the effects of specimen size on high-performance concrete

8/13/2019 The Effects of Specimen Size on High-Performance Concrete

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The Effects of Specimen Size on High-

Performance Concrete with BottomAsh and Slag for Rigid Pavements


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Introduction


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Demand for pavement to be opened to trafficimmediately.

High-performance concrete (HPC) offers solution.

Materials for HPC are expensive.

The use of alternative materials (bottom ash andslag) which are environmentally friendly and relatively

inexpensive.


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Objectives

Main Objective

The main objective of this study is to investigate the

influence of using steel slag and bottom ash as partialreplacement for coarse and fine aggregates on its physical

and mechanical properties on high-performance concrete

for rigid pavement.


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Specific Objectives

Specifically, this study aims:

To verify the physical properties of high-performance concrete

with steel slag and bottom ash as partial replacement for fine

aggregates.

To verify the mechanical property of high-performance concrete

with steel slag and bottom ash as partial replacement for fine

aggregates.

To determine the optimum mix design in terms of percentage

replacement of bottom ash as fine aggregates.


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Scope and LimitationMaterials for HPC are limited to the following:

Cement (Type III) = High-early strength cement

Coarse aggregates = MSA (19 mm or )

Fine Aggregate = White natural sand

steel slag

Bottom Ash = from Calaca, Batangas

5 Mix Proportions for HPC with 0%, 20%, 30%, 40% and50% bottom ash as partial replacement for fine aggregate

while steel slag will be fixed at 50% of the required coarse

aggregate in the mix.


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Scope and Limitation

The target slump for concrete mixes will be 75 mm to100 mm (3to 4)

Determination of Physical Properties of HPC is limited

to its consistency (slump) and unit weight.

Determination of Mechanical Property is limited to

flexural strength test using center-point loading (at 7, 14,28, 56 days).


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Review of Related Literature


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The research by P. Aggarwal, Y. Aggarwal, S.M. Gupta

presents the experimental investigations carried out to

study the effect of use of bottom ash as a replacement

of fine aggregates.

The strength development for various percentages (0-

50%) replacement of fine aggregates with bottom ash

can easily be equated to the strength development ofnormal concrete at various ages.


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From an experimental investigation, it was generally

observed that the flexural behavior of steel slag

concrete is comparable to that of other types of natural

aggregate concretes, and this investigation givesencouraging results for steel slag to be used as coarse

aggregate in the production of structural concrete

(Saaid I. Zaki, 2004).


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Methodology


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oMaterials

Cement (Type III)

Bottom AshFrom Calaca, Batangas


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steel slag - which has a nominal MSA of 19 mm

(3/4 inch)

Fine AggregateNatural white sand from river

source

Coarse Aggregate100% crushed aggregate

which has a nominal MSA of 19 mm (3/4 inch)


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oMaking and Curing Test Specimens

AASHTO T23: Making and Curing Concrete Test

Specimens in the Field

oDetermination of Physical Properties of HPC

AASHTO T121: Determination of Unit Weight, Yield,

and Air Content (Gravimetric) of Concrete


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AASHTO T 177 and ASTM C 293: Flexural Strength of Concrete

(Using Simple Beam with Center-Point Loading)

oDetermination of Flexural Strength of Concrete

2

2

3

bd

PlR

R= modulus of rupture, MPa (psi),

P= maximum applied load indicated

by the testing machine, (N or lbf),

l= span length, mm (in.),b= average width of specimen, mm

(in.), and

d= average depth of specimen, mm

(in.)


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Concrete Mix Proportions (per 0.18 cu.m.)

Mix No. %

Replace

ment of

Bottom

Ash

Cement

(kg)

Coarse

Aggrega

te (kg)

Slag (kg) Fine

Aggrega

te (kg)

Bottom

Ash (kg)

Water

(kg)

1 0 90 90 90 135 0 36

2 20 90 90 90 108 27 36

3 30 90 90 90 94.5 40.5 36

4 40 90 90 90 81 54 36

5 50 90 90 90 67.5 67.5 36


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oNumber of Specimens

Mix No. 7 Days 14 Days 28 Days 56 Days Total

1 3 3 3 3 12

2 3 3 3 3 12

3 3 3 3 3 12

4 3 3 3 3 12

5 3 3 3 3 12

Total: 60


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Finished Product

Slump Determination


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Preparation of Specimen

Curing of Specimen

Determination of Density


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Testing of Specimen for Flexure

Specimen at Failure


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Results and Discussion


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Slump (Consistency)

0

20

40

60

80

100

120

140

160

0.00% 20.00% 30.00% 40.00% 50.00%

Slump(mm)

Percentage Replacement of Bottom Ash

Slump Measurement (mm)


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Flexural Strength Result

Mix Design Flexural Strength (MPa)

7 Days 14 Days 28 Days 56 Days

1 (0 % B. A.) 5.850 6.580 6.853 7.217

2 (20 % B. A.) 5.192 5.231 6.092 6.853

3 (30 % B. A.) 4.786 5.245 5.824 6.183

4 (40 % B. A.) 6.659 6.774 6.972 7.910

5 (50 % B. A.) 6.249 6.484 7.198 7.763


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Flexural Strength Result

0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

7 Days 14 Days 28 Days 56 Days

MPa

Testing Days

Flexural Strength

0%

20%

30%

40%

50%


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The density or unit weight of concreteincreases as the percentage of bottom ash

as replacement increases. This is due to

the fact that the specific gravity of bottomash is higher than the specific gravity of

ordinary fine aggregate.


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All the design mixes including the control

mix passed the required flexural strength of4.1 MPa after 14 days. The required flexural

strength was achieved as early as 7 days

because of the use of high-early strengthcement. Mix design 4 (40 % bottom ash) has

the highest flexural strength while mix design

3 (30 % bottom ash) has the lowest lowest

flexural strength due to a higher slump of themix compared to the other mixes.


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The optimum design mix based from theresults is mix design 4 (40 % bottom ash)

since this mix design has the highest

flexural strength results and increasingfurther the percentage of bottom ash

replacement above 40 % resulted indecrease of flexural strength.


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Recommendation


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Since this study used a fixed percentage of

steel slag for the different mixes for reason of

economy, the researchers recommend for future

studies the use of different percentages of steel

slag in the mix.


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The researchers also recommends for future

research works the use of different percentages

of bottom ash replacement to fine aggregatesabove 50% to validate our conclusion that the

flexural strength results started to decrease

above 40% bottom ash replacement.


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THANKSFOR

LISTENING!


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Introduction

High-Performance Concrete (HPC)

High-strength concrete

High-early strength concrete

Materials for HPC

Type III Cement (High-Early Strength)

Bottom AshSteel Slag

Coarse Aggregate

Fine Aggregate


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steel Slag

B A h

the effects of specimen size on high-performance concrete

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