Comparing the compressive strength of concrete utilizing natural pozzolana as a partial replacement

CAPE COAST POLYTECHNIC SCHOOL OF ENGINEERING

CIVIL ENGINEERING DEPARTMENT

COMPARING THE COMPRESSIVE STRENGTH OF CONCRETE UTILIZING NATURAL POZZOLANA AS A PARTIAL REPLACEMENT OF ORDINARY PORTLAND CEMENT IN CONCRETE PRODUCTION

BY ASARE OSEI SAMUEL (02/07/0012/D/CVE)

ODOOM ANTHONY (02/07/0029/D/CVE)

A PROJECT WORK SUBMITTED IN PARTIAL FULFILLMENT OF THE AWARD OF CERTIFICATE IN HIGHER NATIONAL DIPLOMA (HND) IN CIVIL ENGINEERING.

JUNE, 2010.

TABLE OF CONTENT

CONTENT

PAGE

Declaration

i

Certification

ii

Dedication

iii

Acknowledgement

iv

List of Tables

v

List of Figures

vi

Abstract

vii

CHAPTER ONE 1.0 introduction

1

1.1 Purpose of the study

1

1.2 statement of the problem

3

1.3 aim of the study

4

1.4 project objectives

4

1.5 significance

4

1.6 scope of the study

5

CHAPTER TWO 2.0 literature review

6

2.1 introduction

6

2.2 background

8

2.3 materials

12

2.3.1 Cement

12

2.3.2 Aggregate

14

2.4 concrete production

15

2.4.1 Proportioning and mixing concrete

16

2.4.2 Conveying

16

2.4.3 Placing

17

2.4.4 Curing

18

2.4.4.1 Curing methods

19

2.4.4.1.1 water cure

19

2.4.4.1.2 Water retaining method

19

2.4.4.1.3 Waterproof paper or plastic film seal

19

2.4.4.1.4 Chemical membranes

19

2.5 quality control

20

2.5.1 Slump test

21

2.5.2 Compaction factor test

22

2.6 pozzolana

23

2.6.1 Engineering properties of pozzolana

28

2.6.1.1 Fineness

28

2.6.1.2 Pozzolanic activity (chemical composition and mineralogy)

28

2.6.1.3 Loss on ignition

28

2.6.1.4 Moisture content

29

2.6.1.5 Workability

29

2.6.1.6 Time of setting

29

2.6.1.7 Bleeding

29

2.6.1.8 Pumpability

29

2.6.1.9 Strength development

29

2.6.1.10 Heat of hydration

30

2.6.1.11 Permeability

30

2.6.1.12 Resistance to freeze-thaw

30

2.6.1.13 Sulphate resistance

31

2.6.1.14 Alkali-silica reactivity

31

2.6.2 Advantages of the natural pozzolan

32

2.6.2.1 Litification

32

2.6.2.2 Autogenously healing

32

2.6.2.3 Reduced permeability and voids

32

2.6.2.4 Reduces expansion and heat of hydration

32

2.6.2.5 Reduces creep and cracks

33

2.6.2.6 Reduces microcracking

33

2.6.2.7 Increases compressive strength

33

2.6.2.8 Increases resistance to chloride attack

33

2.6.2.9 Increases resistance to sulphate attack

33

2.6.2.10 reduces alkali-aggregate reaction

34

2.6.2.11 protects steel reinforcement from corrosion

34

2.6.2.12 increases abrasion resistance

34

2.6.2.13 lowers water requirement with high fluidity, Self-levelling and compression

34

2.6.2.14 improves durability

34

2.7 design considerations

35

2.7.1mix design

35

CHAPTER THREE 3.0 methodology

37

3.1 introduction

37

3.2 data collection

37

3.3 desk study

37

3.4 mix proportion

37

3.5 casting and curing

38

3.6 test procedures

38

3.6.1 Slump test

38

3.6.2 Setting times

38

3.6.3 Compressive strength

38

CHAPTER FOUR 4.0 Data Presentation and Analysis

39

4.1 Silt Test Results and Analysis

39

4.2 Properties of Fresh Concrete

44

4.2.1 Slump Test

44

4.2.2 Compaction Factor Test

47

4.3 Compressive Strength

56

CHAPTER FIVE 5.0 Conclusion and Recommendations

63

5.1 Conclusion

63

5.2 Recommendations

64

References

65

Appendices

66

DECLARATION

We the undersigned declare that this project work is the result of our own investigation carried out on assessing the properties of concrete cubes utilizing natural pozzolana as a partial replacement under the supervision of Mr Emmanuel Nana Jackson of Cape Coast Polytechnic.

Name

Signature

SAMUEL OSEI ASARE

ANTHONY ODOOM

Date

nanakwame

anthony odoom

i

2nd July, 2010

2nd July, 2010

CERTIFICATION

The appendix signature certifies that this project is an original work undertaken and presented in accordance with the regulation governing the preparation and presentation of a project work in cape coast polytechnic for acceptance of dissertation entitle study to assess the properties of concrete cubes utilizing natural pozzolana as a partial replacement

This report is submitted by SAMUEL OSEI ASARE (02/07/0012/D/CVE) and ANTHONY ODOOM (02/07/0029/D/CVE) to the department of civil engineering in partial fulfilment of the requirement for the award of higher national diploma (HND) in Civil Engineering.

nana kackson

2nd July, 2010

Mr Emmanuel Nana Jackson (Supervisor)

date

ii

DEDICATION This project work is dedicated to the almighty God and the department of Civil Engineering, Cape Coast Polytechnic.

iii

ACKNOWLEDGEMENT

Acknowledgement is due to the department of Civil Engineering, Cape Coast Polytechnic for the use of the laboratory for the purpose of this work. The investigators would also like to thank Mr Emmanuel Nana Jackson for his dedication and assistance with the entire work as well to our families for their financial and morale support and to all those who contributed immensely to the success of this work especially to Mr Nathan Kofi Kakra Asare, (Sonitra Ghana), Mr Daniel Kofi Panyin Asare (MTN Ghana Ltd), madam Felicia Adu, Evelyn Essel and to Madam Cecielia Mensah, Madam Veronica Odum, and Michael Odoom. The investigators are thankful to all staff of The Civil Engineering Department, Cape Coast Polytechnic for their assistance in diverse ways for the successful completion of this project.

iv

LIST OF TABLES Table 2.1:

chemical and physical analysis of cement

13

Table 4.1:

Results of obtained from silt test conducted sand sample

39

Table 4.2:

Mix proportion details

40

Table 4.3:

Results of grading test for coarse aggregate

41

Table 4.4:

Results of grading test for fine aggregate

42

Table 4.5:

Slump properties of fresh concrete

45

Table 4.6:

Results of Compaction factor test of concrete incorporating pozzolan

46

Table 4.7:

Detail results of Compressive strength of concrete grade 20 at all ages

48

Table 4.8:

compressive strength incorporating pozzolan at all ages of test

56

Table 4.9:

A one sampe statistics standard deviation and standard error mean for various concrete from 7 -28 days

61

Table 4.10:

95% Confidence Interval of the Difference for Various Concrete From 7 -28 Days

61

Table 4.11:

A Correlation Matrix for Various Concrete From 7 -28 Days

63

Table 4.12:

An Explanation of the Total Variance of Concrete From 7 -28 Days

64

v

LIST OF FIGURES

Fig. 4.1:

Grading curve for coarse aggregate

41

Fig. 4.2:

Grading curve for fine aggregate

43

Fig. 4.3

Effect of pozzolanic material on the slump of concrete

45

Fig. 4.4:

Effect of pozzolanic material on the compaction factor of concrete

46

Fig. 4.5:

Effect of pozzolanic replacement on the compressive strength of concrete at 7days

58

Fig. 4.6:

Effect of pozzolanic replacement on the compressive strength of concrete at 14 days

58

Fig. 4.7:

Effect of pozzolanic replacement on the compressive strength of concrete at 21 days

59

Fig. 4.8:

Effect of pozzolanic replacement on the compressive strength of concrete at 28 days

59

Fig. 4.9:

Effect of pozzolanic replacement on the compressive strength of concrete at all ages

60

Fig. 4.10:

line diagram illustrating the effect of pozzolanic replacement on the compressive Strength of concrete at all ages

60

vi

RÉSUMÉ Naturelles matériau pouzzolanique est disponible en sacs de 50kg de la construction et l'institut de recherche routière (BRRI) au Ghana. Ce projet de recherche avait pour but l'étude préliminaire de la performance du béton en utilisant le matériau naturel pouzzolanique. Le matériau de la pouzzolane BRRI a été constituée dans le béton pour remplacer le ciment partielle d'étudier les effets du niveau de remplacement sur le développement de la résistance à la compression du béton à différents âges. Facteur Slump et le compactage du béton frais ont

également

été

mesurées.

Les résultats montrent que l'inclusion de pouzzolanes naturelles dans le béton pour remplacer le ciment partielle ne nuit pas à des propriétés du béton frais. Son incorporation dans le béton a augmenté de manière significative la résistance à la compression à tous les âges pour le mélange de remplacement de pouzzolane 30% par rapport à d'autres mélanges. Une augmentation de la force moyenne de 1,1 MPa a été enregistré à partir du test Cependant remplacement partiel des mélanges de 70%, 60% et 80% de pouzzolane n'a pas atteint la résistance de calcul de 20 N/mm2. Résistance à la compression et les essais maniabilité suggéré que la pouzzolane, pourrait être remplacé par du ciment Portland jusqu'à 30%

dans

la

fabrication de

béton sans

perte

de

maniabilité

ou

de

force.

Afin d'améliorer le développement de la résistance, la réactivité pouzzolanique des pouzzolanes pourrait être sensiblement améliorée / modifiée en utilisant un ou une combinaison de plusieurs méthodes de traitement. Cependant, toutes les méthodes peut être possible d'atteindre le niveau optimal. Par conséquent, il est fortement recommandé que, outre employant diverses méthodes de traitement, l'applicabilité de faisabilité et pratiques de chaque méthode doit être étudié en détail.

vii

ABSTRACT Natural pozzolanic material is available in bags of 50kg from the building and road research institute (BRRI) in Ghana. This research project was aimed preliminary study of the performance of concrete utilizing the natural pozzolanic material. The pozzolan material from the BRRI was incorporated in concrete as partial cement replacement to study the effects of replacement level on the compressive strength development of concrete at various ages. Slump and compaction factor of fresh concrete were also measured.

The results show that the inclusion of natural pozzolana in the concrete as partial cement replacement was not detrimental to for the properties of fresh concrete. Its incorporation in the concrete increased the compressive strength significantly at all ages for the replacement mix of 30% pozzolana as compared to other mixes. An average strength increase of 1.1 Mpa was recorded from the test However Partial replacement mixes of 70%, 60% and 80% pozzolana did not attain the design strength of 20 N/mm2 . Compressive strength and workability tests suggested that pozzolan, could be substituted for Portland cement at up to 30% in the manufacture of concrete with no loss in workability or strength.

