Effect of Different Aspect Ratio Steel Fiber in Slag based Geopolymer Concrete

Effect of Different Aspect Ratio Steel Fiber in Slag based Geopolymer Concrete

Abhijit Solanki

Civil Engineering Department

Chhotubhai Gopalbhai Patel Institute of Technology Bardoli, Gujarat, India.

Payal Patel

Disha Parmar

Civil Engineering Department

Chhotubhai Gopalbhai Patel Institute of Technology Bardoli, Gujarat, India.

Civil Engineering Department

Chhotubhai Gopalbhai Patel Institute of Technology Bardoli, Gujarat, India.

Abstract Global warming is one of the most pronounced terms in this present century. Five to eight percent of the worlds manmade Greenhouse gas emissions are from the Cement industry itself. Geopolymers are showing great potential and several researchers have critically examined the various aspects of their ability as binder system. Thus Geopolymer based Concrete is highly environment friendly and the same time it can be made as high performance concrete. The mixes of binder is combined alkaline solution of sodium hydroxide and sodium silicate with ground granulated blast furnace slag. So in this study an attempt is made to know the strength of geopolymer concrete by adding hooked end steel fiber in the mix . The acid attack of sulfuric acid is studied to check the durability properties of geopolymer concrete and change in mass of concrete. It has been concluded that the steel fiber used in geopolymer concrete upto 0.7% is improved compressive strength and flexural strength. Average 13% increases in compressive strength when added steel fiber in geopolymer concrete with different proportion and 8% increases in compressive strength in normal geopolymer concrete without steel fiber. The cost savings in production of M25 grade GPC is 2.15% compared to M25 grade of OPC which leads to maintain high strength element.

Keywords Ground Granulated Blast Furnace Slag, Alkaline Liquid, Steel Fiber, Compressive Strength, Acid Attack.

1. INTRODUCTION

   The term geopolymer was introduced by Davidovits to represent the mineral polymers resulting from geochemistry. The polymerization process involves a chemical reaction under highly alkaline conditions on Al- Si minerals, yielding polymeric Si-O-Al-O bonds. Poly(sialates) are chain and ring polymers with Si4+ and Al3+ in IV-fold coordination with oxygen and range from amorphous to semi crystalline with the empirical

   Formula as described by1 ,

   Mn( – (SiO2)z – AlO2)n : wH2O

   Where M is the alkaline element, the symbol indicates the presence of a Bond, z is 1,2, or 3, and n is the degree of polymerization. Exact Mechanism by which geopolymer setting and hardening occur is not yet clear and is under

   research. The reaction of fly-ash with an aqueous solution contains NaOH and Na2SiO3 in their mass ratio, results in a material with 3D polymeric chain and ring structure consisting of Si-O-Al-O bonds. The schematic formation of geo-polymer material can be shown as described by Equation A and B and the end product of this process is an amorphous polymeric material Geopolymer concrete is a type of concrete which does not utilize any Portland cement in its production but, the binder is produced by the reaction of an alkaline liquid with a source material that is rich in silica and alumina.

2. CONSTITUENT MATERIALS OF GEOPOLYMER

   CONCRETE

   Geopolymeric source materials (GSMs) are rich in silica and alumina, which could be natural minerals (such as kaolinite, clays, etc) or industrial by-products (such as fly ash, silica fume, slag, rice-husk ash etc). – Alkaline Activator Solution (AAS) based on alkali metals (commonly Sodium or Potassium) based. The most common AAS is a combination of alkali hydroxide (NaOH, KOH) and alkali silicate (Sodium or potassium silicate) minerals containing reactive oxides of silicon and aluminium can be activated by suitably formulated highly alkaline liquid to obtain inorganic polymeric binding material [Sindhunata, 2006]. The following are the constituents for ambient curing.

   • Ground Granulated Blast Furnace Slag (GGBS),

   • Fine aggregates (in the form of river sand),

   • Coarse aggregates (in the form of crushed granite stone),

   • Alkaline Activator Solution (combination of solutions of alkali silicates and hydroxides, besides distilled water)

     A. Basic mixture proportions

     No standard mix design approaches are yet available for GPCs. D.Hardjito, et al (2004), showed that the geopolymer paste binds the coarse aggregates, fine aggregates and other un-reacted materials together to form the GPC, and usual concrete technology methods to produce GPC mixes can be often employed Mixture proportions are characterized by an alkaline liquid to

     GGBS by mass of 0.35 and aggregate to total mass proportion of approximately 75% with the nominal strengths. The Alkaline liquid to GGBS ratio should be taken 0.4. The silicon and the aluminium in the GGBS are activated by a combination of sodium hydroxide and sodium silicate. Below table shows the mix proportion of concrete (kg/m3) which is carried out for research work. The steel fiber proportion should be taken 0.5% and 0.7% with different aspect ratio like 40, 50 and 60.

