Geopolymer concrete ppt

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Information about Geopolymer concrete ppt

Published on December 12, 2016

Author: VibhanshuSingh5

Source: slideshare.net

1. PHYSICAL PROPERTIES AND APPLICATIONS OF GEOPOLYMER CONCRETE

2. CONTENTS • Introduction • Why not OPC? • OPC usage without environmental impact • Why geopolymer concrete? • Constituents • Process and Mechanism • Types of GPC • Test on GPC • Properties • Applications • Advantages and disadvantages • Discussion on future development • Conclusion

3. INTRODUCTION • Geopolymer concrete is an innovative, eco-friendly construction material. • It is used as replacement of cement concrete. • In geopolymer concrete cement is not used as a binding material. • Fly ash, silica-fume, or GGBS, along with alkali solution are used as binders. 1

4. FIGURE 1-GEOPOLYMER CONCRETE 2

5. WHY NOT OPC? • It is the most consumed commodity in the world after water. • It is also the most energy intensive material • Cement production leads to high carbon-dioxide emission. - 1 ton of CO2 is produced for every 1 ton of cement. -It is produced by calcination of limestone and burning of fossil fuels 3

6. IS THERE A WAY TO USE OPC WITHOUT ENVIRONMENTAL IMPACT? -replacing some limestone with fly ash and blast furnace slag called as blended cement -using carbon dioxide emission captures and storage(CCS) -accelerated carbonation where CO2 penetrate concrete reacting with Ca(OH)2 in presence of H2O forming CaCO3 4

7. WHY GEOPOLYMER CONCRETE? • Reduces the demand of OPC which leads CO2 emission. • Utilise waste materials from industries such as fly ash, silica-fume, GGBS. • Protect water bodies from contamination due to fly ash disposal. • Conserve acres of land that would have been used for coal combustion products disposal. • Produce a more durable infrastructure. 5

8. CONSTITUENTS • Coarse aggregate • Fine aggregate - sand or bottom ash can be used • Admixture - superplasticizers(naphthalene based or naphthalene sulphonate based) • Alkaline activators -Alkaline activation is a process of mixing powdery aluminosilicate with an alkaline activator . -It produce a paste which sets and hardens within short duration 6

9. -Alkaline activators commonly used are sodium or potassium hydroxide. -They are used in combination with sodium silicate(water glass) or potassium silicate solution. -NaOH and Na2SiO3 are more commonly used as it leads to higher geopolymerisation rate. -K2SiO3 solution rarely used because of high cost and lack of easy availability. -Alkali hydroxide is used for dissolution and sodium-silicate solution as binder. 7

10.  Sodium hydroxide - dissolved in water to form a semi-solid paste -higher amount reduces ettringite -makes crystalline product which is stable in aggressive environment  Potassium hydroxide -improve porosity and compressive strength  Sodium silicate(water glass) -available in gel form -for good pozzolanic reaction it is mixed with NaOH 8

11. • Fly ash -combustion by-product of coal in coal fired power plants -two classes of fly ash are F and C TABLE1:CHEMICAL COMPOSITION OF FLY ASH OXIDES PERCENTAGE SiO2 52 Al2O3 33.9 Fe2O3 4 CaO 1.2 K2O 0.83 Na2O 0.27 MgO 0.81 SO3 0.28 LOI 6.23 SiO2/Al2O3 1.5 9

12. -fly ash used in concrete to increase life cycle expectancy -helps in increasing durability -improves permeability by lowering water-cement ratio -spherical shape of fly ash improves consolidation of concrete 10

13. • GGBS -a mineral admixture of silicates and aluminates of Ca and other bases - same main chemical constituents as OPC but in different proportions - improves compressive strength of GPC TABLE 2-CHEMICAL COMPOSITION OF GGBS CEMICAL CONSTITUTION CEMENT(%) GGBS(%) Calcium oxide 65 40 Silicon dioxide 20 35 Aluminium oxide 5 10 Magnesium oxide 2 8 11

14. • Silica fume -also called as micro silica or condensed silica fume -produced during manufacture of silicon by electric arc furnace -another artificial pozzolan 12