In order to enhance the strength development, the pozzolanic reactivity of pozzolans could be significantly improved/modified by using one or a combination of several treatment methods. However, not all methods may be feasible to achieve the optimum level. Therefore, it is strongly recommended that, besides employing various treatment methods, the feasibility and practical applicability of each method needs to be investigated in details.

viii

CHAPTER ONE 1.0 INTRODUCTION

1.1 PURPOSE OF THE STUDY Manufacturing of Portland cement requires high energy and releases a very large amount of green-house gases to the atmosphere; approximately 13,500 million tonnes is produced from this process worldwide, which accounts for 7% of the green house gas produced annually [Sumrerng Rukzon, 2009]. The use of pozzolana, especially waste pozzolana, to replace part of Portland cement is therefore receiving a lot of attention. Historically, Pozzolans are named after the volcanic additives used in mortar by the Romans. Pozzolans are fine materials containing silica and/or alumina and while they do not have any cementing properties of their own, in the presence of calcium oxide (CaO) or Calcium Hydroxide (Ca(OH2), silica and alumina in the pozzolana reacts and form cementitious material. Ash from some agricultural by-products such as rice husk ash, bagasse ash and palm oil fuel ash have been shown to be good Pozzolan. Their uses are receiving more attention now since the properties of the blended cement concrete using them are generally improved. In addition, they can also save the cost of construction materials and reduce the negative environmental effects. Palm oil fuel ash is one promising Pozzolans and is available in many parts of the world. It is a by-product obtained from a small power plant, which uses the palm fibre, shells and empty fruit bunches as fuels which are burnt at 800-1000°C. The main chemical composition of palm oil fuel ash is silica, which is the main ingredient of pozzolanic material. At present, palm oil fuel ash is sent to landfill which is a problem for all power plants because it has not been proven useful yet and treated as a waste. The use of pozzolana to replace part of Portland cement improves durability of concrete through the pore refinement and the reduction of calcium hydroxide in the cement paste -1-

matrix. Resistance to chloride penetration, acid solution attack, and sulphate attack of the concrete containing Pozzolan is generally enhanced. The other important property, which also influences the performance of concrete, is carbonation in steel reinforcement. The ingress of carbon dioxide into the cement matrix results in a reduction in the ability of the cement matrix to protect the steel reinforcement as the passive layer at the surface of the reinforcing bars is destroyed. The carbonation is usually severe in the high carbon dioxide environment and in the relatively dry or indoor environment of 50-60% relative humility (RH). In particular when thin concrete sections, such as slabs and thin walls, are involved, the concrete covering of steel reinforcements is small and protection of the steel reinforcement by the cement matrix against penetration of carbon dioxide is much reduced. Although paint and other surface covering of concrete surface can help reduce the carbonation, the modern designs using dare concrete surfaces are often preferred. The use of these agricultural by-products ashes as Pozzolan usually requires grinding to produce relatively fine Pozzolana. Their use reduces the bulk density of the concrete products, as their specific gravity is usually around 2.0-2.3, which is much lower than the overall 3.15 of Portland cement. Other advantages are that the product is less stiff, which gives better performance in terms of noise absorption and fire resistance [Sumrerng Rukzon, 2009]. The application of these materials in concrete for indoor use is therefore very attractive. The fineness of the Pozzolan is known to have a large influence on the properties of concrete through increase in the packaging effect and pozzolanic activity thus ultimately improves the durability of the matrix through pore refinement and reduced Ca (OH) 2. The parameter used to quantify this is the Blaine number, a surface area measurement that has been used since the 1940s to determine cement quality. Cement is responsible for 7% of the world’s total emission of CO 2, which is a major green house gas implicated in global warming. The addition of industrial waste and natural resources such as slag, fly ash, silica fume or natural pozzolana to cement during manufacturing contributes to a decrease in energy consumption and the amount of CO2 released into the air. Hence, low cost environmental friendly cement is obtained. Also, when used as a concrete admixture, the amorphous silica present in these additives combined with the calcium hydroxide liberated during the hydration of cement in concrete to form additional cementitious compound, namely calcium silicate hydrate (CSH). The resultant binder matrix is more chemically resistant by virtue of its denser microscopic pore structure.

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A large number of studies have shown that different additions, when used as partial cement replacement materials in mortar and concrete have many advantages but also some disadvantages. [Nehdi, 2001]. It should be possible, by the systematic adjustment of the proportions to produce ternary blended cement (OPC-NP-SF) which utilizes the desirable characteristics of one addition which compensating for the undesirable characteristic of the other. For example, SF increase the low early strength caused by the inclusion of NPJ and the NP decrease the high water demand of SF. On the other hand, the best combined of these mineral additions, can lead to excellent durability [Sumrerng Rukzon, 2009].

The objective of this research work is to access the strengths and durability of concrete using a mixture of ordinary Portland cement and natural pozzolana. The result could be beneficial to the understanding of the mechanism involve as well as future applications of these materials in the construction industry based on the strengths and durability of concrete.

1.2 STATEMENT OF THE PROBLEM The requirement for high durability concrete structures exposed to harsh environment such as seafloors, offshore structures, tunnels, highway bridges, sewage pipes etc. cannot be easily achieved using Ordinary Portland Cement. The phenomenon of the widespread deterioration of concrete structures during the past two decades has become a matter of global concern. The issue of ensuring long-term durability of concrete structures has therefore assumed great importance. As a result, new materials and composites are being investigated and improved cements are produced. The present state of the art in concrete research has demonstrated the benefits of pozzolanic materials as partial replacement. In addition, the use of pozzolanic materials conserves energy and has environmental benefits as a result of the reduced use of cement (the production of which is associated with high carbon dioxide emission). Pozzolanic materials are divided into natural and by-product materials. By-product materials are fly ash, slag and silica fumes whereas natural pozzolanic material is obtained from volcanic rocks.

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Since the past decade the use of pozzolanic materials in concrete is gaining impetus because of its benefits. Most of the research has been concentrated on by-product pozzolanic materials and little effort was dedicated to natural pozzolanic materials, Regarding Ghana’s natural pozzolanic material, no information pertaining to engineering and durability related properties is available. Therefore, there is a need to investigate and explore the potential of this material for the use in concrete [Khan and Alhozaimy, 2005].

1.3 AIM OF THE STUDY The aim of the study was to compare the strength of concrete using a mixture of pozzolana and Ordinary Portland Cement (OPC) as a binder to that of OPC only in concrete production.

1.4 PROJECT OBJECTIVES 1. This project was intended to investigate the performance of locally available natural pozzolanic material in the republic of Ghana. 2. To investigate the influence of the pozzolan on the properties of fresh concrete and compressive strength development.

1.5 SIGNIFICANCE The high economy associated with concrete works with the use of cement as a binder has necessitated the study into the benefits of partial replacement of concrete with natural pozzolanic material, which will reduce the effect of carbon-dioxide emission, increase durability and reduce cost of production of concrete.

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1.6 SCOPE OF THE STUDY The area under study was Cape Coast Metropolitan Assembly and its environs in the Central Region of Ghana. The materials for the study were all found in Cape Coast and its environs. The laboratory tests were done in the Cape Coast Polytechnic Civil Engineering laboratory. This research was strictly based on testing of concrete cubes with the mixture of pozzolana and ordinary Portland cement and ordinary Portland cement only as binders. The research was limited to testing of concrete cubes and the factors affecting the compressive strength of concrete were accessed.

-5-

CHAPTER TWO 2.0 LITERATURE REVIEW 2.1 INTRODUCTION It is now well established that in order to produce a durable concrete, a dense homogeneous concrete microstructure, especially in the interface region between hydrated paste and aggregate, is required [Aitcin and Neville 1994]. The densification and homogeneity of the interfacial region are achieved through the incorporation of natural and by-products pozzolanic material. In addition, the incorporation of natural and by-product material in concrete can significantly enhance its basic properties in both the fresh and hardened states. Blended cements with mineral admixtures offer improved performance over that of ordinary Portland cement with respect to microstructure and durability of concrete [Malhotra and Mehta, 1996], [Gjorv, 1994]. The incorporation of pozzolanic materials in concrete reduces bleeding and segregation and enhances cohesiveness of concrete, reduces heat evolution during hydration leading to lower tendency for crack formation during hardening which is beneficial in mass concrete application. The inclusion of natural pozzolana or slag or silica fume results in concrete with reduced or similar permeability to that of plain concrete; such concrete increases the resistance against chloride attack [Malhotra and Mehta, 1996] and performs satisfactorily against Sulphate attack [Alhoziamy; Soroushian and Mirza, 1996]. The research on by-products material namely, natural pozzolana, slag and silica fume is well documented while research on natural pozzolana is hardly available. Natural pozzolanic material behaves in similar manner to that of by-product pozzolanic admixtures. It is reported that natural pozzolanic material tends to increase the water demand. However, this excess water is consumed by pozzolanic reaction at the later stages [Malhotra and Mehta, 1996]. Setting time of natural pozzolanic material is retarded as compared to ordinary Portland cement concrete, as is the case in the by-product pozzolanic material. Due to the inference provided by finely divided particles and the absorption by microporous, natural pozzolan reduces the bleeding of concrete. This reduction in the internal bleeding improves the interfacial zone of the concrete hence the strength of the concrete. [Mehta and Monteiro, 1995], [Neville, 1996].

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The incorporation of natural pozzolanic materials delays the rate of strength development like natural pozzolana and slag. It reported that the concrete mixes containing 10, 20 and 30% natural pozzolanic material (Santorin earth) demonstrated less strength at 7 days as compared to that of control mix. At 28 days, concrete with 10% replacement showed higher strength than that of control mix. Further, the inclusion of natural pozzolanic material in concrete did not demonstrate the significant change in drying shrinkage as compared to the control mix [Mehta, 1981]. The addition of natural pozzolan enhances the hydration products of Portland cement; however, the rate of enhancement depends on its characteristics. [Cook, 1986]. Pozzolanic material efficiently decreases the permeability, thereby increasing the resistance of concrete to deterioration by aggressive chemicals such as chlorides [Malhotra and Mehta, 1996)]. Therefore, the incorporation of pozzolanic material in the concrete has become an increasingly accepted practice in the construction of structures exposed to harsh environments. Natural pozzolana is reported to have similar influence on the permeability of concrete as that of natural pozzolana and slag. Concrete containing natural pozzolana improves permeability and pore size distribution of the concrete [Mehta, 1981]. The scientific information on by-product pozzolanic materials such as natural pozzolana, slag and silica fume are well documented and little effort has been dedicated to the natural pozzolanic materials. The technical information on locally available natural pozzolanic material is not available. Therefore, there is a need to investigate and explore the potential of this material for use in concrete as partial cement replacement.

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2.2 BACKGROUND Concrete is a stone-like material obtained by permitting carefully proportioned mixture of cement, sand and gravel or other aggregate, and water to harden in forms of the shape and dimensions of the desired structure. The bulk of the material consists of fine and coarse aggregate. Cement and water interact chemically to bind the aggregate particles into a solid mass. Additional water, over and above that needed for this chemical reaction, is necessary to give the mixture the workability that enables it to fill the forms and surrounds the embedded reinforcing steel prior to hardening. Concrete with a wide range of properties can be obtained by appropriate adjustment of the proportions of the constituent materials. Special cements (such as high early strength cements), special aggregate (such as various lightweight or heavy weight aggregate), admixtures such as plasticizers, air-entraining agents, silica fume, and natural pozzolana), and special curing methods (such as steam curing) permit an even wider variety of properties to be obtained. These properties depend to a very substantial degree on the proportions of the mix, on the thoroughness with which the various constituents are intermixed, and on the conditions of humidity and temperature in which the mix is maintained from the moment it is placed in the forms until it is fully hardened. Curing is done to control the conditions after placement. To protect against the unintentional production of substandard concrete, a high degree of skillful control and supervision is necessary throughout the process, from the proportioning by weight of the individual components, through mixing and placing, until the completion of curing. The factors that make concrete a universal building material are so pronounced that it has been used, in more primitive kinds and ways than at present, for thousands of years starting with lime mortars from 12,000 to 6000 B.C. in Crete, Cyprus, Greece and the Middle East. The facility with which, while plastic, it can be deposited and made to fill forms or moulds of almost any practical shape is one of these factors. Its high fire and weather resistance are evident advantages. Most of the constituent materials, with the exception of cement and additives, are usually available at low cost locally. Its compressive strength, like that of natural stones, is high, which makes it suitable for members primarily subject to compression, such as columns and arches. On the other hand, again as in natural stones, it is relatively brittle material whose tensile strength is small compared with its compressive strength. This prevents its economical use in structural members that are subject to tension either entirely -8-

(such as in tie rods) or over part of their cross sections (such as in beams or other flexural members). Concrete (construction), artificial engineering material made from a mixture of Portland cement, water, fine and coarse aggregates, and a small amount of air. It is the most widely used construction material in the world. Concrete is the only major building material that can be delivered to the job site in a plastic state. This unique quality makes concrete desirable as a building material because it can be moulded to virtually any form or shape. Concrete provides a wide latitude in surface textures and colours and can be used to construct a wide variety of structures, such as highways and streets, bridges, dams, large buildings, airport runways, irrigation structures, breakwaters, piers and docks, sidewalks, silos and farm buildings, homes, and even barges and ships. Other desirable qualities of concrete as a building material are its strength, economy, and durability. Depending on the mixture of materials used, concrete will support, in compression, 700 or more kg/sq. cm (10,000 or more lb. /sq. in). The tensile strength of concrete is much lower, but by using properly designed steel reinforcing, structural members can be made that are as strong in tension as they are in compression. The durability of concrete is evidenced by the fact that concrete columns built by the Egyptians more than 3600 years ago are still standing.

