CONCRETE FORMULA, USING
POZZOLANA/PORTLAND CEMENT FOR
SUPERSTRUCTURES IN NUCLEAR
ENGINEERING
By;
Bright J. A. Y. Sogbey: - 2nd Year M. Phil Student
Department of Nuclear Engineering
University of Ghana
1
Paper Presentation; Ghana Nuclear Society Annual Conference : November, 2010
OUTLINE OF PRESENTATION
Abstract
Introduction
Questions
Literature review
Experimental Work
Methods of calculation
Preliminary Results And Discussion
Conclusion
Acknowledgments
References
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ABSTRACT
This paper presents an overview of preliminary results of
structural strength analysis of concrete made from a mixture of
Pozzolana and ordinary Portland cement (OPC) at varied ratios
(0%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 100%), that
confirmed the above title.
Destructive tests (Compression tests) performed so far have
shown that concrete of Pozzo/Port cement at a particular ratio has
more compressive strength than that of the OPC at ages seven (7)
days, Fourteen (14) days andTwenty-eight (28) days.
Further tests, including shielding, ultrasonic and flexure, for its
suitability for nuclear engineering applications are underway.
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INTRODUCTION
Today it is possible to have an alternative building material to
the ordinary Portland cement (OPC), which is cheaper in
cost.
This material (Pozzolana) when used in combination with
4
Portland cement at a particular ratio can exhibit strength
comparable to that of pure Portland cement, thereby
reducing material cost.
Pozzolana was named after Pozzuoli (or Pozzoli), a place
where variety of volcanic stuff was found near the Bay of
Naples in Rome.
Portland cement, on the other hand, was named after the Isle
of Portland in England when engineer Joseph Aspdin
patented the product in 1824.
INTROD...
A typical concrete mixture will consist of Portland cement,
water, aggregates, and possibly admixtures.
Curing the concrete in the correct conditions is essential to
obtain the desired results.
An ideal environment for concrete curing is one in which the
concrete is kept hydrated until the process of hydration is
complete.
Good hydration will decrease the permeability of the
concrete and will ultimately increase the strength of the
concrete.
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QUESTIONS
Can Pozzolana cement, which is cheaper than the Portland
cement be used all alone in construction?
If it can be used alone, what is its strength?
If it can be mixed with the Portland cement, then at what
ratio or percentage can it exhibit maximum strength?
What are the radiological shielding properties of the
Portland/Pozzolanic cement?
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LITERATURE REVIEW
PORTLAND CEMENT
It is a predetermined and homogeneous mixture of materials
principally containing :
lime (CaO) and silica (SiO2) with a smaller proportion of
Alumina (Al2O3) and iron oxide (Fe2O2).
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LITERATURE REVIEW...
POZZOLANA
It is an essentially siliceous material possessing little or no
cementitious properties.
In finely divided form and in the presence of water, it reacts
with calcium hydroxide at ambient temperature to form
compounds possessing cementitious properties.
The term Pozzolana includes calcined clay, fly ash and slag.
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LITERATURE REVIEW...
CONCRETE
Concrete is an artificial building material made of the
mixture of hydraulic binding material, aggregate, and water.
Typical strengths range from 15 MPa to 50 MPa.
For simple driveways, footpaths and other domestic work,
typical strengths are in the order of 15 MPa to 25 MPa.
The structural concrete required for bridge deck slabs
should be about 32 MPa, columns and superstructures 40 or
50 MPa and concrete pavements about 30 MPa.
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CHEMICAL COMPOSITION OF PORTLAND AND POZZOLANA CEMENT (%wt)
10
Compound/Element
Pozzolana
Portland
SiO
46.25
27.43
Al2O3
17.34
5.40
Fe2O3
10.26
3.48
CaO
10.18
53.71
MgO
2.90
1.41
K2O
1.64
0.92
Na2O
3.64
0.16
SO3
0.80
2.59
Cl-
0.01
0.004
Source: SBEIDCO 1st Int. Conference
Table 1
EXPERIMENTAL WORK
Materials used
The Pozzolana is obtained from BRRI-CSIR, Kumasi.
The OPC used as reference is from the cement factory
(GHACEM).
