Volume 6, Issue 1 JUN 2017

IJRAET

MECHANICAL CHARACTERISTIC OF GEOPOLYMER

CONCRETE

Name: CHIGURU NIKHITHA(15641D2005),M.Tech (structural engineering) Vaagdevi college of engineering, bollikunta,Warangal urban

Guide : DR .S. SUNIL PRATHAP REDDY, head of the department of civil engineering, vaagdevi college of engineering, bollikunta ,Warangal urban

ABSTRACT

Concrete is most commonly used construction material. Indian plays 2nd role in production of cement. Portland cement is more produced due to that large amount of co2 is emitted into the atmosphere by production of cement environment is largely polluted. The alternate material for cement is geopolymer. The geopolymer is the formation of flyash and GGBS by adding NAOH(Sodium hydroxide) and sodium silicate based geopolymer with M20 grade concrete. This paper shows on investigating mechanical characteristics of geopolymer concrete with various proportions of replacement of cement with flyash100% ggbs0%,flyash 90% ggbs 10%, flyash 80% ggbs 20%,flyash 70% ggbs 30%, flyash 60% ggbs 40% with concentration of 8M. Indoor, outdoor and oven curing is done. The results show that spilt tensile strength 40% slag has better results. For 60% flyash ggbs 40% gives maximum compressive strength of 50.35 N/mm2

KEY WORDS: Flyash, ground granulated blast furnance slag, geopolymer concrete, sodium hydroxide

INTRODUCTION

Nowadays concrete plays a major role in the human life. It has become in such a way that the

usage of concrete became second only to water around the world. In the last two decades

environmental issues in the concrete industry have been paid a lot of attention, aiming at

reducing the total environmental impact of concrete structures to a minimum, without

compromising on their performance. A lot of different tools have been developed in order to

reduce the environmental impact of concrete.

Ordinary Portland cement (OPC) is the primary binding material used in the preparation of

concrete. As we know cement is the backbone for global infrastructural development. It was

estimated that 7% of the world’s carbon dioxide is attributable to Portland cement industry.

Volume 6, Issue 1 JUN 2017

IJRAET

Because of the significant contribution to the environmental pollution & to the high

consumption of natural resources like limestone etc., we can’t go producing more and more

cement.

Amount of the carbon dioxide released during the manufacture of OPC due to the

calcinations of limestone and combustion of fossil fuel is in the order of one ton for every ton

of OPC produced. In addition, the extent of energy required to produce OPC is only next to

steel and aluminium.

So there is a need to economise the use of cement. One of the practical solutions to

economise cement is to replace with supplementary cementations materials like fly ash, slag

and metakaolin.

MATERIALS

1. Fly ash

In the present experimental work, low calcium, Class F (American Society for Testing and

Materials 2001) dry fly ash obtained from the silos of Ramagundam Thermal Power Plant

was used as the base material.

Fly ash particles are typically spherical ranging in diameter from 1 to 150 microns. The type

of dust collection equipment used largely determines the range of particle size in any given

fly ash. The fly ash from boilers where mechanical collectors are used is coarser than fly ash

from electrostatic precipitators. Fly ash consists of the large part of solid or hollow spherical

particles of siliceous and aluminous gas with small proportions of thin walled, multifaceted

polyhedrousiron content and are irregularly shaped, relatively porous carbon or carbon coated

particles. The fineness of fly ash in many a case is to the same extent as that of Portland

cement. The colour varies from light to dark grey depending upon its carbon contents. The

quality of fly ash varies from source to source and is seldom uniform even for the same

source because of the important factors like the nature and size of coal, the type of

combustion equipment, control of combustion process, mode of fly ash collection etc. the

product from a modern power plant when working on base-load is normally quite consistent

In Indian fly ashes, contents of SiO2, Al2O3 are relatively higher than Fe2O3, SO3. The

crystalline phases were identified as mullite, magnetite, hematite and quartz. The chemical

composition of fly ash and its particle size differ widely for different power plants. This is

Volume 6, Issue 1 JUN 2017

IJRAET

due to different types of coal used, their various treatment and different types adopted for

combustion. Generally, fly ash is differentiated on the basis of degree of fineness and their

carbon contents.