The two major components of concrete are a cement paste and inert materials. The cement paste consists of Portland cement, water, and some air either in the form of naturally entrapped air voids or minute, intentionally entrained air bubbles. The inert materials are usually composed of fine aggregate, which is a material such as sand, and coarse aggregate, which is a material such as gravel, crushed stone, or slag. In general, fine aggregate particles are smaller than 6.4 mm (.25 in) in size, and coarse aggregate particles are larger than 6.4 mm (.25 in). Depending on the thickness of the structure to be built, the size of coarse aggregate particles used can vary widely. In building relatively thin sections, a small size of coarse aggregate, with particles about 6.4 mm (.25 in) in size, is used. At the other extreme, aggregates up to 15 cm (6 in) or more in diameter are used in large dams. In general, the maximum size of coarse aggregates should not be larger than one-fifth of the narrowest dimensions of the concrete member in which it is used. When Portland cement is mixed with water, the compounds of the cement react to form a cementing medium. In properly mixed concrete, each particle of sand and coarse aggregate is -9-

completely surrounded and coated by this paste, and all spaces between the particles are filled with it. As the cement paste sets and hardens, it binds the aggregates into a solid mass. Under normal conditions, concrete grows stronger as it grows older. The chemical reactions between cement and water that cause the paste to harden and bind the aggregates together require time. The reactions take place very rapidly at first and then more slowly over a long period of time. In the presence of moisture, concrete continues to gain strength for years. For instance, the strength of just-poured concrete may be about 70,307 g/sq. cm (1000 lb./sq. in) after drying for a day, 316,382 g/sq.cm (4500 lb./sq. in) in 7 days, 421,842 g/sq. cm (6000 lb./sq. in) in 28 days, and 597,610 q/sq. cm (8500 lb./sq. in) after 5 years. Concrete mixtures are usually specified in terms of the dry-volume ratios of cement, sand, and coarse aggregates used. A 1:2:3 mixtures, for instance, consists of one part by volume of cement, two parts of sand, and three parts of coarse aggregate. Depending on the applications, the proportions of the ingredients in the concrete can be altered to produce specific changes in its properties, particularly strength and durability. The ratios can vary from 1:2:3 to 1:2:4 and 1:3:5. The amount of water added to these mixtures is about 1 to 1.5 times the volume of the cement. For high-strength concrete, the water content is kept low, with just enough water added to wet the entire mixture. In general, the more water in a concrete mix, the easier it is to work with, but the weaker the hardened concrete becomes. Concrete can be made to have any degree of water tightness. It can be made to hold water and resist the penetration of wind-driven rains. On the other hand, for purposes such as constructing filter beds, concrete can be made porous and highly permeable. Concrete can also be given a polished surface that is as smooth as glass. By using heavy aggregates, including steel fragments, dense concrete mixtures can be made that weigh 4005 or more kg/cu m (250 or more lb. /cu ft.). Concrete that weighs only 481 kg/cu m (30 lb. /cu ft.) can be made by using special lightweight aggregates and foaming techniques. Forms consisting of such lightweight aggregates can be floated on water, sawed into pieces, or nailed to another surface. For small jobs and minor repairs, concrete can be mixed by hand, but machine mixing ensures more uniform batches and, therefore, superior performance. For most home repairs and improvements—for example, floors, walks, driveways, patios, and garden pools—the recommended proportion is a 1:2:3 mix. - 10 -

After exposed surfaces of concrete have hardened sufficiently to resist marring, they should be cured by sprinkling or ponding (covering) with water or by using moisture-retaining materials such as waterproof paper, plastic sheets, wet burlap, or sand. Special curing sprays are available. The longer concrete is kept moist, the stronger and more durable it will become. In hot weather, it should be kept moist for at least three days. In cold weather, drying concrete must not be allowed to freeze. This can be accomplished by covering the cement with a tarpaulin or some other material that helps trap the heat generated by the chemical reactions within the concrete that cause it to harden [Microsoft ® Encarta ® 2009]

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2.3 MATERIALS 2.3.1 CEMENT Cementitious material is one that has the adhesive and cohesive properties necessary to bond inert aggregate into a solid mass of adequate strength and durability. This technologically important category of materials includes not only cements proper but also limes, asphalts, and tars as they are used in roads building, and others. For making structural concrete, so-called hydraulic cements are used excessively. Water is needed for the chemical process (hydration) in which the cements powder sets and hardens into one solid mass. Of the various hydraulic cements that have been developed, Portland cement, which was first patented in England in 1824, is by far the most common. Portland cement is finely powdered, grayish material that consists chiefly of calcium Aluminium silicates. The common raw materials from which it is made are limestone, which provide CaO, and clays or shale, which furnish SiO2 and Al2O3. These are ground, blended, fused to clinkers in a kiln, and cooled. Gypsum is added and the mixture is ground to required fineness. Over the years, five standard types of Portland cement have been developed. When cement is mixed with water to form a soft paste, it gradually stiffens until it becomes solid. This process is known as setting and hardening. The cement is said to have set when it gains sufficient rigidity to support an arbitrarily defined pressure, after which it continues for a long time to harden i.e., to gain further strength. The water in the paste dissolves material at the surfaces of the cement grains and forms a gel that gradually increases in volume and stiffness. This leads to a rapid stiffening and hardening of the mass. The principal products of hydration are calcium silicate hydrate, which is insoluble, and calcium hydroxide, which is soluble. In ordinary concrete, the cement is probably never completely hydrated. The get structure of the hardened paste seems to be the chief reason for the volume changes that are caused in concrete by variations in moisture, such as the shrinkage of concrete as it dries. For complete hydration of a given amount of cement, an amount of water equal to about 25 percent of that of cement, by weight – i.e. a water-cement ratio of 0.25 is needed chemically. An additional amount must be present, however, to provide mobility for the water in the cement paste during the hydration process so that it can reach the cement particles and to provide the necessary workability of the concrete mix. For normal concretes, the water- 12 -

cement ratio is generally in the range of 0.40 to 0.60, although for high-strength concretes, ratios as low as 0.21 have been used. In this case the needed workability is obtained through the use of admixtures. Any amount of water above that consumed in the chemical reaction produces pores in the cement paste. The strength of hardened paste decreases in inverse proportion to the fraction of the total volume occupied by pores. Put differently, since only the solids, and not the voids, resist stress, strength increases directly as the fraction of the total volume occupied by the solids. That is why the strength of the cement paste depends primarily on, and decreases directly with an increasing water-cement ratio. The chemical process involved in the setting and hardening liberates heat, known as heat of hydration. In large concrete masses, such as dams, this heat is dissipated very slowly and results in temperature rise and volume expansion of the concrete during hydration, with subsequent cooling and contraction. To avoid the serious cracking and weakening that may result from this process; special measures must be taken for its control. The source of cement, manufactured by GHACEM in Ghana was used in this investigation. The chemical and physical properties of cement are given in table 2.1. It complies with ASTM C150.

Table 2.1: Chemical and physical analysis of cement Properties

Source

SiO2 (%)

19.90

Al2O3 (%)

5.13

Fe2O3 (%)

3.75

CaO (%)

63.59

MgO (%)

1.50

SO3 (%)

2.75

Loss on ignition (%)

2.21

Fineness- Blaine (cm2/g)

3282

Source: Dr. Muhammad and Dr. Alhozaimy (2005).

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2.3.2 AGGREGATE In ordinary structural concretes the aggregates occupy about 70 to 75 percent of the volume of the hardened mass. The remainder consist of hardened cement paste, uncombined water (i.e. water not involved in the hydration of the cement), and air voids. The latter two evidently do not contribute to the strength of the concrete. In general, the densely the aggregate can be packed, the better the durability and economy of the concrete. It is there considerably important that particle size in the aggregate is properly graded. It is also important that the aggregate has good strength, durability, and weather resistance; that its surface is free from impurities such as loam, silt, clay and organic matter that may weaken the bond with cement paste; and that no unfavourable chemical reaction takes place between it and the cement. Natural aggregates are generally classified as fine and coarse. Fine aggregate (typically natural sand) is any material that will pass a No. 4 or 0.150mm. Materials which are coarser than 0.150mm are classified as coarse aggregate. When favourable gradation is desired, aggregate are separated by sieving into two or three size groups of sand and several size groups of coarse aggregate. These can then be combined according to grading charts to result in densely packed aggregate.

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2.4 CONCRETE PRODUCTION Concrete is a mixture of two components: aggregates and paste. The paste, comprised of cement and water, binds the aggregates (usually sand and gravel or crushed stone) into a rocklike mass as the paste hardens because of the chemical reaction of the cement and water. Supplementary cementitious materials and chemical admixtures may also be included in the paste. The processes used vary dramatically, from hand tools to heavy industry, but result in the concrete being placed where it cures into a final form. When initially mixed together, Portland cement and water rapidly form a gel, formed of tangled chains of interlocking crystals. These continue to react over time, with the initially fluid gel often aiding in placement by improving workability. As the concrete sets, the chains of crystals join up, and form a rigid structure, gluing the aggregate particles in place. During curing, more of the cement reacts with the residual water (Hydration). This curing process develops physical and chemical properties. Among other qualities mechanical strength, low moisture permeability, and chemical and volumetric stability. [http://en.wikipedia.org]

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2.4.1 PROPORTIONING AND MIXING CONCRETE The various components of a mix are proportioned so that the resulting concrete has adequate strength, proper workability for placing, and low cost. To achieve low cost in concrete production requires the use of minimum amount of cement (which is the most costly component) that will achieve adequate properties. The better the gradation of aggregate, i.e. the smaller the volume of voids, the less cement paste is needed to fill these voids. In addition to the water required for hydration, water is needed for wetting the surface of the aggregate. As water is added, the plasticity and fluidity of the mix increases (i.e. its workability improves), but the strength decreases because of the larger volume of voids created by the free water. To reduce the free water while retaining the workability, cement must be added. Therefore, as for the cement paste, the water-cement ratio is the chief factor that controls the strength of the concrete. For a given water-cement ratio, the minimum amount of cement that will secure the desired workability is selected.

2.4.2 CONVEYING Conveying of most building concretes from the mixer or truck to form is done in bottomdump trucks or by pumping through steel pipelines. The chief danger during conveying is that of segregation. The individual components of concrete tend to segregate because of their dissimilarity. In overly wet concrete standing in containers or forms, the heavier gravel components tend to settle, and the lighter materials, particularly water, tend to rise. Lateral movement, such as flow within the forms, tends to separate the coarse gravel from the finer components of the mix

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2.4.3 PLACING Placing is done by transferring the fresh concrete from the conveying device to its final place in the forms. Prior to placing, loose rust must be removed from the reinforcement, forms must be cleaned, and hardened surface of previous concrete lifts must be cleaned and treated appropriately. Placing and consolidation are critical in their effect on the final quality of the concrete. Proper placement must avoid segregation, displacement of forms or of reinforcement in the forms, and poor bond between successive layers of concrete. Immediately upon placing, the concrete should be consolidated, usually by means of vibrators. This prevents honeycombing, ensures close contact with forms and reinforcements, and serves as a partial remedy to possible prior segregation. Consolidation is achieved by high-frequency, power-driven vibrators. Fresh concrete gains strength most rapidly during the first few days and weeks. Structural design is generally based on the 28-day strength, about 70 percent of which is reached at the end of the first week after placing. The final concrete strength depends greatly on the conditions of moisture and temperature during this initial period. Curing is then done to maintain the proper conditions. Thirty percent of the strength or more can be lost by premature drying of the concrete; similar amounts may be lost by permitting the concrete temperature to drop to 40⁰F (4.4⁰C) during the first few days unless the concrete is kept continuously moist for a long time thereafter. Freezing of fresh concrete may reduce its strength by 50 percent or more. To prevent such damage, concrete should be protected from loss of moisture for at least 7 days and in. more sensitive work, up to 14 days. When high early strength cements are used, curing periods can be cut in half. Curing can be achieved by keeping exposed surfaces continually wet through sprinkling, ponding, or covering with plastic film or by use of sealing compounds, which, when properly used, form evaporationretarding membranes. In addition to improving strength, proper moist curing provides better shrinkage control. To protect the concrete against low temperature during cold weather, the mixing water, and occasionally the aggregates, is heated; temperature insulation is used where possible; and special admixtures are employed. When air temperatures are very low external heat may have to be supplied in addition to insulation [ACI Manual of Concrete Practice, Part 2, 2003]

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2.4.4 CURING Curing is the process of controlling the rate and extent of moisture loss from concrete during cement hydration. It may be either after it has been placed in position (or during the manufacture of concrete products), thereby providing time for the hydration of the cement to occur. Since the hydration of cement does take time – days, and even weeks rather than hours – curing must be undertaken for a reasonable period of time if the concrete is to achieve its potential strength and durability. Curing may also encompass the control of temperature since this affects the rate at which cement hydrates. The curing period may depend on the properties required of the concrete, the purpose for which it is to be used, and the ambient conditions, i.e. the temperature and relative humidity of the surrounding atmosphere. Curing is designed primarily to keep the concrete moist, by preventing the loss of moisture from the concrete during the period in which it is gaining strength. Curing may be applied in a number of ways and the most appropriate means of curing may be dictated by the site or the construction method. In all but the least critical applications, care needs to be taken to properly cure concrete, and achieve best strength and hardness. This happens after the concrete has been placed. Cement requires a moist, controlled environment to gain strength and harden fully. The cement paste hardens over time, initially setting and becoming rigid though very weak, and gaining in strength in the days and weeks following. In around 3 weeks, over 90% of the final strength is typically reached though it may continue to strengthen for decades. [ACI Manual of Concrete Practice, Part 2, 2003] Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying and shrinkage due to factors such as evaporation from wind during placement may lead to increased tensile stresses at a time when it has not yet gained significant strength, resulting in greater shrinkage cracking. The early strength of the concrete can be increased by keeping it damp for a longer period during the curing process. Minimizing stress prior to curing minimizes cracking. High early-strength concrete is designed to hydrate faster, often by increased use of cement which increases shrinkage and cracking. During this period concrete needs to be in conditions with a controlled temperature and humid atmosphere. In practice, this is achieved by spraying or ponding the concrete surface with water, thereby protecting concrete mass from ill effects of ambient conditions. The

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pictures to the right show two of many ways to achieve this, ponding – submerging setting concrete in water, and wrapping in plastic to contain the water in the mix. Properly curing concrete leads to increased strength and lower permeability, and avoids cracking where the surface dries out prematurely. Care must also be taken to avoid freezing, or overheating due to the exothermic setting of cement (the Hoover Dam used pipes carrying coolant during setting to avoid damaging overheating). Improper curing can cause scaling, reduced strength, poor abrasion resistance and cracking.