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EQUIPMENT
Compression Testing Machine
Flexural Testing Machine
Ultrasonic Testing Machine
Gamma Testing Machine
Electronic Balance
Measuring cylinder
Electronic vibrator
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TESTS
Compression Test
Flexural Test
Ultrasonic Test
Gamma Test
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PORTLAND/POZZOLANA COMPOSITION
(RATIOS)
Sample
(S)
Port
land
Pozzola
na
14
S1
S2
S3
Contro
l
80%
70%
0%
20%
30%
S4 S5
S6
S7
S8
50%
40%
30%
20%
0%
40% 50%
60%
70%
80%
Contro
l
60%
S9
Table 2
Variables and tests
The variables considered in the experimental study were:
Mineral(Pozzolana) addition percentage: 0%, 20%, 30%,
40%, 50%, 60%, 70%, 80%, and 100%
Curing temperature: 20 ±1°C;
The pastes were elaborated in cubic moulds of 15 x 15 x 15
cm.
The compressive strengths were tested at determined ages
(7, 14, and 28 days).
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METHODS OF CALCULATION
Compressive stress (δ) =
16
(1)
CALCULATIONS...
Flexural str (δfs) =
for a circular cross section (2)
for rectangular cross section (3)
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CALCULATIONS...
Where
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F= applied force
L= distance between support points
R= radius of cylindrical concrete
b= breadth of rectangular concrete
d = depth of rectangular concrete
CALCULATIONS...
ULTRASONIC TEST
E d=
(4)
(5)
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CALCULATIONS...
Where,
v = the longitudinal pulse velocity,
L = the path length,
T = the time taken by the pulse to traverse that length.
ρ= density of the concrete
Ed= dynamic Modulus of elasticity.
Ѵ= Poisson ratio
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CALCULATIONS...
RADIOLOGICAL TEST (GAMMA RAY)
I = Ioe-µx
(6)
Where
I = transmitted photon intensity
Io = incident photon intensity
µ = attenuation coefficient
x = thickness of object
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PRELIMINARY RESULTS AND DISCUSSION
Seven (7) Days Compressive Strength
Pozzolana Percentage (%)
Compressive Strength (MPa)
S1 (Control) Portland
16.89
S2 (20% Pozzolana)
19.26
S3 (30% Pozzolana)
12.45
S4 (40% Pozzolana)
11.85
S5 (50% Pozzolana)
8.27
S6 (60% Pozzolana)
5.18
S7 (70% Pozzolana)
4.15
S8 (80% Pozzolana)
2.67
S9 Pozzolana
0
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Table 3
Graph of Compressive Strength (MPa
(MPa)
MPa)
vs. Pozzolana Percentage (%) [7Days]
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Figure1
Fourteen Days (14) Compressive
Strength
Pozzolana Percentage (%)
Compressive Strength (MPa)
S1 (Control) Portland
18.37
S2 (20% Pozzolana)
24.89
S3 (30% Pozzolana)
14.00
S4 (40% Pozzolana)
13.63
S5 (50% Pozzolana)
10.67
S6 (60% Pozzolana)
8.59
S7 (70% Pozzolana)
6.96
S8 (80% Pozzolana)
4.56
S9 (Control) Pozzolana
0
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Table 4
Graph of Compressive Strength (MPa
(MPa)
MPa)
vs. Pozzolana Percentage (%) [14Days]
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Figure 2
TwentyTwenty-eight Days (28)Compressive
Strength
Pozzolana Percentage (%)
S1 (Control) Portland
S2 (20% Pozzolana)
S3 (30% Pozzolana)
S4 (40% Pozzolana)
S5 (50% Pozzolana)
S6 (60% Pozzolana)
S7 (70% Pozzolana)
S8 (80% Pozzolana)
S9 (Control) Pozzolana
Compressive Strength (MPa)
28.44
31.70
24.00
20.63
17.67
14.59
11.96
8.56
0
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Table 5
Graph of Compressive Strength (MPa
(MPa)
MPa) vs.