2. GROUND GRANULATED BLASTFURNACE SLAG (GGBS)

In the present experimental work, Ground Granulated Blast Furnace Slag (GGBS) was

obtained from the Thosali Cement Pvt Ltd, Bayyavaram and Andhra Pradesh and used as the

base material

Colour:

GGBS powder is almost white in colour in the dry state as shown in Figure 2. Fresh GGBS

concrete may show mottled green or bluish-green areas on the surface mainly due to the

presence of a small amount of sulphide. This colour fades subsequently after casting, as - 11 -

the sulphide decomposes in air to form hydrogen sulphide (Slag Cement Association, 2005).

Volume 6, Issue 1 JUN 2017

IJRAET

Chemical Composition of GGBS

The basic components of GGBS comprise generally CaO (30%-48%), MgO (28%-45%),

Al2O3 (5%-18%) and SiO2 (1%-18%), which are in principle the same as that of Portland

cement (Wang & Reed, 1995). Other minor components including Fe2O3, MnO, TiO2 and

SO3 are also present in GGBS. The compositions do not change very much so long as the

sources of iron ore, coke and flux are consistent (Bye, 1999).

Fig 1. Extraction of GGBS as Slag from Iron Manufacturing Process

3. Super plasticiser To improve the workability of the fresh geo polymer concrete, a naphthalene Sulphonate

super plasticiser, Conplast SP430 was used in the Experimental study work.

Volume 6, Issue 1 JUN 2017

IJRAET

Alkaline liquids

In the present study we have used a combination of sodium hydroxide (NaOH) and sodium

silicate (Na2SiO3) solutions. The sodium hydroxide solids were either a technical grade in

flakes form (3 mm), 98% purity, and obtained from National scientific company,

Vijayawada, or a commercial grade in pellets form with 97% purity, obtained from

National Scientific, Vijayawada.

The sodium hydroxide (NaOH) solution was prepared by dissolving either the flakes or the

pellets in distil water. The mass of NaOH solids in a solution varied depending on the

concentration of the solution expressed in terms of molar, M. Molar concentration or

molarities is most commonly in units of moles of solute per litre of solution. For use in

broader applications, it is defined as amount of solute per unit volume of solution. For

instance, NaOH solution with a concentration of 8M consisted of 8x40 = 320 grams of NaOH

solids (in flake or pellet form) per litre of the solution, where 40 is the molecular weight of

NaOH. The mass of NaOH solids was measured as 262 grams per kg of NaOH solution of

8M concentration. Sodiummeta silicate (Na2O3.Si.9H2O)solution with a concentration of 8M

consisted of 8 x 282.40=2259.2 grams of sodium meta silicate solids per litre of the solution,

where 284.20 is the molecular weight of sodium Meta silicate

Volume 6, Issue 1 JUN 2017

IJRAET

4. Aggregates:

In the present study locally available aggregate were used. Coarse aggregates were obtained in crushed form and majority of the particles were of granite-type. The fine aggregate was obtained from the sand dunes in uncrushed form.

Four different combinations of coarse aggregate were used in the present study. They are 20mm, 16 mm, 12.5mm and 10mm aggregates were used. In total coarse aggregate

20 mm aggregate is 30%,

16 mm aggregates is 20%,

12.5 mm aggregates is 25%,

10 mm aggregates is 25%.

The coarse aggregates are taken in saturated surface dry condition (SSD).

Mix design:

a) Design stipulations: 1) Characteristic compressive strength required in the field at 28 days is

20Mpa 2) Max size of aggregate = 20mm(angular) 3) Type of exposure = mild

b) Test data for materials: 1) Specific gravity of fly-ash = 2.63

Coarse aggregate = 2.6

Fine aggregate = 2.6

2) Water absorption; Coarse aggregate = nill

Fine aggregate = nill

3) Free( surface) moisture;

Coarse aggregate - nil

Fine aggregate – nil

Super plasticiser = 1.5% of fly ash content

Volume 6, Issue 1 JUN 2017

IJRAET

Mixing

It was found that the fresh fly ash-GGBS based geo polymer concrete was dark in colour (due to the dark colour of the fly ash), and was cohesive. The amount of water in the mixture played an important role on the behaviour of fresh concrete. When the mixing time was long, mixtures with high water content bleed and segregation of aggregates and the paste occurred. This phenomenon was usually followed by low compressive strength of hardened concrete.