2.4.4.1 CURING METHODS

2.4.4.1.1 Water cure: The concrete is flooded, ponded, or mist sprayed. This is the most effective curing method for preventing mix water evaporation. 2.4.4.1.2 Water retaining methods: Use coverings such as sand, canvas, burlap, or straw that is kept continuously wet. The material used must be kept damp during the curing period. 2.4.4.1.3 Waterproof paper or plastic film seal: Are applied as soon as the concrete is hard enough to resist surface damage. Plastic films may cause discoloration of the concrete-do not apply to concrete where appearance is important. 2.4.4.1.4 Chemical Membranes: The chemical application should be made as soon as the concrete is finished. Note that curing compounds can effect adherence of resilient flooring, your flooring contractor and/or chemical membrane manufacturer should be consulted.

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2.5 QUALITY CONTROL The quality concrete is assured by the producer, who must exercise systematic quality controls, usually specified pertinent standards. Concrete is produced at or close to the site, and its final quality is affected by a number of factors. Thus, the systematic quality control must be instituted at the construction site. The main measure of the structural quality of concrete is its compressive strength. Test for this property are made on cylindrical specimen of height equal to twice the diameter, usually 150 ×300 mm. impervious molds of this shape are filled with concrete during the operation of placement as specified by ASTM C 172 ―Standard Method of Sampling Freshly Mixed Concrete,‖ and ASTM C 31, ―Standard Practice for Making and Curing Concrete Test Specimens in the Field‖. The cylinders are moist-cured at about 70⁰F (21.1⁰C), generally for 28 days, and then tested in the laboratory at a specified rate of loading. The compressive strength obtained from such tests is known as the cylinder strength ƒ’c and is the main property specified for design purposes. To provide structural safety, continuous control is necessary to ensure that the strength of concrete is furnished is in satisfactory agreement with the value called for by the designer. It is evident that, if concrete were proportioned so that its mean strength were just equal to the required strength ƒ’c it would not pass these quality requirements because about half of its strength test results would fall below the required ƒ’c. It is therefore necessary to proportion the concrete so that it’s mean strength ƒ’cr used as the basis for selection of suitable proportions, exceeds the required design strength ƒ’c by an amount sufficient to ensure that the two quoted requirements are met.

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2.5.1 SLUMP TEST The slump test is the most well-known and widely used test method to characterize the workability of fresh concrete. The inexpensive test, which measures consistency, is used on job sites to determine rapidly, whether a concrete batch should be accepted or rejected. The test method is widely standardized throughout the world, including in ASTM C 143 in the United States and EN 12350-2 in Europe. The slump test is however, not considered applicable for concrete with a maximum coarse aggregate size greater than 1.5 inches. For concrete with aggregate greater than 1.5 inches in size, such larger particles can be removed by wet sieving. Additional qualitative information on the mobility of fresh concrete can be obtained after reading the slump measurement. Concretes with the same slump can exhibit different behavior when tapped with a tamping rod. A harsh concrete with few fines will tend to fall apart when tapped and be appropriate only for applications such as pavements or mass concrete. Alternatively, the concrete may be very cohesive when tapped, and thus be suitable for difficult placement conditions.

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2.5.2 COMPACTION FACTOR TEST The compaction factor test [Powers 1968; Neville 1981; Bartos 1992, Sonebi, and Tamimi 2002] measures the degree of compaction resulting from the application of a standard amount of work. The test was developed in Britain in the late 1940s and has been standardized as a British Standard 1881-103. The compaction factor is defined as a ratio of the mass of concrete compacted in the compaction factor apparatus to the mass of the fully compacted concrete. The standard test is appropriate for maximum aggregate sizes of up to 20mm. a larger apparatus is available for concretes with maximum aggregate sizes of up to 40mm. [ICAR]

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2.6 POZZOLANA A pozzolan is a material which, when combined with calcium hydroxide, exhibits cementitious properties. Pozzolans are commonly used as an addition (the technical term is "cement extender") to Portland cement concrete mixtures to increase the long-term strength and other material properties of Portland cement concrete and in some cases reduce the material cost of concrete. Pozzolans are primarily vitreous siliceous materials which react with calcium hydroxide to form calcium silicates; other cementitious materials may also be formed depending on the constituents of the pozzolan. The pozzolanic reaction may be slower than the rest of the reactions that occur during cement hydration, and thus the short-term strength of concrete made with pozzolans may not be as high as concrete made with purely cementitious materials; conversely, highly reactive pozzolans, such as silica fume and high reactivity metakaolin can produce "high early strength" concrete that increase the rate at which concrete gains strength. The first known pozzolan was pozzolana, a volcanic ash, for which the category of materials was named. The most commonly used pozzolan today is fly ash, though silica fume, highreactivity metakaolin, ground granulated blast furnace slag, and other materials are also used as pozzolans. A pozzolan is a siliceous or aluminosiliceous material, which is highly vitreous. This material independently has few/fewer cementitious properties, but in the presence of a lime-rich medium like calcium hydroxide, shows better cementitious properties towards the later day strength (> 28 days). The mechanism for this display of strength is the reaction of silicates with lime to form secondary cementitious phases (calcium silicate hydrates with a lower C/S ratio) which display gradual strengthening properties usually after 7 days. The extent of the strength development depends upon the chemical composition of the pozzolan: the greater the composition of alumina and silica along with the vitreous phase in the material, the better the pozzolanic reaction and strength display. Many pozzolans available for use in construction today were previously seen as waste products, often ending up in landfills. Use of pozzolans can permit a decrease in the use of Portland cement when producing concrete; this is more environmentally friendly than limiting cementitious materials to Portland cement. As experience with using pozzolans has increased over the past 15 years, current practice may permit up to a 40 percent reduction of - 23 -

Portland cement used in the concrete mix when replaced with a carefully designed combination of approved pozzolans. When the mix is designed properly, concrete can utilize pozzolans without significantly reducing the final compressive strength or other performance characteristics. It’s rare to find in nature natural stones with exceptional resistance to every chemical and mechanical corrosion; many silicates have these features and, among these, the natural Pozzolana is the only natural material that can be used as such with lime to form cement able to harden and resist indefinitely in water. The natural pozzolana is a natural fine volcanic ash, typical of the volcanic region of Pozzuoli (from here, its name) near Naples, Italy, but present in other volcanic zones of Italy and other Countries. It was used for the first time by the ancient Romans who started using just the pozzolana extracted at Pozzuoli. Just the buildings of the ancient Pozzuoli (Puteoli, in Latin) were built using the pozzolana as cement as well as the early days Forts and castles in the then Gold Coast, and they resisted for many centuries till today to the action of sea waters that submerged their imposing ruins because of the bradyseism, typical of that area. The pozzolana is formed by volcanic ashes cemented by the heat of deep magmas and then, after their eruption, exposed to a long action of the atmospheric agents, H 2O and CO2, so that the original complex silicates were transformed in a fine dust of simple silicates and oxides (SiO2, Al2O3, Fe2O3). When these oxides react with lime, Ca(OH) 2, they harden relatively quickly, also under water, forming complex and insoluble calcium silicates and aluminates, more and more resistant with the passing time and not needing to react also with CO2 to form CaCO3 (limestone) as it happens in the cement, like that used by the Romans before they discovered the pozzolana. The Romans were able to build exceptional monuments and palaces, like the Pantheon dome in Rome and the foundations of their harbours just with this volcanic cement, the "opus coementicium". The Roman architect Vitruvium already distinguished 4 types of pozzolana; white, yellow, gray and red.

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After the fall of the Roman Empire, the use of this cement was lost and forgotten; buildings like the Pantheon become impossible during the middle Ages, for the absence of equally resistant cement to water. Only Filippo Brunelleschi, the genial Florence architect of the first half of the XV century, started to use again the pozzolana and, since the late Renaissance, this cement has been used frequently for some specific works, reaching again the building quality of the ancient Romans and it's still in use. Very used is also the artificial pozzolana, prepared heating at about 700C a clay mixture formed by SiO2, Al2O3, MgO and CaO. The natural pozzolana is still extracted today in many volcanic zones but it's replaced, in most of cases, by the hydraulic cement, discovered in England about 1750 and made of lime and the much more common clay, with the same function of pozzolana. Various mixtures of this new cement were improved during the XIX century, until reaching the formula of the Portland cement (1924), formed by limestone and 40% of clay that hardens with higher speed than pozzolana. Then, mixtures of the Portland cement with natural or artificial pozzolana started to be available, in the last century, to improve cement resistance to water. So, pozzolana is again more and more frequent in some cement used for modern restoring works and for building bio-compatible houses. Concrete is a compound material made from sand, gravel and cement. The cement is a mixture of various minerals which when mixed with water, hydrate and rapidly become hard binding the sand and gravel into a solid mass. The oldest known surviving concrete is to be found in the former Yugoslavia and was thought to have been laid in 5,600 BC using red lime as the cement. The first major concrete users were the Egyptians in around 2,500BC and the Romans from 300 BC The Romans found that by mixing a pink sand-like material which they obtained from Pozzuoli with the informal lime-based concretes they obtained a far stronger material. The pink sand turned out to be fine volcanic ash and they had inadvertently produced the first 'pozzolanic' cement. Pozzolana is any siliceous or siliceous and aluminous material which possesses little or no cementitious value in itself but will, if finely divided and mixed with

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water, chemically react with calcium hydroxide to form compounds with cementitious properties. The Romans made many developments in concrete technology including the use of lightweight aggregates as in the roof of the Pantheon, and embedded reinforcement in the form of bronze bars, although the difference in thermal expansion between the two materials produced problems of spalling. It is from the Roman words ―caementum‖ meaning rough stone or chipping and 'concretus' meaning grown together or compounded, that we have obtained the names for these two now common materials. Lime and Pozzolana concretes continued to be used intermittently for nearly two millennia before the next major development occurred in 1824 Cement was, made from a mixture of clay and limestone, which had been crushed and fired in a kiln, was an immediate success. Although many developments have since been made, the basic ingredients and processes of manufacture are the same today The oldest known form of concrete is to be found in the Middle East and it dates back to 5600 BC; the Egyptians (XXVI Century BC) used mixed with straw to bind dried bricks, gypsum and lime mortars in stone masonry (in particular for the construction of pyramids). The Greeks living in Crete and Cyprus used lime mortars as well (Eight Century BC), whereas Babylonians and Syrians used bitumen to construct stone and brick masonries. The Ancient Greeks, similarly, used calcined limestone, while the Romans made the first concrete: mixed lime putty with brick dust or volcanic ash. They used it with stone to construct roadways, buildings and aqueducts. The Romans used pozzolana, a particular type of sand from Pozzuoli, near the volcano Vesuvio (Southern Italy), to construct buildings of crucial importance, such as the Pantheon or the Colosseo. Pozzolana is an uncommon kind of sand which reacts chemically with lime and water, becoming a rocklike mass; furthermore, it is siliceous and aluminous and it reacts with calcium hydroxide to form compounds with cementation properties. The domed Pantheon, constructed in the Second Century AD, is one of the structural masterpieces of Roman time: it has a sophisticated structure with a large number of voids, niches and small vaulted spaces aimed at reducing its weight; in particular the dome shows a - 26 -

thicker structure at its base, whereas its thickness tends to diminish gradually, according to the increased height of the dome (in other words, the dome thickness is inversely proportional to its height). Pliny reported a mortar of lime and sand (one part of lime to four parts of sand), and Marco Vitruvio Pollione (First Century BC) reported a mixture of pozzolana and lime (two parts of pozzolana to one part of lime) and we have also an essay of him as regards the properties of concrete. The cementitious composition comprises pozzolanic material. Pozzolanic materials are inorganic materials, either naturally occurring or industrial by- products typically comprising siliceous compounds or siliceous and aluminous compounds. Examples of suitable pozzolans include, but not necessarily limited to one or a combination of commercially available pozzolanic including coal natural pozzolana, silica fume, diatomaceous earth, calcined or uncalcined volcanic ash, bagasse ash, rice hull ash, natural and synthetic zerolites, metakaolin, slag and other sources of amorphous silica. Preferred pozzolanic materials are selected from the group consisting of natural pozzolana, calcined or uncalcined volcanic ash, rice hull ash, and combinations thereof. Examples of suitable natural pozzolana include, but are not necessarily limited to, class F, class C or class N as defined in ASTM C-618, ―Specifications for coal Natural pozzolana and Raw or Calcined Natural Pozzolan for use as a Mineral Admixture in Portland Cement Concrete All of the alkaline earth metal (preferably calcium-containing material) may be replaced by the pozzolanic material; however, effective curing conditions for cementitious compositions that do not include calcium-containing material generally include higher temperatures, especially autoclaving at about 80⁰ C. In one embodiment, the cementitious composition is composed of up to about 95% by weight pozzolanic material g suitably from about 10% to 95% by weight pozzolanic material, preferably from about 40% to about 90% by weight pozzolanic material. In a preferred embodiment, the pozzolanic material makes up approximately 80% or more by weight, based on the total weight of the cementitious composition. Preferably the cementitious composition comprises from about 80% to about 95% by weight, more preferably from about 80 wt. % to about 90 wt. % of the cementitious composition, based on the total weight of the cementitious composition. Suitable pozzolanic material comprise from about 10% to about 50% by weight amorphous silica or vitreous silica (hereafter ―silica‖), preferably from about 20% to about 40% by weight silica, even more preferably about 35% silica.