Pozzolana Percentage (%) [28 Days]
Compressive Strength (MPa)
35
30
25
20
15
10
5
0
Compressive Strength
(MPa)
Figure 3
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EVOLUTION OF COMPRESSIVE STRENGTHS
AT 7, 14,AND 28 DAYS OF AGING
35
30
25
20
15
10
5
0
28
Compressive Strength
(MPa) at 7 Days
Compressive Strength
(MPa) at 14 Days
Compressive Strength
(MPa) at 28 Days
DISCUSSION
Water demand
It has been observed that the Pozzolana needs more water to
have a normal consistency than an OPC.
On the other hand, the increase of Pozzolana percentage
increases the water demand of mix cement paste.
This increase of water demand may be essentially due to the
(Ca/Si) ratio; this ratio decreases with increase of Pozzolana
percentage (rich in silica dioxide).
The quantity of water necessary for all compound cement
pastes studied is higher than the quantity demanded by OPC
which has a higher (Ca/Si) ratio.
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DISCUSSION...
Mechanical behavior
The analysis of the compressive strength evolution of the
studied cement pastes indicates that since the early age of 7
days ‘fig.4’, pastes with 20% of Pozzolana, give resulting
strengths higher than the paste of reference (control).
Whereas, the compressive strengths developed by the paste
with 30 % or more of Pozzolana are still lower than those of
the paste of reference (control).
The trend continues from 14 until 28 days ‘figs.5 and
6’, which signifies that the Pozzolana has accelerated the
kinetic of the cement paste hydration.
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CONCLUSION
The preliminary conclusions obtained from this work so far are:
These results indicate that the Pozzolana reacts more in the
mixtures with proportions ≤ 20% of addition, and contribute
a heavy manner to the development of the compressive
strength.
It is the mixture with 20 % of Pozzolana that gives the
highest results.
However, observations are still underway as the tests are
being performed using both the destructive and
nondestructive techniques.
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ACKNOWLEDGMENTS
Almighty God who made all things possible
Prof. E. H. K. Akaho; Head; Department of Nuclear
Engineering and Director-General Ghana Atomic Energy
Commission.
Dr. K. A. Danso: Head, Dept. of Nuclear Engineering and
Materials Science;
Ghana Atomic Energy Commission.
Prof. J. J. Fletcher: Head, Dept. of Nuclear Science and
Applications; Graduate School of Nuclear and Allied
Sciences, University of Ghana.
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ACKNOWLEDGMENTS...
Mr Nikolas Sosu, Head, Engineering Section, Ghana
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Standards Board: Mr. William Nimako, Head, Civil
Engineering Laboratory, GSB, Messrs Francis and Mawuli
all of Civil Engineering lab, GSB.
Hon. Ibrahim Said Ibrahim, Egyptian Embassy, Accra. [M
Phil. Nuclear Engineering, University of Ghana]
Mr. Lawson; Department of Nuclear Engineering and
Materials Science; Ghana Atomic Energy Commission.
W.O Armah, Ghana Air Force. [M Phil. Physics], University
of Ghana, Legon.
All who help in diverse ways.
REFERENCES
SBEIDCO – 1st International Conference on Sustainable
Built Environment Infrastructures in Developing Countries.
ENSET Oran (Algeria) - October 12-14, 2009
BOUNDY, C.A.P., HONDROS, G., Rapid Field Assessment
of Strength of Concrete by Accelerated Curing and Schmidt
Rebound Hammer, ACI J., Proc. 61 (9) (1964) 1185.
BOWERS, D.G.G., Assessment of Various Methods of Test
for Concrete Strength, Connecticut Department of
Transportation/Federal Highway Administration, December
1978 (available through National Technical Information
Service, NTIS No. PB 296317, Springfield,VA).
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REFERENCES ...
BRADFIELD, G., GATFIELD, E., Determining the Thickness
of Concrete Pavements by Mechanical Waves: Directed Beam
Method, Mag. Concr. Res., 16 (46) (1964) 49.
BRITISH STANDARDS INSTITUTION, Non-destructive
methods of test for concrete – electromagnetic cover
measuring devices, British Standard 4408, London, 1.
Guidebook On Non-Destructive Testing Of Concrete
Structures IAEA,Vienna, 20
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THANK YOU
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