     Steel fiber = 0.5 % of GGBS = 1.97 kg/m3 Steel fiber = 0.7 % of GGBS = 2.76 kg/m3

     Table 1 mixture proportions

     Ingredients		Units	GPC
     GGBS		kg/m3	394
     Fine Aggregate		kg/m3	647
     Coarse Aggregate	20mm	kg/m3	721
     	10mm	kg/m3	480
     Sodiun Silicate		kg/m3	113
     Sodium Hydroxide		kg/m3	46
     Extra water		kg/m3	59.1

3. FRESH GEOPOLYMER CONCRETE

   Fresh geopolymer concrete has been reported to be highly viscous and cohesive with low workability fresh geopolymer concrete became stiff in a short time, thus implying a short initial setting time. To improve the workability of mortar, superplasticiser or extra water can be added. As such, extra water gives higher workability than addition of superplasticiser upt0 15% with GGBS. The density of the geopolymer concrete was 2380 ±60 kg/m3.

4. FACTORS AFFECTING STRENGTH OF

   GEOPOLYMERS

   In the table the other mix proportion should be same. There should be variables in parametric study.

   Table 2 mixture proportions of parametric study

   Mix	NaOH (kg)	Na2SiO3 (kg)	Extra Water (kg)	Compressive strength (N/mm2)
   				7 days	14 days
   1	52.5	106	39.4	14.39	19.34
   2	52.5	106	59.1	15.25	22.91
   3	46	113	59.1	16.39	25.55
   4	46	113	39.4	15.58	23.66

   1. Sodium silicate to Sodium hydroxide ratio

      The efect of variation in sodium silicate to sodium hydroxide by mass on compressive strength of concrete has been observed by comparing results of M25 grade slag based geopolymer. On compressive strength For Na2SiO3 to NaOH ratio of 2.5, geopolymer concrete shows higher compressive strength. The Na2SiO3 to NaOH ratio of 2.0 has been able to reduction in compressive strength as compared to that of ratio 2.5.

      compressive strength

      40

      35

      30

      25

      20

      15

      10

      5

      0

      Mix 3 Mix 4

      Mix Name

      Compressive

      Strength (N/mm2)

      Figure 1 Compressive strength of Sodium silicate to Sodium hydroxide ratio

   2. Water to geopolymer solids ratio.

   Compressive

   Strength (N/mm2)

   Water in geopolymer concrete mix does not take any part in the chemical reaction. In opc concrete, water in the mix chemically reacts with the cement to produce a Paste that binds the aggregates. The chemical reaction that occurs in geopolymers Produces water that is eventually expelled from the binder. It has been observed that Additional water content in the geopolymer concrete mixture affected the properties of concrete in the fresh state as well as in the hardened state. In case of slag based geopolymer concrete water content is more require as compare to the fly ash based geopolymer concrete. Thus, 15% water is used for proper workability. The effect of water content of mix on compressive strength of geopolymer concrete can be observed by comparing results of M25 grade slag based geopolymer concrete. The concrete mixes have been cast using additional water of 15% by mass of slag.

   compressive strength

   40

   35

   30

   25

   20

   15

   10

   5

   0

   Mix 2

   Mix 3

   Mix Name

   Figure 2 Compressive strength of Water to geopolymer solids ratio

5. RESULT AND ANALYSIS GPC1,GPC2,GPC3 defines the 0.5% usage of steel fiber with Aspect Ratio 40,50,60 respectively. GPC4,GPC5,GPC6 defines the 0.7% usage of steel fiber with Aspect Ratio 40,50,60 respectively.

   And GPC7 defines the normal geopolymer concrete without steel fiber.

   1. Mechanical Properties

      In comparison between 28 days and 56 days, Average 13% increases in compressive strength when added steel fiber in geopolymer concrete with different proportion and 8% increases in compressive strength in normal geopolymer concrete without steel fiber.