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2.6.1 ENGINEERING PROPERTIES OF POZZOLANA Some of the engineering properties of natural pozzolana that are of particular interest when natural pozzolana is used as and admixture or a cement addition to PCC mixes include fineness, LOI, chemical composition, moisture content and pozzolanic activity. Most specifying agencies refer to ASTM C618 when citing acceptance criteria for the use of natural pozzolana in concrete. 2.6.1.1 Fineness: fineness is the primary physical characteristics of natural pozzolana that relates to pozzolanic activity. As the finess increases, the pozzolanic activity can be expected to increase. Current specifications include a requirement for the maximum allowable percentage retained on a 0.045 mm (No. 325) sieve when wet sieved. ASTM C618 specifies a maximum of 34 percent retained on a 0.045mm (No 325). Fineness can also be assessed by methods that estimate specific surface area, such as the Blaine air permeability test commonly used for Portland cement. 2.6.1.2 Pozzolanic Activity (chemical composition and Mineralogy): pozzolanic activity refers to the ability of the silica and alumina component of natural pozzolana to react with available calcium and/ or magnesium from the hydration products of Portland cement. ASTM C618 requires that the pozzolanic activity index with Portland cement, as determined in accordance with ASTM C311 be a minimum of 75 percent of the average 28-day compressive strength of control mixes made with Portland cement.

2.6.1.3 Loss on Ignition: many state transportation departments specify a maximum LOI value that does not exceed 3 or 4 percent, even though the ASTM criteria are a maximum LOI content of 6 percent (2of 11). This is because carbon contents (reflected by LOI) higher than 3 to 4 percent have an adverse effect on air entrainment. Natural pozzolana must have a low enough LOI (usually less than 3.0 percent) to satisfy ready –mix concrete producers, who t are concerned about product quality and the control of air-entraining admixtures. Furthermore, consistent LOI values are almost as important as low LOI values to ready –mix producers, who are most concerned with consistent and predictable quality.

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2.6.1.4 Moisture Content: ASTM C618 specifies a maximum allowable moisture content of 3.0 percent. Some of the properties of fly ash-concrete mixes that are of particular interest include mix workability, time of setting, bleeding, pumpability, strength development, heat of hydration, permeability, resistance to freeze-thaw, sulfate resistance, and alkali-silica reactivity. 2.6.1.5 Workability: At a given water-cement ratio, the spherical shape of most fly ash particles permits greater workability than with conventional concrete mixes. When fly ash is used, the absolute volume of cement plus fly ash usually exceeds that of cement in conventional concrete mixes. The increased ratio of solids volume to water volume produces a paste with improved plasticity and more cohesiveness. 2.6.1.6 Time of Setting: When replacing up to 25 percent of the Portland cement in concrete, all Class F fly ashes and most Class C fly ashes increase the time of setting. However, some Class C fly ashes may have little effect on, or possibly even decrease, the time of setting. Delays in setting time will probably be more pronounced, compared with conventional concrete mixes, during the cooler or colder months. 2.6.1.7 Bleeding: Bleeding is usually reduced because of the greater volume of fines and lower required water content for a given degree of workability. 2.6.1.8 Pumpability: Pumpability is increased by the same characteristics affecting workability, specifically, the lubricating effect of the spherical fly ash particles and the increased ratio of solids to liquid that makes the concrete less prone to segregation. 2.6.1.9 Strength Development: Previous studies of fly ash concrete mixes have generally confirmed that most mixes that contain Class F fly ash that replaces Portland cement at a 1:1 (equal weight) ratio gain compressive strength, as well as tensile strength, more slowly than conventional concrete mixes for up to as long as 60 to 90 days. Beyond 60 to 90 days, Class F fly ash concrete mixes will ultimately exceed the strength of conventional PCC mixes. For mixes with replacement ratios from 1.1 to 1.5:1 by weight of Class F fly ash to the Portland cement that is being replaced, 28-day strength development is approximately equal to that of conventional concrete. Class C fly ashes often exhibit a higher rate of reaction at early ages than Class F fly ashes. Some Class C fly ashes are as effective as Portland cement in developing 28-day strength. Both Class F and Class C fly ashes are beneficial in the production of high-strength concrete. - 29 -

However, the American Concrete Institute (ACI) recommends that Class F fly ash replace from 15 to 25 percent of the Portland cement and Class C fly ash replace from 20 to 35 percent. 2.6.1.10 Heat of Hydration: The initial impetus for using fly ash in concrete stemmed from the fact that the more slowly reacting fly ash generates less heat per unit of time than the hydration of the faster reacting Portland cement. Thus, the temperature rise in large masses of concrete (such as dams) can be significantly reduced if fly ash is substituted for cement, since more of the heat can be dissipated as it develops. Not only is the risk of thermal cracking reduced, but greater ultimate strength is attained in concrete with fly ash because of the pozzolanic reaction. Class F fly ashes are generally more effective than Class C fly ashes in reducing the heat of hydration.

2.6.1.11 Permeability: Fly ash reacting with available lime and alkalies generates additional cementitious compounds that act to block bleed channels, filling pore space and reducing the permeability of the hardened concrete. The pozzolanic reaction consumes calcium hydroxide (Ca(OH)2), which is leachable, replacing it with insoluble calcium silicate hydrates (CSH). The increased volume of fines and reduced water content also play a role. 2.6.1.12 Resistance to Freeze-Thaw: As with all concretes, the resistance of fly ash concrete to damage from freezing and thawing depends on the adequacy of the air void system, as well as other factors, such as strength development, climate, and the use of deicer salts. Special attention must be given to attaining the proper amount of entrained air and air void distribution. Once fly ash concrete has developed adequate strength, no significant differences in concrete durability have usually been observed. There should be no more tendency for fly ash concrete to scale in freezing and thawing exposures than conventional concrete, provided the fly ash concrete has achieved its design strength and has the proper air void system. 2.6.1.13 Sulphate Resistance: Class F fly ash will generally improve the sulfate resistance of any concrete mixture in which it is included. Some Class C fly ashes may improve sulfate resistance, while others may actually reduce sulfate resistance and accelerate deterioration. Class C fly ashes should be individually tested before use in a sulfate environment. The relative resistance of fly ash to sulfate deterioration is reportedly a function of the ratio of calcium oxide to iron oxide. - 30 -

2.6.1.14 Alkali-Silica Reactivity: Class F fly ash has been effective in inhibiting or reducing expansive reactions resulting from the alkali-silica reaction. In theory, the reaction between the very small particles of amorphous silica glass in the fly ash and the alkalis in the Portland cement, as well as the fly ash, ties up the alkalis in a nonexpansive calcium-alkali-silica gel, preventing them from reacting with silica in aggregates, which can result in expansive reactions. However, because some fly ashes (including some Class C fly ashes) may have appreciable amounts of soluble alkalis, it is necessary to test materials to be used in the field to ensure that expansion due to alkali-silica reactivity will be reduced to safe levels. Fly ash, especially Class F fly ash, is effective in three ways in substantially reducing alkalisilica expansion: 1) It produces a denser, less permeable concrete; 2) When used as a cement replacement it reduces total alkali content by reducing the Portland cement; and 3) Alkalis react with fly ash instead of reactive silica aggregates. Class F fly ashes are probably more effective than Class C fly ashes because of their higher silica content, which can react with alkalis. Users of Class C fly ash are cautioned to carefully evaluate the longterm volume stability of concrete mixes in the laboratory prior to field use, with ASTM C441 as a suggested method of test. [Coal Fly Ash journal, 2009]

- 31 -

2.6.2 ADVANTAGES OF THE NATURAL POZZOLAN

2.6.2.1 Lithification: Once the Natural pozzolan-lime mixture is hydrated, the pozzolanic reaction begins immediately and continues for many years. Eventually, the mass will reach complete lithification, forming a rocky material similar to plagioclase with some content of magnetite. The compressive strength as well as the flexural strength will continue to increase for a long time. This unique characteristic is one of the main reasons many great ancient structures have lasted for over two thousand years. 2.6.2.2 Autogenous Healing: A unique characteristic of Natural pozzolan is its inherent ability to actually heal or re-cement cracks within the concrete by means of the continuation of pozzolanic reaction with the calcium hydroxide freed from the cement hydration reaction. This results in the filling up of most of the gaps inside the hardened concrete matrix 2.6.2.3 Reduced Permeability and Voids: The leaching of water-soluble calcium hydroxide produced by the hydration of Portland cement can be a significant contributor to the formation of voids. The amount of "water of convenience" used to make the concrete workable during the placing process creates permeable voids in the hardened mass. Natural pozzolan can increase the fluidity of concrete without "water of convenience," so that the size and number of capillary pores created by the use of too much water can be minimized. 2.6.2.4 Reduces Expansion and Heat of Hydration: Experiments show that replacing 30% Portland cement with Natural pozzolan can reduce the expansion and heat of hydration to as low as 40% of normal. This may be because there is no heat produced when Natural pozzolan reacts with calcium hydroxide and

that the free calcium oxide in the cement can hydrate

with natural pozzolan to form C-S-H. Natural pozzolan decreases the heat generated by cement hydration and delays the time of peak temperature. The graphic pattern of Natural pozzolan - Portland cement mixture is extended longer and lower, to form a much more moderate curve than the heat of hydration curve of Portland cement itself. 2.6.2.5 Reduces Creep and Cracks: While concrete is hardening, the "water of convenience" dries away. The surface of the hardening mass then begins to shrink as the temperature goes down from outside. This results in the formation of creep and cracks. Natural pozzolan moderates the expansion and shrinkage of concrete. It also helps to lower

- 32 -

the water content of the fresh concrete. Therefore, the creep and cracks can be significantly reduced without the process of water cooling. 2.6.2.6 Reduces Microcracking: The expansion and shrinkage mentioned above also create microcracks inside the hardened C-S-H paste and in-between the aggregate and the C-S-H paste. These microcracks significantly contribute to concrete permeability as well as other concrete defects. The Natural pozzolan- Portland cement mixture expands these shrinks so moderately that there is no microcracking inside the C-S-H paste after drying. 2.6.2.7 Increases Compressive Strength: The pozzolanic reaction between natural pozzolan and calcium hydroxide happens after the C3S and C2S in the cement begins to hydrate. At the early stage of curing, 30% Natural pozzolan substituting Portland cement mixture is slightly lower than reference OPC [Ordinary Portland Cement} in regard to compressive strength. As time goes by, natural pozzolan continues to react with the calcium hydroxide produced by cement hydration and increases the compressive strength by producing additional C-S-H. After 21 curing days, the 30% Natural pozzolan 70% Portland cement mixture begins to exceed reference OPC in compressive strength. After 28 days, it exceeds reference OPC by about 15%. The pozzolanic reaction continues until there is no free calcium hydroxide available in the mass and the compressive strength exceeds the reference OPC by 30-40%. 2.6.2.8 Increases Resistance to chloride Attack: Concrete deterioration caused by the penetration of chloride occurs quickly when chloride ions react with calcium. The expansion of hydrated calcium oxy-chloride enlarges the microcracks and increases the permeability that causes quicker chloride penetration and more damage from freezing and thawing action. The 30% Natural pozzolan added into cement can react with almost all the free calcium hydroxide and form a much denser past. Thus, the penetration of chloride can be minimized and the few penetrated chloride ions cannot find free calcium hydroxide with which to react. 2.6.2.9 Increases resistance to sulfate attack: There are three chemical reactions involved in sulfate attack on concrete: 1) Combination of free calcium hydroxide and sulfate to form gypsum

(CaSO 4-2H2O).