15. • PROCESS -Si and Al atoms in source materials dissolved using alkaline solution. -Source materials include fly ash ,GGBS, silica-fume. - gel formed by applying heat. -This gel binds aggregates and unreacted source material forming geopolymer concrete 13

16. • MECHANISM -dissolution of Si and Al atoms takes place through the action of OH ions -precursor ions condense to form monomers -polycondensation of monomers to form polymeric structures -this framework formed is called as polysilates -silate stands for silicon-oxo-aluminate building unit -chains and rings formed and cross linked through Si-O-Al bridge 14

17. TYPES OF GEOPOLYMER  Slag based geopolymer -Slag is a mixture of metal oxides and silicon dioxide - a transparent by-product material formed in the processing of melting iron ore. -OPC replacement with slag improve workability and reduce lifecycle costs -it also increase its compressive strength -corex slag, steel slag, iron blast furnace slag are examples 15

18.  Rock based geopolymer -MK-750 in the slag based geopolymer replaced by natural rock forming minerals forms this geopolymer -feldspar and quartz are natural rock forming minerals 16

19.  Fly ash based geopolymer - improves workability and increase compressive strength -reduce cost of OPC along with CO2 emission -reduce drying shrinkage -class F fly ash used commonly Alkali activated geopolymer: Heat curing at 60 to 80 οC is done. Into 1:2 aluminosilicate gel fly ash particles are embedded. Slag based geopolymer:It contains silicate, blast furnace slag and fly ash 17

20.  Ferro-silicate based geopolymer -same properties as that of rock based geopolymers -has a red colour -high iron oxide content -poly type geopolymer formed by substituting some of the aluminium atoms in the matrix 18

21. TEST ON GPC • CREEP TEST -three 150x300 mm cylinders prepared - placed on creep testing frame with hydraulic loading system -before loading 7th day compressive strength determined -load corresponding to 40% of mean compressive strength applied -strain values measured and recorded -test conducted at 23οC and relative humidity 40-60% 19

22. • creep of GPC smaller than that of OPC • smaller creep due to block polymerisation concept • presence of micro-aggregates increase creep resisting function in GPC • in OPC creep caused by cement paste 20

23. • DRYING SHRINKAGE TEST -75x75x285 mm prisms with gauge studs used -specimens kept in a controlled temperature environment -temperature at 23οC and relative humidity 40-60% -shrinkage strain measurements taken on third day of casting concrete -specimen demoulded and 1st measurement taken -horizontal length comparator used for measurement -next measurement taken on 4th day -further measurements taken till one year 21

24. • drying shrinkage of GPC is very less • ambient temperature cured GPC shows more shrinkage than heat cured GPC • excess water evaporates during heat curing reducing dry shrinkage • drying shrinkage of GPC at ambient temperature is same as that of OPC • GPC undergoes shrinkage of 100 micro strains after one year • 500-800 micro strains experienced by OPC 22

25. FIGURE 2 - DRYING SHRINKAGE OF HEAT CURED AND AMBIENT CURED SPECIMEN 23

26. • COMPRESSIVE STRENGTH -higher compressive strength when heat activated -slag addition improves compressive strength at ambient temperature curing FIGURE 3- COMPRESSIVE STRENGTH OF GEOPOLYMER CONCRETE IN AMBIENT CONDITION Time(days) 24

27. • compressive strength of GPC decreased with increasing fly ash content • it increased with higher aggregate content • higher strength at lower alkali content • compressive strength increased with age • Polycondensation of silica and alumina contribute to high strength 25

28. • MODULUS OF ELASTICITY AND POISSON’S RATIO -modulus of elasticity increased with compressive strength in OPC -similar trend in GPC but values lower than OPC -GPC cured at elevated temperature yields higher value of E than cured at ambient temperature -Poisson’s ratio of GPC similar to that of OPC and increased with compressive strength 26

29. TABLE 3 -YOUNG’S MODULUS AND POISSON’S RATIO 27

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31. PROPERTIES • Workability -increase in NaOH and sodium silicate solution reduce flow of mortar -superplasticizer or extra water can be added to increase workability • Compressive strength -it depends on curing time and temperature -it increase with fly ash content -it increase with fineness of fly ash 29

