. It isAddition of higher soluble silicate, inhibits the observed that flow diameter decreases with theprocess of polycondensation resulted in higher settingtime. increase in alkali content. Increase in alkali concentration increases viscosity of Geopolymer mix resulted in reduction in flow diameter.3.3 Workability The workability of fresh Geopolymer mortar 3.3.2 Effect of %SiO2 on Workabilitywas studied according to ASTM C-124, using mini Table 3.3.2 presents mix proportion and the flow diameter of the fly ash based Geopolymers mortarslump cone. The flow diameter was measured prepared by varying silicate ratio SiO2/Na2O. The %immediately after completion of mixing of Na2O t and water to binder ratio of the mix wad keptGeopolymer mortar in Hobart mixer. The workability constant to 8% and 0.325 respectively.of mix was determined by measuring diameter of 2144 | P a g e
  4. 4. Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.Table 3.3.2 Effect of %SiO2 on flow diameter of place and specimen with uniform structure could notGeopolymer mortar be casted. % %SiO2 Water/ Flow MIX Na2O Fly Diameter 3.3.4 Effect of dosage of plasticizer ID ash Geopolymers mortar prepared by varying SWM5 8 0.00 0.325 218± 11mm dosage of Naphthalene based superplasticiser from 0% to 4%. The superplasticiser was added by weight SWM6 8 4.5 0.325 178± 9mm with respect to weight of fly ash in Geopolymer mix. The % Na2O and %SiO2 were 8% . The water to fly SWM7 8 8.75 0.325 156± 8mm ash ratio was kept constant 0.325 . SWM8 8 13 0.325 137± 7mm Table 3.3.4: Effect of dosage of superplasticizer on SWM9 8 17.00 0.325 127± 5mm flow diameter of Geopolymer mortar MIX % %SiO2 Water / Dosage Flow ID Na2O Fly ash of Dia It is observed that flow diameter decreased ratio Plasticizeralmost linearly with increasing %SiO2. The viscosity 8 155±of the Geopolymer mix increases with increase in SWMP1 8 0.325 0% 6mmsoluble silicate dosage. Higher %SiO2 yielded lowest SWMP2 8 8 164± 0.325 1%flow diameter of 127±5 mm as the mix was highly 7mmviscous. SWMP3 8 8 193± 0.325 2% 9mm SWMP4 8 8 224±3.3.3 Effect of water content on Workability 0.325 3% 10mmThe change in water to fly ash ratio was achived by SWMP5 8 8 270±increasing water content of the mix from 325% to 0.325 4% 11mm365% keeping quantity of fly ash constant. % Na2Oand %SiO2 was kept constant to 8% . It has been observed that flow diameter increased with increasing dosage of plasticiser. AtTable 3.3.3 Effect of water content on flow lower dosage of 1% there is no substantialdiameter of Geopolymer mortar improvement in workability. However , plasticiser Water/ dosage above 1% indicated rapid improvement inMIX % Flow %SiO2 Fly workability was observed. At 1% dosage ofID Na2O Diameter ash plasticizer, the flow was moderate whereas at 4% 8 8 167± dosage it was very high.SWM1 0.325 6mmSWM2 8 8 176± 3.3.5 Loss of workability with time 0.335 8mm The loss of workability was measured withSWM3 8 8 178± respect to relative reduction in flow diameter of 0.345 9mm mortar with time. Decrease in flow was measuredSWM4 8 8 210± with respect to initial mortar flow measured 0.355 9mm immediately after mixing of mortar. Table 3.3.5SWM5 8 8 258± shows the values relative flow diameter Relative flow 0.365 11mm , at different alkali content of the mix (% Na 2O) with respect to time. The flow diameter was measured at It has been observed that the flow diameter every 30 minute interval using mini slump cone.increased with increasing water to fly ash ratio from0.325 to 0.365. The rate of increase flow is lessbelow water to fly ash ratio of 0.345. However,increasing water to fly ash ratio above 0.345, veryrapid increase in flow was observed.Increasing water content of the mix reduces molarconcentration of alkali activator which resulted inreduction in viscosity of mix as well as slow rate ofGeopolymerisation resulted in increasing workability.The Geopolymer mortar mix with water to binderratio of 0.325 was found suitable for mixing andcasting of Geopolymer specimens. At higher water tobinder ratio of 0.365 some segregation of sand took 2145 | P a g e