2) Combination of gypsum and calcium aluminate hydrate (C-A-H) to form ettringite (C3A3CaSO-32H2O).

- 33 -

3) Combination of gypsum and calcium carbonate with C-S-H to form thaumasite (CaCO3CaSiO3-CaSO4-15H2O). All these reactions result in the expansion and disruption of concrete. Thaumasite in particular is accompanied by a very severe damaging effect which is able

to transform

hardened concrete into a pulpy mass. 2.6.2.10 Reduces alkali-aggregate reaction: Because Natural pozzolan is shattered into such a fine particle size resulting in dramatically increased reactive surface area, it can react quickly with calcium hydroxide and can trap the alkali inside the cement paste. Thus, it helps to form a denser paste with almost no alkali aggregate reaction at all. 2.6.2.11 Protects steel reinforcement from corrosion: The preceding discussions make it very clear that concrete made from 30% Natural pozzolan/ 70% Portland cement mixture can protect steel reinforcement because it creates an environment so densely packed that no liquids or gases can penetrate through it to cause corrosion to the steel. 2.6.2.12 Increases abrasion resistance: Natural pozzolan increases the compressive strength of concrete and makes the concrete matrix stronger and denser. It also prevents the formation of pulpy, crispy, or water-soluble materials created by chemical attack. Therefore, it helps the concrete to durably resist abrasion 2.6.2.13 Lowers water requirement with high fluidity, self-leveling, and compression: In normal operations, the bulk volume of concrete in the constructions are placed and compacted by use of high frequency poke vibrators. The rapid vibration induces segregation phenomena of all orders of magnitude in the fresh concrete, e.g., stone segregation, internal bleeding giving bonding failures, and inhomogeneous cement paste and air-void systems. Under proper use of vibratory compaction, Natural Pozzolan minimizes or eliminates these problems due to the amorphous structure of the pozzolan particles. 2.6.2.14 Improves Durability: The benefits and characteristics of Natural Pozzolan mentioned above clearly explain why the ancient structures built by the Greeks have survived over 2000 years of weathering. [Lawluvi and Odei, 2009 unpublished project work]

- 34 -

2.7 DESIGN CONSIDERATIONS 2.7.1Mix Design Concrete mixes are designed by selecting the proportions of the mix components that will develop the required strength, produce a workable consistency concrete that can be handled and placed easily, attain sufficient durability under exposure to in-service environmental conditions, and be economical. Procedures for proportioning fly ash concrete mixes differ slightly from those for conventional concrete mixes. Basic mix design guidelines for normal concrete [Coal Fly Ash journal, 2009] One mix design approach commonly used in proportioning fly ash concrete mixes is to use a mix design with all Portland cement, remove some of the Portland cement, and then add fly ash to compensate for the cement that is removed. Class C fly ash is usually substituted at a 1:1 ratio. Class F fly ash may also be substituted at a 1:1 ratio, but is sometimes specified at a 1.25:1 ratio, and in some cases may even be substituted at a 1.5:1 ratio. [Coal Fly Ash journal, 2009] There are some states that require that fly ash be added in certain mixes with no reduction in cement content The percentage of Class F fly ash used as a percent of total cementitious material in typical highway pavement or structural concrete mixes usually ranges from 15 to 25 percent by weight. This percentage usually ranges from 20 to 35 percent when Class C fly ash is used. Mix design procedures for normal, as well as high-strength, concrete involve a determination of the total weight of cementitious materials (cement plus fly ash) for each trial mixture that is being investigated in the laboratory. The ACI mix proportioning guidelines recommend a separate trial mix for each 5-percent increment in the replacement of Portland cement by fly ash. If fly ash is to replace Portland cement on an equal weight (1:1) basis, the total weight of cementitious material in each trial mix will remain the same. However, because of differences in the specific gravity values of Portland cement and fly ash, the volume of cementitious material will vary with each trial mixture. When a Type IP (Portland-pozzolan) or Type I-PM blended cement is used in a concrete mix, fly ash is already a part of the cementing material. There is no need to add more fly ash to a concrete mix in which blended cement is being used, and it is recommended that no fly ash

- 35 -

be added in such cases. The blended cement can be used in the mix design process in essentially the same way as Type I Portland cement. To select a mix proportion that satisfies the design requirements for a particular project, trial mixes must be made. In a concrete mix design, the water-cement (w/c) ratio is a key design parameter, with a typical range being from 0.37 to 0.50 When using a blended cement, the water demand will probably be somewhat reduced because of the presence of the fly ash in the blended cement. When fly ash is used as a separately batched material, trial mixes should be made using a water-cement plus fly ash (w/c+f) ratio, sometimes referred to as the water-cementitious ratio, instead of the conventional w/c ratio. [Coal Fly Ash journal, 2009] The design of any concrete mix, including fly ash concrete mixes, is based on proportioning the mix at varying water-cementitious ratios to meet or exceed requirements for compressive strength (at various ages), entrained air content, and slump or workability needs. The mix design procedures stipulated in ACI 211.1 provide detailed, step-by-step directions regarding trial mix proportioning of the water, cement (or cement plus fly ash), and aggregate materials. Fly ash has a lower specific gravity than Portland cement, which must be taken into consideration in the mix proportioning process.

- 36 -

CHAPTER THREE 3.0 METHODOLOGY

3.1 INTRODUCTION Review of data for the study comprised of conduction of test, desk study and review of the reports to achieve the objectives of this study, which is ―Comparing the compressive strength of concrete utilizing natural pozzolana as a partial replacement of Ordinary Portland Cement‖ in concrete production.

3.2 DATA COLLECTION The under listed methods of data collection were used to obtain the necessary data;  Desk study and review of reports  Laboratory test methods

3.3 DESK STUDY In order to accomplish information on this study, a comprehensive review of previous data gathered about the study by other researchers were used.

3.4 MIX PROPORTION The concrete was designed and water/cement ratio was found to be 0.55 for all mixes. Mixing was done in revolving drum mixer in accordance with ASTM C 192. The pozzolana replacements were selected at ratios of 50:50, 60:40, 70:30, and 80:20 as a partial cement replacement by weight of cement content.

- 37 -

3.5 CASTING AND CURING Ninety (96) concrete cubes were cast and compacted in three layers by tamping. After casting, the samples were leveled and kept in the mould for 24 hours. The samples were then demoulded the following day and cured in a curing tank at temperature of 20±2ºC.

3.6 TEST PROCEDURES Tests were conducted to help prove the study.

3.6.1 SLUMP TEST Slump tests were performed according to ASTM C 143. The reductions in slump in time were measured. During the standing time, the concrete were covered to minimize water loss through evaporation.

3.6.2 COMPRESSIVE STRENGTH The compressive strengths of concrete were determined, using 150mm cubes prepared and tested according to BS1881. Three cubes per measurement were cast to determine the compressive strengths at various ages (7days, 14days, 21days and 28days). The compressive strengths were taken on the three samples and the average was reported as a result.

- 38 -

CHAPTER FOUR 4.0 DATA PRESENTATION AND ANALYSIS

4.1 SILT TEST RESULTS AND ANALYSIS SAMPLE 1

SAMPLE 2

SAMPLE 3

Level of Content

150

150

150

Depth of Sand without silt (ml)

70

70

70

thickness of visible silt (ml)

20

15

10

Volume of Water (ml)

60

65

70

Percentage by volume of silt depth to sand thickness (%)

29

21

14

Table 4.1: Results of obtained from silt test conducted sand sample. (Source: Laboratory test 2010)

The average silt content from the results is given as =

29+21+14 3

= 21.333%

This is 17.333% above the standard provided by BS 812. The effect of high silt content on concrete is excessive drying shrinkage thereby decreasing the compressive strength. Since results obtained from the silt test was 17.333% above the standard and the shrinkage test on the cubes were immeasurable, the sand used could not have negative influence on the results of the compressive strength.

- 39 -

Table 4.2: Details of Mix proportion

WEIGHT OF CEMENT (kg)

WEIGHT OF POZZOLANA (kg)

WEIGHT OF SAND (kg)

WEIGHT OF STONES (kg)

WEIGHT OF WATER (kg)

W/C RATIO

CONTROL

14000

0

28000

56000

7700

0.55

POZO 30%

9800

4200

28000

56000

7700

0.55

POZO 70%

4200

9800

28000

56000

7700

0.55

POZO 40%

5600

8400

28000

56000

7700

0.55

POZO 60%

8400

5600

28000

56000

7700

0.55

POZO 20%

2800

11200

28000

56000

7700

0.55

POZO 80%

11200

2800

28000

56000

7700

0.55

POZO 50%

7000

7000

28000

56000

7700

0.55

MIX

(Source: Laboratory Test, 2010)

40

Table 4.3: Results of Grading Test for Coarse Aggregates

Weight retained (g)

Sieve size

Weight passed(g)

% retained

% passing

Lower limit

Upper limit

38

0.000

8.900

0.000

100.0

100.0

100.0

19

0.916

7.984

11.070

88.9

80.0

100.0

10

5.200

2.784

62.870

26.1

0.0

20.0

2.155

0.629

26.050

0.0

0.0

5.0

5 (Source: laboratory test, 2010) 120.0 100.0 % passing

80.0 60.0 40.0 20.0

0.0 -20.0 0.1

1

10

Sieve Size, mm upper limit

lower limit

grading curve for coarse aggregate

Fig. 4.1: Grading Curve for Coarse Aggregates

41

Table 4.4: Results of Grading Test for Fine Aggregates BS Recommended Nominal Size Passing (%) Sieve size (mm)

Weight retained (g)

Weight passed(g)

% retained

% passing Lower limit

Upper limit

10 5 2.8(No. 7) 1.4(No. 14)

0.000 0.000 0.009 0.067

0.400 0.400 0.391 0.324

0.000 0.000 2.860 2.270

100.0 100.0 97.1 75.9

100.0 90.0 75.0 55.0

100.0 100.0 100.0 90.0

600 µ(No. 25) 300µ(No. 52)

0.07 0.068

0.254 0.186

22.22 21.5

53.65 32.06

35 10

60 30

0.101

0.085

32.06

0

0

10

150µ(No. 100) (Source: laboratory test, 2010)

42

120 100 80 60 40 20 0 0.01

0.1 lower limit

1 upper limit

grading curve for fine aggregate

Fig. 4.2: Grading Curve for Fine Aggregates

43

10

A mechanical analysis of the inert material was conducted for the purpose of this work. Dry sieving was used. After passing the sample through BS sieves, the percentages passing each sieve were plotted on sand and gravel fraction of a semi-logarithmic chart as shown in Fig. 4.1 for coarse sample and Fig. 4.2 for fine sample. Comparing the results of the percent passing BS sieves from the test analysis with the BS Recommended Nominal Size Passing (%) it is shown from the grading curves that the particle size distribution curves is satisfied.

4.2 PROPERTIES OF FRESH CONCRETE This section reports on workability using slump test and compaction factor test for concrete containing natural pozzolana as partial replacement. 4.2.1 Slump Test The initial slump of all mixes was within the range of 12±1 mm (Table 4.5). The slump of pozzolanic concrete as compared to the control is shown in Fig. 4.3. This figure demonstrates that there is little or no significant variation in slump of pozzolanic concrete mix (30%, 70%, 40%, 60%, 20%, 80% and 50%) and the control mix. However, it was also observed in other research work on slump loss of pozzolanic mixes that pozzolanic concrete mixture starts with a slightly higher slump and drops slightly steeper with time as compared to the control mix.

44

Table 4.5: Slump properties of fresh concrete.

Mix

Height of Slump

Control Pozo 30% Pozo 70% Pozo 40% Pozo 60% Pozo 20% Pozo 80% Pozo 50%

12 13 20 5 6 12 13 12

(Source: Laboratory test 2010)

25

Slump. Mm

20 15 10 Height of slump 5 0

Control Pozo 30%

Pozo 70%

Pozo 40%

Pozo 60%

Pozo 20%

Pozo 80%

Pozo 50%

Mix

Fig. 4.3 Effect of pozzolanic material on the slump of concrete

According to Neville, the slump ranging from 15 to 30 is low. The 70% pozzolana mix is of a low slump while the control and all other mixes are of very low slump.

45

4.2.2 Compaction Factor Table 4.6: Results Of Compacting Factor Tests Of Test Specimen Weight of Partially Compacted Conc.

Weight of Fully Compacted Conc.

Compaction Factor

Control

9599

11818

0.81

Pozo 30%

9259

11721.5

0.79

Pozo 70%

8382

11318

0.74

Pozo 40%

8875

11620

0.76

Pozo 60%

8159

11434

0.71

Pozo 20%

9525

10820

0.88

Pozo 80%

7760

10903

0.71

Pozo 50%

9415

11479

0.82

Mix

(Source: Laboratory Test, 2010)

1.00 0.90 Compaction Factor

0.80 0.70 0.60 0.50

compaction factor

0.40 0.30 0.20 0.10 0.00 ControlPozo 30%Pozo 70%Pozo 40%Pozo 60%Pozo 20%Pozo 80%Pozo 50% Mix

Fig. 4.4: Effect of pozzolanic material on the compaction factor of concrete

46

The compacting factor test conducted on concrete grade 20 indicates an adequate workability of the concrete using a water/cement ratio of 0.55. From the results obtained, the compacting factor for the control mix and Pozo 50% and Pozo 20% are of good workability as compared to the remaining mix ratios.