      Table 3 Compressive Strength result

      Compressive Strength (N/mm2) At 28 Days
      GPC1	GPC2	GPC3	GPC4	GPC5	GPC6	GPC7
      29.62	32.03	30.66	30.58	33.59	31.60	29.42
      Compressive Strength (N/mm2) At 56 Days
      GPC1	GPC2	GPC3	GPC4	GPC5	GPC6	GPC7
      34.05	36.97	34.90	35.89	38.94	36.95	32.01

      Slag based geopolymer concrte with 0.7% steel fiber usage of 50 aspect ratio gives better results in terms of compressive strength as compare to other two aspect ratio and 9% increase in compressive strength.

      Slag based geopolymer concrte with 0.5% steel fiber usage of 50 Aspect ratio gives better results in terms of compressive strength as compare to other two Aspect ratio and 7% increase in compressive strength.

      But 0.7% steel fiber usage of 50 Aspect Ratio gives the better result than the 0.5% steel fiber usage of 50 Aspect Ratio in terms of compressive strength.

      Compressive Strength

      (N/mm2)

      Comparison of normal geopolymer concrete and steel fiber usage geopolymer concrete, there should be 12% compressive strength increases.

      45

      40

      35

      30

      25

      20

      15

      10

      5

      0

      28 days

      56 days

      Mix Name

      Figure 3 comparison of compressive strength result for all mixes

   2. Durability Properties

   It should be observed that there should be changed in mass of cube after acid attack.

   The average density of slag based geopolymer concrete is changed after acid attack.

   The compressive strength of the cube after acid attack should be decreased. 11% of compressive strength decreases in 0.5% usage of steel fiber and 9% compressive strength decreases in 0.7 % usage of steel fiber in slag based geopolymer concrete after 28 days of acid attack.

   Normal Geopolymer concrete (without steel fiber) has decreases 19% the compressive strength more compared to steel fiber usage geopolymer concrete cube.

   Table 4 Compressive Strength result after acid attack

   Compressive Strength (N/mm2) At 28 Days
   GPC1	GPC2	GPC3	GPC4	GPC5	GPC6	GPC7
   29.62	32.03	30.66	30.58	33.59	31.60	29.42
   Compressive Strength (N/mm2) At 56 Days (After Acid Attack)
   GPC1	GPC2	GPC3	GPC4	GPC5	GPC6	GPC7
   27.22	30.79	28.41	28.58	31.51	29.33	25.44

   40

   28 days

   56 days(after acid attack)

   35

   30

   25

   20

   15

   10

   5

   0

   Mix Name

   Compressive Strength

   (N/mm2)

   Figure 4 comparison of compressive strength result for all mixes after acid attack

6. CONCLUSION

   The sodium silicate to sodium hydroxide ratio by mass equal to ratio 2.5 gives higher results as compared to ratio

   2.0 for slag based geopolymer concrete. Compressive strength of slag based geopolymer concrete decreases with increase the water content. In case of slag 15 % water by mass of slag is require. The slump value of the fresh geopolymer concrete increases with the increase of extra water added to the mixture. The average density of slag

   based geopolymer concrete is similar to that of control concrete.0.7% steel fiber usage of 50 Aspect Ratio gives the better result than the 0.5% steel fiber usage of 50 Aspect Ratio in terms of compressive strength. In comparison between 28 days and 56 days, Average 13% increases in compressive strength when added steel fiber in geopolymer concrete with different proportion and 8% increases in compressive strength in normal geopolymer concrete without steel fiber. Normal Geopolymer concrete (without steel fiber) has decreases 19% the compressive strength more compared to steel fiber usage geopolymer concrete cube after acid attack. The weight loss of Geopolymer concrete is very low when geopolymer concrete mixes are exposed to 5% acid attack. Average 1.4% weight loss observed after acid attack. . The cost savings in production of M25 grade GPC is 2.15% compared to M25 grade of OPC which leads to maintain high strength element.

7. ACKNOWLEDGEMENT

   I have taken efforts in this paper. However, it would not have been possible without the kind support of Prof. Disha Parmar and help of Prof. Payal Patel. I would like to extend my sincere thanks to all of them. I am highly indebted for their guidance and constant supervision as well as for providing necessary information. I would like to express my gratitude towards my parents for giving encouragement which helped me a lot. My thanks and appreciations also go to my college (CGPIT) for providing continuous support.

8. REFERENCES

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