  5. 5. Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp. content , silica content and water to binder ratio . Strong alkali solutions are needed to dissolve fly ash during the process of geopolymerisation. Water Table 3.3.5 : Relative flow at various time for plays important role during dissolution, different alkali content polycondensation and hardening stages of Relative flow at different alkali geopolymerisation. The water content should be content of the mix (% Na2O) adjusted to the minimum level considering desired Time 4.25% 6.25% (min.) Flow Relative Flow Relative workability of the geopolymer mix. dia Flow diameter Flow (mm) (mm) REFERENCES 0 262 1.00 186 1.00 30 261 0.99 188 1.00 1. Collins, F, Sanjayan, J. G, Early Age 60 257 0.98 186 1.00 Strength and Workability of Slag Pastes 90 249 0.95 181 0.97 Activated by NaOH and Na2CO3, Cement 120 238 0.92 173 0.92 and Concrete Research, 28, 1998, pp. 655- 150 224 0.86 161 0.87 664. 180 206 0.77 147 0.80 210 189 0.72 135 0.74 2. Criado, M, Palomo, A, Fernandez- 240 170 0.66 128 0.68 Jimenez, A, Palomo, A, Sobrados, I and Sanz, J, Effect of the SiO2/Na2O ratio on the 8.25% 10.25% Flow Relati Flow Relati alkali activation of fly ash. Part II: 29Si diame ve diame ve MAS-NMR Survey”, Journal of ter Flow ter Flow Microporous and Mesoporous Materials, (mm) (mm) 109, 2008, pp. 525-534. 154 1.00 134 1.00 154 1.00 138 1.00 3. Davidovits, J, Geopolymer chemistry and 156 1.00 139 1.00 properties, Proceedings of 1st International 150 0.99 133 0.99 Conference on Geopolymer’88, France, 1-3 143 0.95 127 0.95 June 1988, Vol.1, pp. 25-48. 137 0.89 120 0.91 127 0.84 111 0.84 4. De Silva, P, Sagoe-Crenstil K, 116 0.77 104 0.78 Sirivivatnanon, V, Kinetics of 106 0.73 98 0.72 geopolymerisation: Role of Al2O3 and SiO2, Relative flow is the ratio of flow at time zero to Cement and Concrete Research, 37, 2007, flow at any time. pp. 512-518. It has been observed that the flow of mortar 5. Fernández-Jiménez A, Palomo, A, andis almost linearly decreased with elapsed time. The Cecilio López-Hombrados, Engineeringrate of flow loss increased with alkali content properties of Alkali-Activated Fly Ashindicating higher rate of Geopolymerisation reaction Concrete, ACI Materials Journal, 103, 2006,at higher alkali content. It was found that during pp. 106-112.initial 30-60 minutes after mixing slight improvement 6. García-Lodeiro I, Palomo, A, Fernández-in flow was observed. It may be due to the some Jiménez A, Alkali-aggregate reaction inquantity of water released during the process of activated fly ash systems, Cement andGeopolymerisation. However, with increasing time Concrete Research, 37, 2007, pp.175-183.higher rate of reaction generated more quantity of gel 7. Hardjito, D, Wallah, S.E, Sumajouw,making mortar mix more viscous resulted in D.M.J and Rangan, B.V, On Developmentreduction of flow diameter. It has been observed that of Fly ash Based Geopolymer Concrete, ACIthe rate of loss of flow was higher for higher alkali Materials Journal, 2004, pp. 467-472.content. Maximum reduction in flow up to 90% for 8. Hardjito, D and Rangan, B.V,all mortar mix indicated that the mix could be Development and properties of low calciumhandled up to 120minutes without any effect on other fly ash based geopolymer concrete,properties. In the present study, when alkali content Research Report GC-1, Faculty ofof the mix increased beyond 10.25% very rapid Engineering, Curtin University ofsetting of the Geopolymer mix took place. At higher Technology, Pert, Australia.alkali content large quantity of oligomeric precursor 9. IS 3812 (Part-1), Pulverized Fuel ashis made available in a very short time due to faster Specifications, Part-1, For Use as Pozzolansdissolution rate. in Cement, Cement Mortar and Concrete, Bureau of Indian Standard, New Delhi,CONCLUSION India, 2003. The study on effect of geopolymer 10. IS 3812 (Part-2), Pulverized Fuel ashsynthesizing parameters revealed that the Specifications, Part-2, For Use asdevelopment of setting time and workability as well Admixtures in Cement, Cement Mortar andas microstructure depended basically on alkali Concrete, Bureau of Indian Standard, New Delhi, India, 2003. 2146 | P a g e
  6. 6. Kushal Ghosh, Dr. Partha Ghosh/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.11. Keyte, L.M, Lukey, G.C, van Deventer, J.S.J, The effect of Coal Ash Chemistry on the tailored design of waste-based geopolymeric products, Department of Biomolecular Engineering, The University of Melbourne, Victoria 3010 Australia, 2005.12. Rangan, B.V, Fly Ash-Based Geopolymer Concrete, Research Report GC4, 2008, Faculty of Engineering, Curtin University of Technology, Perth, Australia.13. Thakur, Ravindra N., Ghosh, Somnath., Book on Fly ash based Geopolymer composites :- Manufacturing and Engineering properties – Published by Lap Lambert Publishing House – Germany14. van Jaarsveld, J.G.S, van Deventer, J.S.J, Effect of the alkali metal activator on the properties of fly ash based geopolymers, 2006, Industrial and Engineering Chemistry Research, 38, 2006, pp. 3932 – 3941. 2147 | P a g e