47

4.3 COMPRESSIVE STRENGTH Table 4.7: Detail results of Compressive strength of concrete grade 20 at all ages

CONTROL CONCRETE COMPRESSIVE STRENGHT TEST RESULTS FOR CONTROL MIX DESCRIPTION:

CONTROL WEIGHT (kg)

DESCRIPTION:

2.421

367.401

16.329

8144 8079

2.413 2.394

380.273 359.351

16.901 15.971

CONTROL

DUARATION: 14DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8103 8186

2.401 2.425

451.615 444.870

20.072 19.772

8259

2.447

458.583

20.381

CONTROL WEIGHT (kg)

DESCRIPTION:

MAX LOAD (kN)

STRENGTH (Mpa)

8170

WEIGHT (kg)

DESCRIPTION:

DUARATION: 7DAYS DENSITY (kg/dm3)

DUARATION: 21DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8153

2.415

451.191

20.053

8310

2.462

454.522

20.201

8068

2.391

457.615

20.338

CONTROL WEIGHT (kg)

DUARATION: 28DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8153

2.397

591.281

26.279

8101

2.422

564.752

25.100

8242

2442.000

578.017

25.090

- 48 -

SLUMP:

12mm

AVERAGE

16.4

SLUMP:

12mm

AVERAGE

20.1

SLUMP:

12mm

AVERAGE

20.2

SLUMP: AVERAGE

25.7

12mm

POZZOLANA 30% CONCRETE COMPRESIVE STRENGHT TEST RESULTS POZO 30% DESCRIPTION:

POZO 30% WEIGHT (kg)

DESCRIPTION:

MAX LOAD (kN)

STRENGTH (Mpa)

2.385

372.032

16.535

8023

2.377

365.689

16.253

8026

2.378

405.501

18.022

POZO 30%

DUARATION: 14DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

7977

2.364

479.815

21.325

8008

2.373

445.976

19.821

8088

2.396

440.256

19.567

POZO 30% WEIGHT (kg)

DESCRIPTION:

DENSITY (kg/dm3)

8049

WEIGHT (kg)

DESCRIPTION:

DUARATION: 7DAYS

DUARATION: 21DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8070

2.391

520.476

23.132

8113

2.404

536.217

23.832

8014

2.375

543.036

24.135

POZO 30% WEIGHT (kg)

DUARATION: 28DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8038

2.382

605.381

26.906

7997

2.369

564.123

25.072

8012

2.374

581.282

25.835

- 49 -

SLUMP:

13mm

AVERAGE

16.9

SLUMP:

13mm

AVERAGE

20.2

SLUMP:

13mm

AVERAGE

23.7

SLUMP: AVERAGE

25.9

13mm

POZZOLANA 70% CONCRETE COMPRESSIVE STRENGHT TEST RESULTS FOR POZO 70% DESCRIPTION:

POZO 70% WEIGHT (kg)

DESCRIPTION:

2.319

117.331

4.671

7822

2.318

110.220

4.899

7592

2.249

113.244

3.180

POZO 70%

DUARATION: 14DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

7752

2.297

105.107

4.671

7800

2.311

135.857

6.038

7705

2.283

113.244

5.033

POZO 70% WEIGHT (kg)

DESCRIPTION:

MAX LOAD (kN)

STRENGTH (Mpa)

7826

WEIGHT (kg)

DESCRIPTION:

DUARATION: 7DAYS DENSITY (kg/dm3)

DUARATION: 21DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

7767 7782

2.301 2.306

165.311 161.422

7.347 7.174

7650

2.267

134.921

5.996

POZO 70% WEIGHT (kg)

DUARATION: 28DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

7799

2.311

160.270

7.123

7778

2.305

184.370

8.194

7845

2.324

170.280

7.568

- 50 -

SLUMP:

20mm

AVERAGE

4.4

SLUMP:

20mm

AVERAGE

5.2

SLUMP:

20mm

AVERAGE

6.8

SLUMP: AVERAGE

7.6

20mm

POZZOLANA 40% CONCRETE COMPRESSIVE STRENGHT TEST RESULTS FOR POZO 40 % DESCRIPTION:

POZO 40% WEIGHT (kg)

DESCRIPTION:

2.403

274.269

12.190

8050

2.385

295.946

13.153

8056

2.387

311.789

13.857

POZO 40%

DUARATION: 14DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8008

2.373

292.489

13.000

8055

2.387

319.350

14.193

8017

2.375

317.478

14.110

POZO 40% WEIGHT (kg)

DESCRIPTION:

MAX LOAD (kN)

STRENGTH (Mpa)

8109

WEIGHT (kg)

DESCRIPTION:

DUARATION: 7DAYS DENSITY (kg/dm3)

DUARATION: 21DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8043

2.383

358.454

15.931

8040

2.382

353.485

15.710

8133

2.410

357.230

15.877

POZO 40% WEIGHT (kg)

DUARATION: 28DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

7951

2.356

368.392

16.373

8052 8148

2.386 2.414

370.806 344.844

16.480 15.326

- 51 -

SLUMP:

5mm

AVERAGE

13.1

SLUMP:

5mm

AVERAGE

13.8

SLUMP:

5mm

AVERAGE

15.8

SLUMP: AVERAGE

16.1

5mm

POZZOLANA 6O% CONCRETE COMPRESSIVE STRENGHT TEST RESULTS FOR POZO 60% DESCRIPTION:

POZO 60% WEIGHT (kg)

DESCRIPTION:

2.271

132.400

5.884

7890

2.338

177.913

7.907

7831

2.320

155.733

6.921

POZO 60%

DUARATION: 14DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

7924

2.348

196.061

8.714

7711

2.285

209.024

9.290

2369

2.369

106.043

4.713

POZO 60% WEIGHT (kg)

DESCRIPTION:

MAX LOAD (kN)

STRENGTH (Mpa)

7663

WEIGHT (kg)

DESCRIPTION:

DUARATION: 7DAYS DENSITY (kg/dm3)

DUARATION: 21DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

7908

2.343

257.130

11.428

2353

2.353

112.308

4.991

7551

2.237

227.316

10.103

POZO 60% WEIGHT (kg)

DUARATION: 28DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

7802

2.312

276.213

12.276

7736

2.292

274.845

12.215

7731

2.291

253.745

11.278

- 52 -

SLUMP:

6mm

AVERAGE

6.9

SLUMP:

6mm

AVERAGE

7.6

SLUMP:

6mm

AVERAGE

8.8

SLUMP: AVERAGE

11.9

6mm

POZZOLANA 20% CONCRETE COMPRESSIVE STRENGHT TEST RESULTS FOR POZO 20% DESCRIPTION:

POZO 20% WEIGHT (kg)

DESCRIPTION:

2.404

338.074

15.026

8104

2.401

353.269

15.701

8063

2.389

361.119

16.050

POZO 20%

DUARATION: 14DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8090

2.397

365.080

16.226

8142 8188

2.412 2.426

397.486 408.503

17.666 18.156

POZO 20% WEIGHT (kg)

DESCRIPTION:

MAX LOAD (kN)

STRENGTH (Mpa)

8115

WEIGHT (kg)

DESCRIPTION:

DUARATION: 7DAYS DENSITY (kg/dm3)

DUARATION: 21DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8100

2.400

441.199

19.609

8003

2.371

366.880

16.306

8134

2.410

372.353

16.549

POZO 20% WEIGHT (kg)

DUARATION: 28DAYS DENSITY (kg/dm3)

MAX LOAD (kN)

STRENGTH (Mpa)

8010

2.373

374.153

16.629

8119

2.406

465.036

20.668

8074

2.392

372.065

16.536

- 53 -

SLUMP:

12mm

AVERAGE

15.6

SLUMP:

12mm

AVERAGE

17.3

SLUMP:

12mm

AVERAGE

17.5

SLUMP: AVERAGE

17.9

12mm

POZZOLANA 80% CONCRETE COMPRESSIVE STRENGHT TEST RESULTS FOR POZO 80% DESCRIPTION:

POZO 80% WEIGHT (kg)

DESCRIPTION:

MAX LOAD (kN)

STRENGTH (Mpa)

2.318

63.122

2.805

7691

2.279

63.410

2.818

7690

2.279

56.785

2.524

POZO 80%

DUARATION: DENSITY (kg/dm3)

MAX LOAD (kN)

14DAYS STRENGTH (Mpa)

7559

2.240

67.443

2.997

7678 7725

2.275 2.289

69.891 69.748

3.106 3.100

POZO 80% WEIGHT (kg)

DESCRIPTION:

DENSITY (kg/dm3)

7DAYS

7823

WEIGHT (kg)

DESCRIPTION:

DUARATION:

DUARATION: DENSITY (kg/dm3)

MAX LOAD (kN)

21DAYS STRENGTH (Mpa)

7808

2.313

78.461

3.487

7686

2.277

61.178

2.719

7808

2.313

70.828

3.148

POZO 80% WEIGHT (kg)

DUARATION: DENSITY (kg/dm3)

MAX LOAD (kN)

28DAYS STRENGTH (Mpa)

7683

2.276

80.808

3.591

7735

2.292

93.728

4.166

7623

2.259

72.988

3.244

- 54 -

SLUMP:

13mm

AVERAGE

2.7

SLUMP:

13mm

AVERAGE

3.1

SLUMP:

13mm

AVERAGE

3.1

SLUMP:

13mm

AVERAGE

3.7

POZZOLANA 50% CONCRETE COMPRESSIVE STRENGHT TEST RESULTS FOR POZO 50% DESCRIPTION:

POZO 50% WEIGHT (kg)

DESCRIPTION:

MAX LOAD (kN)

STRENGTH (Mpa)

2.333

211.328

9.392

7919

2.346

265.627

11.806

7990

2.367

240.998

10.711

POZO 50%

DUARATION: DENSITY (kg/dm3)

MAX LOAD (kN)

14DAYS STRENGTH (Mpa)

8006

2.372

262.315

11.658

7905 8014

2.342 2.375

251.188 256.913

11.164 11.418

POZO 50% WEIGHT (kg)

DESCRIPTION:

DENSITY (kg/dm3)

7DAYS

7873

WEIGHT (kg)

DESCRIPTION:

DUARATION:

DUARATION: DENSITY (kg/dm3)

MAX LOAD (kN)

21DAYS STRENGTH (Mpa)

7932

2.350

279.238

12.411

7938

2.352

328.136

14.584

7812

2.315

262.675

11.674

POZO 50% WEIGHT (kg)

DUARATION: DENSITY (kg/dm3)

MAX LOAD (kN)

28DAYS STRENGTH (Mpa)

7928

2.349

262.891

11.684

8031

2.380

296.882

13.195

8093 2.398 (Source: laboratory test 2010)

359.822

15.992

- 55 -

SLUMP:

12mm

AVERAGE

10.6

SLUMP:

12mm

AVERAGE

11.4

SLUMP:

12mm

AVERAGE

12.9

SLUMP: AVERAGE

13.6

12mm

Table 4.8: Average Compressive Strengths Incorporating Pozzolan at all Ages of Test. Compressive Strength, Mpa Mix 7-days

14-days

21-days

28-days

Control

16.4

20.1

20.2

25.7

Pozo 30%

16.9

20.2

23.7

25.9

Pozo 70%

4.4

5.2

6.8

7.6

Pozo 40%

13.1

13.8

15.8

16.1

Pozo 60%

6.9

7.6

8.8

11.9

Pozo 20%

15.6

17.3

17.5

17.9

Pozo 80%

2.7

3.1

3.1

3.7

Pozo 50% 10.6 (Sources: Laboratory Test, 2010)

11.4

12.9

13.6

Compressive strength was measured on concrete containing various combinations of pozzolanic material. As presented in Tables 4.7 and 4.8. All the mixes prepared with pozzolanic materials demonstrated lower compressive strength at all ages as compared to that of corresponding control mix. However, partial replacement mix of 30% pozzolana showed an early strength gain compared to the control and a significant strength gain in later ages too. The effect of pozzolanic replacement on the compressive strength can be seen in fig. 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, and 4.10 These figures shows the compressive strengths of concrete prepared with 30%, 70%, 40%, 60%, 20%, 80%, and 50% pozzolanic material as cement replacement. The selection of these ratios was on the basis of information from earlier research work conducted in the Civil Engineering Department of Cape Coast polytechnic in 2009 that 30% pozzolan replacement of cement recorded higher compressive strength and could be used as alternative to control. [Hope and Nasir Odei, 2009. Unpublished project work]. Initially it was expected that pozzolanic concrete might show enhancement in strength at later ages. As expected, mix with 30% replacement showed higher strengths as compared to the control at all ages as well as higher strength compared to the other mix ratios at all ages. - 56 -