It is preferable to mix the sodium Meta silicate solution and the sodium hydroxide solution together at least one day before adding the liquid to the solid constituents. Compaction of fresh concrete in cubes & cylinders steel moulds was achieved by applying sixty manual strokes per layer in three equal layers, followed by compaction on a vibration table for ten seconds. After casting, the specimens were covered using vacuum.

Fig 4 Mixing of Constituent Materials of Geopolymer Concrete

From the preliminary work, it was decided to observe the following standard process of mixing in all further studies:

• Mix sodium hydroxide solution and sodium Meta silicate solution together at least one day prior to adding the liquid to the dry materials.

• Mix all dry materials in the pan mixer for about three minutes. Add the liquid component of the mixture at the end of dry mixing, and continue the wet mixing for another four minutes.

Volume 6, Issue 1 JUN 2017

IJRAET

Workability:

To improve the workability of low calcium fly ash- GGBS based geo polymer concrete we added a naphthalene sulphonate super plasticiser (CONPLAST SP 430) of 2% of Binder content

Rest Period:

After casting, the specimens are rested for one day before going to curing process for better compressive strengths.

Curing

The demoulded specimens were left in sunlight until tested without any special curing regime. For each set of parameter, 3cubes were cast, for determining 7days,28 days strengths. After the rest period of 24 hours the cubes are kept in Sun for Curing.

Detention period

After the curing process, the cubes are taken out and cooled at room temperature for 1 day before test.

Fig 2 Super plasticizer Being Added to the Geopolymer Concrete

TEST RESULTS FOR GEOPLOYMER CONCRETE:

Molarity=8M

Design mix = 1:2.15:3.03:0.6

Volume 6, Issue 1 JUN 2017

IJRAET

Table 1.1 Details of Mechanical Charcteristics of Geo Polymer Concrete for Different Curing

Fig 3 Compressive strength Vs % of replacement of binder in indoor curing

For 7 days and 28 days

100F 90F10G 80F20G 70F30G 60F40G

Series1 4.44 12.88 16.72 19.55 22.76

Series2 10.42 13.36 18.45 20.82 27.45

0

5

10

15

20

25

30

Aver

age

Com

pres

sive

Str

engt

h (M

Pa)

Variation of Fly ash and GGBS Content

Compressive Strength for indoor curing

S.No compressive strength N/mm2

Flexural strength N/mm2 Split tensile strength N/mm2

indoor Outdoor oven indoor Outdoor Oven

indoor Outdoor Oven

A1F100G0 10.42 12.86 17.8 1.2 1.5 1.7 1.130 1.32 1.45

A2F90G10 13.36 15.24 20.3 1.5 1.8 1.98 1.160 1.362 1.67

A3F80G20 18.45 22.36 25.40 1.8 2.1 2.3 1.25 1.485 2.32

A4F70G30 20.82 25.68 26.95 2.1 2.4 2.7 1.27 1.8 2.56

A5F60G40 27.45 44.81 50.35 2.5 2.9 3.1 1.69 2.06 3.44

Volume 6, Issue 1 JUN 2017

IJRAET

Fig 4 Compressive strength Vs % of replacement of binder in sun curing

For 7 days and 28 days

Fig 5 Compressive strength Vs % of replacement of binder in oven curing

For 7 days and 28 days

100F 90F10G 80F20G 70F30G 60F40G

Series1 7.33 13.77 20.88 24.44 36.19

Series2 12.86 15.24 22.36 25.68 44.81

05

101520253035404550

Aver

age

Com

pres

sive

Str

engt

h (M

Pa)

