Geopolymer Concrete Lab Report

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3. MIX DESIGN

3.1 Design of Geopolymer Concrete Mixtures:
In the mix design of geopolymer concrete the role and the influence of aggregates are considered to be the same as in the case of Portland cement concrete. The mass of combined aggregates may be taken to be between 75% and 80% of the mass of geopolymer concrete. Coarse and fine aggregate together were taken as 77% of entire mixture by mass. Fine aggregate was taken 30% of total aggregate. Fly ash and alkaline liquids was taken 23% of density of concrete. From past literatures, it is clear that the average density of fly ash based geopolymer concrete is similar to that of OPC concrete (2400kg/m3). Knowing the density of concrete the combined mass of alkaline liquid and fly ash can
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This GPC mix has two limitations such as delay in setting time and necessity of heat curing to gain strength. In order to overcome these limitations of GPC mix, 10% of fly ash was replaced by OPC to overcome the limitation necessity of heat curing and 5% of fly ash was replaced by Ground-Granulated Blast-Furnace Slag (GGBS) to overcome the limitation delay in setting time. In case of Glass fiber reinforced geopolymer concrete composites (GFRGPCC) mixes Glass fibers were added to the geopolymer concrete composites (GPCC mix) in three volume fractions such as 0.01%, 0.02% and 0.03% by density of glass fiber. The mix design was altered according which results in geopolymer concrete composites (GPCC mix). To prepare 12 molarity concentration of sodium hydroxide solution, 480 grams (molarity x molecular weight).The mass of NaOH solids was measured as 361 grams per kg of NaOH solution with a concentration of 12 Molar. The sodium hydroxide solution thus prepared is mixed with sodium silicate solution one day before mixing the concrete to get the desired alkaline solution. The solid constituents of the GPCC mix i.e. fly ash, OPC, GGBS and the aggregates were dry mixed in the pan mixer for about three minutes. After dry mixing, alkaline solution was added to the dry mix and wet mixing was done for 4 minutes. In case of glass fiber reinforced GPCC mixes fibers were added to the wet mix in three …show more content…
Initially coarse aggregate, fine aggregate, cement, fly ash, and GGBS were dry mixed for three minutes in the mixer. After dry mixing, alkaline activator solution was added to the dry mix and wet mix was done for 4 minutes. Finally, extra water along with super plasticizer was added. The mixing of total mass was continued until the binding paste covered all the aggregates and mixture become homogeneous and uniform in color. The fresh geopolymer concrete was used to cast cubes of size 150x150x150mm to determine its compressive strength. The fresh geopolymer concrete was used to cast prisms of size 100x100x500mm to determine its flexural strength. The fresh geopolymer concrete was used to cast cylinders of size 150x300mm to determine its split tensile strength. The casted cubes, cylinders & prisms. Each specimen was cast in three layers by compacting manually as well as by using vibrating table. Each layer received 25 strokes of compaction by standard compaction rod for concrete, followed by further compaction on the vibrating table. The specimens were removed from the mould immediately after 24 hours since they set in a similar fashion as of conventional concrete. All the specimens were left at room temperature in ambient curing till the date of

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