18.0

Compressive strength, Mpa

16.0 14.0 12.0 10.0 8.0 7 days

6.0 4.0 2.0 0.0 Control Pozo 30% Pozo 70% Pozo 40% Pozo 60% Pozo 20% Pozo 80% Pozo 50% Mix

Fig. 4.5: Effect Of Pozzolanic Replacement On The Compressive Strength Of Concrete At 7 Days

Compressive strength, Mpa

25.0

20.0

15.0

10.0

14 days

5.0

0.0 Control Pozo 30%Pozo 70%Pozo 40%Pozo 60%Pozo 20%Pozo 80%Pozo 50% Mix

Fig. 4.6: Effect of pozzolanic replacement on the compressive strength of concrete at 14days

- 57 -

Compressive strength, Mpa

25.0

20.0

15.0

10.0

21 days

5.0

0.0 Control Pozo 30% Pozo 70% Pozo 40% Pozo 60% Pozo 20% Pozo 80% Pozo 50% Mix

Fig. 4.7: Effect of pozzolanic replacement on the compressive strength of concrete at 21 days

30.0

Compressive strength, Mpa

25.0

20.0 15.0 28 days 10.0

5.0 0.0 Control Pozo 30% Pozo 70% Pozo 40% Pozo 60% Pozo 20% Pozo 80% Pozo 50% Mix

Fig. 4.8: Effect of pozzolanic replacement on the compressive strength of concrete at 28 days

- 58 -

Compressive strength, Mpa

30.0 25.0 20.0 7 days

15.0

14 days 10.0

21 days

5.0

28 days

0.0 Control Pozo 30% Pozo 70% Pozo 40% Pozo 60% Pozo 20% Pozo 80% Pozo 50% Mix

Fig. 4.9: Effect of pozzolanic replacement on the compressive strength of concrete at all ages

30.0

Compressive Strength, MPa

Control

Pozo 30%

Pozo 70%

20.0 Pozo 40%

Pozo 60%

Pozo 20%

10.0

0.0 0

7

14 days Age,

21

28

Fig. 4.10: line diagram illustrating the effect of pozzolanic replacement on the compressive strength of concrete at all age

- 59 -

Table 4.9: A One -Sample Statistics for Various Concrete From 7 -28 Days

N

Mean

Std. Deviation

Std. Error Mean

Control

3

25.6897

.58950

.34035

Pozo 30%

3

25.9377

.92130

.53191

Pozo 70%

3

7.6283

.53804

.31064

Pozo 40%

3

16.0597

.63762

.36813

Pozo 60%

3

11.9230

.55942

.32298

Pozo 20%

3

17.9443

2.35922

1.36210

Pozo 80%

3

3.6670

.46567

.26886

Pozo 50%

3

13.6237

2.18576

1.26195

Table 4.10: 95% Confidence Interval of the Difference for Various Concrete From 7 -28 Days

Test Value = 0

t

df

Sig. (2tailed)

Control

75.481

2

.000

Pozo 30%

48.763

2

Pozo 70%

24.557

Pozo 40%

Mean Difference

95% Confidence Interval of the Difference Lower

Upper

25.68967

24.2253

27.1541

.000

25.93767

23.6490

28.2263

2

.002

7.62833

6.2918

8.9649

43.625

2

.001

16.05967

14.4757

17.6436

Pozo 60%

36.916

2

.001

11.92300

10.5333

13.3127

Pozo 20%

13.174

2

.006

17.94433

12.0837

23.8050

Pozo 80%

13.639

2

.005

3.66700

2.5102

4.8238

Pozo 50%

10.796

2

.008

13.62367

8.1939

19.0534

- 60 -

Confidence interval (interval estimator) is a formula that tells how to use sample data to calculate an interval that estimates a population parameter. The chosen confidence level of 95% implies that the method used to construct each of the intervals has 5% long-run error rate. In the correct interpretation, the level of 95% refers to the success rate of the process being used to estimate the proportions and does not refer to the population proportion itself. Based on the information provided by the various mix proportions, we can be 95% confident that the mean total of the samples are between their corresponding 95% confidence interval of the differences. The intervals are relatively wide indicating that the values of the population mean have not been estimated more precisely in either case. This is not surprising given the reported sample size. Also it is noted that most of the intervals are relatively overlapping and this may cause a sceptical statement that a particular sample has a higher 95% confidence level in terms of average 28 day compressive strength compared to others, ―however we are 95% confident that the intervals for the various mixes actually does contain the true value p” this means that if we were to select many different samples of the same mixes and construct the corresponding intervals, 95% of them would actually contain the value of the population proportion.

- 61 -

Table 4.11: A Correlation Matrix for Various Concrete From 7 -28 Days Contro l Sig. (1tailed)

Pozo 30%

Pozo 70%

Pozo 40%

Pozo 60%

Pozo 20%

Pozo 80%

Pozo 50%

.031

.031

.473

.483

.173

.288

.388

.062

.496

.452

.204

.319

.357

.442

.486

.142

.257

.419

.044

.300

.185

.139

.344

.229

.095

.115

.439

Control Pozo 30%

.031

Pozo 70%

.031

.062

Pozo 40%

.473

.496

.442

Pozo 60%

.483

.452

.486

.044

Pozo 20%

.173

.204

.142

.300

.344

Pozo 80%

.288

.319

.257

.185

.229

.115

Pozo 50%

.388

.357

.419

.139

.095

.439

.324 .324

Table 4.12: An Explanation of the Total Variance of Concrete From 7 -28 Days Initial Eigenvalues

Compon

Extraction Sums of Squared Loadings

ent

Total

% of Variance

Cumulative %

Total

% of Variance

Cumulative %

1

4.673

58.409

58.409

4.673

58.409

58.409

2

3.327

41.591

100.000

3.327

41.591

100.000

3

4.054E-16

5.067E-15

100.000

4

1.252E-16

1.565E-15

100.000

5

6.385E-17

7.981E-16

100.000

6

-7.461E-18

-9.326E-17

100.000

7

-1.245E-16

-1.557E-15

100.000

8

-1.931E-16

-2.414E-15

100.000

Extraction Method: Principal Component Analysis.

- 62 -

CHAPTER FIVE CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION This study was conducted to assess the performance of concrete cubes utilizing natural pozzolanic material as a partial replacement to ordinary Portland cement. The following conclusions were drawn from the present study. 

The partial replacement mix of 30% pozzolana attained the highest compressive strength after 28 days as proved by other researchers in earlier works.



Pozzolana concrete could be used in project when early age strength is required without having detrimental effect on the early age or later age strength development. The early age compressive strength in this research was found to be higher than that of Portland Cement concrete (Control)



The inclusion of natural pozzolana in the concrete as a partial replacement was not detrimental to the properties of concrete. Slump loss, compaction factor and compressive strength were similar to that of corresponding control mix.



Partial replacement mixes of 20%. 40%, 50%, 60%, 70% and 80% Pozzolana did not attain the design strength of 20 N/mm2 after 28 days.

- 63 -

5.2 RECOMMENDATIONS Generally the use of pozzolana has the advantage of lower costs and better durability. After appraising the results and conclusion from the study the following recommendations were made: 

Compressive strength and workability tests suggested that pozzolan, could be substituted for Portland cement at up to 30% in the production of concrete with no loss in workability or strength.



The pozzolanic reactivity could be significantly improved by using one or a combination of several treatment methods. However, all methods may not be feasible to achieve the optimum level. Therefore, it is strongly recommended that, besides employing various treatment methods, the feasibility and practical applicability of each method needs to be investigated in greater details.

- 64 -

REFERENCES 1. Aitcin P.C and Neville A. ―High-Performance Concrete Demystified,‖ Concrete International, Vol. 15, No. 1 pp. 21-26, 1993][O.E. Gjorv, ―High Strenght Concrete,‖ Advances in Concrete Technology,. Malhotra V. M, Ed., CANMET, Energy, Mines sand Resources, Canada, 1994, pp. 19-82. 2. Alhoziamy A.; Soroushian P. and F. Mirza, ―Effects of Curing Conditions and Age on Chloride Permeability of Fly Ash Mortar‖, ACI Material Journal, Vol. 93 No. 1, pp. 87-95, Jan-Feb 1996. 3. Coal Fly Ash journal. (2009), pp.2 4. Cook D.J., ― Natural Pozzolana,‖ Cement Replacement Material Vol. 3, Editor, Swamy R.N., Surry Press, UK, 1986 5. Dr. Muhammad Iqbal khan (PI) Dr. Abdurrahman M. Alhozaimy (2005). King Saud University College of engineering research center. Final research report no. 423 / 33. 6. Gjorv O.E ―High Strenght Concrete,‖ Advances in Concrete Technology,V. M. Malhotra, Ed., CANMET, Energy, Mines sand Resources, Canada, 1994, pp. 19-82 7. Guide for MEASURING, Transporting, and Placing Concrete.‖ ACI Committee 304, ACI Manual of Concrete Practice, Part 2, 2003. 8. http://en.wikipedia.org/wiki/Concrete#Concrete_production, 21/12/09 9. ICAR, Summary of Concrete Workability Test Method, 2001 10. Malhotra V.M. and. Mehta P.K, ―Pozzolanic and Cementitious Materials-Advances in Concrete Technology,‖ Vol. I, Gordon ND Breach Publishers, Amsterdam, Netherlands, 1996 11. Mehta P. K. and Monteiro P.J.M, ―Concrete Structure, Properties and Materials,‖ Prentice Hall, USA. 1995 12. Mehta P.K., ―Studies on Blended Portland Cement Containing Santorin Earth,‖ Cement and Concrete Research, Vol. 11 pp. 507-518, 1981 13. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation 14. Nehdi, M. (2001) Tenary and quaternary cement for sustainable development. Concrete International, 23 (4), PP.35-42. 15. Neville A.M, ―Properties of Concrete,‖ Fourth Edition, Longman, UK, 1996. 16. Sumrerng Rukzon,‖Construction Building and Design‖, SAGE publication, London,2009.

- 65 -

APPENDIX A

- 66 -

- 67 -

- 68 -

APPENDIX B DESIGN MIX CALCULATION It was supposed that the concrete is required for use on roadwork, that it is to be compacted by power-operated machines, that OPC is to be used, that the aggregate will be supplied in two sizes and that the concrete is to have a minimum strength of 20 C at 28 days. Reference to Table 1, shows that under such conditions the minimum strength may be expected to be about 60 percent of the average strength. The average strength to be aimed at in this design procedure would, therefore, be 𝟐𝟎 × 𝟏𝟎𝟎 = 𝟑𝟑. 𝟑𝟑 ≈ 𝟑𝟒 𝑵/𝒎𝒎𝟐 𝟔𝟎 Water cement ratio = 0.55 Workability required = medium Aggregate size and shape = 19mm Angular Total Aggregate weight after sieve analysis test= 8.930g (See Tables 4.3 and 4.4 for sieve analysis test results) Percentage error =

𝟗 𝒌𝒈−𝟖.𝟗𝟑 𝒌𝒈 ×𝟏𝟎𝟎 𝟖.𝟗𝟑 𝒌𝒈

= 𝟎. 𝟕𝟖% Appendix B. Table 1a 1

2

3

4

19

100

92.0

100

92

100

93

100

93

10

45

48.4

55

52

65

57

75

62

5

30

30.0

35

35

42

42

48

48

No 7

23

30.4

28

34

35

41

42

46

No 14

16

22.3

21

26

28

29

34

36

No 25

8

16.0

14

18

21

23

27

26

No 52

2

10.0

3

11

5

14

12

16

No 100

0

0.0

0

0

0

0

1.5

0

Source: Laboratory test, 2010 Grading curve selected from sieve analysis = curve 4 (Appendix B. Table 1a)

- 69 -

Aggregate cement Ratio (for medium size aggregate) from table 3 = 1:6.4

Percentage of fine to course aggregate = 48%

RATIOS W/C

:

CEMENT

:

𝟎. 𝟓𝟓 ∶

𝟏

∶

𝟎. 𝟓𝟓 ∶

𝟏

∶

𝟎. 𝟓𝟓 ∶

𝟏

∶

AGGREGATE 𝟔. 𝟒 𝟒𝟖 𝟏𝟎𝟎

× 𝟔. 𝟒 ∶

𝟑. 𝟎𝟕

∶

𝟔. 𝟒 −

𝟒𝟖 𝟏𝟎𝟎

× 𝟔. 𝟒

𝟑. 𝟑𝟑

Comparing the design ratio, 1:3.07:3.33 to the natural ratios, then the mix ratio of 1:2:4 for the design.

- 70 -