Variation of Fly ash and GGBS Content

Compressive Strength for outdoor curing

100F 90F10G 80F20G 70F30G 60F40G

Series1 12.6 16.8 23.4 25.7 45.33

Series2 17.8 20.3 25.4 26.95 50.35

0

10

20

30

40

50

60

Aver

age

Com

pres

sive

Str

engt

h (M

Pa)

Variation of Fly ash and GGBS Content

Compressive Strength for Oven curing

Volume 6, Issue 1 JUN 2017

IJRAET

Fig 6 Split Tensile strength Vs % of replacement of binder in indoor curing

Fig 7 Split Tensile strength Vs % of replacement of binder in outdoor curing

1.13 1.161.25 1.27

1.69

00.20.40.60.8

11.21.41.61.8

100F 90F10G 80F20G 70F30G 60F40G

Aver

age

Split

Ten

sile

Stre

ngth

Variation of Fly ash and GGBS

Split Tensile Strength for indoor curing

1.32 1.3621.485

1.82.06

0

0.5

1

1.5

2

2.5

100F 90F10G 80F20G 70F30G 60F40G

Aver

age

Split

Ten

sile

Stre

ngth

Variation of Fly ash and GGBS

Split Tensile Strength for Outdoor curing

Volume 6, Issue 1 JUN 2017

IJRAET

Fig 8 Split Tensile strength Vs % of replacement of binder in oven curing

DISCUSSIONS:

From Table 1.1 and Figs 3 -8 shows the details of compressive and split tensile strength results for different variations of Fly ash and GGBS.

i. It is observed that specimens cured in oven has higher compressive and split tensile strength when compared with

Indoor cured and sun cured specimens.

ii. It is observed that by replacement of Fly ash with GGBS upto 40% increases the performance of the geo polymer

concrete.

iii. Over all it is concluded that the specimens with 60 % Fly ash and 40% GGBS cured in oven had given more

mechanical strengths when compared with other variations and different curing methods.

Conclusions 1. Due to the constant increase in the percentage of slag content there was a constant increase in compressive strength was observed.

2. Split tensile strength and modulus of rupture of mix (40% replacement of slag) concrete given better result when compared with all the mixes.

3. The necessity of heat curing of concrete was eliminated by incorporating GGBS and fly ash in a concrete mix

1.451.67

2.322.56

3.44

0

0.5

1

1.5

2

2.5

3

3.5

4

100F 90F10G 80F20G 70F30G 60F40G

Aver

age S

plit

Tens

ile S

tren

gth

Variation of Fly ash and GGBS

Split Tensile Strength for Oven curing

Volume 6, Issue 1 JUN 2017

IJRAET

4. It was observed that the mix of 60% fly ash and 40% GGBS gave maximum compressive strength of 50.35 N/mm2

FURTHER SCOPE OF STUDY

1. For a particular ܌ܑܝܙܑܔ ܍ܖܑܔ܉ܓܔۯܐܛ܉ ܡܔ

ratio, the strength variations may be studied by varying

the rest period from 1 day to 4 days.

2. Further investigation may be done by increasing the molarities of NaOH (for example

12, 14, 16). While maintaining the molarities of sodium Meta silicate at 8 only.

3. Further investigation may also be made by replacing the fly ash with pozzolanic

materials like Metakaolin & G.G.B.S.

References

1) ACI Committee 232 (2004). Use of Fly Ash in Concrete. Farmington Hills,

Michigan, USA, American Concrete Institute: 41.

2) ACI Committee 363 (1992). State of the Art Report on High-Strength Concrete,

American Concrete Institute, Detroit, USA.

3) Aitcin, P. C. and P. K. Mehta (1990). "Effect of Coarse-Aggregate Characteristics on

Mechanical Properties of High-Strength Concrete." ACI Materials Journal87(2): 103-107.

4) American Society for Testing and Materials (2001). Standard Specification for Coal

Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete.

5) Balaguru, P. (1998). Geopolymer for Protective Coating of Transportation

Infrastructures, CAIT/Rutgers: 23.