32. • Resistance against aggressive environment -used in constructing marine structures -in OPC white layer of crystals formed on acid exposed surface -in GPC there is no gypsum deposition and no visible cracks -a soft and powdery layer formed during early stages of exposure which later becomes harder -mass loss on exposure to H2SO4 in GPC was 3% and in OPC 20-25% -higher the alkali content higher the weight loss -GPC showed better resistance 30

33. • Behaviour of geopolymer at elevated temperature -high strength loss during early heating period(up to 200οC) -beyond 600οC no further strength loss -no visible cracks up to 600 οC -minor cracks at 800 οC -GPC with more compatability between aggregates and matrix led to less strength loss • Bond strength -very high -about one third of its compressive strength -four times than that of OPC 31

34. APPLICATIONS • PAVEMENTS -light pavements can be cast using GPC -no bleed water rise to the surface -aliphatic alcohol based spray used to provide protection against drying FIGURE 5 – PLACING OF PAVEMENT USING GEOPOLYMER CONCRETE 32

35. • RETAINING WALL -40MPa precast panels were used to build a retaining wall -panels were 6m long and 2.4m wide -these panels were cured under ambient condition FIGURE 6 – PRECASTE GEOPOLYMER RETAINING WALLS FOR A PRIVATE RESIDENCE 33

36. • WATER TANKS -two water tanks were constructed, one with 32MPa concrete with blended cement and other with GPC -autogenous healing occurred in OPC due to calcium hydroxide deposition -in GPC tank there is little calcium hydroxide -nominal leaking in tank healed rapidly due to gel swelling mechanism FIGURE 7 - INSITU WATER TANKS WITH BLENDED CONCRETE (LEFT) AND GEOPOLYMER CONCRETE (RIGHT) 34

37. • BOAT RAMP -approach slab on ground to ramp was made using geopolymer reinforced with FFRP -entire constituents remained dormant until activator chemicals were added FIGURE8 – BOAT RAMP CONSTRUCTED WITH BOTH IN-SITE AND PRECAST GEOPOLYMER CONCRETE. 35

38. • PRECAST BEAM -GPC beams formed three suspended floor levels of GCI building -beams had arched curved soffit -water pipes were placed inside them for temperature controlled hydronic heating of building spaces above and below FIGURE 9 – GEOPOLYMER CONCRETE BEAM CRANED TO POSITION 36

39. ADVANTAGES  high compressive strength  high tensile strength  low creep  low drying shrinkage  resistant to heat and cold  chemically resistant  highly durable  fire proof 37

40. DISADVANTAGES  difficult to create -requires special handling -chemicals like sodium hydroxide are harmful to humans -high cost of alkaline solution  Pre-mix only -sold only as pre-mix or pre-caste material  Geopolymerisation process is sensitive -lacks uniformity 38

41. DISCUSSION ON FUTURE DEVELOPMENT -more studies and wide scale acceptance for using GPC in precast concrete products -making GPC more user friendly by using lower amount of alkaline solution -producing more cost effective geopolymer -replacing fine aggregate with quarry sand as demand for natural sand is increasing -studies on fibre reinforced geopolymer concrete for improving flexural strength 39

42. CONCLUSION • Geopolymer concrete is a promising construction material due to its low carbon dioxide emission • High early strength, low creep and shrinkage, acid resistance, fire resistance makes it better in usage than OPC • Wide spread applications in precast industries due to -its high production in short duration -less breakage during transportation • Enhanced research along with acceptance required to make it great advantage to the industry 40

43. REFERENCES • Aslani (2015); Thermal Performance Modelling of Geopolymer Concrete, Journal of Materials in Civil Engineering • Shankar H Sanni (2012); Performance of Geopolymer Concrete under severe environmental conditions, International Journal on Civil and Structural Engineering • Ramujee et al (2014), Development of Low Calcium Fly Ash Based Geopolymer Concrete, IACSIT International Journal of Engineering and Technology, Volume 6 • Lloyd et al (2010);Geopolymer concrete: A review of development and opportunities • Bakharev, T., (2005(a)), Resistance of geopolymer materials to acid attack, Cement and Concrete Research, 35, pp 658-670. 41

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